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Exam 2 Review Slides
Lectures 5-8
Chapters 3 and 22 (Sec. 22.1-22.4)
Cell Membranes
Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001
2
Passage of Materials through the Cell Membrane
Carrier/channel
proteins required
for all but fatsoluble molecules
and small
uncharged
molecules
oxygen, carbon
dioxide and other
lipid-soluble
substances diffuse
freely through the
membrane
3
Cellular Organelles
Table 1 of 2
CELL COMPONENT
DESCRIPTION/
STRUCTURE
FUNCTION(S)
CELL MEMBRANE
Bilayer of phospholipids with proteins
dispersed throughout
cell boundary; selectively permeable
(i.e. controls what enters and
leaves the cell; membrane
transport)
CYTOPLASM
jelly-like fluid (70% water)
suspends organelles in cell
NUCLEUS
Central control center of cell; bound
by lipid bilayer membrane;
contains chromatin (loosely
colied DNA and proteins)
controls all cellular activity by
directing protein synthesis (i.e.
instructing the cell what
proteins/enzymes to make.
NUCLEOLUS
dense spherical body(ies) within
nucleus; RNA & protein
Ribosome synthesis
RIBOSOMES
RNA & protein; dispersed throughout
cytoplasm or studded on ER
protein synthesis
ROUGH ER
Membranous network studded with
ribosomes
protein synthesis
SMOOTH ER
Membranous network lacking
ribosomes
lipid & cholesterol synthesis
GOLGI
“Stack of Pancakes”; cisternae
modification, transport, and packaging
of proteins
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Cellular Organelles
Table 2 of 2
CELL COMPONENT
DESCRIPTION/
STRUCTURE
FUNCTION(S)
LYSOSOMES
Membranous sac of digestive enzymes
destruction of worn cell parts
(“autolysis) and foreign particles
PEROXISOMES
Membranous sacs filled with oxidase
enzymes (catalase)
detoxification of harmful substances
(i.e. ethanol, drugs, etc.)
MITOCHONDRIA
Kidney shaped organelles whose inner
membrane is folded into “cristae”.
Site of Cellular Respiration;
“Powerhouse of Cell”
FLAGELLA
long, tail-like extension; human sperm
locomotion
CILIA
short, eyelash extensions;
human trachea & fallopian tube
to allow for passage of substances
through passageways
MICROVILLI
microscopic ruffling of cell membrane
increase surface area
CENTRIOLES
paired cylinders of microtubules at
right angles near nucleus
aid in chromosome movement during
mitosis
5
Cell Death
• Two mechanisms of cell death
– Necrosis
– Programmed cell death (PCD or apoptosis)
• Necrosis
– Tissue degeneration following cellular injury or
destruction
– Cellular contents released into the environment
causing an inflammatory response
• Programmed Cell Death (Apoptosis)
– Orderly, contained cell disintegration
– Cellular contents are contained and cell is
immediately phagocytosed
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Stem and Progenitor Cells
Stem cell
• can divide to form two new stem cells
• can divide to form a stem cell and a progenitor cell
• totipotent – can give rise to any cell type (Embryonic stem
cells)
• pluripotent – can give rise to a restricted number of cell
types
Progenitor cell
• committed cell
• can divide to become any of a restricted number of cells
• pluripotent
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Cancer
Two types of tumors
• benign – usually remains
localized
• malignant – invasive and can
metastasize; cancerous
Genes that cause cancer
• oncogenes – activate other
genes that increase cell division
• tumor suppressor genes –
normally regulate mitosis; if
inactivated they will not
regulate mitosis
Oncology is the study of tumors
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Cancer
Metastasis is the
spread of a cancer
from its site of
origin to other
areas of the body
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Lecture Review
TRANSPORT
PROCESS
IS
ENERGY
NEEDED?
CONCENTRATION
GRADIENT
GENERAL
DESCRIPTION
EXAMPLE
IN
HUMANS
SIGNIFICANCE
SIMPLE
DIFFUSION
NO
[HIGH]
TO
[LOW]
spreading out of
molecules to
equilibrium
O2 into cells; CO2
out of cells.
Cellular
Respiration
FACILITATED
DIFFUSION
NO
[HIGH]
TO
[LOW]
Using a special
cm carrier protein
to move
something
through the cell
membrane (cm)
Process by which
glucose enters
cells
OSMOSIS
NO
[HIGH]
TO
[LOW]
water moving
through the cm to
dilute a solute
maintenance
of osmotic
pressure of 0.9%.
Same
FILTRATION
NO
[HIGH]
TO
[LOW]
using pressure to
push something
through a cm
(sprinkler hose)
manner in which
the kidney filters
things from blood
removal of
metabolic wastes
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Lecture Review
TRANSPORT
PROCESS
IS
ENERGY
NEEDED?
CONCENTRATION
GRADIENT
GENERAL
DESCRIPTION
EXAMPLE
IN
HUMANS
ACTIVE
TRANSPORT
YES
[LOW]
TO
[HIGH]
opposite of
diffusion at
the expense
of energy
K+-Na+-ATPase
pump
maintenance of the
resting
membrane
potential
ENDOCYTOSIS
YES
[LOW]
TO
[HIGH]
bringing a
substance
into the cell
that is too
large to
enter by
any of the
above
ways;
Phagocytosi: cell
eating;
Pinocytosis: cell
drinking.
Phagocytosed
(foreign)
particles
fuse with
lysosomes
to be
destroyed
help fight infection
EXOCYTOSIS
YES
[LOW]
TO
[HIGH]
expelling a
substance
from the
cell into
ECF
Exporting
proteins;
dumping
waste
Same
SIGNIFICANCE
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Osmotic Pressure/Tonicity
Osmotic Pressure (Osmolarity) – ability of solute to generate
enough pressure to move a volume of water by osmosis
*Osmotic pressure increases as the number of nonpermeable
solutes particles increases
0.9% NaCl
• isotonic – same
5.0% Glucose
osmotic pressure as a
second solution
• hypertonic – higher
osmotic pressure
• hypOtonic – lower
osmotic pressure
Crenation
The O in
o
hyp tonic
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Some Definitions…
*Chromatin – combination of DNA plus histone proteins
used to pack DNA in the cell nucleus
Gene – segment of DNA that codes for a protein or RNA
- About 30,000 protein-encoding genes in humans
- DNA’s instructions are ultimately responsible for the
ability of the cell to make ALL its components
Genome – complete set of genes of an organism
- Human Genome Project was complete in 2001
- Genomes of other organisms are important also
Genetic Code – method used to translate a sequence of
nucleotides of DNA into a sequence of amino acids
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Structure of Nucleic Acids
Purines: Adenine and Guanine (double ring)
Pyrimidines: Cytosine, Thymine, and Uracil (single ring)
Figure from: Alberts et al., Essential Cell Biology, Garland Press, 1998
15
Structure of DNA
5'
3'
A double-stranded
DNA molecule is
created by BASEPAIRING of the
nitrogenous bases
via HYDROGEN
bonds.
Notice the
orientation of the
sugars on each
stand.
5'
3'
*DNA is an antiparallel, double-stranded polynucleotide helix16
Structure of DNA
Complementary base pairing…
Base pairing in DNA is VERY specific.
- Adenine only pairs with Thymine (A-T)
- Guanine only pairs with Cytosine (G-C)
Note that there are:
- THREE hydrogen bonds in G-C pairs
- TWO hydrogen bonds in A-T pairs
- A purine (two rings)base hydrogen
bonds with a pyrimidine base (one ring)
Figure from: Martini, “Human Anatomy & Physiology”, Prentice Hall, 2001
17
DNA Replication
5’
THINGS TO NOTE:
1. DNA is replicated in the
S phase of the cell cycle
3’
5’
3’
3. DNA polymerase has a
proofreading function
(1 mistake in 109
nucleotides copied!)
5’
3’
3’
5’
3’
Figure from: Martini, “Human Anatomy &
Physiology”, Prentice Hall, 2001
2. New strands are
synthesized in a 5’ to 3’
direction
5’
4. Semi-conservative
replication describes
pairing of postreplication strands of
DNA (1 new, 1 old) 18
RNA
• RNA is a polynucleotide with important
differences from DNA
– Uses Uracil (U) rather than Thymine (T)
– Uses the pentose sugar, ribose
– Usually single-stranded
• There are three important types of RNA
– mRNA (carries code for proteins)
– tRNA (the adapter for translation)
– rRNA (forms ribosomes, for protein synthesis)
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Transciption/Translation
• Transcription
– generates mRNA from DNA
– Occurs in nucleus of the cell
– Uses ribonucleotides to synthesize mRNA
• Translation
– generates polypeptides (proteins) from mRNA
– Occurs in the cytoplasm of the cell
– uses tRNA and ribosomes
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The Genetic Code
1. Codon – group of three ribonucleotides found in mRNA that specifies an aa
2. Anticodon – group of three ribonucleotides found in tRNA that allows specific
hydrogen bonding with mRNA
3. AUG is a start codon and also codes for MET. UAA, UAG, and UGA are stop codons
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that terminate the translation of the mRNA strand.
Find the AMINO ACID SEQUENCE that corresponds to the following
gene region on the DNA:
Template -> G A T T G A A T C
Coding
-> C T A A C T T A G
tRNAs
Transfer RNAs (tRNA) function as
‘adapters’ to allow instructions in the
form of nucleic acid to be converted
to amino acids.
Figures from:
Martini,
Anatomy &
Physiology,
Prentice Hall,
2001
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Eukaryotic Genes
The template strand of DNA is the one that’s transcribed.
The coding strand of DNA is used as the complementary
strand for the template strand in DNA and looks like the
codons.
Figure from: Alberts et al., Essential Cell Biology, Garland Publishing, 1998
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Eukaryotic mRNA Modification
Newly made eukaryotic
mRNA molecules
(primary transcripts)
undergo modification in
the nucleus prior to
being exported to the
cytoplasm.
1. Introns removed
2. 5' guanine cap added
3. Poly-A tail added
Figure from: Alberts et al., Essential Cell Biology, Garland Publishing, 1998
25
The Fate of Proteins in the Cell
• Breakdown of proteins regulates the amount of a given
protein that exists at any time.
• Each protein has unique lifetime, but the lifetimes of
different proteins varies tremendously.
• Proteins with short life-spans, that are misfolded, or that
become oxidized must be destroyed and recycled by the cell.
Enzymes that degrade proteins are
called proteases. They are hydrolytic
enzymes.
Most large cytosolic proteins in
eukaryotes are degraded by enzyme
complexes called proteasomes.
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Enzymes
• Enzymes are biological catalysts
– Highly specific for their substrate
– Lower activation energy needed to start a reaction
– Are not consumed during reaction
– May require cofactors/coenzymes
– Effectiveness is greatly affected by temperature, pH, and
the presence of required cofactors
Cofactors
• make some enzymes
active
• ions or coenzymes
Coenzymes
• complex organic molecules
that act as cofactors (so
coenzymes ARE cofactors)
• vitamins
• NAD+
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Harnessing Energy from Carbohydrates
General Reaction sequence in carbohydrate catabolism
OXIDATION
C6H12O6 + 6 O2  6 CO2 + 6 H2O + ENERGY
REDUCTION
Electrons (H·) “fall” in energy from organic molecules
to oxygen during cellular respiration.
That is, e- LOSE potential energy during this process
and this energy is captured to make ATP
However, electrons CANNOT be transferred directly
from glucose to the electron transport chain. There
are intermediates – activated carrier molecules
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Energy for Metabolic Reactions
Energy
• ability to do work or change something (potential, kinetic)
• heat, light, sound, electricity, mechanical energy, chemical
energy
• changed from one form to another, but NEVER destroyed
(law of conservation of energy)
• involved in all metabolic reactions
Release of chemical energy
• most metabolic processes depend on chemical energy
• oxidation of glucose generates chemical energy
• cellular respiration releases chemical energy slowly from
molecules and makes it available for cellular use
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Oxidation and Reduction Revisited
Oxidation Is Loss of electrons;
Oxidation
Reduction Is Gain of electrons
• gain of O2
“OIL RIG”
• loss of e
• loss of H (since a H carries an electron with it)
• increase in oxidation number, e.g., Fe2+ -> Fe3+
Reduction
• loss of O2
• gain of e• gain of H
• decrease in oxidation number, e.g., Fe3+ -> Fe2+
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ATP – An Activated Carrier Molecule
• each ATP molecule has three parts:
• an adenine molecule These two components
together are called a ?
• a ribose molecule
• three phosphate molecules in a chain
• ATP carries its energy in the form or P
(phosphate)
• ATP is a readily interchangeable form
of energy for cellular reactions
(“common currency”)
High-energy
bonds
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NAD(H) – An Activated Carrier Molecule
NAD+
NAD (and NADP) are
specialized to carry
high-energy e- and H
atoms
A “packet” of energy =
H·
NADH + H+
NAD+
NADH
These packets of energy will be passed to oxygen in
the electron transport chain, and their energy used
to drive the synthesis of ATP
Important carriers of e- in catabolism: NADH, FADH2
Figure from: Alberts et al., Essential Cell Biology, Garland Press, 1998
32
Summary Table of Cell Respiration
Where it takes
place
Products Produced
Purpose
What goes on
GLYCOLYSIS
TCA
ETC
Cytoplasm
Mitochondria
Mitochondria
ATP
NADH
Pyruvate
Breakdown of glucose
(6 carbons) to 2
molecules of pyruvate
(3 carbons)
1. Glucose is
converted to pyruvate,
which is converted to
acetyl CoA when there
is sufficient O2
present.
2. Acetyl CoA enters
the TCA cycle.
3. If O2 is not present,
pyruvate is converted
to lactic acid to
replenish the supply of
NAD+ so glycolysis
can continue to make
ATP
ATP
NADH,FADH2
CO2
Generation of energy
intermediates (NADH,
FADH2, ATP) and CO2
ATP
NAD,FAD
H2O
Generation of ATP and reduction
of O2 to H2O(Recall that
reduction is the addition of
electrons)
1. The energy in acetyl CoA 1. Chemiosmosis (oxidative
is trapped in activated
phosphorylation) uses the
carriers of electrons (NADH, electrons donated by NADH and
FADH2) and activated
FADH2 to eject H+ from the
carriers of phosphate groups matrix of the mitochondria to the
(ATP).
intermembrane space.
2. The carries of electrons
that trap the energy from
2. These H+ then flow down
acetyl CoA bring their high
their concentration gradient
energy electrons to the
through a protein (ATP synthase)
electron transport chain.
that makes ATP from ADP and
phosphate.
3. During this process, the H+
that come through the channel in
ATP synthase are combined with
O2 to make H2O.
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Summary of
Catabolism of
Proteins,
Carbohydrates,
and Fats
Acetyl CoA is a
common intermediate
in the breakdown of
most fuels.
Acetyl CoA can be
generated by
carbohydrates, fats,
or amino acids
Acetyl CoA can be
converted into fatty
acids
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Pyruvate is a Key Junction in Metabolism

Lipogenesis
Lipolysis

*
Glycogenolysis


Glycogenesis
Pyruvate is used
to synthesize
amino acids and
Acetyl CoA
Pyruvate can
also be used to
synthesize
glucose via
gluconeogenesis.
Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001
35
Carbohydrate Storage
Excess glucose can be
• stored as glycogen by glycogenesis (liver and muscle cells)
• stored as fat by lipogenesis
• converted to amino acids
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Terms to Know…
-olysis  breakdown of
-genesis  creation of
-neo  new
• Glycolysis – metabolism of glucose to pyruvate
• Gluconeogenesis – metabolism of pyruvate to
glucose (making CHO from non-CHO source)
• Glycogenesis – metabolism of glucose to glycogen
• Glycogenolysis – metabolism of glycogen to
glucose
• Lipogenesis – creation of new triglyceride (lipid,
fat)
• Lipolysis – breakdown of triglyceride into
glycerol and fatty acids
37