cellular level of organization...module 3.1: cellular differentiation produces specialized cells...
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Lecture Presentation by
Lori Garrett
3Cellular Level of
Organization
© 2018 Pearson Education, Inc.
Section 1: Introduction to Cells
Learning Outcomes
3.1 Describe the cell theory and the process of cellular
differentiation.
3.2 Describe a body cell and its organelles, including
the structure and function of each.
3.3 Describe the structural and functional features of
the plasma membrane.
3.4 Differentiate among the structures and functions of
the cytoskeleton.
© 2018 Pearson Education, Inc.
Section 1: Introduction to Cells
Learning Outcomes (continued)
3.5 Describe the ribosome and smooth and rough
endoplasmic reticula, and indicate their specific
functions.
3.6 Describe the Golgi apparatus, and indicate its
specific functions.
3.7 Describe the structure of a mitochondrion, and
explain the significance of mitochondria to cellular
function.
© 2018 Pearson Education, Inc.
Module 3.1: Cellular differentiation produces specialized cells
Typical cell
Smallest living unit in the body
~0.1 mm in diameter
Could not be examined until invention of microscope
in 17th century
© 2018 Pearson Education, Inc.
Module 3.1: Introduction to Cells
Cell theory
1. Cells are building blocks of all plants and animals
2. All new cells come from division of preexisting
cells
3. Cells are smallest living units that perform all vital
physiological functions
© 2018 Pearson Education, Inc.
Module 3.1: Introduction to Cells
Cell cooperation
Each cell maintains homeostasis at cellular level
Coordinated activities of cells allow homeostasis at
higher organizational levels
All cells are descendants from a single cell: the
fertilized ovum
At fertilization, zygote forms
• Fertilized ovum contains genetic potential to become
any cell
• First cell divisions create smaller parcels of cytoplasm
© 2018 Pearson Education, Inc.
Module 3.1: Introduction to Cells
Cellular differentiation
Regional differences in original ovum cytoplasm
means now different composition of cytoplasm in
resulting daughter cells
Cytoplasmic differences affect DNA in daughter cells
and cause specific genes to turn on or off
• Result is specialization of cells
• Process of gradual specialization is called cellular
differentiation
• Specialized cells form tissues of the body
© 2018 Pearson Education, Inc.
Cell differentiation
© 2018 Pearson Education, Inc.
Module 3.1: Review
A. Describe the cell theory.
B. Identify the cell from which all the cells of your
body are descendants.
C. Define cellular differentiation.
Learning Outcome: Describe the cell theory and
the process of cellular differentiation.
© 2018 Pearson Education, Inc.
Module 3.2: Cells are the smallest living units of life
Body fluid distribution
Cells surrounded by watery medium called
extracellular fluid
• Called interstitial fluid (interstitium, something
standing between) in most tissues
Fluid inside cell is intracellular fluid or cytosol
Cell plasma membrane separates cell contents
(cytoplasm) from extracellular fluid
© 2018 Pearson Education, Inc.
Module 3.2: The cell and its organelles
Basic cell structure
Surrounded by a plasma membrane
Contains cytoplasm
• Material of varying consistency found between cell
membrane and nuclear membrane
• Subdivided into:
– Cytosol (intracellular fluid)—the fluid part of cytoplasm
– Organelles (“little organs”)—intracellular structures
with specific functions
© 2018 Pearson Education, Inc.
Module 3.2: The cell and its organelles
Organelles
Divided into membranous
and nonmembranous
Nonmembranous
• Not completely enclosed
by membranes
• In direct contact with
cytosol
Membranous
• Enclosed in a
phospholipid membrane
• Isolated from cytosol
© 2018 Pearson Education, Inc.
Module 3.2: The cell and its organelles
Peroxisome
STRUCTURE:
• Vesicles containing
degradative enzymes
FUNCTION:
• Break down organic
compounds
• Neutralize toxic
compounds
© 2018 Pearson Education, Inc.
Module 3.2: The cell and its organelles
Lysosome
STRUCTURE:
• Vesicles containing
digestive enzymes
FUNCTION:
• Break down organic
compounds and
damaged organelles or
pathogens
© 2018 Pearson Education, Inc.
Module 3.2: The cell and its organelles
Microvilli
STRUCTURE:
• Membrane extensions
containing
microfilaments
FUNCTION:
• Increase surface area
for absorption
© 2018 Pearson Education, Inc.
Module 3.2: The cell and its organelles
Golgi apparatus
STRUCTURE:
• Stacks of flattened
membranes (cisternae)
containing chambers
FUNCTION:
• Store, alter, and
package synthesized
products
© 2018 Pearson Education, Inc.
Module 3.2: The cell and its organelles
Nucleus
STRUCTURE:
• Fluid nucleoplasm
containing enzymes,
proteins, DNA, and
nucleotides
• Surrounded by double
membrane called
nuclear envelope
FUNCTION:
• Controls metabolism
• Stores and processes genetic information
• Controls protein synthesis
© 2018 Pearson Education, Inc.
Module 3.2: The cell and its organelles
Endoplasmic reticulum
(ER)
STRUCTURE:
• Network of
membranous
sheets and channels
FUNCTION:
• Synthesizes secretory
products; stores and
transports within cell;
detoxifies drugs and
toxins
© 2018 Pearson Education, Inc.
Module 3.2: The cell and its organelles
Endoplasmic reticulum
(ER) (continued)
• Smooth ER
– No attached
ribosomes
– Synthesizes lipids
and carbohydrates
• Rough ER
– Attached ribosomes
– Modifies/packages
newly synthesized
proteins
© 2018 Pearson Education, Inc.
Module 3.2: The cell and its organelles
Ribosomes
STRUCTURE: RNA
and proteins
• Fixed: attached to
endoplasmic reticulum
• Free: scattered in
cytoplasm
FUNCTION:
• Synthesize proteins
© 2018 Pearson Education, Inc.
Module 3.2: The cell and its organelles
Mitochondrion
STRUCTURE:
• Double membrane
• Inner membrane
contains metabolic
enzymes
FUNCTION:
• Produces 95 percent
of cellular ATP
© 2018 Pearson Education, Inc.
Module 3.2: The cell and its organelles
Cytoskeleton
STRUCTURE:
• Proteins organized into
fine filaments or slender
tubes
• Centrosome
– Organizing center
containing pair of
centrioles
FUNCTION:
• Strengthens and
supports cell
• Moves cellular structures and materials within the cell
© 2018 Pearson Education, Inc.
Module 3.2: Review
A. Distinguish between the cytoplasm and cytosol.
B. Identify the membranous organelles, and
describe their functions.
C. Describe the functions of the cytoskeleton.
D. Describe the external environment of most of
the body’s cells.
Learning Outcome: Describe a body cell and its
organelles, including the structure and function of
each.
© 2018 Pearson Education, Inc.
Module 3.3: The plasma membrane isolates the cell from its environment and performs varied functions
Plasma membrane—selectively permeable barrier
separating inside of cell from extracellular fluid
Controls:
• Entry of ions and nutrients
• Elimination of wastes
• Release of secretions
© 2018 Pearson Education, Inc.
Module 3.3: Plasma membrane
Composed of:
Phospholipid bilayer
Proteins
1. Integral
2. Transmembrane
3. Peripheral
4. Glycocalyx—layer formed by superficial membrane
carbohydrates
© 2018 Pearson Education, Inc.
Plasma membrane
© 2018 Pearson Education, Inc.
Module 3.3: Plasma membrane
Phospholipid bilayer
Measures 6–10 nm
Two layers of phospholipids
• Hydrophilic heads at
membrane surface
• Hydrophobic tails facing
each other on the inside
Phospholipids interspersed
with cholesterol molecules
• Cholesterol has hydrophilic and hydrophobic
portions (amphipathic)
• Functions to “stiffen” the plasma membrane
© 2018 Pearson Education, Inc.
Module 3.3: Plasma membrane
Proteins
Integral proteins
• Part of cell membrane and cannot be removed
without damaging cell
• Often span entire cell membrane (these are called
transmembrane proteins)
• Can transport water or solutes
Peripheral proteins
• Attached to cell membrane inner or outer surface
• Easily removable
• Fewer than integral proteins
• May have regulatory or enzymatic functions
© 2018 Pearson Education, Inc.
Module 3.3: Plasma membrane
Plasma membrane components
Glycocalyx
Components of complex molecules
• Proteoglycans (carbohydrates with protein attached)
• Glycoproteins (protein with carbohydrates attached)
• Glycolipids (lipids with carbohydrates attached)
Functions
• Cell recognition
• Binding to extracellular structures
• Lubrication of cell surface
© 2018 Pearson Education, Inc.
Module 3.3: Plasma membrane
Plasma membrane
functions
Physical isolation
Regulation of exchange
with external environment
Sensitivity to environment
Structural support
Lipid bilayer provides
isolation
Proteins perform most
other functions
© 2018 Pearson Education, Inc.
Module 3.3: Review
A. Which structural component of the plasma
membrane is mostly responsible for isolating a cell
from its external environment?
B. List the general functions of the plasma membrane.
C. Which type of integral protein allows water and
small ions to pass through the plasma membrane?
D. What characteristics of phospholipids accounts for
their packing into a double layer?
Learning Outcome: Describe the structural and
functional features of the plasma membrane.
© 2018 Pearson Education, Inc.
Module 3.4: The cytoskeleton plays both a structural and a functional role
Cytoskeleton
Functions as cell’s skeleton
Provides internal protein framework
Gives cytoplasm strength and flexibility
Components include:
1. Microfilaments
2. Intermediate filaments
3. Microtubules
© 2018 Pearson Education, Inc.
Module 3.4: The cytoskeleton
Microfilaments
6 nm in diameter
(smallest cytoskeletal
element)
Typically composed of
actin
Commonly at periphery
of cell
© 2018 Pearson Education, Inc.
Module 3.4: The cytoskeleton
Microfilaments (continued)
Microvilli
• Finger-shaped extensions
of cell membrane
• Have core of
microfilaments to stiffen
and anchor
• Enhance surface area
of cell for absorption
Terminal web
(microfilaments inside
plasma membrane in cells
forming a layer or lining)
© 2018 Pearson Education, Inc.
Module 3.4: The cytoskeleton
Intermediate filaments
7–11 nm in diameter
Strongest and most
durable cytoskeletal
elements
© 2018 Pearson Education, Inc.
Module 3.4: The cytoskeleton
Microtubules
~25 nm in diameter
Hollow tubes built from globular protein tubulin
Largest components of cytoskeleton
Extend outward from centrosome (near nucleus)
© 2018 Pearson Education, Inc.
Module 3.4: The cytoskeleton
Centrioles
Composed of
microtubules (9 groups
of triplets)
Two in each
centrosome
Control movement of
DNA strands during cell
division
• Cells without centrioles
cannot divide
– Red blood cells
– Skeletal muscle cells
© 2018 Pearson Education, Inc.
Module 3.4: The cytoskeleton
Cilia
Long, slender plasma
membrane extensions
Motile cilia common in
respiratory and
reproductive tracts
• Microtubules
surrounding a central
pair
• Anchored to cell surface
with basal body
© 2018 Pearson Education, Inc.
Motile cilia beat rhythmically
© 2018 Pearson Education, Inc.
Module 3.4: The cytoskeleton
Cilia (continued)
Primary cilium functions as sensor
Flagella are longer than cilia and beat in a wavelike
fashion
© 2018 Pearson Education, Inc.
© 2018 Pearson Education, Inc.
Module 3.4: Review
A. List the three basic components of the
cytoskeleton.
B. Which cytoskeletal component is common to
both centrioles and cilia?
C. What is the function of motile cilia?
D. Which cytoskeletal structure is found only in
males?
Learning Outcome: Differentiate among the
structures and functions of the cytoskeleton.
© 2018 Pearson Education, Inc.
Module 3.5: Ribosomes and endoplasmic reticulum
Ribosomes
Responsible for protein synthesis
Two subunits (1 large, 1 small) containing special
proteins and ribosomal RNA (rRNA)
• Must join together before synthesis begins
© 2018 Pearson Education, Inc.
Module 3.5: Ribosomes and endoplasmic reticulum
Ribosomes (continued)
Free ribosomes
• Throughout cytoplasm
• Manufactured proteins enter cytosol
Bound or fixed ribosomes
• Attached to rough endoplasmic reticulum
• Synthesize proteins for export out of cell
© 2018 Pearson Education, Inc.
Module 3.5: Ribosomes and endoplasmic reticulum
Endoplasmic reticulum (ER)
Network of intracellular membranes continuous with
nuclear envelope, which surrounds nucleus
Forms hollow tubes, sheets,
and chambers (cisternae,
singular, cisterna, reservoir
for water)
Synthesizes and stores
proteins, lipids, and
carbohydrates
© 2018 Pearson Education, Inc.
Module 3.5: Ribosomes and endoplasmic reticulum
Two types of endoplasmic reticulum (ER)
1. Smooth (SER)
• Lacks ribosomes
• Cisternae are often tubular
© 2018 Pearson Education, Inc.
Module 3.5: Ribosomes and endoplasmic reticulum
Two types of endoplasmic reticulum (ER)
(continued)
2. Rough (RER)
• Has attached (fixed) ribosomes
• Modifies newly synthesized proteins
• Exports those proteins to Golgi apparatus
Proportion of SER to
RER depends on the
cell and its functions
© 2018 Pearson Education, Inc.
Module 3.5: Ribosomes and endoplasmic reticulum
Polypeptide formation in RER
Polypeptide synthesized on attached ribosome
• Growing chain enters cisterna of RER
Polypeptide assumes secondary/tertiary structures
Completed protein may become enzyme or
glycoprotein
Products not destined for RER are packaged into
transport vesicles
• Deliver products
to Golgi apparatus
© 2018 Pearson Education, Inc.
Module 3.5: Review
A. Describe the immediate cellular destinations of
newly synthesized proteins from free ribosomes
and fixed ribosomes.
B. Compare and contrast the structure of SER and
RER.
C. Why do certain cells in the ovaries and testes
contain large amounts of SER?
D. The ER is connected to and continuous with what
other organelle in the cell?
Learning Outcome: Describe the ribosome and smooth
and rough endoplasmic reticula, and indicate their
specific functions.
© 2018 Pearson Education, Inc.
Module 3.6: The Golgi apparatus is a packaging center
Golgi apparatus (Golgi complex)
Functions
1. Renews or modifies plasma membrane
2. Modifies or packages secretions into secretory
vesicles for release from cell (exocytosis)
3. Packages special enzymes within vesicles for use in
cytosol (lysosomes)
Typically consists of 5–6 flattened discs (cisternae)
May be more than one apparatus in a cell
Situated near nucleus
© 2018 Pearson Education, Inc.
Module 3.6: Golgi apparatus
Golgi apparatus process
1. Transport vesicles filled with proteins and/or
glycoproteins from rough ER arrive at cis face
(“receiving side”) of Golgi apparatus.
2. Transport vesicles fuse, forming new cisternae.
Enzymes in Golgi apparatus modify arriving
products.
3. Products modified and re-packaged as they
move toward trans face (“shipping side”).
4. Finalized products packaged in secretory
vesicles and released from trans face.
© 2018 Pearson Education, Inc.
Golgi apparatus process
© 2018 Pearson Education, Inc.
Module 3.6: Golgi apparatus
Golgi apparatus products
1. Membrane renewal vesicles
• Add to plasma membrane
• Allow alteration of plasma membrane properties,
changing sensitivity and functions of cells
2. Secretory vesicles
• Contain hormones or enzymes for extracellular
release
3. Lysosomes
• Contain digestive enzymes for intracellular use
© 2018 Pearson Education, Inc.
Module 3.6: Golgi apparatus
Lysosomes
Vesicles that isolate digestive processes from the
rest of the cytoplasm
Three basic functions
1. Fusion with another organelle and digestion of
contents
2. Fusion with another vesicle containing fluid or solid
extracellular materials and digestion of contents
3. Release of digestive enzymes within the cytoplasm
when cell is injured or dying, resulting in autolysis
(enzymes destroy cytoplasm)
– Leads to “suicide packets”—name for lysosomes
© 2018 Pearson Education, Inc.
Lysosomes
© 2018 Pearson Education, Inc.
Module 3.6: Golgi apparatus
Membrane flow
Continuous movement and exchange of materials
between organelles using vesicles
Can replace parts of cell membrane to allow cell to
grow, mature, or respond to changing environment
In an actively secreting cell, the entire membrane
surface can be replaced in 1 hour.
© 2018 Pearson Education, Inc.
Module 3.6: Review
A. List the three major functions of the Golgi
apparatus.
B. What do lysosomes contain?
C. Describe three functions of lysosomes.
Learning Outcome: Describe the Golgi apparatus,
and indicate its specific functions.
© 2018 Pearson Education, Inc.
Module 3.7: Mitochondria are the powerhouses of the cell
Mitochondria (mitos, thread + chondrion, granule)
Produce energy (ATP) for cells
Vary in number per cell depending on cell’s energy
requirements (more energy needs = more
mitochondria)
• Mitochondria account for 30 percent of the heart
cardiac muscle cells
• Red blood cells have no mitochondria
Contain their own DNA (mtDNA) and ribosomes
© 2018 Pearson Education, Inc.
Module 3.7: Mitochondria
Mitochondrial double membrane
Outer membrane surrounds organelle
Inner membrane contains folds called cristae
• Inner membrane encloses liquid called matrix
• Cristae increase surface area exposed to matrix
• Metabolic enzymes in matrix catalyze reactions
providing energy for cellular function
© 2018 Pearson Education, Inc.
Cut-away view of mitochondrion organelle
© 2018 Pearson Education, Inc.
Mitochondrion organelle
© 2018 Pearson Education, Inc.
Module 3.7: Mitochondria
Steps of ATP production
1. Glycolysis (glycos, sugar -lysis, a loosening)
• Occurs in cytosol
• 1 glucose → 2 pyruvate
• Pyruvate absorbed into mitochondria
2. In mitochondrial matrix:
• CO2 removed from pyruvate
• Enters citric acid (or TCA, tricarboxylic acid) cycle
– Systematically removes CO2 and hydrogen atoms
© 2018 Pearson Education, Inc.
Module 3.7: Mitochondria
Steps of ATP production (continued)
3. Enzymes and coenzymes use hydrogen atoms to catalyze ATP from ADP
• Also forms H2O
4. ATP leaves mitochondrion
© 2018 Pearson Education, Inc.
ATP Production
© 2018 Pearson Education, Inc.
Module 3.7: Mitochondria
Aerobic metabolism or cellular respiration
ATP production that requires oxygen
Occurs in the mitochondria
Much more efficient than ATP production without
oxygen (e.g., glycolysis)
Produces about 95 percent of ATP needed by cell
• Remaining 5 percent produced by enzymatic
reactions in the cytoplasm
© 2018 Pearson Education, Inc.
Module 3.7: Review
A. Describe the structure of a mitochondrion.
B. Most of a cell’s ATP is produced within its
mitochondria. What gas do mitochondria require
to produce ATP, and what gas results?
C. What does the presence of many mitochondria
imply about a cell’s energy requirements?
Learning Outcome: Describe the structure of a
mitochondrion, and explain the significance of
mitochondria to cellular function.
© 2018 Pearson Education, Inc.
Section 2: Structure and Function of the Nucleus
Learning Outcomes
3.8 Describe the role of the nucleus in maintaining
homeostasis at the cellular level.
3.9 Describe the functions of the cell nucleus, and
distinguish between chromatin and a
chromosome.
3.10 Discuss the nature of the genetic code, and
summarize the process of protein synthesis.
3.11 Summarize the process of transcription.
3.12 Summarize the process of translation.
© 2018 Pearson Education, Inc.
Module 3.8: The nucleus is the control center for cellular homeostasis
Nucleus
Usually largest cellular structure
Control center for cellular operations
• Can direct synthesis of >100,000 different proteins
• Genetic information coded in sequence of nucleotides
• Determines cell structure and function
Usually only one per cell
• Exceptions
– Skeletal muscle cells have many
– Mature red blood cells have none
o Because of no nucleus, they disintegrate within
3–4 months© 2018 Pearson Education, Inc.
Module 3.8: Role of the nucleus
The nucleus directs cellular responses to
environmental (ECF) changes
Short-term adjustments
• Enzyme activity changes
Long-term adjustments
• Changes in enzymes
produced
• Changes in cell structure
from changes in structural
proteins
• Often occur as part of
growth, development,
and aging
© 2018 Pearson Education, Inc.
Module 3.8: Review
A. How is genetic information coded in the cell?
B. How many nuclei do most body cells contain?
C. Describe why the nucleus is said to be the
control center for the cell.
Learning Outcome: Describe the role of the
nucleus in maintaining homeostasis at the cellular
level.
© 2018 Pearson Education, Inc.
Module 3.9: The nucleus contains DNA, RNA, organizing proteins, and enzymes
Nuclear structures and functions
Nuclear envelope
• Separates nucleus from cytoplasm
• Double membrane
– Perinuclear space (peri-, around)
o Space between layers
Nuclear pores
• Passageways that allow chemical communication
between nucleus and cytoplasm
• Movement of ions and small molecules regulated by
proteins at the pores
• Account for about 10% of the surface of the nucleus
© 2018 Pearson Education, Inc.
Module 3.9: Contents of the cell nucleus
Nucleoplasm
• Fluid contents of nucleus
• Contains network of fine filaments for structural
support
• Also contains ions,
enzymes, nucleotides,
and small amounts
of RNA and DNA
© 2018 Pearson Education, Inc.
Module 3.9: Contents of the cell nucleus
Nucleoli (singular, nucleolus)
Transient nuclear organelles
Composed of RNA,
enzymes, and proteins
(histones)
Assemble RNA subunits
Most prominent in cells
manufacturing large
amounts of proteins
• Examples: liver, nerve,
muscle cells
© 2018 Pearson Education, Inc.
Module 3.9: Contents of the cell nucleus
DNA in the nucleus
Stores instructions for protein synthesis
Strands in nucleus coiled, allowing much to be
packed in small space
• Wrap around histone molecules forming
nucleosomes
• Loosely coiled
(chromatin) in
nondividing cells
• Tightly coiled
(chromosomes)
in dividing cells
© 2018 Pearson Education, Inc.
Module 3.9: Contents of the cell nucleus
DNA during cell division
Starts by becoming tighter and more complex,
forming chromosomes
Two copies of each chromosome held together at
centromere
23 paired chromosomes in somatic (general body)
cells
• One each from
mother/father
Carry instructions for
proteins and RNA
Also some regulatory and unknown functions
© 2018 Pearson Education, Inc.
Module 3.9: Review
A. Describe the contents and the structure of the
nucleus.
B. What molecule in the nucleus contains instructions
for making proteins?
C. How many chromosomes are contained within a
typical somatic cell?
D. The total length of the DNA within a human cell
nucleus is approximately 2 meters. How does the
DNA fit into the relatively small space of a human
nucleus, which ranges some 6–10 µm in diameter?
Learning Outcome: Describe the functions of the cell
nucleus, and distinguish between chromatin and a
chromosome.© 2018 Pearson Education, Inc.
Module 3.10: Protein synthesis involves DNA, enzymes, and three types of RNA
DNA
Long parallel chains of
nucleotides
Chains held by hydrogen
bonds between
nitrogenous bases
Four nitrogenous bases
1. Adenine (A)
2. Thymine (T)
3. Cytosine (C)
4. Guanine (G)
© 2018 Pearson Education, Inc.
Module 3.10: The genetic code and protein synthesis
DNA (continued)
Genetic information stored in sequence of base pairs
• Known as the genetic code
• Triplet code
– Sequence of three nitrogenous bases (triplet)
– Specifies single amino acid
Gene
• Functional unit of heredity
• Contains all the DNA nucleotides to produce a specific
protein
• Size varies (~3003000 nucleotides)
© 2018 Pearson Education, Inc.
Module 3.10: The genetic code and protein synthesis
© 2018 Pearson Education, Inc.
Module 3.10: The genetic code and protein synthesis
Steps in protein synthesis
1. Gene activation
• Removal of histones and DNA uncoiling
2. DNA strands separate
© 2018 Pearson Education, Inc.
Module 3.10: The genetic code and protein synthesis
3. Enzymes assemble nucleotides into a single
strand of messenger RNA (mRNA)
• Complementary base pairing matches DNA
nucleotide sequence with new mRNA sequence
(A-U; G-C)
• Series of three RNA nucleotides called a codon
– Each codon codes for specific amino acid
4. mRNA leaves nucleus
through nuclear pores
© 2018 Pearson Education, Inc.
Module 3.10: The genetic code and protein synthesis
5. At a ribosome in the cytoplasm, codons of mRNA
bind to anticodons (triplets of corresponding
nucleotides) on transfer RNA (tRNA)
6. tRNA carries a specific amino acid (associated
with specific anticodon)
© 2018 Pearson Education, Inc.
Module 3.10: The genetic code and protein synthesis
7. Ribosomal RNA (rRNA) of the ribosome strings
amino acids together
© 2018 Pearson Education, Inc.
Protein synthesis
© 2018 Pearson Education, Inc.
Module 3.10: The genetic code and protein synthesis
© 2018 Pearson Education, Inc.
Module 3.10: Review
A. What is a gene?
B. Why is the genetic code described as a triplet
code?
C. List the three types of RNA involved in protein
synthesis.
D. Which type of RNA links the genetic information
in the nucleus with the cytoplasmic sites of
protein synthesis?
Learning Outcome: Discuss the nature of the
genetic code, and summarize the process of
protein synthesis.
© 2018 Pearson Education, Inc.
Module 3.11: Transcription encodes genetic instructions on a strand of RNA
Transcription (“to copy” or “rewrite”)
Takes place in the nucleus
Production of RNA from DNA template
All three types of RNA are formed
© 2018 Pearson Education, Inc.
Module 3.11: Transcription
Steps of transcription
1. Gene activation
• Occurs at control
segment or promoter
(1st segment of gene)
• Only template strand
of DNA used to
synthesize RNA
© 2018 Pearson Education, Inc.
Module 3.11: Transcription
Steps of transcription
2. Beginning of
assembly
• RNA polymerase
(enzyme) binds to
promoter
• Begins assembly of
mRNA strand
© 2018 Pearson Education, Inc.
Module 3.11: Transcription
Steps of transcription
(continued)
3. Continuation of mRNA strand
• RNA polymerase promotes
hydrogen bonding between
nucleotides on DNA template
strand and complementary RNA
nucleotides in nucleoplasm
– Example: (DNA triplet TAC =
mRNA AUG)
• Nucleotides connected by
covalent bonding
© 2018 Pearson Education, Inc.
Module 3.11: Transcription
Steps of transcription
(continued)
4. Transcription ends
• Stop codon reached
• mRNA detaches
• Complementary DNA
strands reassociate (with
hydrogen bonding
between complementary
base pairs)
© 2018 Pearson Education, Inc.
Steps of transcription
© 2018 Pearson Education, Inc.
Module 3.11: Transcription
Final processing of mRNA
Initial strand of mRNA called
immature mRNA or
pre-mRNA
Before leaving nucleus,
mRNA requires additional
processing
• Introns (noncoding sequences) removed
• Remaining coding segments (exons) spliced together
• Changing the “editing” can produce mRNA for
different proteins
© 2018 Pearson Education, Inc.
Module 3.11: Review
A. What is transcription?
B. Define DNA template strand.
C. Name the substrates and product in the
enzymatic reaction catalyzed by RNA
polymerase.
D. What process would be affected if a cell could
not synthesize the enzyme RNA polymerase?
Learning Outcome: Summarize the process of
transcription.
© 2018 Pearson Education, Inc.
Module 3.12: Translation builds polypeptides as directed by an mRNA strand
Translation
Formation of a linear chain of amino acids from an
mRNA strand
“Translates” genetic information from nucleic acids
to proteins
Occurs in cytoplasm on ribosomes
Three phases
1. Initiation
2. Elongation
3. Termination
© 2018 Pearson Education, Inc.
Module 3.12: Translation
Steps of translation
1. Initiation phase
• mRNA binds to small ribosomal subunit near the
P site
• tRNA binds to P site and to start codon on mRNA
strand
– Binding occurs between mRNA codons and tRNA
complementary anticodons
• Small and large ribosomal subunits interlock around
mRNA strand forming initiation complex
• Additional tRNA binds to A site
– More than 20 kinds of tRNA
– Each carries an amino acid
© 2018 Pearson Education, Inc.
Initiation phase
© 2018 Pearson Education, Inc.
Module 3.12: Translation
Steps of translation (continued)
2. Elongation
• Ribosomal enzymes remove amino acid from tRNA at
P site and attach it to tRNA in A site
• Ribosome links amino acids forming dipeptide
• Ribosome moves to next codon on mRNA strand
• tRNA from P site moves to E site and is released
– This tRNA can go bind to another amino acid
• More tRNAs arrive, match codon to anticodon, and
continue forming polypeptide
© 2018 Pearson Education, Inc.
Elongation
© 2018 Pearson Education, Inc.
Module 3.12: Translation
Steps of translation
(continued)
3. Termination
• Stop codon on mRNA
• Recognized by protein
releasing factor
• Ribosomal enzyme breaks
bond between polypeptide
and tRNA in P site
• Ribosomal subunits
detach
– Leaves intact mRNA and
new polypeptide
© 2018 Pearson Education, Inc.
Module 3.12: Translation
© 2018 Pearson Education, Inc.
Module 3.12: Translation
Translation
Produces a typical protein in ~20 seconds
mRNA can interact with other ribosomes and
produce more proteins
Multiple ribosomes can attach to a single mRNA
strand to quickly produce many proteins
© 2018 Pearson Education, Inc.
BioFlix: Protein Synthesis
© 2018 Pearson Education, Inc.
Module 3.12: Review
A. What is translation?
B. The nucleotide sequence of three mRNA
codons is AUU-GCA-CUA. What is the
complementary anticodon sequence for the
second codon?
C. During the process of transcription, a nucleotide
was deleted from an mRNA sequence that
coded for a protein. What effect will this deletion
have on the amino acid sequence of the
protein?
Learning Outcome: Summarize the process of
translation.
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Section 3: How Substances Enter and Leave the Cell
Learning Outcomes
3.13 Contrast permeable, selectively permeable, and
impermeable membranes.
3.14 Explain the process of diffusion, and identify its
significance in the body.
3.15 Explain the process of osmosis, and identify its
significance in the body.
© 2018 Pearson Education, Inc.
Section 3: How Substances Enter and Leave the Cell
Learning Outcomes (continued)
3.16 Describe carrier-mediated transport and its role in
the absorption and removal of specific
substances.
3.17 Describe vesicular transport as a mechanism for
facilitating the absorption or removal of specific
substances from cells.
© 2018 Pearson Education, Inc.
Module 3.13: The plasma membrane is a selectively permeable membrane
Permeability
Property determining which substances can enter or
leave cytoplasm
• Freely permeable
– Any substance can pass (not found in living cells)
• Selectively permeable
– Some substances cross
• Impermeable
– No substances can pass (not found in living cells)
Plasma membrane must allow some movement in
and out of cells to enable intercellular
communication and coordination© 2018 Pearson Education, Inc.
Module 3.13: Permeability of membranes
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Module 3.13: Permeability of membranes
Selectively permeable membranes
Permit free passage of some materials and restrict
others
1. Characteristics of material to pass
– Size
– Molecular shape
– Lipid solubility
– Electrical charge
– Other factors
2. Characteristics of cell membrane
– What lipids and proteins present
– How components are arranged
© 2018 Pearson Education, Inc.
Module 3.13: Permeability of membranes
Types of membrane transport
1. Passive (do not
require ATP)
• Diffusion
• Carrier-mediated
transport
2. Active (require ATP)
• Vesicular transport
• Carrier-mediated
transport
© 2018 Pearson Education, Inc.
Module 3.13: Review
A. Define permeability.
B. Identify three different types of membranes
based on permeability.
C. Distinguish between passive and active
processes of membrane passage.
D. What kinds of molecules are involved in both
active and passive processes of membrane
passage.
Learning Outcome: Contrast permeable, selectively
permeable, and impermeable membranes.
© 2018 Pearson Education, Inc.
Module 3.14: Diffusion is passive movement driven by concentration differences
Diffusion
Net movement of a substance from higher
concentration to lower concentration.
Concentration gradient
• Concentration difference when molecules are not
evenly distributed
At an even distribution, molecular motion continues
but no net movement
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Module 3.14: Diffusion
Diffusion (continued)
Slow in air and water but important over small
distances
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Module 3.14: Diffusion
Movement of water and solutes across plasma
membrane: Selectively restricted diffusion
Movement across lipid portion of membrane
• Examples: lipids, lipid-soluble molecules, soluble
gases
Movement through membrane channel
• Examples: water, small water-soluble molecules, ions
Movement using carrier molecules
• Example: large molecules
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Diffusion across a plasma membrane
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EXTRACELLULAR
FLUID
Module 3.14: Diffusion
Factors that influence diffusion rates
Distance
• Shorter distance = faster diffusion
Molecule or ion size
• Smaller size = faster diffusion
Temperature
• Higher temperature = faster diffusion
Concentration gradient
• Steeper gradient = faster diffusion
Electrical forces
• Attraction of opposite charges (+,–)
• Repulsion of like charges (+,+ or –,–)
© 2018 Pearson Education, Inc.
Module 3.14: Review
A. Define diffusion.
B. Describe the colliding molecules in the figure
below (with the sugar cube in water).
C. Identify factors that influence diffusion rates.
D. How would a decrease in the oxygen
concentration in the lungs affect oxygen
diffusion into the blood?
Learning Outcome: Explain the process of
diffusion, and identify its significance in the body.
© 2018 Pearson Education, Inc.
Module 3.15: Osmosis is the diffusion of water molecules across a selectively permeable membrane
Osmosis (osmos, a push)
Net diffusion of water across a membrane
Maintains similar overall solute concentrations
between the cytosol and extracellular fluid
Osmotic flow
• Movement of water driven by osmosis
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Module 3.15: Osmosis
Osmosis (continued)
Osmotic pressure
• Indication of force of pure water moving into a
solution with higher solute concentration
• Hydrostatic pressure
– Fluid force
– Can be estimate of osmotic pressure when applied to
stop osmotic flow
© 2018 Pearson Education, Inc.
Water movement through a selectively permeable membrane
© 2018 Pearson Education, Inc.
Module 3.15: Osmosis
Osmolarity and tonicity
Osmolarity (osmotic concentration)
• Total solute concentration in an aqueous solution
Tonicity
• Effect of osmotic solutions on cell volume
• How a solution affects a cell
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Module 3.15: Osmosis
Three effects of tonicity
1. Isotonic (iso-,
same tonos, tension)
• Solution that does not
cause osmotic flow
across membrane
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Module 3.15: Osmosis
Three effects of tonicity
(continued)
2. Hypotonic
• Causes osmotic flow into
cell
• Example: swelling and
hemolysis (hemo-,
blood + lysis, loosening)
of red blood cell
© 2018 Pearson Education, Inc.
Module 3.15: Osmosis
Three effects of tonicity
(continued)
3. Hypertonic
• Causes osmotic flow out
of cell
• Example: shriveling and
crenation of RBCs
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Effects of tonicity
© 2018 Pearson Education, Inc.
Module 3.15: Osmosis
Importance of tonicity vs. osmolarity
Administering large fluid volumes to patients with
blood loss or dehydration
• If administered solution has same osmolarity as ICF
but higher concentrations of individual ions/molecules
– Diffusion of solutes may occur across cell membrane
– Water will follow through osmosis
– Cell volume increases
Normal saline often administered in emergency
• 0.9 percent or 0.9 g/dL of NaCl
• Isotonic with blood
© 2018 Pearson Education, Inc.
Module 3.15: Review
A. Describe osmosis.
B. Describe osmotic pressure, and state in which
solution below it is greater.
C. Contrast the effects of a hypotonic solution and
a hypertonic solution on a red blood cell.
D. Some pediatricians recommend using a 10
percent salt solution to relieve nasal congestion
in infants. Explain the effects this treatment
would have on the cells lining the nasal cavity.
Would it be effective?
Learning Outcome: Explain the process of
osmosis, and identify its significance in the body.
© 2018 Pearson Education, Inc.
Module 3.16: In carrier-mediated transport, integral proteins facilitate membrane passage
Carrier proteins
Transport hydrophilic or large molecules across cell
membrane
Many move specific molecules through the plasma
membrane in only one direction
Some move more than one substance in the same
direction (cotransport)
Some move more than one substance in opposite
directions
• Process called countertransport
• Carrier called an exchange pump
© 2018 Pearson Education, Inc.
Module 3.16: Carrier-mediated transport
1. Facilitated diffusion
Requires no ATP
Passive transport (moves from high concentration to
low concentration)
Carrier binds to molecule, then changes shape to
move molecule across membrane
Rate of transport limited
by number of available
carrier proteins
• Once all carrier proteins
saturated, no increase
in rate of transport
© 2018 Pearson Education, Inc.
Module 3.16: Carrier-mediated transport
2. Active transport
Active process requiring
energy molecule or ATP
Independent of
concentration gradient
Examples:
• Ion pumps (Na+, K+,
Ca2+, and Mg2+)
• Sodium–potassium
ATPase
– Exchanges 3
intracellular sodium ions
for 2 extracellular
potassium ions© 2018 Pearson Education, Inc.
Module 3.16: Carrier-mediated transport
3. Secondary active transport
Transport mechanism itself does not require ATP
Cell often needs ATP to maintain homeostasis
associated with transport
Movement for one of two substances follows
concentration gradient
Example:
• Sodium and
glucose
cotransporter
© 2018 Pearson Education, Inc.
A&P Flix: Membrane Transport
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Module 3.16: Review
A. Describe the process of carrier-mediated transport.
B. What two factors limit the rate of facilitated diffusion
across a plasma membrane?
C. What do the transport processes of facilitated
diffusion and active transport have in common?
D. During digestion, the concentration of hydrogen
ions (H+) in the stomach contents increases to
many times that in cells lining the stomach. Which
transport process could be responsible?
Learning Outcome: Describe carrier-mediated transport
and its role in the absorption and removal of specific
substances.
© 2018 Pearson Education, Inc.
Module 3.17: In vesicular transport, vesicles selectively carry materials into or out of cell
Vesicular transport
Materials move across cell membrane in small
membranous sacs called vesicles
• Sacs form at or fuse with plasma membrane
Two major types (both require ATP)
1. Endocytosis
– Importing extracellular substances into vesicles called
endosomes
2. Exocytosis
– Movement of wastes or secretory products from
intracellular vesicle to outside the cell
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Module 3.17: Vesicular transport
Receptor-mediated endocytosis
Brings specific molecules into cell using receptor
molecules on membrane surface
a. Target molecule (ligand) binds to receptor
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Module 3.17: Vesicular transport
Receptor-mediated endocytosis (continued)
b. Plasma membrane folds around receptors bound to
ligands, forming pocket that pinches off
c. Endosome called clathrin-coated vesicle forms
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Module 3.17: Vesicular transport
Receptor-mediated endocytosis (continued)
d. Vesicle fuses with lysosomes
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Module 3.17: Vesicular transport
Receptor-mediated endocytosis (continued)
e. Ligands freed from receptors and enter cytoplasm
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Module 3.17: Vesicular transport
Receptor-mediated endocytosis (continued)
f. Lysosome detaches from vesicle
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Module 3.17: Vesicular transport
Receptor-mediated endocytosis (continued)
g. Vesicle fuses with plasma membrane again
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Receptor-mediated endocytosis
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Module 3.17: Vesicular transport
Pinocytosis (“cell drinking”)
Formation of endosomes with ECF
No receptor proteins involved
Brings fluid and small molecules into cell
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Module 3.17: Vesicular transport
Phagocytosis (“cell eating”)
Produces phagosomes containing solids
No receptors involved
Cytoplasmic extensions
(pseudopodia) surround
object and bring it
into cell
Only specialized
cells (phagocytes
or macrophages)
perform phagocytosis
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Module 3.17: Vesicular transport
Exocytosis—functional opposite of endocytosis
Vesicle contents are released to extracellular
environment
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Module 3.17: Review
A. Describe endocytosis.
B. Describe the three types of endocytosis.
C. Describe exocytosis.
D. Some white blood cells engulf bacteria and
bring them into the cell. What is this process
called?
Learning Outcome: Describe vesicular transport as
a mechanism for facilitating the absorption or
removal of specific substances from cells.
© 2018 Pearson Education, Inc.
Section 4: Cell Life Cycle
Learning Outcomes
3.18 Distinguish between interphase and cell division
in the cell cycle.
3.19 Describe interphase, and explain its significance.
3.20 Describe the process of mitosis and its role in the
cell life cycle.
3.21 Clinical Module: Discuss the relationship
between cell division and cancer.
© 2018 Pearson Education, Inc.
Module 3.18: Interphase and cell division make up the life cycle of a cell
Life starts as a single cell
At maturity, roughly 75 trillion cells in the body
Cell division—form of cellular reproduction
• Responsible for initial increase in cell number
• Essential to continued development and survival
Cells have varying life spans and abilities to divide
• Often genetically controlled death occurs (apoptosis)
Cell life cycle ends when cell dies
© 2018 Pearson Education, Inc.
Module 3.18: Cell life cycle
Two types of cell division
1. Mitosis
• 2 daughter cells produced
• Each with 46 chromosomes
2. Meiosis
• Produces sex cells
• Each with only 23 chromosomes
© 2018 Pearson Education, Inc.
Module 3.18: Cell life cycle
Mitosis
Form of cellular
reproduction
Division of single cell
produces pair of
daughter cells
• Half the size of parent
cell
• Grow to size of original
cell before dividing
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Module 3.18: Cell life cycle
Divisions of cell life cycle
1. Interphase (nondividing period)
• Cell performs normal activities
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Module 3.18: Cell life cycle
Divisions of cell life cycle (continued)
2. Cell division
• Begins with mitosis
– Distribution of identical copies of chromosomes
to each daughter cell
• Ends with cytokinesis (division of the cytoplasm)
© 2018 Pearson Education, Inc.
Module 3.18: Review
A. Explain why cell division is important.
B. Define apoptosis.
C. When does cell division begin and end?
Learning Outcome: Distinguish between interphase
and cell division in the cell cycle.
© 2018 Pearson Education, Inc.
Module 3.19: During interphase, the cell prepares for cell division
Division of interphase
Somatic (body) cells spend most of their lives in
interphase
For cells not preparing to divide, they stay in:
• G0 phase
– Performing normal cell functions
– Examples:
o Skeletal muscle cells and most neurons
Stay in this phase forever
o Stem cells
Never enter G0
Divide repeatedly
© 2018 Pearson Education, Inc.
Module 3.19: Interphase
For cells preparing to divide,
interphase divided into:
G1 phase
• Normal cell functions,
cell growth, duplication
of organelles, protein
synthesis
S phase
• DNA replication, synthesis
of histones and other
proteins to allow duplication of chromosomes
G2 phase
• Last minute protein synthesis and centriole replication
© 2018 Pearson Education, Inc.
Module 3.19: Interphase
DNA replication process
DNA helicase
• Unwinds DNA strands
• Disrupts hydrogen bonds between bases
DNA polymerase
• Binds to exposed bases
• Promotes bonding between current DNA strand and
complementary nucleotides in nucleoplasm
• Covalently links nucleotides together
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Module 3.19: Interphase
DNA replication process (continued)
DNA polymerase (continued)
• Works only in one direction
– One polymerase works continuously along one strand
toward “zipper” forming the leading strand
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Module 3.19: Interphase
DNA replication process (continued)
DNA polymerase (continued)
• Works only in one direction
– One polymerase works away from “zipper” forming the
lagging strand
o As “unzipping” occurs, another polymerase binds
closer point of unzipping
o Two new DNA segments spliced together with DNA
ligases
• Two identical DNA strands formed
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DNA replication
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A&P Flix: DNA Replication
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Module 3.19: Review
A. Describe interphase, and identify its stages.
B. A cell is actively manufacturing enough
organelles to serve two functional cells. This
cell is probably in what phase of interphase?
C. What enzymes must be present for DNA
replication to proceed normally?
D. DNA replication occurs during what two cellular
processes?
Learning Outcome: Describe interphase, and
explain its significance.
© 2018 Pearson Education, Inc.
Module 3.20: Mitosis distributes chromosomes before cytokinesis separates the daughter cells
M phase of cell cycle
Includes mitosis and cytokinesis
Mitosis
• Division and duplication of the cell’s nucleus
• Divided into four stages:
1. Prophase
2. Metaphase
3. Anaphase
4. Telophase
Cytokinesis
• Division of cytoplasm
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Module 3.20: Mitosis
Interphase—DNA replicated, DNA is loosely coiled
and no visible chromosomes
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Module 3.20: Mitosis
Phases of mitosis
1. Prophase (pro-, before)
• Nuclear envelope
disintegrates
• Chromosomes coil and
become visible under light
microscope
• Replicated centrioles move
to poles
– Astral rays (extend from
centrioles)
– Spindle fibers (interconnect
centriole pairs)
© 2018 Pearson Education, Inc.
Module 3.20: Mitosis
Phases of mitosis
(continued)
1. Prophase (continued)
• Each copy of chromosome
called chromatid
– Pair connected at
centromere
– Raised region
(kinetochore) at
centromere attaches to
spindle fibers
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Module 3.20: Mitosis
Phases of mitosis
(continued)
2. Metaphase (meta,
after)
• Chromosomes align
at metaphase plate
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Module 3.20: Mitosis
Phases of mitosis
(continued)
3. Anaphase (ana-, apart)
• Centromere splits
• Chromatids separate
• Chromatids drawn toward
opposite sides along
spindle apparatus
© 2018 Pearson Education, Inc.
Module 3.20: Mitosis
Phases of mitosis
(continued)
4. Telophase (telo-, end)
• Cells prepare to enter
interphase
• Cytoplasm constricts
along metaphase plate
(cleavage furrow)
• Nuclear membranes
re-form
• Nuclei enlarge
• Chromosomes uncoil to
chromatin
© 2018 Pearson Education, Inc.
Module 3.20: Mitosis
Cytokinesis (cyto-, cell +
kinesis, motion)
Begins with formation of
cleavage furrow
Continues through
telophase
Completion marks end of
cell division
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Module 3.20: Mitosis
© 2018 Pearson Education, Inc.
A&P Flix: Mitosis
© 2018 Pearson Education, Inc.
Module 3.20: Review
A. Define mitosis, and list its four stages.
B. What is a chromatid, and how many are present
during normal mitosis in a human cell?
C. What would happen if spindle fibers failed to
form in a cell during mitosis?
Learning Outcome: Describe the process of mitosis
and its role in the cell life cycle.
© 2018 Pearson Education, Inc.
Module 3.21: CLINICAL MODULE: Tumors and cancer are characterized by abnormal cell growth and division
Cancer
Illness that disrupts normal rates of cell division
Characterized by permanent DNA sequence
changes (mutations)
Most common in tissues with actively dividing cells
• Examples: skin, intestinal lining
Cancerous cells compete with normal cells for
resources
Usually begins with single abnormal cell
© 2018 Pearson Education, Inc.
Module 3.21: CLINICAL MODULE: Tumors and cancer
Tumor (neoplasm)
Mass or swelling produced by abnormal cell growth
and division
1. Benign tumor
– Cells remain within original tissue
– Seldom a threat
– Can be removed surgically
if necessary
© 2018 Pearson Education, Inc.
Module 3.21: CLINICAL MODULE: Tumors and cancer
Malignant tumor
Cells divide rapidly
Released chemicals stimulate blood vessel
growth (angiogenesis) to tumor area
© 2018 Pearson Education, Inc.
Module 3.21: CLINICAL MODULE: Tumors and cancer
Malignant tumor (continued)
Accelerated growth due to blood vessel growth and
supply to the area
Tumor spreads to surrounding tissue by invasion
Cells migrate to other areas and establish new
tumors (called metastasis)
© 2018 Pearson Education, Inc.
Module 3.21: CLINICAL MODULE: Tumors and cancer
Malignant cells disrupt
function
No longer perform original
functions or:
Perform functions in an
abnormal way
Example:
• Malignant tumor of thyroid gland produces abnormal
amounts of thyroid hormone
Cancer cells compete with normal cells for space and
nutrients
© 2018 Pearson Education, Inc.
Module 3.21: Review
A. Define cancer.
B. What is a benign tumor?
C. Define metastasis.
D. How does angiogenesis aid tumor growth?
Learning Outcome: Discuss the relationship
between cell division and cancer.
© 2018 Pearson Education, Inc.
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