aerobic respiration Flashcards
describe respiration
- a catabolic process involving a series of enzyme-catalysed reactions in cells
- energy-rich substrates are hydrolysed to release energy
- some energy is trapped as chemical energy in ATP and some is released as heat energy
how is ATP produced from respiration?
during respiration, high energy C-C, C-H and C-OH bonds are broken by enzymes in a series of small steps
define aerobic respiration
the release of large quantities of ATP energy from glucose or another organic substrate in the presence of oxygen
- carbon dioxide is produced
define anaerobic respiration
takes place in the absence of oxygen and produces lactate in animal cells and carbon dioxide and ethanol in yeast cells
- produces a small yield of ATP energy
name 3 substrates that can be used to release energy in respiration
- glucose
- amino acids
- fatty acids + glycerol
most of the energy released during respiration is used to synthesise ATP. how is the rest of the energy released?
heat
give similarities and differences between aerobic and anaerobic respiration
SIMILARITIES:
- both produce ATP
- both produce carbon dioxide
DIFFERENCES:
- anaerobic doesn’t require oxygen, aerobic does
- yield of energy lower for anaerobic
what does ATP stand for?
adenosine triphosphate
name 6 roles of ATP
- protein synthesis
- active transport
- secretion/exocytosis
- nerve transmission
- muscle contraction
- DNA replication
describe the formation of ATP
- the enzyme ATP synthase combines ADP (adenine diphosphate) and Pi (inorganic phosphate) in a condensation reaction.
- this requires an input of energy (30.6kJ mole-1) in an ENDERGONIC reaction
what is phosphorylation?
the addition of inorganic phosphate to ADP
describe the hydrolysis of ATP
- the enzyme ATPase hydrolyses the terminal phosphate bond releasing a small packet of energy (30.6kJ mol-1) in an EXERGONIC reaction.
- this forms ADP and Pi
how are the properties, structure and formation of ATP linked to its role in cells?
- the hydrolysis of ATP to ADP releases immediate energy. the hydrolysis of glucose takes much longer and involves many intermediate reactions
- only one enzyme is needed to release energy from ATP, whereas many are needed in the case of glucose
- ATP releases energy in small packets when and where it is needed
- ATP is the universal energy in many reactions in all living organisms
- ATP is easily transported across membranes
what are the stages of respiration?
where do they occur?
- glycolysis - cytoplasm
- link reaction - mitochondrial matrix
- krebs cycle - mitochondrial matrix
- electron transport chain - inner mitochondrial matrix
what is an example of redox reactions in respiration?
- NAD is reduced to form reduced NAD (NAD/H+)
- FAD is reduced to form reduced FAD (FADH2)
define oxidation and reduction
oxidation - loss of electrons / hydrogen
reduction - gain of electrons / hydrogen
describe redox reactions in respiration
hydrogen atoms are removed from intermediate compounds and split into protons and electrons
how does glucose enter the cytoplasm?
- active transport
- facilitated diffusion
in glycolysis, per glucose molecule how much:
- reduced NAD produced?
- gross ATP produced?
- used ATP?
- net total ATP produced?
reduced NAD produced - 2
gross ATP produced - 4
used ATP - 2
net total ATP produced - 2
what is glycolysis?
initial biochemical pathway in both aerobic and anaerobic respiration
describe the process of glycolysis
- glucose is phosphorylated to form hexose phosphate. this requires the addition of 2 ATP molecules
- hexose phosphate splits into two triose phosphate molecules
- each triose phosphate molecule is oxidised to pyruvate. this means that hydrogen is removed by a dehydrogenase enzyme in a dehydrogenation reaction. the hydrogen is accepted by NAD forming reduced NAD
- the production of pyruvate from triose phosphate also results in the phosphorylation of 2 ADP molecules to produce 2 ATP - this is substrate level phosphorylation
glycolysis results in a small yield of chemical energy in the form of ATP. What other form of energy is also released?
heat / thermal energy
why is pyruvate provided as a respiratory substance for mitochondria and not glucose?
glucose can only be hydrolysed in the cytoplasm during glycolysis.
- pyruvate can enter by facilitated diffusion into the mitochondria for the link reaction
describe the link reaction
in the presence of oxygen, pyruvate diffuses from the cytoplasm into the mitochondrial matrix where the link reaction takes place:
- pyruvate is decarboxylated by a decarboxylase enzyme which removes one molecule of CO2.
- pyruvate is also oxidised to acetate : dehydrogenase enzymes remove hydrogen which is accepted by NAD to form reduced NAD ; acetate is produced
- acetate combines with coenzyme A to form acetyl coenzyme A which enters krebs cycle
overall in the link reaction, 2 molecules of CO2, 2 molecules of reduced NAD and 2 molecules of acetyl coenzyme A are produced per glucose molecule