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