chapter 3 cells and tissues -...

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Chapter 3

Cells and Tissues


2

Objectives

• Identify and discuss the basic structure

and function of the three major

components of a cell

• List and briefly discuss the functions of

the primary cellular organelles

• Compare the major passive and active

transport processes that act to move

substances through cell membranes


3

Objectives

• Compare and discuss DNA and RNA

and their function in protein synthesis

• Discuss the stages of mitosis and

explain the importance of cellular

reproduction


4

Objectives

• Explain how epithelial tissue is grouped

according to shape and arrangement of

cells

• List and briefly discuss the major types

of connective and muscle tissue

• List the three structural components of a

neuron


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Cells

• Size and shape

– Human cells vary considerably in size

– All are microscopic

– Cells differ notably in shape


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Cells

• Composition

– Cells contain cytoplasm—substance found

only in cells

– Organelles are specialized structures

within the cytoplasm

– Cell interior is surrounded by a plasma

membrane


What cells can be seen with

the naked eye

• Human Ovum

• Giant Bacteria• Epulopiscium fischelsoni was believed to be the largest. It sometimes reaches

500 micrometers or half a millimeter in size, which is the size of a period after a

sentence. It lives in the guts of some species of fish off the Australian coastline

and in the Red Sea. The largest known bacterium, however, is Thiomargarita

namibiensis, a bacterium found off the coast of Namibia in Africa that can

reach 750 micrometers in diameter--a veritable giant among bacteria.

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Cells seen with the naked eye

• Giant Amoebas- can grow to 1.2 inches in

diameter

• Squid Nerve Cells

• Bird Eggs-look in your refridgerator

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Cells

• Composition

– Parts of the cell

• Plasma membrane

– Forms outer boundary of cell

– Composed of a thin, two-layered membrane of

phospholipids containing proteins

– Is selectively permeable


Plasma membrane

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Cells

• Composition

– Structural parts• Cytoplasm—internal cell fluid and numerous

organelles– Ribosomes

» May attach to rough ER or lie free in cytoplasm

» Made of two tiny subunits of mostly ribosomal RNA

» Manufacture enzymes and other protein compounds

» Often called protein factories


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Cells

• Composition

– Structural parts

• Cytoplasm

– Organelles

» Endoplasmic reticulum (ER)

- Network of connecting sacs and canals

- Carry substances through fluid cytoplasm

- Two types—rough and smooth

- Rough ER collects, folds, and transports proteins made by

ribosomes

- Smooth ER synthesizes chemicals; makes new membrane


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Cells

• Composition


• Cytoplasm

– Organelles

» Golgi apparatus

- Group of flattened sacs near nucleus

- Collect chemicals into vesicles that move

from the smooth ER outward to plasma membrane

- Called the chemical processing and packaging

center


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Cells

• Composition


• Cytoplasm

– Organelles

» Mitochondria

- Composed of inner and outer membranous sacks

- Involved with energy-releasing chemical reactions

- Often called power plants of the cell

- Contains one DNA molecule


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Cells

• Composition


• Cytoplasm

– Organelles

» Lysosomes

- Membranous-walled organelles

- Contain digestive enzymes

- Have protective function (eat microbes)

- Formerly thought to be responsible for

apoptosis (programmed cell death)


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Cells

• Composition


• Cytoplasm

– Organelles

» Centrioles

- Paired organelles that lie at right angles to each

other near the nucleus

- Function in cell reproduction


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Cells

• Composition


• Cytoplasm

– Organelles

» Microvilli

- Small, fingerlike extensions of the plasma membrane

- Increase absorptive surface area of the cell


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Cells

• Composition


• Cytoplasm

– Organelles

» Cilia

- Fine, hairlike extensions found on free or exposed

surfaces of some cells

- Capable of moving in unison in a wavelike fashion


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Cells

• Composition


• Cytoplasm

– Organelles

» Flagella

- Single projections extending from cell surfaces

- Much larger than cilia

- ―Tails‖ of sperm cells only example of flagella in

humans


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Cells

• Composition

– Nucleus

• Controls cell because it contains DNA, the genetic

code—instructions for making proteins, which in turn

determine cell structure and function

• Component structures include nuclear envelope,

nucleoplasm, nucleolus, and chromatin granules

• DNA molecules become tightly coiled chromosomes

during cell division

• Each cell has 46 chromosomes in the nucleus


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Relationship of Cell

Structure and Function

• Every human cell has a designated

function—some help maintain the cell;

others regulate life processes of the

body itself

• Specialized functions of a cell differ

depending on number and type of

organelles


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Relationship of Cell

Structure and Function

• Relationship of structure to function apparent

in number and type of organelles seen in

different cells

– Heart muscle cells contain many mitochondria

required to produce adequate energy needed for

continued contractions

– Flagellum of sperm cell gives motility, allowing

movement of sperm through female reproductive

tract, thus increasing chances for fertilization


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Movements of Substances

Through Cell Membranes

• Passive transport processes do not

require added energy and result in

movement ―down a concentration

gradient‖


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• Diffusion

– Substances scatter themselves evenly

throughout an available space

– It is unnecessary to add energy to the

system

– Movement is from high to low

concentration


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• Diffusion

– Osmosis and dialysis are specialized

examples of diffusion across a selectively

permeable membrane

– Osmosis is diffusion of water (when some

solutes cannot cross the membrane)

– Dialysis is diffusion of solutes


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• Filtration

– Movement of water and solutes caused by

hydrostatic pressure on one side of

membrane

– Responsible for urine formation


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• Active transport processes occur only in

living cells

– Movement of substances is ―up the

concentration gradient‖

– Requires energy from ATP


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• Ion pumps

– Ion pump: a protein complex in the cell membrane

– Ion pumps use energy from ATP to move

substances across cell membranes against their

concentration gradients

– Examples: sodium-potassium pump; calcium

pump

– Some ion pumps work with other carriers so that

glucose or amino acids are transported along with

ions


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• Phagocytosis and pinocytosis

– Both are active transport mechanisms

because they require cell energy

– Phagocytosis is a protective mechanism

often used to destroy bacteria

– Pinocytosis is used to incorporate fluids or

dissolved substances into cells


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• Several severe diseases result from

damage to cell transport processes


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• Cell transport and disease

– Cystic fibrosis, characterized by abnormally thick secretions in the airways and digestive ducts, results from failed Cl–transport

– Cholera is a bacterial infection that causes Cl– and water to leak from cells lining the intestines, resulting in severe diarrhea and water loss


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Cell Reproduction and Heredity

• DNA—molecule and genetic information

– DNA molecule resembles a long, narrow

ladder twisted round and round its axis;

shaped in a double helix

– Each molecule made of a sugar

(deoxyribose), bases, and phosphate units

– Bases are nitrogen-containing chemicals:

adenine, thymine, guanine, and cytosine


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Cell Reproduction

• DNA– Complementary base pairing—each step of DNA

ladder contains a base pair; adenine-thymine or cytosine-guanine

– A gene is a specific segment of base pairs in a chromosome

– Genetic code—sequence of base pairs determines heredity

• Coded information in genes controls protein and enzyme production

• Enzymes facilitate chemical reactions

• Cellular chemical reactions determine cell structure and function


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• DNA

– RNA molecules and protein synthesis• DNA—contained in cell nucleus

• Protein synthesis—occurs in cytoplasm, thus genetic information must pass from the nucleus to the cytoplasm

• Process of transferring genetic information from nucleus to cytoplasm where proteins are produced requires completion of transcriptionand translation


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• DNA

– Transcription• Double-stranded DNA separates to form

messenger RNA (mRNA)

• Each strand of mRNA duplicates a particular gene (base-pair sequence) from a segment of DNA

• mRNA molecules pass from the nucleus to the cytoplasm, where they direct protein synthesis in ribosomes and ER


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• DNA

– Translation

• Involves synthesis of proteins in cytoplasm by

ribosomes

• Requires use of information contained in mRNA

• Codon—a series of three nucleotide bases that

act as a code for a specific amino acid


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• Cells, genetics, and disease

– Abnormal DNA that is inherited, or that

results from damage, is often the basis of

disease

– Factors that cause damage to DNA

molecules include chemical or mechanical

irritants, radiation, bacteria, and viruses


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• Cell division—reproduction of cell involving division of the nucleus (mitosis) and the cytoplasm– Two daughter cells result from the division

– Period when the cell is not actively dividing is called interphase

– DNA replication—process by which each half of a DNA molecule becomes a whole molecule identical to the original DNA molecule; precedes mitosis


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• Cell division

– Mitosis—process in cell division that

distributes identical chromosomes (DNA

molecules) to each new cell formed when

the original cell divides

• Enables cells to reproduce their own kind

• Makes heredity possible


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• Cell division

– Mitosis

• Prophase—first stage

– Chromatin granules become organized

– Chromosomes (pairs of linked chromatids) appear

– Centrioles move away from nucleus

– Nuclear envelope disappears, freeing genetic

material

– Spindle fibers appear


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• Cell division

– Mitosis

• Metaphase—second stage

– Chromosomes align across center of cell

– Spindle fibers attach themselves to each chromatid


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• Cell division

– Mitosis

• Anaphase—third stage

– Centromeres break apart

– Separated chromatids now called chromosomes

– Chromosomes are pulled to opposite ends of cell

– Cleavage furrow develops at end of anaphase


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• Cell division

– Mitosis

• Telophase—fourth stage

– Cell division is completed

– Nuclei appear in daughter cells

– Nuclear envelope and nucleoli appear

– Cytoplasm is divided (cytokinesis)

– Daughter cells become fully functional


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• Changes in cell growth and

reproduction

– Hypertrophy—increase in size of individual

cells; increasing size of tissue

– Atrophy—decrease in size of individual

cells; decreasing size of tissue


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• Changes in cell growth and reproduction

– Hyperplasia—increase in cell reproduction, increasing size of tissue

– Anaplasia—production of abnormal, undifferentiated cells

– Uncontrolled cell reproduction results in formation of a benign or malignant neoplasm (tumor)


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Tissues

• Epithelial tissue

– Covers body and lines body cavities

– Cells packed closely together with little matrix

– Classified by shape of cells • Squamous

• Cuboidal

• Columnar

• Transitional


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Tissues


– Classified by arrangement of cells

• Simple

• Stratified

– Simple squamous epithelium

• Single layer of scalelike cells

• Transport (e.g., absorption) is function

– Stratified squamous epithelium

• Several layers of closely packed cells

• Protection is primary function


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Tissues

• Epithelial tissue– Simple columnar epithelium

• Columnar cells arranged in a single layer

• Line stomach and intestines

• Contain mucus-producing goblet cells

• Specialized for absorption

– Stratified transitional epithelium • Found in body areas, such as urinary bladder, that

stretch

• Up to 10 layers of roughly cuboidal-shaped cells that distort to squamous shape when stretched


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Tissues


– Pseudostratified epithelium

• Each cell touches basement membrane

• Lines the trachea


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Tissues


– Simple cuboidal epithelium • Often specialized for secretory activity

• Cuboidal cells may be grouped into glands

• May secrete into ducts, directly into blood, and on body surface

• Examples of secretions include saliva, digestive juice, and hormones

• Cuboidal epithelium also forms the urine-producing tubules of the kidney


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Tissues

• Connective tissue

– Most abundant tissue in body

– Most widely distributed tissue in body

– Multiple types, appearances, and functions

– Relatively few cells in intercellular matrix


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Tissues

• Connective tissue

– Types

• Areolar—glue that holds organs together

• Adipose (fat)—lipid storage is primary function

• Fibrous—bundles of strong collagen fibers; e.g., tendon

• Bone—matrix is calcified; function is support and

protection

• Cartilage—matrix is consistency of gristle-like gel;

chondrocyte is cell type

• Blood—matrix is fluid; functions are transportation and

protection


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Tissues

• Muscle tissue

– Types

• Skeletal muscle tissue—attaches to bones; also called

striated or voluntary; control is voluntary; striations

apparent when viewed under a microscope

• Cardiac muscle tissue—also called striated or

involuntary; composes heart wall; ordinarily cannot

control contractions

• Smooth muscle tissue—also called nonstriated (visceral)

or involuntary; no cross striations; found in blood vessels

and other tube-shaped organs


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Tissues

• Nervous tissue

– Function—rapid communication between

body structures and control of body

functions

– Neurons—conduction cells


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Tissues

• Nervous tissue

– Neurons• All neurons have a cell body and two types of

processes: axon and dendrite

• Axon (one) carries nerve impulse away from cell body

• Dendrites (one or more) carry nerve impulse toward the cell body

– Glia (neuroglia)—supportive and connecting cells


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Tissues

• Tissue repair—usually accomplished by

means of regeneration of tissue

– Epithelial and connective tissues

regenerate easily

– Muscle and nervous tissues have very

limited abilities to repair themselves

chapter 3 cells and tissues -...

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