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Cell Energy, Division, and Reproduction

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-Self feeders
-Make their own organic mols from inorganic ones.
Heterotrrophs
-Must aquire their organic mos in their diet.
Sun
-Source of energy for nearly all life on Earth
-Enters web of life thru photosynthesis.
Aerobic Cell Respiration
-Main degradative metabolic pathway to break down glucose.
-Complete breakdown of glucose to CO2 +H20 using O.
-Main function is to provide the energy needed for ATP synthesis.
-36 ATP/glucose
2 Mechanisms for ATP synthesis
1.Substrate-level phosphorylation-some enzymes in glycolysis and the Kreb's cycle can directly transfer a P group to ADP to form ATP.
2.Chemiosmosis-a H ion concentration gradient across a membrane drives ATP production. Involves an e transport chain and a channel protein.
Aerobic Respiration Occurs In 4 Stages
1.Glycolysis
2.Pyruvate Conversion/Oxidation
3.Kreb's Cycle
4.E Transport Chain
Glycolysis
-In cytoplasm
-Makes 2 pyruvates, 2 NADH, + 2ATP
-If O is present, pyruvates are transported into the mitochondrial matrix.
Pyruvate Conversion/Oxidation
-In mitochondrial matrix
-Each 3-C pyruvate is converted into 2-C acetyl CoA w/ formation of CO2 + another NADH (occurs 2ce for ea. glucose broken down.
Kreb's Cycle
-In mitochodrial matrix
-Ea AcetylCoA goes thru Kreb cycle+is broken down to CO2s.
rest of Hs pull off+e+some H ions stored in NADH+FADH2.
-1 ATP made per turn of cycle (cycle must go around 2ce/glucose)
-End of Cycle: 10NADH, 2 FADH2 + 4 ATP
Electron Transport Chain
-Inner mitochondrial membrane.
-All coenzymes give up their e+H ions for use by an e transport system in inner mitochondrial membrane.
-E transport system has 3 big complexes ( proton pumps when chain is running), w/ 2 mobile e carriers that travel btw them.
Electron Transport Chain 2
-NADH gives up e to 1st complex.
-FADH2 gives up e after 1st complex.
-E passed from mol to mol until they reach final e acceptor:O.
-O can accept 2 e, can pick up 2 protons to form H20.
-When e transport chain is running, 3 complexes pump H ions into inter-membrane space.
Electron Transport Chain
-Then H ions move down conc. gradient to matrix thru membrane channel protein(ATP synthase) b/c its the enzyme that catalyzes the reaction: ADP+P->ATP.
-Channel protein/enzyme couples diffusion of H ions thru it to formation of ATP by chemiosmosis.
Anaerobic Pathways
-Don't use O.
-Conversion of pyruvate to other subs is to regenerate NAD so it doesnt get tied up- no glucose could then be broken down.
1.Anaerobic cell respiration-similar to aerobic, but some inorganic sub other than O used as final e acceptor.
2.Fermentation-incomplete breakdown of glucose.
-Final e acceptor is an organic mol.
-Virtually identical to glycolysis, doesn't use O.
-Occurs in cytoplasm.
A)Alcohol fermentation-
glucose-->pyruvate+NADH+2ATP-->ethanol+NAD
B)Lactate fermentation-
glucose-->pyruvate+NADH+2ATP-->lactate+NAD
Prokaryotes
-No nucleus.
-Divide by binary fission.
-Single circular chromosome copied;cell grows to 2ce its size, divides in two.
Eukaryotes
-Larger cells+more DNA (as linear chromosomes).
-More complex division.
Chromosomes
-Threadlike chromatin(complex of protein+long strand of DNA)
-DNA strand looped around protein "spool" made of histones
(looks like string of beads).
-Ea histone w/ looped is nucleosome.
-Coiled further to make chromatin fiber to make highly condensed portion visible chromosome.
Heterochromatin:
-never expressed
-highly condensed part of chromosome.
Euchromatin:
-Expressed part of genetic material.
-Condensed only during cell division.
-Usually in looser chromatin form.
Human Genes
-Carried on a set of 23 chromosomes.
-Body(somatic)cells have 2 sets of chromosomes= diploid cell (2N).
-Cells have 2 of ea type of chromosome(homologous pairs).
-Before cell division ea chromosome must duplicate self.
-Condensed chromosomes at beginning of cell division,2 identical copies of chrom(sister chromatids) are attached by their centromeres.
Gametes
-(Eggs + Sperm).
-Haploid (IN).
-Have only one set of chromosomes.
Cell Cycle
-Repeating cycle of growth + division.
1)Interphase
2)M ohase
3)C phase
4)GO
5)Spindle
6)Mitosis
7)Prophase
8)Metaphase
9)Anaphase
Interphase
-Nondividing portion of cell cycle(90--95% of cell cycle).
1)G1-1st stage after division, growth of new cell.
2)S-synthesis of DNA, chromosomes duplicate.
3)G2-2nd growth period, preparations for cell division
M phase
-Division of nuclear contents.
C phase
-Division of cytoplasmic contents.
GO
-Resting state in G1.
-Some cells, neurons,+ muscle stay here permanently.
Spindle
-Array of microtubules seen only in cell division.
-Critical to chromosome separation.
Mitosis
-Basis of asexual reproduction(1 parent).
-1 parent cell produces 2 daughter cells that are gen. identical to parent cell (Clones).
-Chromosome #+content remain same for every generation.
Prophase
-Chromatin condenses.
-Nuclear envelope disintegrates.
-Spindle forms.
Metaphase
-Duplicated chromosomes line up on spindle equator(metaphase plate).
-Attach by kinectochores.
Anaphase
-Sister chomatids move to opp. poles of cell.
Telophase
-Chromosomes reach opp poles, decondense, nuclear envelope reappears.
Cytokinesis
-Involves formation of cleavage furrow in animal cells.
-Involves formation of cell plate in plant cells.
Cell Division Controlled By 2 Types of Proteins
-Cyclins +Cyclin.
-Dependent protein kinases+a variety of genes that stimulate/inhibit cell division.
-problems w/ any of these may lead to uncontrolled cell division (cancer).
Meiosis
-Forms basis of sexual reproduction along w/ fertilization.
-Special type of nuclear division that cuts chromosome# in 1/2. (Reduction Division).
-Occurs only in germ cells of reprod. organs to produce gametes(eggs+sperm).
-Invovles replication of DNA + then 2 mr divisions.
-Results in formation of 4 haploid gametes.
-None are identical to original parent cell(diploid germ cell).
Meiosis Vs. Mitosis
1)Meiosis I:
Prophase1:duplicated homologous chroms pair up(synapsis)
Form synaptonemal complexes leading to crossing over.
Exchange = amts of DNA btw nonsister chromatids.
Metaphase1:paired homolgues line up on spindle equator.
Anaphase1:duplicated homologues sep,move to opp poles.
Telophase1:duplicated chroms reach opp poles.
-Cytokinesis usually occurs.
-Cell may/not go directly into Meiosis II.
-Resting period called interkinesis.
Meiosis Vs. Mitosis (2)
2)Meiosis II:
ProphaseII:spindle forms
MetaphaseII:duplicated chroms line up single file on spindle equator.
AnaphaseII:sister chromatidsmove to opp poles.
TelophaseII:chroms reach opp poles of cell
Nuclear envelopes reforn, cytokinesis.
-Now 4 haploid cells-none identical to parent cell(b/c crossing over).
-Proper chrom # is restored in fertilization.
Parthenogensis
Development of unfertilized egg into an adult.
Sources of Genetic Variation
1)Crossing over.
2)Independent assortment of maternal+paternal chroms.
3)Random fertilization.
4)Mutation-the only one that has nothing to do w/ sexual reproduction.