Respiration Flashcards
Need for respiration?
Transport substances across membranes
E.g active raw port of sodium potassium pump in cell membranes
Anabolic reactions
E.g synthesis of DNA from nucleotides
Sysnthesis of proteins from amino acids
Movement
E.g Cellular movement of chromosomes via spindle
Contraction of muscles
Maintain body temp
What is respiration?
Release energy from breakdown of organic molecules
- involves transfer of chemical potential energy from nutrient molecules into a USABLE ENERGY form that can be used for work within organism
Glucose + oxygen —> CO2 + H2O + energy
Function/structure of mitochondrion?
Function: Site of aerobic respiration in eukaryotic cells - synthesis ATP
Structure: Rod-shaped organelles , 0.5 -1.0 µm diameter
2 phospholipid membranes:
OUTER membrane is SMOOTH/PERMEABLE
INNER membrane is folded (cristae), less permeable, site of ETC , location of ATP synthase enzymes
Inter membrane space : low pH due to high conc of protons
Matrix: aqueous solution within inner membranes of mitochondrion - contain ribosomes, enzymes, circular mitochondrial DNA
How does mitochondrial structure help its function?
Large SA due to cristae —> allows membrane to hold many ETC proteins / ATP synthase enzymes —> MORE ATP PRODUCED
- more cell types can have larger mitochondria with longer/tightly packed cristae enabling synthesis of more ATP
No. Mitochondria each cell has varies depending on cell activity - muscle cells with have many
What is aerobic respiration and the 4 stages?
Process of breaking down a respiratory substrate (e.g glucose) to produce ATP using oxygen
- GLYCOLYSIS (phosphorylation/splitting of glucose) - cytoplasm
- LINK REACTION (decarboxylation/dehydrogenation of pyruvate)- matrix of mitochondria
- KREBS CYCLE (cyclical pathway with enzyme controlled reactions)- matrix of mitochondria
- OXIDATIVE PHOSPHORYLATION (production of ATP through oxidation of hydrogen atoms)- inner membrane of mitochondria
Stage 1: glycolysis ?
PHOSPHORYLATION: glucose (6C) phorphorylated by 2 ATP forming FRUCTOSE BISPHOSPHATE (6C)
Glucose + 2ATP → Fructose bisphosphate
LYSIS: fructose bisphosphate (6C) split into 2 molecule of TRIOSE PHOSPHATE (3C)
OXIDATION: hydrogen removed from each TP and transferred to con enzyme NAD to form 2 reduced NAD
4H + 2NAD → 2NADH + 2H+
DEPHOSPHORYLATION: phosphates transferred from intermediate substrate molecules to from 4ATP through substrate-level phosphorylation
4Pi + 4ADP → 4ATP
PYRUVATE PRODUCED
2 Triose phosphate → 2 Pyruvate
Products of glycolysis?
2 pyruvate molecules - goes to Link reaction
Net gain 2 ATP (4 made, 2 used at start)
2 NADH - goes to oxidative phosphorylation resction
Stage 2: link reaction?
When O2 available, pyruvate move across double membrane of mitochondria into matrix via active transport - REQUIRES TRANSPORT PROTEIN/ATP
Pyruvate OXIDISED by enzymes —> ACETATE and CO2 (require reduction of NAD TO NADH + H+)
In Combination with COENZYME A —> ACETYL COENZYME A (acetyl CoA)
(2)pyruvate + (2)NAD + (2)CoA → (2)acetyl CoA + (2)carbon dioxide + (2)reduced NAD
REACTION OCCURS TWICE AS 2 PYRUVATE MOLECULES MADE PER GLUCOSE IN GLYCOLYSIS
Role of CoA?
Coenzymes are molecules that help enzymes carry out its function, but not used in reaction itself
CoA consists of a NUCLEOSIDE (ribose and adenine) and a vitamin
CoA binds to remainder of pyruvate molecule to from acetyl CoA - supplies acetyl group to KREBS cycle
How many pyruvate molecules made per glucose molecule in glycolysis?
2
Stage 3: KREBS Cycle?
Consists of series of enzyme controlled reactions
1. Acetyl CoA (2C) enter circular pathway from link reaction in glucose metabolism
(if acetyl CoA formed from fatty acids/amino acids , enters KREBS cycle from other metabolic pathway)
2. 4C oxaloacetate accepts 2C acetyl fragment from acetyl CoA —> 6C citrate (Coenzyme A released/reused in link reaction)
3. Citrate converted back to oxaloacetate through series of redox reactions
REACTION OCCURS TWICE AS 2 PYRUVATE MOLECULES MADE PER GLUCOSE IN GLYCOLYSIS
How is oxaloacetate regenerated in KREBS cycle?
Series of redox reactions:
DECARBOXYLATION of citrate - release 2CO2
OXIDATION (dehydrogenation) of citrate - release H atoms that reduce coenzymes NAD and FAD
8H + 3NAD + FAD → 3NADH + 3H+ + FADH2
SUBSTRATE LEVEL PHOSPHORYLATION:phosphate transferred from an intermediate to ADP —> 1 ATP
REACTION OCCURS TWICE AS 2 PYRUVATE MOLECULES MADE PER GLUCOSE IN GLYCOLYSIS
Products per glucose molecule:
6NADH , 2FADH2 , 2ATP, 4CO2
Role of coenzymes NAD and FAD?
HYDROGEN CARRIERS in aerobic respiration
NAD /FAD are reduced when GAIN HYDROGEN
Oxidised when LOSE HYDROGEN
They transfer hydrogen atoms from different stages of respiration to ETC on inner mitochondrial membrane
How are hydrogen ions and electrons important in ETC to synthesis ATP?
Electrons from reduced NAD (NADH) and reduced FAD (FADH2) given to electron transport chain
Hydrogen ions from NADH and FADH2 are released too.
ETC drives movement of hydrogen ions( PROTONS) across inner mitochondrial membrane —> INTERMEMBRANE space - create PROTONS GRAD
Movement of hydrogen ions down proton grad into mitochondrial matrix , gives energy required for ATP synthesis
Source of NADH AND FADH2 ?
NADH : 2 from glycolysis
2 from link reaction
6 from KREBS cycle
FADH2: 2 from KREBS cycle
