Respiration Flashcards
What is the function of mitochondria?
- site of aerobic respiration in eukaryotic cells
-
synthesises ATP during oxidative phosphorylation
- relies on membrane proteins: make up electron transport chain + ATP synthase enzyme
What is the structure of mitochondria?
- 2 phospholipid membranes
- outer: smooth + permeable to some small molecules
- inner: folded cristae, less permeable + site of electron transport chain + ATP synthase (used in oxidative phosphorylation)
- intermembrane space = low pH bc of high conc. of protons
- conc gradient across inner membrane formed during oxidative phosphorylation = needed for ATP synthesis
-
matrix = (aq) solution within inner membrane
- contains ribosomes, enzymes + circular mitochondrial DNA
What is the relationship between the structure + function of mitochondria?
- large SA of inner membrane due to cristae: enables membrane to hold many electron transport chain proteins + ATP synthase enzymes
- more active cells may have larger mitochondria w longer + more tightly packed cristae = larger SA so synthesises more ATP
What does work in a living organism require?
- energy
- usable carbon compounds
What are the diff. types of essential work within organisms?
- transporting substances across membranes: active transport in cell membranes + exocytosis
- anabolic reactions: synthesising DNA from nucleotides + protein from AAs
- movement: movement of chromosomes via spindles + muscle contraction
- maintaining body T°C: in mammals + birds only
What is the primary source of energy for most organisms?
- the sun
How do reactions of photosynthesis store energy in organic molecules?
- light energy transformed into chemical potential energy to synthesis carbs.
- used to synthesis ATP or are combined + modified to form usable organic molecules: essential for all metabolic processes in plant
What does respiration involve?
- releasing energy from breakdown of organic molecules
- the transfer of chemical potential energy from nutrient molecules into usable energy used for work in an organism
What is the equation for respiration?
- glucose + oxygen —-> carbon dioxide + water + energy
- C6H12O6 + 6O2 —-> 6CO2 + 6H2O +2870kJ
What are autotrophs + heterotrophs?
- autotrophs: organisms able to synthesis their own usable carbon compounds from CO2 in atmo. through photosynthesis
- heterotrophs: require pre-made supply of usable carbon compounds from food
What is aerobic respiration?
- process of breaking down a respiratory substrate ( mainly glucose) in order to produce ATP using oxygen
What are the 4 stages of aerobic respiration + where does each stage occur?
- glycolysis: cell cytoplasm
- link reaction: matrix of mitochondria
- Krebs cycle: matrix of mitochondria
- oxidative phosphorylation: inner membrane of mitochondria
What is glycolysis?
- phosphorylation + splitting of glucose in 1st stage of respiration
Describe the stages of glycolysis.
- phosphorylation: glucose made more reactive by adding 2 Pi molecules, from hydrolysis of 2 ATP molecules to ADP, to form glucose phosphate (6C)
- which is split into 2 triose phosphate molecules (3C)
- oxidation: H+ is removed from each molecule + transferred to NAD (coenzyme) to form 2 reduced NAD/NADH
- enzyme controlled reactions convert each oxidised triose phosphate into pyruvate (3C) which regenerates 2 ATP molecules from ADP
What products are formed from glycolysis?
- 2 ATP (net gain)
- 2 reduced NAD
- 2 pyruvate (3C)
How does pyruvate + reduced NAD/NADH enter matrix of the mitochondria from cytoplasm?
- moves across double membrane of mitochondria via active transport
- requires a transport protein + small amount of ATP
What does the link reaction do?
- links glycolysis to the Krebs cycle
Describe the stages of the link reaction.
- pyruvate (made in glycolysis) is oxidised (loses an electron [H+]) by enzymes to acetate + CO2 in which NAD picks up the H+ to form reduced NAD
- acetate combines w coenzyme A to produce acetyl coenzyme A (acetyl CoA)
What is a coenzyme?
- biological molecule that binds to an enzymes active site to help enzymes catalyse reactions
- not an enzyme
What products are formed from the link reaction?
-
1 glucose molecule produces 2 pyruvate molecules which each produce:
- 1 acetyl coenzyme A
- 1 CO2
- 1 reduced NAD
What is the Krebs cycle?
- 2nd stage of respiration consisting of a series of enzyme-controlled reactions
Describe the stages of the Krebs cycle.
- acetyl coenzyme A (produced from link reaction) reacts w a 4-carbon molecule, releasing coenzyme A (can be reused in link reaction), + forming a 6-carbon molecule
- a series of redox reactions causes the 6C molecule to regenerate into a 4C molecule by losing 2 CO2 molecules [decarboxylation] + H+ (used to reduce coenzymes NAD [3] + FAD [1])
- 1 ATP molecule is also formed due to substrate-linked phosphorylation
What products are formed from the Krebs cycle?
-
1 glucose molecule produces 2 acetyl CoA which each produce:
- 3 reduced NAD
- 1 reduced FAD
- 1 ATP
- 2 CO2
What are the 2 coenzymes involved in aerobic respiration?
- NAD
- FAD
What is the role of the coenzymes NAD + FAD in aerobic respiration?
- to transfer H atoms (H+ + e-) from diff stages of respiration to electron transport chain, on cristae, where coenzymes lose H atoms (oxidised)
How many reduced NAD + FAD are produced, during glycolysis - Krebs cycle, from 1 glucose molecule?
- NADH = 10
- FADH = 2
What is the current model for oxidative phosphorylation?
- chemiosmotic theory
Describe the stages of oxidative phosphorylation.
- NADH + FADH, produced from glycolysis to Krebs cycle, releases H+ + e- (oxidised)
- energy, produced from e- passed along ETC, allows H+ ions to move from matrix into intermembrane space, creating a conc. gradient
- H+ move down conc gradient, by facilitated diffusion, through ATP synthase back into matrix
- produces energy for phosphorylation of ADP into ATP by ATP synthesis
- O2 combines w e- at end of ETC, + H+ passed through ATP synthase, to produce water
What products are formed from oxidative phosphorylation?
- 1 glucose molecule produces:
- 30-32 ATP
- 6 H2O
Why is oxygen so important for aerobic respiration?
- O2 acts as the final e- acceptor
- w/o O2 the ETC can’t continue bc e- have nowhere to go
- so reduced coenzymes, NADH + FADH2 can’t be oxidised to regenerate NAD + FAD, so can’t transport more H2 from link reaction + Krebs cycle
What is anaerobic respiration + where does it occur?
- respiration in the absence of O2
- occurs in cytoplasm
How is energy released during anaerobic respiration?
- pyruvate, produced in glycolysis, is reduced to form ethanol + CO2 in plants, or lactate in animals, by gaining the H+ from NADH
- this oxidises NAD, so it can be reused in glycolysis, so small amounts of ATP is still produced
How is ethanol produced by anaerobic respiration?
- pyruvate, produced from glycolysis, loses a CO2 molecule (decarboxylated) to form ethanal
- which is reduced (gains a H+ from NADH) to ethanol by alcohol dehydrogenase
How is lactate produced by anaerobic respiration?
- pyruvate, produced from glycolysis, is reduced (gains a H+ from NADH) to lactate by lactate dehydrogenase
- it can then be oxidised back to pyruvate (to be used in Krebs cycle) or converted into glycogen for storage in liver
