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A&P I Exam 2 Review Slides

Lectures 5-8

Ch. 2, 3, and 24 (cell resp.)

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A Closer Look at Mitochondria

Strategically

placed in cell

where ATP

demand is high

Concentration of enzymes in the matrix is so high that there is

virtually no hydrating water. Enzyme-linked reactions and

pathways are so crowded that normal rules of diffusion do not apply!

Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001

(Impermeable to charged or polar molecules)

Mitochondria

• membranous sacs with

inner partitions

• contain their own DNA

• generate energy

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Overview of Cellular RespirationFigure from: Martini, Anatomy & Physiology, Prentice Hall, 2001

Cellular

respiration

(aerobic)

AnaerobicATP

*Most ATP from here

ATP

• Structural – Functional Relationship - Inner membrane:

• Contains Matrix where TCA cycle takes place

• Has enzymes and molecules that allow Electron Transport System to be carried out

e-

+ e-

ETS

e-

e-

2

4

Overview of Glucose Breakdown

Figure from: Hole’s Human A&P, 12th edition, 2010

NAD+

NAD+

NAD+, FAD

NADH

NADH

FADH2

NADH

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Anaerobic Glycolysis & Lactic Acid

During glycolysis, if O2 is not

present in sufficient quantity,

lactic acid is generated to keep

glycolysis going so it continues

to generate ATP (even without

mitochondria)

NOTE what happens with and

without O2 being available…

Figure from: Hole’s Human A&P, 12th edition, 2010

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GLYCOLYSIS TCA ETC

Where it takes

place

Cytoplasm Mitochondria Mitochondria

Products Produced ATP

NADH

Pyruvate

ATP

NADH,FADH2

CO2

ATP

NAD+,FAD

H2O

Purpose Breakdown of glucose

(6 carbons) to 2

molecules of pyruvate

(3 carbons)

Generation of energy

intermediates (NADH,

FADH2, ATP) and CO2

Generation of ATP and reduction

of O2 to H2O (Recall that

reduction is the addition of

electrons)

What goes on 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

1. The energy in acetyl CoA

is trapped in activated

carriers of electrons (NADH,

FADH2) and activated carriers of phosphate groups

(ATP).

2. The carriers of electrons

that trap the energy from

acetyl CoA bring their high

energy electrons to the

electron transport chain.

1. Chemiosmosis (that drives

oxidative phosphorylation) uses

the electrons donated by NADH

and FADH2 to eject H+ from the matrix of the mitochondria to the

intermembrane space.

2. These H+ then flow down

their concentration gradient

through a protein (ATP synthase)

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.

Summary Table of Cell Respiration

3

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Some Definitions…

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

*Chromatin – combination of DNA plus histone proteins

used to pack DNA in the cell nucleus

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

Figure from: Alberts et al., Essential Cell Biology, Garland Press, 1998

Purines: Adenine and Guanine (double ring)

Pyrimidines: Cytosine, Thymine, and Uracil (single ring)

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Structure of DNA

A double-stranded

DNA molecule is

created by BASE-

PAIRING of the

nitrogenous bases

via HYDROGEN

bonds.

Notice the

orientation of the

sugars on each

stand.

*DNA is an antiparallel, double-stranded polynucleotide helix

5'3'

5'3'

4

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Structure of DNA

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

Complementary base pairing…

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DNA Replication

Figure from: Martini, “Human Anatomy &

Physiology”, Prentice Hall, 2001

THINGS TO NOTE:

1. DNA is replicated in the

S phase of the cell cycle

2. New strands are

synthesized in a 5’ to 3’

direction

3. DNA polymerase has a

proofreading function

(1 mistake in 109

nucleotides copied!)

4. Semi-conservative

replication describes

pairing of post-

replication strands of

DNA (1 new, 1 old)

5’

5’

5’

5’

3’

3’

5’

3’

3’

3’

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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)

5

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Transciption/Translation

• Transcription

– generates mRNA from DNA

– Occurs in nucleus of the cell

– Uses ribonucleotides and RNA polymerase to synthesize mRNA

• Translation

– generates polypeptides (proteins) from mRNA

– Occurs in the cytoplasm of the cell

– Uses 3 components: mRNA, tRNA w/aa, 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

that terminate the translation of the mRNA strand.

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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

Figure from: Alberts et al., Essential Cell Biology, Garland Publishing, 1998

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.

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Eukaryotic mRNA Modification

Figure from: Alberts et al., Essential Cell Biology, Garland Publishing, 1998

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

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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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Cell Membranes

Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001

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Passage of Materials through the Cell Membrane

oxygen, carbon

dioxide and other

lipid-soluble

substances diffuse

freely through the

membrane

Carrier/channel

proteins required

for all but fat-

soluble molecules

and small

uncharged

molecules

Cellular Transport ReviewTRANSPORT

PROCESS

IS

ENERGY

NEEDED?

CONCEN-

TRATION

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 carrier

protein to move

something through the

cell membrane (cm)

Process by which

glucose enters

cells

OSMOSIS NO [HIGH]

TO

[LOW]

water (solvent) moving

through the cell

membrane to dilute a

solute

maintenance

of osmotic

pressure.

Same

FILTRATION NO [HIGH]

TO

[LOW]

using pressure to push

something through a cell

mmembrane (sprinkler

hose)

manner in which

the kidney filters

things from blood

Separates small

from large

molecules using

hydrostatic pressure

ACTIVE

TRANSPORT

YES [LOW]

TO

[HIGH]

opposite of diffusion at

the expense of energy

K+-Na+-ATPase

pump

maintenance of the

resting

membrane

potential

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Cellular Transport Review

TRANSPORT

PROCESS

IS

ENERGY

NEEDED?

CONCEN-

TRATION

GRADIENT

GENERAL

DESCRIPTION

EXAMPLE

IN

HUMANS

SIGNIFICANCE

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

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

• isotonic – same

osmotic pressure as a

second solution

• hypertonic – higher

osmotic pressure

• hypOtonic – lower

osmotic pressure

0.9% NaCl

5.0% Glucose

Crenation

The O in

hypotonic

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Cell Nucleus

• control center of cell

• nuclear envelope

(membrane)• porous double membrane

• separates nucleoplasm from

cytoplasm (*eukaryotes only)

• nucleolus• dense collection of RNA and

proteins

• site of ribosome production

• chromatin• fibers of DNA and proteins

• stores information for synthesis

of proteinsFigure From: Marieb & Hoehn, Human Anatomy & Physiology, 9th ed., Pearson

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Cellular Organelles

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

Table 1 of 2

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Cellular Organelles

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 alignment and

movement during metaphase,

anaphase, and telophase of mitosis

Table 2 of 2

The Cell Cycle

• series of changes a cell

undergoes from the time it

forms until the time it divides

• stages

• interphase

• mitosis

• cytoplasmic division

• differentiation

Differentiated cells may spend all their time in ‘G0’ (neurons, skeletal muscle, red

blood cells). Stem cells may never enter G0

Figure From: Marieb & Hoehn, Human Anatomy & Physiology, 9th ed., Pearson

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Why the Cell Cycle Must Have Controls

1. DNA/Cell replication must not proceed unless a ‘signal to proceed’ is received

2. DNA must be completely and correctly replicate before mitosis takes place otherwise it should not occur.

3. Chromosomes must be correctly positioned during mitosis so they are separated correctly

What are the Controls of the Cell Cycle?

• cell division capacities vary greatly among cell types• skin and bone marrow cells divide often

• liver cells divide a specific number of times then cease

• chromosome tips (telomeres) that shorten with each mitosis

provide a mitotic clock (cell senescence)

• cells divide to provide a more favorable surface area to

volume relationship

• growth factors and hormones stimulate cell division• hormones stimulate mitosis of smooth muscle cells in uterus

• epidermal growth factor stimulates growth of new skin

• tumors are the consequence of a loss of cell cycle control

• contact inhibition

• Cyclins and Cyclin-dependent kinases provide central control

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Mitosis and MeiosisFigures from: Martini, Anatomy & Physiology, Prentice Hall, 2001

Mitosis – production of two identical diploid daughter cells

Meiosis – production of four genetically varied, haploid gametes

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The Cell Cycle and Mitosis

• I (INTERPHASE)

• PASSED (PROPHASE)

• MY (METAPHASE)

• ANATOMY (ANAPHASE)

• TEST (TELOPHASE/CYTOKINESIS)

Interphase and Mitosis (IPMAT)

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Interphase Early Prophase Late Prophase

Metaphase Anaphase Telophase/Cytokinesis

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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 – no inflammation

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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 further along differentiation pathway

• can divide to become only a restricted number of cells

• pluripotent

• *not self-renewing, like stem cells