respiration 5.7 Flashcards
the need for cellular respiration
- cells need a supply of ATP molecules to act as an immediate source of energy such as
- active transport
-maintaining resting potential in neurones
-muscle contraction
-cell division and growth - metabolic reactions e.g. catabolic and metabolic reactions
the structure of the mitochondrion
-outer membrane = compartmentalisation
- inner membrane folds into cristae = increases surface area for oxidative phosphorylation
-inner membrane= contains proteins for electron transport chain
- intermembrane space= between the two membranes
-matrix(liquid that fills the mitochondria) = contains mitochondrial DNA + enzymes for link + Krebs cycle
the process and site of glycolysis
- occurs in the cytoplasm
- glucose is phosphorylated by adding 2 phosphates from ATP. therefore 2ATP’S become ADP
- hexose bisphosphate is created
-hexose bisphosphate is split into two molecules of triose phosphate - triosephosphate is oxidised forming two molecules of pyruvate
- NAD collects the hydrogen ions forming 2 reduced NAD
- 4 molecules of ADP collected the phosphate groups from the triosephosphates (2 each) forming ATP via substrate level phosphorylation
- overall there is a net gain of 2 ATP molecules
the link reacton and its site in the cell
- pyruvate is decarboxylated (one carbon atom is removed in the form of CO2)
- NAD is reduced to NADH collecting hydrogen from pyruvate into acetate.
- acetate is combined with coenzyme A (CoA) to form acetyl coenzyme A
- no ATP is produced in this reaction
- takes place in the matrix of the mitochondria
- each glucose molecule produces 2 pyruvate molecules therefore link reaction + Krebs cycle happen twice for each glucose molecule
krebs cycle
-acetyl group from acetyl CoA produced in the link reaction combines with oxaloacetate to form citrate
- Coenzyme A goes back to the link reaction
- 6C citrate molecule is converted to a 5C molecule during decarboxylation where C02 is removed. dehydrogenation also occurs the hydrogen is used to produce reduced NAD
-the 5C molecule is converted to a 4C molecule (oxaloacetate)
- decarboxylation and dehydrogenation occur producing one molecule of reduced FAD, 2 reduced NAD and 1 ATP. from substrate-level phosphorylation
- occurs in the matrix
-produced 2 molecules of ATP
oxidative phosphorylation
- Hydrogen atoms are released from reduced NAD and FAD . so they are oxidised to their original form.
- the H atoms split into H ions (H+) and electrons (e-)
- the electrons move along the electron transport chains loosing energy at each carrier which is located in the inner membrane folded into cristae to maximise respiration
- energy is used by the electron carrier to pump H+ ions from the matrix into the intermembrane space (active transport)
- concentration of H+ is higher in the intermembrane space than matrix forming a electrochemical gradient
-H+ moves across the electrochemical gradient back into the matrix via ATP synapse (chemiosmosis) . causes ATP synapse to spin producing ATP - in the mitochondrial matrix at the end. H+, electrons and o2 from the blood combine to form water.
- oxygen is said to be the final acceptor
the importance of coenzymes in cellular
respiration
NAD and FAD accept hydrogen and are consequently reduced. The now reduced NAD and FAD carry electrons to the electron transport chain for oxidative phosphorylation and also carry hydrogen ions for chemiosmosis.
two types of anaerobic respiration
lactate fermentation and alcoholic fermentation
lactate fermentation
- reduced NAD from glycolysis transfers hydrogen to pyruvate to form lactase and NAD.
- NAD can then be reused in glycolysis
-occurs in mammals
ethanol fermentation
- occurs in fungi and plants
-pyruvate is decarboxylased to form ethanal
-reduced NAD transfers hydrogen to ethanal to form ethanol and NAD. - NAD can then be reused in glycolysis
respiratory substrates
- Lipids have the highest energy value, followed by proteins and carbohydrates
- more hydrogen atoms= more ATP can produced. as oxidative phosphorylation where most ATP is produced requires H atoms from reduced NAD and FAD.
- lipids= can be hydrolysed to glycerol and fatty acids. glycerol = can be converted to triose phosphate and be respire
- fatty acids= long chain hydrocarbons. hydrogens can be used as a source of hydrogens for oxidative phosphorylation
- carbohydrates= can be hydrolysed for glucose
-proteins= can be hydrolysed to amino acids which can be converted to pyruvate or acetate to enter the Krebs cycles
respiratory quotient
- useful because it tells you which kind of respiratory substrate an organisms is respiring and what type of respiration
= volume of C02 released/ volume of 02 consumed - high RQs greater than 1 means organisms are respiring anaerobically as they are short of oxygen
-carbohydrates= 1
Proteins = around 0.9
-lipids around 0.7
Why would mitochondria appear different in a microscopy image
- they have been cut along different planes
