knowledge organisers unit3 Flashcards
What is respiration
A catabolic, enzyme-controlled
reaction occurs inside cells to
provide energy.
What is the excess energy in respiration used for
to phosphorylate ADP to
form ATP or is released as heat
energy.
Why does the link reaction and kerbs cycle happen twice for each molecule of glucose
because each molecule of glucose leads to the formation of two triose phosphate in glycolysis
Net yield of ATP from substrate level phosphorylation (for one molecule of glucose)
2 from glycolysis, 2 from Kreb’s
How many reduced NAD from glycolysis
2 reduces NAD, releasing 6 ATP
How many reduced NAD from link reaction
2 reduced NAD, releasing 6 ATP
How many reduced NAD from krebs cycle
6 reduced NAD, releasing 18 ATP
How many reduced FAD from kerb’s cycle
2 reduced FAD, releasing 4 ATP
How does respiration work?
- Energy rich respiratory substrates e.g. glucose or fatty acids broken to release energy.
- high energy bonds are broken and lower energy bonds formed.
- excess energy released is used to phosphorylate ADP to form ATP or is released as heat energy
Glycolysis in cytoplasm
- Glucose is phosphorylated using 2ATP into hexose phosphate.
- The hexose phosphate splits into two triose phosphate molecules.
- The oxidation of these 2 triose phosphate molecules yield 2 ATP each by substrate level phosphorylation. Overall glycolysis
has a net gain of 2ATP. Dehydrogenation releases 2 Hydrogen that are picked up by NAD. The 2 pyruvate diffuse into the mitochondria.
Link reaction in mitochondrial matrix
- Oxidative decarboxylation of pyruvate catalysed by decarboxylase releases carbon dioxide.
- Dehydrogenation catalysed by
dehydrogenase releases pairs of hydrogen atoms converting NAD to reduced NAD. - The addition of coenzyme A forms acetyl CoA (2C) which enters the Krebs cycle.
Krebs cycle in mitochondrial matrix
- The acetate from acetyl CoA combines with a 4C compound to form a 6C compound.
- Decarboxylation forms a 5C compound and dehydrogenation occurs reducing NAD.
- Decarboxylation forms a 4C compound and dehydrogenation to reduce NAD. There is also substrate level phosphorylation
giving 1 ATP. - Dehydrogenation forming reduced FAD.
- Dehydrogenation forming reduced NAD.
Electron transport chain on inner mitochondrial membrane
- Reduced NAD and reduced FAD, from glycolysis, link and Kreb’s reactions, deliver pairs of hydrogen atoms to the ETC.
- They are oxidised, delivering protons (H+) and high-energy electrons (e–) to proton pumps on the inner mitochondrial membrane.
- Each reduced NAD utilises all 3 proton pumps, releasing 3ATP. Each reduced FAD utilises only 2 proton pumps, releasing 2 ATP.
- Oxygen is the final acceptor in the electron transfer chain and is reduced to water.
What are the respiratory substrates
Glucose, lipids, proteins
How are lipids used in aerobic respiration
- Glycerol is converted into triose phosphate for use in glycolysis.
- Fatty acids are split into 2C acetate fragments which feed into the Krebs cycle as acetyl CoA
How are proteins used in aerobic respiration
Amino acids are deaminated in the liver into ammonia and keto acids, one of which (pyruvate) is used in the link reaction while the others are fed into the Krebs cycle as
intermediates
How does anaerobic respiration occur in the absence of oxygen
Without oxygen to act as the final electron acceptor, biochemical reactions inside the mitochondria grind to a halt as any reduced NAD and FAD cannot be re-oxidised to pick up more hydrogen.
How does a mechanism in glycolysis allow reduced NAD to transfer hydrogen to pyruvate
Allows NAD to accept hydrogen
from glucose. Glycolysis can proceed giving a net yield of 2 ATP for each glucose entering the reaction.
Aerobic respiration in animals and bacteria
- Glycolysis occurs. Triose phosphate is converted to pyruvate with the release of ATP and reduction of NAD.
- Reduced NAD reduces the pyruvate, forming lactate.
- The oxidised NAD can again be reduced during glycolysis. The cycle continues.
Aerobic respiration in plants and fungi
- Glycolysis occurs.
- Triose phosphate is converted to pyruvate with the release of ATP and reduction of NAD.
- Pyruvate is decarboxylated, releasing carbon dioxide and forming ethanal.
- Reduced NAD reduces the ethanal, forming ethanol.
- The oxidised NAD can again be reduced during glycolysis. The cycle continues
ATP produced from substrate level phosphorylation in anaerobic respiration (per molecule of glucose) IN GLYCOLYSIS
2
ATP produced from substrate level phosphorylation in anaerobic respiration (per molecule of glucose) IN LINK REACTION
0
ATP produced from substrate level phosphorylation in anaerobic respiration (per molecule of glucose) IN KREBS CYCLE
2
Reduced NAD produced in anaerobic (per molecules of glucose. 3 ATP each) IN GLYCOLYSIS
2
Reduced NAD produced in anaerobic (per molecules of glucose. 3 ATP each) IN LINK REACTION
2
Reduced NAD produced in anaerobic (per molecules of glucose. 3 ATP each) IN KREBS CYCLE
6
Reduced FAD produced in anaerobic (per molecules of glucose. 2 ATP each) IN GLYCOLYSIS
0
Reduced FAD produced in anaerobic (per molecules of glucose. 2 ATP each) IN LINK REACTION
0
Reduced FAD produced in anaerobic (per molecules of glucose. 2 ATP each) IN KREBS CYCLE
2
ATP from oxidative phosphorylation of reduced coenzymes NAD or FAD in anaerobic (per molecule of glucose) IN GLYCOLYSIS
6
ATP from oxidative phosphorylation of reduced coenzymes NAD or FAD in anaerobic (per molecule of glucose) IN LINK REACTION
6
ATP from oxidative phosphorylation of reduced coenzymes NAD or FAD in anaerobic (per molecule of glucose) IN KREBS CYCLE
22
Total yield of ATP in aerobic conditions
8 from glycolysis, 6 from link reaction, 24 from krebs. 38 TOTAL
Total yield of ATP in anaerobic conditions
2 TOTAL (from glycolysis only)
Why is the maximum yield of aerobic respiration of 38 ATP rarely achieved?
Because of losses. Some protons can leak through the inner mitochondrial membrane without passing through ATP synthetase. Transport of reactants such as ADP, Pi and pyruvate into the mitochondria can have an energy cost.
What happens to the energy not used to synthesis ATP
Released as heat energy
Why is the permeability of the tubule of collecting duct under hormonal control
To control the volume of water lost in urine.
What does ADH (anti diuretic hormone) do
Controls the permeability of the collecting duct to water. When it’s more permeable, more water is reabsorbed to the blood and less water is excreted as urine
What happens when blood water potential is lower than the set point
Osmoreceptors in the hypothalamus detect the change
ADH process steps
- osmoreceptors in hypothalamus detect when blood water potential lower than set point.
- posterior pituitary gland releases ADH to bloodstream.
- ADH attach to receptors on cells on collecting duct. Aquaporins fuse with membrane of the cells next to the lumen.
- Water moves into cells by osmosis then passes into bloodstream: raising water potential of blood.
- Low volume of concentrated urine produced.
- production of ADH decreases as w.p of the blood increases. Lead to less permeable membrane so loose less water and large volume of dilute urine.
What is negative feedback
The detection of a change away from normal conditions and consequent processes to move conditions back towards normal.
What treatments are available if the kidneys fail
- dialysis to remove urea from the blood.
- kidney transplant.
- medication used to control K+ and Ca2+ levels to help balance fluids.
- low protein diet reduces number of excess amino acids and urea made.
- drugs to lower blood pressure.
How are dialysis machines adapted to be effective
- temp of 40°C to increase rate of diffusion and for patient body temp.
- dialysis tubing is semipermeable membrane to allow only small molecules e.g urea, water and salt through.
- counter current flow of blood and fluid to maintain a conc gradient
What is deforestation
removal of trees to use as timber or fuel or to repurpose the land use for agriculture or building
Consequence of deforestation on the soil
Soil erosion - no longer protected from rain by the canopy; as roots decompose, they no longer hold the soil together so it is eroded by wind and rain.
Consequence of deforestation (flooding…)
Evaporation from soil removes less water than transpiration, waterlogging encourages denitrification and soil
loses nitrates
Consequence of habitat loss
Reduces biodiversity
Consequence of deforestation due to less trees
Less photosynthesis so less CO2 removed from atmosphere. Leads to global warming and climate change
Solution of deforestation
- selective felling.
- protecting areas.
- replanting the correct mix of species, the correct distance apart, and allowing them to regenerate.
What is overfishing
where fish are caught at a higher rate than they reproduce and grow. This occurs to the point where increased fishing efforts lead to declining catches.
Consequences of overfishing
- populations may be reduced in size to the extent that they lose genetic diversity.
- size of fish caught reduced as they have no time to grow.
- population has fewer individuals and can’t replace harvested fish.
Solutions to overfishing
- Quotas = maximum mass of fish that can be harvested; heavy fines imposed for exceeding quotas.
- Restricted fishing seasons, particularly to allow fish to reproduce.
- Exclusion zones preventing fishing in certain areas.
- Increased mesh sizes allows smaller fish to escape and grow to breeding size.
- limiting the size of fishing fleets so that not as many fish can be caught
What is fish farming
where fish are intensively reared in ponds/tanks or nets; sea-fish are usually reared in large netted areas of the sea. This is one solution to overfishing
positives of fish farming
- Less fish need to be harvested from the wild, allowing fish stocks to replenish.
- Fish have been selected for high growth rates and therefore large size and increased yield.
Consequences of fish farming
- Excess fish food, egesta and excreta fall out of the nets and
can cause eutrophication in the marine habitats. - Parasites and diseases spread quickly through the overcrowded fish.
- Prophylactic antibiotic use may lead to antibiotic resistance and using pesticides to control parasites will harm marine
invertebrates. - If farmed fish escape they could outcompete wild fish or interbreed with them, passing on the alleles for fast growth, pushing wild fish to extinction – some farmed fish have been engineered to be triploid to avoid this issue.
- The feed is often made from harvested wild fish
What is extinction
The total loss of a species
What are endangered species
Species at the risk of becoming extinct because there are few breeding pairs left
Reasons for extinction
- natural selection.
- habitat destruction e.g. deforestation.
- hunting and collecting.
- competition from domestic animals
- pollutions e.g PCBs can cause female dog whelks to grow false penises and become infertile.
