A&P I Exam 2 Review SlidesSpring 2014

Lectures 5-8Ch. 2, 3, and 24 (cell resp.)

2

Cell Membranes

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

3

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 ReviewTRANSPORTPROCESS

ISENERGYNEEDED?

CONCEN-TRATIONGRADIENT

GENERALDESCRIPTION

EXAMPLEIN HUMANS

SIGNIFICANCE

SIMPLEDIFFUSION

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

Cellular Transport Review

TRANSPORTPROCESS

ISENERGYNEEDED?

CONCEN-TRATIONGRADIENT

GENERALDESCRIPTION

EXAMPLEIN 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% NaCl5.0% Glucose

Crenation

The O in

hypotonic

7

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

9

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

10

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-

11

Overview of Glucose Breakdown

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

NAD+

NAD+

NAD+, FAD

NADH

NADHFADH2

NADH

12

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 ATPNADH

Pyruvate

ATPNADH,FADH2

CO2

ATPNAD+,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 carries 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

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

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

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

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

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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 any of a restricted number of cells • pluripotent• *not self-renewing, like stem cells

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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

24

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)

25

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'

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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…

27

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)

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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.

Find the AMINO ACID SEQUENCE that corresponds to the following gene region on the DNA:

Template -> C T A A G T A C T

Coding -> G A T T C A T G A

32

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

33

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.

34

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 removed2. 5' guanine cap added3. 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.