Energy in cells - Respiration and Gas Exchange

Question 1

what is aerobic respiration?

Answer 1

aerobic respiration is the chemical reaction in cells that uses oxygen to break down nutrient molecules to release energy.

Question 2

what is the word equation for aerobic respiration?

Answer 2

oxygen + glucose —> carbon dioxide + water

Question 3

what is the symbol equation for aerobic respiration?

Answer 3

C6H12O6 + 6O2 —-> 6CO2 + 6H2O

Question 4

which releases more energy and why- aerobic or anaerobic respiration?

Answer 4

aerobic respiration, because it completely oxidises the glucose. in anaerobic respiration, the glucose isn’t completely broken down, so less ATP is produced.

Question 5

what is oxidisation?

Answer 5

when something chemically combines with oxygen.

Question 6

how do animals get glucose?

Answer 6

by breaking down the food they eat.

Question 7

how do humans get glucose?

Answer 7

humans get glucose through foods like carbohydrates.

Question 8

how do plants get glucose?

Answer 8

through the process of photosynthesis.

Question 9

what are the uses of energy?

Answer 9

transporting molecules, contraction of muscle cells, producing movement, maintaining body temperature(suitable for enzyme activity), cell division and chemical reactions (building large molecules from smaller molecules, such as protein).

Question 10

what is anaerobic respiration?

Answer 10

anaerobic respiration is the chemical reaction in cells that breaks down nutrient molecules to release energy without using oxygen.

Question 11

what is an advantage of anaerobic respiration?

Answer 11

it allows cells to obtain a small amount of usable energy even when oxygen supply is limited.

Question 12

what is the word equation for anaerobic respiration in plants and fungi?

Answer 12

glucose —-> ethanol + carbon dioxide

Question 13

how is anaerobic respiration in plants and fungi used in food production?

Answer 13

the equation ‘glucose —-> ethanol + carbon dioxide’ is used to make bread/alcohol with yeast. in these processes, glucose is provided and yeast is kept in low oxygen conditions for anaerobic respiration.

Question 14

what is the word equation for anaerobic respiration in animals?

Answer 14

glucose —-> lactic acid

Question 15

when and how does anaerobic respiration occur in animals/humans?

Answer 15

anaerobic respiration occurs in muscle cells when there is a shortage of oxygen. for example, during intensive exercise, if muscles are overworked, a lot of energy is needed, more energy that can be provided through aerobic respiration. the glycogen stored in muscle cells are broken down into glucose, which is then respired anaerobically which provides an additional energy supply. lactic acid then builds up, causing cramps, which diffuses from the muscles into the blood.

Question 16

how is lactic acid harmful and how is it disposed of and what does that result in?

Answer 16

lactic acid is toxic in high concentrations, so when it is released into your blood in anaerobic respiration, it needs to be oxidised with oxygen debt (the volume of oxygen needed to oxidise lactic acid). this is why we keep breathing heavily after exercise- to supply the extra oxygen needed to dispose of the lactic acid in our bodies.

Question 17

what happens to the rate of respiration when yeast is kept at different temperatures?

Answer 17

as the yeast is kept at a heated temperature, the bubbles in the water increase and increase, but then the enzyme denatures after the optimum temperature is reached. this is due to the kinetic energy increasing which means that more successful collisions will occur between the enzyme and substrate, which would fasten the rate of respiration. however, if the temperature is too high, it would denature the enzyme due to the active site changing shape, the rate of respiration has rapidly decreased. this is because the enzyme can not longer attach with the substrate.

Question 18

what can you do to check the presence of carbon dioxide?

Answer 18

hydrogen carbonate indicator (red to yellow) or limewater (colourless to cloudy)

Question 19

what is cellular respiration?

Answer 19

an exothermic reaction that is continuously occurring in living cells.

Question 20

how can we investigate the production of carbon dioxide and heat from respiration?

Answer 20

as the peas start to grow, they respire, releasing heat. the thermos flask is insulated, so heat isn’t transferred into the surroundings and we can measure a change in temperature. we can only see a temperature rise in the flask with the alive peas, as the peas in the other flask are dead (boiled). in both thermos flasks, the peas were soaked in milton solution (bleach). this is to kill any bacteria, which is also alive, which means that it would also respire, which would affect the results.

Question 21

what is diffusion?

Answer 21

diffusion is the net random movement of particles from an area of high concentration to an area of lower concentration.

Question 22

what are the four main factors which affect the role of diffusion?

Answer 22

• temperature
• concentration
• distance
• surface-area: volume

Question 23

how does temperature affect diffusion?

Answer 23

at higher temperatures, molecules have more kinetic energy and so can diffuse faster.

Question 24

how does the concentration gradient affect diffusion?

Answer 24

if it is a v.large difference in concentration between two areas, molecules will diffuse from a higher to lower concentration quicker.

Question 25

how does the distance affect diffusion?

Answer 25

diffusion takes longer if the molecules have to travel further.

Question 26

how does surface area: volume affect diffusion?

Answer 26

a larger surface area speeds up the rate of diffusion as there are more opportunities for the molecules to move. sa:v is more significant, as the two oppose each other: an efficient exchange surface has a surface area which is v.large compared to the distance the molecules must travel. sa:v is increased when structures are small.

Question 27

what is ventilation?

Answer 27

ventilation is the process of moving air into and out of the lungs (inhalation + exhalation). moving air relies on differences in air pressure between the lungs and the atmosphere.

Question 28

what happens in inhalation?

Answer 28

1. diaphragm contracts, moving down and flattening.
2. intercostal muscles contract, moving the ribcage up + out
3. the volume of the thorax increases
4. air pressure decreases
5. air pressure in the thorax is now less than atmospheric pressure, causing air to move into the lungs.

Question 29

what happens in exhalation?

Answer 29

1. diaphragm relaxes, moving up and doming.
2. intercostal muscles relax , moving the ribcage down + in.
3. the volume of the thorax decreases
4. air pressure increases
5. air pressure in the thorax is now more than atmospheric pressure, causing air to move out of the lungs.

Question 30

where is the gas exchange system located?

Answer 30

in the thorax, the upper part of the body.

Question 31

describe the structure of the breathing system.

Answer 31

• air passes down the trachea (windpipe). this tube is surrounded by c-shaped rings of cartilage, which keep the trachea open but make swallowing easier.
• the trachea splits to form the 2 bronchi- these tubes lead to the lungs. the bronchi divide or branch into smaller and smaller tubes called bronchioles, which carry air deep into the thorax.
• at the end of each bronchiole, there are microscopic air sacks- the alveoli. these are the sites of gas exchange.
• the lungs are surrounded by the pleural membrane- this forms a double layer between the lungs + the thorax walls.
• in between the membranes, there is a thin layer of pleural fluid. together, they form an airtight seal + prevent the lungs from sticking to the thorax wall as they inflate and deflate.
• the ribs help to protect the organs in the thorax. intercostal muscles between the ribs help to connect the bones and are important in moving air into and out of the lungs.
• below the lungs, separating the organs of the thorax and the abdomen, is the diaphragm. this domed sheet of muscle + fibrous tissue is also important in moving air into and out the lungs.

Question 32

explain the process of gas exchange.

Answer 32

in the alveoli, oxygen diffuses from air into red blood cells, where it binds with haemoglobin for transport. carbon dioxide, dissolved in the plasma, diffuses from blood into the alveolus. air leaving the lungs has about 4% less oxygen, and 4% more carbon dioxide, than the air that entered the lungs. there are an enormous number of alveoli in the lungs, giving a total surface are of 60m^2. this large sa increases the rate of diffusion. each alveolus is surrounded by a network of capillaries which constantly carry deoxygenated blood to the alveolus and oxygenated blood away. this maintains a high concentration gradient. the walls of the alveoli are 1cell thick and the capillary walls immediately next to the alveoli are also one cell thick. this means that gases only need to move a v.small distance, speeding up diffusion.

Question 33

what is an experiment for the composition of inhaled and exhaled air?

Answer 33

this investigation compares the content of inhaled and exhaled air , using a T-tube arrangement going from a mouthpiece into two conical flasks or boiling tubes. the inhaled and exhaled air bubbles through the indicator as the student breathes in and out. you could use limewater (colourless to cloudy) or hydrogen carbonate (red to yellow)indicator to compare the inhaled and exhaled air.

Question 34

what is an investigation to measure the effect of exercise on breathing rate?

Answer 34

You can easily compare breathing rates before and after exercise by watching and counting the number
of breaths someone takes in 1 minute (or 30 seconds) at rest. Then ask your subject to exercise (e.g.
jogging on the spot for 5 minutes) – count the number of breaths they take in the first minute after
exercise.

Question 35

why does our breathing rate increase during exercise?

Answer 35

During exercise our breathing rate increases, as well as the depth of each breath. This is in response to
the increased concentration of carbon dioxide in the blood.
Because our breathing rate increases, we excrete carbon dioxide more rapidly. Oxygen can also diffuse
into the blood at a faster rate (as there is a higher concentration gradient). This, along with an increase
in heart rate, supplies more oxygen to the muscles for aerobic respiration. As we learnt in the
respiration topic, our muscles may respire anaerobically during exercise. If this happens our breathing
rate will remain high after exercise, supplying the extra oxygen needed to oxidise the lactic acid.

Question 36

how do unicellular organisms rely on diffusion for the movement of substances in and out of the cell?

Answer 36

gas exchange- single celled organisms, such as amoeba, can exchange gases sufficiently by simple diffusion through the cell membrane

Question 37

what happens in lung disease?

Answer 37

due to your airways narrowing/blocking, the flow of air in and out of your lungs decreases. When that happens, less oxygen gets into your body tissues, and it becomes harder to get rid of the waste gas carbon dioxide. As the disease gets worse, shortness of breath makes it harder to remain active.