chapter 3 the cellular level of organization€¦ · terms of importance 1. diffusion 2. osmosis 3....
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Copyright 2009 John Wiley & Sons, Inc.
Chapter 3
The Cellular Level of
Organization
Warm Up
In this process carrier proteins help molecules
across membranes, but the cell does not input
any energy for this process to occur.
a. active transport
b. facilitated diffusion
c. osmosis
d. diffusion
Copyright 2009 John Wiley & Sons, Inc.
Warm Up
All of the following molecules are part of the cell
membrane except
a. lipids.
b. proteins.
c. cholesterol.
d. nucleic acids.
Copyright 2009 John Wiley & Sons, Inc.
Terms of importance
1. Diffusion
2. Osmosis
3. Hypertonic
4. Hypotonic
5. Active Transport
6. Endocytosis
7. Cytoplasm
8. Plasma membrane
9. Mitosis
10. Ribosomes
11. Endoplasmic
reticulum
12. Golgi Complex
13. Lysosomes
14. Mitochondria
15. Nucleus
Copyright 2009 John Wiley & Sons, Inc.
Copyright 2009 John Wiley & Sons, Inc.
A Generalized Cell
Plasma membrane
- separates the cell’s
internal environment
from the outside
environment
- is a selective
barrier
- plays a role in
communication
Structure of a Membrane
Consists of a lipid bilayer - made up of
phospholipids, cholesterol and glycolipids
Transmembrane proteins – extend through the
entire lipid bilayer (aka integral proteins)
Peripheral proteins - attached to the inner or
outer surface of the membrane, do not extend
through it
Copyright 2009 John Wiley & Sons, Inc.
Fig. 3.1 Generalized Body Cell
Copyright 2009 John Wiley & Sons, Inc.
A Generalized Cell
Cytoplasm
- all the cellular contents between the plasma
membrane and the nucleus
- cytosol - the fluid portion, mostly water
- organelles - subcellular structures
Copyright 2009 John Wiley & Sons, Inc.
A Generalized Cell
Nucleus
- large organelle that contains DNA
- contains chromosomes, each of which
consists of a single molecule of DNA
- a chromosome contains thousands of
hereditary units called genes
Copyright 2009 John Wiley & Sons, Inc.
Membrane Permeability
The cell is either permeable or impermeable
to certain substances
The lipid bilayer is permeable to oxygen,
carbon dioxide, water and steroids, but
impermeable to glucose
Transmembrane proteins act as channels
and transporters to assist the entrance of
certain substances, for example, glucose and
ions
Copyright 2009 John Wiley & Sons, Inc.
Passive vs. Active Processes
Passive processes - substances move across
cell membranes without the input of any
energy; use the kinetic energy of individual
molecules or ions
Active processes - a cell uses energy,
primarily from the breakdown of ATP, to
move a substance across the membrane, i.e.,
against a concentration gradient
Copyright 2009 John Wiley & Sons, Inc.
Copyright 2009 John Wiley & Sons, Inc.
Osmosis
Net movement of water through a selectively permeable membrane from an area of high concentration of water (lower concentration of solutes) to one of lower concentration of water
Water can pass through plasma membrane in 2 ways:
1. through lipid bilayer by simple diffusion
2. through aquaporins, integral membrane proteins
Copyright 2009 John Wiley & Sons, Inc.
An isotonic solution is one in which the concentration of solutes is the same both inside and outside of the cell.
A hypotonic solution is one in which the concentration of solutes is greater inside the cell than outside of it.
A hypertonic solution is one where the concentration of solutes is greater outside the cell than inside it.
Copyright 2009 John Wiley & Sons, Inc.
Tonicity and its effect on RBCS
Copyright 2009 John Wiley & Sons, Inc.
• Simple Diffusion
Channel-mediated Facilitated Diffusion
Carrier-mediated Facilitated Diffusion
Copyright 2009 John Wiley & Sons, Inc.
Transport in Vesicles
Vesicle - a small spherical sac formed by budding off from a membrane
Endocytosis - materials move into a cell in a vesicleformed from the plasma membrane
three types: receptor-mediated endocytosis
phagocytosis
bulk-phase endocytosis (pinocytosis)
Exocytosis - vesicles fuse with the plasma membrane, releasing their contents into the extracellular fluid
Transcytosis - a combination of endocytosis and exocytosis
Copyright 2009 John Wiley & Sons, Inc.
Copyright 2009 John Wiley & Sons, Inc.
Cytoplasm - 2 components
1. Cytosol - intracellular fluid, surrounds the organelles
- the site of many chemical reactions
- energy is usually released by these reactions
- reactions provide the building blocks for cell maintenance, structure, function and growth
2. Organelles
Specialized structures within the cell
The cytoskeleton - network of protein filaments throughout the cytosol
-provides structural support for the cell
-three types according to increasing size: microfilaments, intermediate filaments, and microtubules
The Cytoskeleton
Copyright 2009 John Wiley & Sons, Inc.
Organelles
Centrosome -
located near the
nucleus, consists of
two centrioles
Cilia - short, hair-
like projections
from the cell
surface
Flagella - longer
than cilia, move an
entire cell
Copyright 2009 John Wiley & Sons, Inc.
Organelles
Ribosomes - sites
of protein
synthesis
Endoplasmic
reticulum -
network of
membranes in the
shape of flattened
sacs or tubules
Rough ER - connected to
the nucleus, surface is
studded with ribosomes,
produces proteins
Smooth ER - a network of
membrane tubules, does
not have ribosomes,
synthesizes fatty acids
and steroids, detoxifies
certain drugs
Copyright 2009 John Wiley & Sons, Inc.
Golgi complex – modify and
package proteins for transport
Lysosomes - vesicles that contain
powerful digestive enzymes
Peroxisomes
- smaller than
lysosomes,
detoxify
several toxic
substances
Proteasomes
- destroy
unneeded or
faulty proteins,
Copyright 2009 John Wiley & Sons, Inc.
Organelles
Mitochondria - the
“powerhouses” of the
cell
Generate ATP
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Nuclear envelope - a double membrane that separates the nucleus from the cytoplasm
Nuclear pores - openings in the nuclear envelope
Nucleolus - spherical body that produces ribosomes
Copyright 2009 John Wiley & Sons, Inc.
Genes - are the cell’s hereditary units, control activities and structure of the cell
Chromosomes - long molecules of DNA combined with protein molecules
Packing of DNA
into a
Chromosome of
a Dividing Cell
Copyright 2009 John Wiley & Sons, Inc.
Overview of Gene Expression
Transcription
Process of creating
single stranded RNA
by using DNA as a
template.
The RNA is then
used as a template
to create proteins.
RNA uses Uracil
instead of Thymine
when created.
Copyright 2009 John Wiley & Sons, Inc.
Translation
A ribosome uses
mRNA as a template
to create a chain of
amino acids.
This chain is called a
polypeptide.
What will this
polypeptide become?
A protein!
Copyright 2009 John Wiley & Sons, Inc.
Videos of the processes
Transcription: http://youtu.be/5MfSYnItYvg
Translation: http://youtu.be/8dsTvBaUMvw
Copyright 2009 John Wiley & Sons, Inc.
Copyright 2009 John Wiley & Sons, Inc.
Nuclear Division: Mitosis
Prophase - the chromatin fibers change into
chromosomes
Metaphase - microtubules align the centromeres of
the chromatid pairs at the metaphase plate
Anaphase - the chromatid pairs split at the
centromere and move to opposite poles of the cell;
the chromatids are now called chromosomes
Telophase - two identical nuclei are formed around
the identical sets of chromosomes now in their
chromatin form
Copyright 2009 John Wiley & Sons, Inc.
Cytoplasmic Division: Cytokinesis
Division of a cell’s cytoplasm to form two identical cells
Usually begins in late anaphase
The plasma membrane constricts at its middle forming a cleavage furrow
The cell eventually splits into two daughter cells
Interphase begins when cytokinesis is complete
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