Biology by Bradford
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The subtopic in the middle and twelve tasks round it: label five diagrams, complete two tables, put a process in order and fill 65 gaps. Every standard level statement has a box; the seven boxes for higher level only are dashed and badged HL, and drop off for an SL class. Type into the blanks and check them, or print it on A4, Letter or A3 with an answer key.
of ATP to ADP and phosphate releases energy; joining ADP and phosphate back into ATP energy. The energy released powers across membranes, the synthesis of macromolecules, or , and movement, of whole cells or of parts such as .
Number the steps in order.
Net yield per glucose: ATP and reduced NAD. Each step is catalysed by a different .
Glycolysis needs a supply of NAD. With no oxygen, pyruvate takes the hydrogen from reduced NAD and becomes , the NAD so glycolysis can continue, with a net yield of ATP per glucose. Yeast uses the same pathway, except that pyruvate becomes and CO₂. uses the first; baking uses the gas, which makes dough rise.
Reduced NAD from glycolysis, the link reaction and the Krebs cycle hands a pair of to the first carrier; the energy released as they pass along the chain pumps protons across the membrane. At the end of the chain they are taken up by , together with protons, forming . Protons flow back down their gradient through a channel enzyme that phosphorylates ADP: .
Oxidation is the loss of . Removing hydrogen, with its electron, from a substrate is called , so it oxidises the substrate. NAD accepts the hydrogen and is . Oxidation and reduction always happen together, in reactions.
Removing CO₂ from a molecule is ; removing hydrogen is , a kind of oxidation. Each turn of the cycle includes oxidations, which reduce hydrogen carriers such as NAD, and makes one ATP.
| Lipid | Carbohydrate | |
|---|---|---|
| Energy per gram | lower | |
| Oxygen atoms per carbon | more | |
| Respired without oxygen? | yes | |
| Broken down first by | splitting fatty acids into 2C | , then the link reaction |
123ATP, adenosine , is a . It suits its job as the cell's energy currency: it is in water, so it moves easily round the cell, it is stable until an enzyme hydrolyses it, and each molecule releases a small, usable amount of energy.
Cell respiration releases energy from carbon compounds, step by step, to make . Glucose and are the main substrates, though many other organic compounds can be used, and it goes on in every living cell. Gas exchange is a different process: the of O₂ into the organism and CO₂ out across an exchange , such as the alveoli.
| Aerobic | Anaerobic, in humans | |
|---|---|---|
| Substrates | glucose, fatty acids and others | only |
| Mitochondria needed? | yes | |
| ATP per glucose | about 30 | |
| Word equation | glucose + oxygen → + | glucose → |
Both start in the .
As the organisms respire, the CO₂ they give out is absorbed, so the oxygen they take in is not replaced and the gas volume . If the reading moves 18 mm in 6 minutes, the rate is mm min⁻¹. changes the rate, so the tube should stand in a water bath.
ATP, adenosine triphosphate, is a nucleotide. It suits its job as the cell's energy currency: it is soluble in water, so it moves easily round the cell, it is stable until an enzyme hydrolyses it, and each molecule releases a small, usable amount of energy.
Hydrolysis of ATP to ADP and phosphate releases energy; joining ADP and phosphate back into ATP needs energy. The energy released powers active transport across membranes, the synthesis of macromolecules, or anabolism, and movement, of whole cells or of parts such as chromosomes.
Cell respiration releases energy from carbon compounds, step by step, to make ATP. Glucose and fatty acids are the main substrates, though many other organic compounds can be used, and it goes on in every living cell. Gas exchange is a different process: the diffusion of O₂ into the organism and CO₂ out across an exchange surface, such as the alveoli.
| Aerobic | Anaerobic, in humans | |
|---|---|---|
| Substrates | glucose, fatty acids and others | carbohydrate only |
| Mitochondria needed? | yes | no |
| ATP per glucose | about 30 | 2 |
| Word equation | glucose + oxygen → CO₂ + water | glucose → lactate |
Both start in the cytoplasm.
As the organisms respire, the CO₂ they give out is absorbed, so the oxygen they take in is not replaced and the gas volume falls. If the reading moves 18 mm in 6 minutes, the rate is 3 mm min⁻¹. Temperature changes the rate, so the tube should stand in a water bath.
Oxidation is the loss of electrons. Removing hydrogen, with its electron, from a substrate is called dehydrogenation, so it oxidises the substrate. NAD accepts the hydrogen and is reduced. Oxidation and reduction always happen together, in redox reactions.
Net yield per glucose: two ATP and two reduced NAD. Each step is catalysed by a different enzyme.
Glycolysis needs a supply of NAD. With no oxygen, pyruvate takes the hydrogen from reduced NAD and becomes lactate, regenerating the NAD so glycolysis can continue, with a net yield of two ATP per glucose. Yeast uses the same pathway, except that pyruvate becomes ethanol and CO₂. Brewing uses the first; baking uses the gas, which makes dough rise.
Removing CO₂ from a molecule is decarboxylation; removing hydrogen is dehydrogenation, a kind of oxidation. Each turn of the cycle includes four oxidations, which reduce hydrogen carriers such as NAD, and makes one ATP.
Reduced NAD from glycolysis, the link reaction and the Krebs cycle hands a pair of electrons to the first carrier; the energy released as they pass along the chain pumps protons across the membrane. At the end of the chain they are taken up by oxygen, together with protons, forming water. Protons flow back down their gradient through a channel enzyme that phosphorylates ADP: chemiosmosis.
| Lipid | Carbohydrate | |
|---|---|---|
| Energy per gram | higher | lower |
| Oxygen atoms per carbon | fewer | more |
| Respired without oxygen? | no | yes |
| Broken down first by | splitting fatty acids into 2C acetyl groups | glycolysis, then the link reaction |