2.8 Cell Respiration

Question 1

what is cell respiration?

Answer 1

the controlled release of energy from organic compounds to produce ATP

Question 2

what are the 2 main types of cell respiration? (2)

Answer 2

• anaerobic respiration -> the partial breakdown of glucose in the cytosol for a small yield of ATP
• aerobic respiration -> utilises oxygen to completely breakdown glucose for a larger ATP yield

Question 3

what is ATP (adenosine triphosphate)?

Answer 3

high energy molecules that functions as an immediate source of power for cell processes

Question 4

what are the properties of ATP? (3)

Answer 4

• 1 molecule of ATP contains 3 covalently linked phosphate groups (which store potential energy in their bonds)
• when ATP is hydrolysed (to from ADP+Pi) the energy stored in the phosphate bond is released to be used by the cell
• cell respiration uses energy stored in organic molecules to regenerate ATP from ADP+Pi (via oxidation)

Question 5

what do both aerobic and anaerobic respiration pathway being with?

Answer 5

the anaerobic breakdown of glucose in the cytosol by glycolysis

Question 6

what occurs in glycolysis? (3)

Answer 6

glycolysis breaks down glucose (6C) into 2 molecules of pyruvate (3C)
- produces H carries (NADH) from an oxidised (NAD+)
- a small yield of ATP (net gain of 2 molecules)

Question 7

what is anaerobic respiration?

Answer 7

anaerobic respiration proceeds in the absence of oxygen and does not result in the production of any further ATP molecules

Question 8

what is pyruvate converted to in animals and plants&yeasts? (2)

Answer 8

animals - converted into lactic acid (lactate)
plants&yeasts - pyruvate is converted into ethanol and carbon dioxide

Question 9

what is the purpose of anaerobic respiration?

Answer 9

to restore stock of NAD+ via anaerobic pathways, the organism can continue to produce ATP via glycolysis

Question 10

what is the conversion of pyruvate into lactic acid or ethanol?

Answer 10

• reversible
  so, pyruvate can be restored once oxygen is present and a greater yield of ATP can be produced aerobically

Question 11

why does exercising at high intensity result in anaerobic respiration and the production of ATP?(3)

Answer 11

• muscle contraction requires the expenditure of high amounts of energy and require high levels of ATP
• the cells’ energy demands will exceed what the available levels of O2 can supply aerobically
• so, body begins breaking down glucose anaerobically to maximise ATP production

Question 12

what will exercising at high intensity result in?

Answer 12

increase in the production of lactic acids
- leads to muscle fatigue

Question 13

what is the effect of exercise intensity on carbohydrate consumption?

Answer 13

• at high intensities, the aerobic consumption of fats decreases while the anaerobic consumption of sugars increases
• so, lactate levels increase at higher levels of exercise intensity

Question 14

where does aerobic cell respiration take place?

Answer 14

in the mitochondrion
- requires presence of oxygen

Question 15

what is the process of aerobic respiration? (3)

Answer 15

• pyruvate is broken down into carbon dioxide and water and a large amount of ATP is produced (-34-36 mols)
• aerobic respiration typically begins with glycolysis in carbohydrates, glycolysis is an anaerobic process
• aerobic respiration consists of the link reaction, Krebs cycles and the electron transport chain

Question 16

what does fermentation result in for yeasts?

Answer 16

the production of ethanol and carbon dioxide

Question 17

what can fermentation be used for? (2)

Answer 17

bread - carbon dioxide causes bread to rise (ethanol evaporated during baking)
alcohol - ethanol intoxicating agent

Question 18

what else can undergo fermentation to produce yoghurt and cheese and what does it produce? (2)

Answer 18

bacterial cultures
- lactic acid (anaerobically) which modified milk protein

Question 19

what does a respirometer do?

Answer 19

a device to measure an organisms respiration rate by measuring the rate of exchange of O2 and CO2

Question 20

what different wats can you use a respirometer? (4)

Answer 20

The living specimen is enclosed in a sealed container

Carbon dioxide production can be measured with a data logger or by pH changes if the specimens is immersed in water

when an alkali is included to absorb CO2, oxygen consumption can be measured as a change in pressure within the system
- the pressure change can be detected with a data logger/ via use of a U-tube manometer

Question 21

what are factors which can affect respiration? (5)

Answer 21

• temperature, hydration, light, age and activity levels

Question 22

what do increases in CO2 levels and O2 levels show?

Answer 22

• increase in CO2 levels indicate an increase in respiration
• decrease in O2 levels indicate an increase in respiration