Respiration Flashcards
1
Q
What is the function of mitochondria?
A
- site of aerobic respiration in eukaryotic cells
-
synthesises ATP during oxidative phosphorylation
- relies on membrane proteins: make up electron transport chain + ATP synthase enzyme
2
Q
What is the structure of mitochondria?
A
- 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
3
Q
What is the relationship between the structure + function of mitochondria?
A
- 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
4
Q
What does work in a living organism require?
A
- energy
- usable carbon compounds
5
Q
What are the diff. types of essential work within organisms?
A
- 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
6
Q
What is the primary source of energy for most organisms?
A
- the sun
7
Q
How do reactions of photosynthesis store energy in organic molecules?
A
- 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
8
Q
What does respiration involve?
A
- 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
9
Q
What is the equation for respiration?
A
- glucose + oxygen —-> carbon dioxide + water + energy
- C6H12O6 + 6O2 —-> 6CO2 + 6H2O +2870kJ
10
Q
What are autotrophs + heterotrophs?
A
- 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
11
Q
What is aerobic respiration?
A
- process of breaking down a respiratory substrate ( mainly glucose) in order to produce ATP using oxygen
12
Q
What are the 4 stages of aerobic respiration + where does each stage occur?
A
- glycolysis: cell cytoplasm
- link reaction: matrix of mitochondria
- Krebs cycle: matrix of mitochondria
- oxidative phosphorylation: inner membrane of mitochondria
13
Q
What is glycolysis?
A
- phosphorylation + splitting of glucose in 1st stage of respiration
14
Q
Describe the stages of glycolysis.
A
- 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
15
Q
What products are formed from glycolysis?
A
- 2 ATP (net gain)
- 2 reduced NAD
- 2 pyruvate (3C)
16
Q
How does pyruvate + reduced NAD/NADH enter matrix of the mitochondria from cytoplasm?
A
- moves across double membrane of mitochondria via active transport
- requires a transport protein + small amount of ATP
17
Q
What does the link reaction do?
A
- links glycolysis to the Krebs cycle
18
Q
Describe the stages of the link reaction.
A
- 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)
19
Q
What is a coenzyme?
A
- biological molecule that binds to an enzymes active site to help enzymes catalyse reactions
- not an enzyme
20
Q
What products are formed from the link reaction?
A
-
1 glucose molecule produces 2 pyruvate molecules which each produce:
- 1 acetyl coenzyme A
- 1 CO2
- 1 reduced NAD
21
Q
What is the Krebs cycle?
A
- 2nd stage of respiration consisting of a series of enzyme-controlled reactions
22
Q
Describe the stages of the Krebs cycle.
A
- 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
23
Q
What products are formed from the Krebs cycle?
A
-
1 glucose molecule produces 2 acetyl CoA which each produce:
- 3 reduced NAD
- 1 reduced FAD
- 1 ATP
- 2 CO2
24
Q
What are the 2 coenzymes involved in aerobic respiration?
A
- NAD
- FAD
25
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)
26
How many **reduced NAD + FAD** are produced, during glycolysis - Krebs cycle, from **1** glucose molecule?
- NADH = **10**
- FADH = **2**
27
What is the current **model** for oxidative phosphorylation?
- chemiosmotic theory
28
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**
29
What products are formed from **oxidative phosphorylation**?
- **1** glucose molecule produces:
- **30-32** ATP
- **6** H2O
30
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
31
What is anaerobic respiration + where does it occur?
- respiration in the absence of O2
- occurs in cytoplasm
32
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
33
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
34
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
