Chapters 10-14 Flashcards
Catabolic Pathways yeild energy by oxidizing organic fuels
-Catabolic pathways release stored energy by breaking down complex molecules
Fermentation
- Partial degradation of sugars that occurs without O2
- Alcohol fermentation by yeast: pyruvate–> Ethanol + CO2
- Lactic Acid fermentation: pyruvate–> lactase
- Used by human muscle cells to generate ATP when O2 is scarce
- Produces 2 ATP per glucose
Aerobic respiration
-Consumes organic molecules and O2, yeilds ATP
Anaerobic Respiration
-Similar to aerobic respiration but consumes compounds other than O2
Cellular Respiration
-Both aerobic and anaerobic respiration
-Glucose + Oxygen –> CO2 + water + energy (atp + heat)
Steps:
1. Glycolysis
2. Citric Acid Cycle
3. Oxidative Phosphorylation
-Total ATP: 32
Redox Reactions
- Used to synthesize ATP
- Oxidation: loses electrons
- Reduction: gains electrons
Redox Reactions of Cellular Respiration
-Glucose is oxidized, O2 is reduced
Substrate Level Phosphorylation
- The small amount of ATP formed in glycolysis and the citric acid cycle
- 4 ATP in total (2 from each)
Glycolysis
- Oxidizes glucose into 2 molecules pyruvate
- Major phases: energy investment phase, energy payoff phase
- Occurs whether or not O2 is present, in the cytosol
Cytric Acid Cycle
- W/ presence of O2, pyruvate enters mitochondria, where oxidation of glucose is completed
- To start cycle, pyruvate converted to acetyl CoA
1. Oxidation of pyruvate and release of Co2
2. Reduction of NAD+ to NADH
3. Combinaiton of remaining 2-C fragment and coenzyme A to form acetyl CoA - 2 pyruvates–> 2 ATP, 6 NADH, 2 FADH2
Oxidative Phosphorylation
- NADH and FADH2 donate electrons to electron transport chain, powers ATP synthesis
- Occur in inner membrane of mitochondria
- Chain’s components= proteins
- Electrons pass to O2, forming water
- Electron carriers alternate btwn reduced and oxidized states
Chemiosmosis in Cellular Respiration
- Energy-coupling mechanism
- Energy released as electrons are passed down ETC used to pump H+ through ATP synthase
- Causes ATP synthase to spin, creating ATP
- Uses H+ gradient to drive cell work
Producing ATP w/o oxygen
- Electron transport chain doesn’t work w/o oxygen
- Glycolysis couples w/ anaerobic respiration or fermentation to produce ATP
Chloroplasts
- Organelle in photosynthetic organisms
- Convert solar energy to chemical energy using photosynthesis
- Found in the mesophyll (interior tissue of lead)
- CO2 enters and O2 exits through stomata
- Enveloped by stroma
- Thylakoid= sacs in chloroplast, stacked in grana
- Chlorophyll= green pigment
Photosynthesis
- Converts light energy into food
- H2O+ light energy+ CO2–> O2 + glucose
Pathway of water
- Absorbed through roots and enters leaf through veins
- Veins export sugars to roots and other parts of the plant
Photosynthesis as a redox process
- CO2 reduced to glucose
- H2O oxidized to o2
- Endergonic
The splitting of water in photosynthesis
- O2 given off by plants is derived from H2O
- Chloroplasts split H2O into H and O, release into atmosphere
Light Reactions
- Solar energy–> chemical energy
- Water split to create O2
- Location: tylakoid
Calvin Cycle
- CO2+ organic moleculed (NADPH and ATP) –> glucose
- Location: Stroma
- Anabolic (uses energy)
- Phases: 1. Carbon fixation (catalized by rubisco), 2. reduction, 3. regeneratin of CO2 acceptor (RuBP)
- Must occur 3 times to create 1 G3P
- 9 ATP used, 6 NADPH
Light Reactions process
- Photon (light) hits chlorophyll pigments in photosystem II, excited chain reaction
- Electron transfered to primary electron acceptor
- Water splits–> 2 e-, 2 H+ (in thylakoid space), 1 O (combined w/ another to make O2)
- Excited electrons pass from PEA of PSII to PSI via electron transport chain
- Potential energy of proton gradient is used to make ATP in chemiosmosis
- Light energy transfered to PSI reaction-center complex
- Photoexcited electron transfered to PSI’s PEA, can now accept e- at bottom of PSII PEA
- Excited e- passed from PI’s PEA down 2nd ETC
- Enzyme NADP+ transfers e- –> NADPH, removes H+ from stroma
Linear Electron Flow in Light Reactions
- Light drives the synthesis of ATP and NADPH by energizing the two photosystems embedded in thylakoid membranes of chloroplasts
- Flow of electrons through the photosystems and other molecular components built into thylakoid membrane
Chemiosmosis in Photosynthesis
- Electron transport chain, pumps H+ across membrane, powers ATP-synthase’s creation of ATP
- Electron from water
- Light–> glucose energy
- Stroma holds H+
Carbon Fixation
- Incorportation of CO2 molecules, attached to RuBP (5 carbon sugar)
- Catalyzed by rubisco
- Forms 2 molecules of 3-phosphoglycerate
Reduction (Calvin Cycle)
- 3-phosphoglycerate + Phosphate group from ATP–> 1,3-bisphosphoglycerate–> reduced by NADPH–> Glyceraldehyde 3-phosphate
- 6 G3P formed, 5 used to regenerate RuBp
- Net: 1 G3P
Regeneration of RuBP
- CO2 acceptor
- 5 G3P recycled into 3 RuBp using 3 ATP, continued cycle
Alternative mechanisms of carbon fixation
- On hot, dry days, plants close stomata, which conserves H2O but limits photosynthesis
- Reduces access to CO2, O2 builds up
- Lead to photorespiration
Photorespiration
- Rubisco adds O2 instead of CO2 to Calvin cycle, producing 2-carbon compound
- Consumes O2 and organic fuel and releases CO2 w/o producing ATP or sugar
C3 Plants
-Initial fixation of CO2, via rubisco, forms 3-carbon compound (3-phosphoglycerate)
C4 Plants
- Minimize the cost of photorespiration by incorporating Co2 into 4-C compounds
- Types of cells in leaves that store 4-C
- Bundle-sheath cells are arranged tightly in packed sheaths around veins of leag
- Mesophyll cells packed loosely betwen bundle sheaths and leaf surface
- Bundle-sheath cells are arranged tightly in packed sheaths around veins of leag
CAM Plants
- Open stomata at night, incorporating CO2 into organic acids that are stored via vacuoles
- Stomata close during day, CO2 is released from organic acids and used in Calvin cycle
- Separates initial steps of carbon fixation from calvin cycle
Reception
- Target cell detects a signaling molecule that binds to receptor protein on cell surface
- Binding btwn signal molecule (ligand) and receptor is highly specific
- Receptors found in plasma membrane of proteins
Transduction
- Change in receptor’s shape after binding is initial transduction of signal
- Multistep process
- Binding of signaling molecule to receptor
- activation of another protein, another protein, etc. until the protein producing the response is activated
- At each step signal is transduced into different form (phosphorylation/dephosphorylation)
Response
- Transduced signal triggers a specific response in target cell
- Nuclear and Cytoplasmic
- Regulate the synthesis of enzymes and proteins
G protein-coupled receptors (GCPRs)
- Cell-surface transmembrane receptors
- Work w/ help of G protein
- Binds to energy-rich GTP
- Receptor receives signaling molecule, GDP leaves
- GTP is released and attaches to inactive enzyme (now active)
- Cellular response
- GTP loses phosphate group, goes back to G-protein coupled receptor via G protein as GDP
- Binds to energy-rich GTP
Receptor Tyrosine Kinases (RTKs)
- Membrane receptors that transfer phosphate groups from ATP to another protein
- Can trigger multiple signal transduction pathways at once
1. Signaling molecules attach to inactive monomer, becomes phosphorylated dimer
2. ATP–> ADP (uses phosphates)
3. Cellular responses
Ligand-gated ion channel
- Acts as a gate that opens and closes when the receptor changes shape
- When signal molecule binds as a ligand to the receptor, gate allows specific ions through a channel in the receptor
1. Ligand binds to receptor
2. Channel opens and ions pass through (cellular response)
3. Ligand is removed
4. Channel closes
Protein phosphorylation
- Widespread cellular mechanism for regulating protein activity
- Protein kinases transfer phosphates from ATP to protein
- Many relay molecules in signal transduction are protein kinases, creating phosphorylation cascade
Protein Dephosphorylation
-Protein phosphatases rapidly remove the phosphates from proteins
Second Messengers
- Small, nonprotein, water-soluble molecules or ions that spread throughout a cell by diffusion
- Participate in pathways initiated by GPCRs and RTKs
- Ex: Cyclic AMP and calcium ions
Cyclic AMP
- Widely used second messanger
- cAMP
- Adenylyl cyclase (enzyme) converts ATP to cAMP in response to extracellular signal
Transduction w/ cAMP as 2nd messenger
- Signal molecules trigger formation of cAMP
- other components of cAMP pathways are G proteins, G protein-coupled receptors, and protein kinases
- cAMP activates protein kinase A, phosphorylates various proteins
- Further regulation of cell metabolism is provided by G protein systems that inhibit adenylyl cyclase
Calcium ions as second messenger
- Its concentration in the cytosol is normally much lower than the concentration outside the cell
- Smaller change in # of Ca+ thus represents a relatively large percentage change in C+ concentration
Transduction w/ Ca+
-A signal relayed by a signal transduction pathway may trigger an increase in calcium in the cytosol
Nuclear and Cytoplasmic Responses
- Signalling pathways regulate synthesis of enzymes or proteins by turning genes on or off in the nucleus
- Final activated molecule in signaling pathway functions as transcription factor
- Other pathways may regulate the activity of enzymes rather than synthesis
Regulation of the Response
- Four aspects of signal regulation
1. Pathway leads to single response
2. Pathway branches, leading to two responses
3. Cross-talk btwn 2 pathways
4. Different receptor leads to a diff response - Enzyme cascades amplify the cell’s response to signal
Termination of the Signal
- Inactivation of mecchanisms= essential aspect of cell signaling
- If the ceoncentration of external signaling molecules fall, fewer receptors will be bound
- Unbound receptors revert to inactive state
Apoptosis
- Cells that are infected, damaged, or at end of life undergo programmed cell death
- Components of cell are chopped up and packaged into vesicles that are digested by scavenger cells
- Prevents enzymes from leaking out of dying cells and damaging neighbor cells
Apoptosis examples
- Normal part of development of hands and feet in humans
- Diseases such as parkinsons and alzheimers
- Cancers occur when apoptosis is inhibited, doesn’t kill cells that later divide
Mitosis
- The division of genetic material in the nucleus
- Results in two daughter cells with identical genetic information
1. Prophase
2. Prometaphase
3. Metaphase
4. Anaphase
5. Telophase
Somatic Cells
- Nonreproductive cells
- Have 2 sets of chromosomes (2N), 46 total chromosomes (23 pairs)
Gametes
- Reproductive cells (sperm and egg)
- 1 set of chromosomes
Distribution of Chromosomes during Eukaryotic Cell Division
- DNA is replicated, chromosomes condense
- Each duplicated chromosome has 2 sister chromatids (joined copies of the original chromosome)
- Centromere= narrow waist where chromosomes attach
- Two sister chromatids of each duplicated chromosome separate and move into 2 nuclei (now called chromosomes)
Cytokinesis
- The division of the cytoplasm
- Cells separate
- Process known as cleavage, forms cleavage furrow
- In plants, cell plate forms
Interphase
- Growth and copying of chromosomes in prep for cell division
- Overlaps w/ mitosis
- 3 phases: G1 (growing), S (DNA synthesis, chromosome duplication), G2 (growing, getting ready for mitosis)
Prophase (Mitosis)
- Preparation
- Centrosomes move to opposite sides of cell
- Form mitotic spindles
Metaphase
-Sister chromatids align in the middle, pair up
Anaphase
- Sister chromatids separate, becoming chromatids
- Pull back to outsides of cell
Telophase
- Termination
- 2 identical daughter cells that have almost split
Mitotic Spindle
- Structure made of microtubules
- Controls chromosome movement during mitosis
Centrosome
- Microtubule-organizing center
- Replicates during interphase
- Forms two centrosomes that migrate to opposite ends during prophase and prometaphase
Metaphase Plate
- Where the chromosomes light up in the middle
- Plane midway between the spindle’s two poleds
Genes
- Units of heredity
- Made up of segments of DNA
- Passed to next generation via gametes (sperm or egg)
Karyotype
- Ordered display of pairs of chromosomes from a cell
- Staining, looking at shape and size to determine # of chromosomes
Homologous Chromosomes
- Two chromosomes in each pair
- Same length and shape
- Carry genes w/ same inherited characteristics
Sex Chromosomes
- Determine the sex of the individual (pair 23)
- Female: XX
- Male: XY
- Remaining 22: autosomes
Haploid Cell
- A gamete w/ a single set of chromosomes (23)
- Egg: X
- Sperm: either X or Y
Fertilization
- Union of gametes (sperm and egg)
- Fertilized egg= zygote, 1 set of chromosomes from each parent
- Develops into an adult
Meiosis
- Results in one set of chromosomes from each gamete
- Only produces gametes (sperm and eggs)
- Results in 4 haploid daughter cells
- Meiosis I and II
- Chromosomes duplicate before meiosis (sister chromatids)
Meiosis I
- Prophase I
- Metaphase I
- Anaphase I
- Telophase I
- Cytokinesis
Meiosis II
- Similar to Mitosis
- Prophase II
- Metaphase II
- Anaphase II
- Telophase II
- Cytokinesis
Prophase I
- Chromosome pairs w/ homolog and crossing over occurs
- Chiasmata: sites of crossoves
Metaphase I
- Pairs of homologs line up at metaphase plate (middle)
- Microtubules from one pole are attached to kinetochore of one chromosome of each pair
- Microtubules from 1 pole attach to kinetochore of other chromosome
Anaphase I
- Pairs of homologous chromosomes separate
- One chromosome of each pair moves to opposite pole
- Sister chromatids remain attached at centromere
Telophase I and Cytokinesis
Each half of the cell has haploid set of chromosomes, each 2 sister chromatids
- Cytokinesis forms 2 haploid daughter cells
- **No chromosome replication between end of meiosis I and beginning of meiosis II because chromosomes already replicated
Prophase II
- Spindle apparatus forms
- Chromosomes (still composed of two sister chromatids) move toward metaphase plate
Metaphase II
- Sister chromatids arranged at metaphase plate
- Two sister chromatids no longer identical due to crossover in metaphase I
- Kinetochores of sister chromatids attach to microtubules extending from opposite poles
Anaphase II
- Sister chromatids separate
- Sister chromatids from each chromosome now move as two newly individual chromosome towards poles
Telophase II and Cytokinesis
- The chromosomes arrive at opposite poles
- Nuclei form, chromosomes begin decondensing
- Cytokinesis separates cytoplasm
- 4 haploid daughter cells w/ distinct genetic material
Events unique to meiosis from meiosis I
- Synapsis and crossing over in prophase I
- Homologous pairs at the metaphase plate
- Separation of homologs during anaphase I
Genetic Variation
-Contributes to evolution
-mutations= original source of genetic diversity
-Different versions of genes= alleles
-Shuffling of alleles= genetic variation
Mechanisms that contribute to genetic variation
1. Independent assortment of chromosomes
2. crossing over
3. random fertilization
Independent Assortment of Chromosomes
- Homologous pairs of chromosomes orient randomly during Metaphase I
- Each pair of chromosomes sort maternal and paternal homologs into daughter cells independently of other pairs
Crossing Over
- Produces recombinant chromosomes= combined dna of each parent
- Contributes to genetic variation
- 3 crossovers occur per chromosome
Random Fertilization
- Sperm fuse w/ any ovum
- Each zygote has a unique genetic identity
- Adds to genetic variation
Alleles
- Alternative versions of genes account for variations in inherited characters
- Ex: pea plants two versions= purple and white
Locus
-Specific site one chromosomes where gene resides
Homozygote
-Organism w/ two identical alleles for a character
Heterozygote
- Organism w/ two different alleles for a gene
- Not true-breeding
Phenotype vs. Genotype
- P: trait seen
- G: genetic composition
Law of Segregation
- During gamete formation, the alleles for each gene segregate from each other
- Each gamete carries only one allele for each gene
Law of Independent Assortment
-Genes for different traits can segregate independently during gamete formation
Mendel’s Experiment
- Cross-pollinate purple and white pea plants (p generation)
- Counted offspring in F1 generation= all purple hybrids
- Cross-pollinate purple hybrid w/ purple hybrid
- Counted offspring in F2: 3-1 ratio purple to white
Meiosis #s
- Interphase 46
- Prophase I- 92
- Metaphase I- 46
- Meiosis II- 23 ( 4 haploid gametes)
Complete Dominance
- Phenotypes of heterozygote and dominant homozygote= identical
- Ex: Pp or PP
Incomplete Dominance
- Phenotype of F1 hybrids is somewhere between the two phenotypes of parents
- Ex: Red + white–> pink flower
Codominance
- Two dominant alleles affect the phenotype in separate, distinguishable ways
- Ex: bloodtype, where IAIB both creates AB bloodtype
Multiple Alleles
- Most genes exist in more than two allelic forms
- The four phenotypes of ABO blood are determined by 3 alleles : IA, IB or i
Pleiotropy
- When genes have multiple phenotypic effects
- Diseases such as cysitc fibrosis or sickle-cell
Epistasis
- One gene affects the phenotype of another due to interaction of their gene products
- Ex: Coat color in puppies, where one gene determines coat color, and the other inhibits coat color
- Does not follow mendelian principle
Polygenetic Inheritance
- Additive effect of two or more genes on a single phenotype
- Ex: 180 genes affect height, skin color
Similarities and Difference between CAM and C4
- Both incorporate CO2 into organic intermediates before it enters the Calvin cycle
- C4: separates the initial steps of carbon fixation from the Calvin cycle
- CAM pathway: steps occur in the same cell, but are separated in time
Mendel’s Laws
- Alleles of genes account for variations in inherited characters
- For each character, an organism inherits two alleles, one from each parent
- If two alleles at locus differ, dominant determines appearance, recessive has no effect
- Law of Segregation
