paper 1: Surface Area to Volume Ratio and Gas Exchange

Question 1

give some examples of materials that need to be interchanged between an organism and its environment

Answer 1

• respiratory gases
• heat
• nutrients
• excretory products

Question 2

what is the relationship between the size of an organism and the surface area volume ratio

Answer 2

the larger the organism the smaller the surface area: volume

Question 3

by what process does a single celled organism get everything it needs from its environment

Answer 3

diffusion

Question 4

why do larger animals have an advantage when they need to keep warm

Answer 4

they have a small surface area to volume ration so they lose heat at a slower rate

Question 5

how do you calculate the rate of diffusion

Answer 5

rate of diffusion = surface area X difference in concentration
______________________________
diffusion distance

Question 6

what makes a good exchange surface

Answer 6

• large surface area
• large concentration gradient
• short diffusion distnace

Question 7

why might a logarithmic scale be used to plot body mass of different organisms

Answer 7

dur to a large range of results a logarithmic scale is needed to fit the values of the graph axis

Question 8

label each part of a mammalian respiratory system

Answer 8

Question 9

define ventilation

Answer 9

a sequence of breathing movements that move gases to and from the internal gas exchange surface

Question 10

describe the mechanisms of inhaling

Answer 10

• external intercostal and diaphragm muscles contract
• ribcage moves up and out
• diaphragm flattens
• thoracic volume increases
• lung pressure decreases to below atmospheric pressure
• air flows in from a higher pressure to the lower pressure down a pressure gradient

Question 11

describe the mechanisms of forced exhalation

Answer 11

• diaphragm muscles relax and the internal intercostal muscles contract
• ribcage move in and down
• diaphragm domes
• the thoracic volume decreases
• lung pressure increases above atmospheric pressure
• air flows out from higher pressure to the lower pressure down a pressure gradient

Question 12

what pathway does the oxygen take from the air to get into the blood stream

Answer 12

mouth, trachea, bronchus, bronchioles, alveoli

Question 13

how are mammalian lungs adapted for efficient gas exchange

Answer 13

short diffusion distance:
- alveolar epithelium is only one cell thick
- alveolar epithelial cells squamous
- lung capillary endothelium is one cell thick

large concentration gradient:
- ventilation constantly brings in air rich in oxygen into the alveoli and removes air low in oxygen
- blood capillaries carry oxygenated blood away from the alveoli and bring deoxygenated blood to the alveoli all the time

increased surface area:
- millions of alveoli in each lung
- each alveolus is highly folded
- many capillaries surrounding the alveoli

Question 14

define tidal volume

Answer 14

volume of air in each breath

Question 15

define ventilation rate

Answer 15

the number of breaths per minute

Question 16

define forced expiratory volume

Answer 16

the maximum volume of air that can be breather out in one second

Question 17

define forced vital capacity

Answer 17

maximum volume of air it is possible to breathe forcefully out of the lungs after a deep breath

Question 18

what is active tuberculosis and how does it effect lung function

Answer 18

• holes and cavities in lung tissue
• reduced surface area of gas exchange surface

- reduced surface area of gas exchange surface

Question 19

what is fibrosis and how do it effect lung function

Answer 19

• scar tissue deposited in lung epithelium
• less elastic lung tissue & increases thicknss of gas exchange surface

Question 20

what is asthma and how does it effect lung function

Answer 20

• bronchioles narrow and mucus is secreted
• less air entry & increases thickness of gas exchange surface

Question 21

what is emphysema and how does it effect lung function

Answer 21

• alveoli walls break down and elastic tissue is lost
• • reduced surface area of gas exchange surface & less elastic lung tissue

Question 22

describe the flow of water over a fish’s gills

Answer 22

• mouth opens and operculum shuts
• mouth volume increases and pressure decreases
• water moves in down a pressure gradient
• mouth closes and operculum opens
• volume in mouth decreases and pressure increases
• water forced out over the gills down a pressure gradient

Question 23

draw and label the structure of a fish’s gas exchange system

Answer 23

Question 24

how are fish adapted for efficient gas exchange

Answer 24

Large Surface Area
- many lamellae, increases the rate of diffusion
Short Diffusion Distance
- thin epithelium/ distance between water and blood so short diffusion pathway
Concentration Gradient
- water and blood flow in opposite directions (this maintains a concentration gradient along the whole gill so equilibrium is not reached
- water always has a higher concentration of oxygen than blood
- blood flow removes blood high in oxygen and replaces it with blood low in oxygen to maintain concentration gradient

Question 25

what does ficks law state

Answer 25

diffusion rate is proportional to (surface area x difference in con.) / diffusion distance

Question 26

whta makes a good exchange surface

Answer 26

- large surface area - large concentration gradients - short diffusion distance

Question 27

how is a concentration gradient maitained in the leaf of a xerophyte during the aytime for CO2

Answer 27

- high rate of photosynthesis in the day - mesophyll cells use CO2 so CO2 diffuses into the cells down a concentration gradient from the air spaces - this lowers the CO2 concentration in the air spaces - CO2 diffuses into the leaf through the stomata down a conc grad.

Question 28

what are xerophytes

Answer 28

plants that live in a dry climate which have adapted to reduce water loss

Question 29

explain the adaptations of xerophytic plants

Answer 29

- leaves are spines/ needles: reduces the SA:V ratio - thick waxy, waterproof cuticle: less evaporation from leaf surface and increased diffusion pathway - rolled lead and leaf hairs: traps water vapour which reduces the water potential gradient outisde and inside the leaf - stomata sunk in pits : traps water vapour so water potential gradient is decreased

Question 30

what is a dicotlyedonous leaf

Answer 30

a flowering plant

Question 31

label the sturtcure of a dicotyledonous leaf

Answer 31

Question 32

how do gases enter an leave the leaf

Answer 32

through stomata

Question 33

how do guard cells contol water loss

Answer 33

by opening and closing the stomata

Question 34

what is the word equation for photosynthesis

Answer 34

carbon dioxide + water -> glucose + oxygen

Question 35

write the word equation for aerobic respiration

Answer 35

glucose + oxygen -> carbon dioxide + water

Question 36

what deatures do insects have to reduce water loss

Answer 36

- Some have a small surface area to volume ratio - They have a waterproof cuticle covering their body - They close their spiracles

Question 37

draw and label the structure of an insects respiratory system

Answer 37

Question 38

Describe how a diffusion gradient of oxygen is formed in the tracheal system.

Answer 38

- Cells aerobically respire using oxygen, which reduces the concentration of oxygen at the muscle tissue. - Oxygen diffuses from a high concentration in the tracheae to low at the muscle tissue. - This lowers the oxygen concentration in the tracheae so oxygen diffuses into the tracheae from outside the insect via the spiracles.

Question 39

how are insects adapted for effcient gas exchange

Answer 39

- many tracheoles for a large surface area - highly branched tracheoles so short diffusion pathway - tracheoles have thin walls - short diffusion pathway - large inseacts move thier body to move gases in and out ( removes air low in O2 to inrease the oxygen conc. grad.)

Question 40

why is water present in the ends of tracheoles at rest

Answer 40

there is a higher water potential in the tissue cells rather than in the tracheoles so water moves into tracheoles by osmosis

Question 41

when the insect is active, explain why the wtaer moves into the muscle cells and how does this increase the rate of gas exchange

Answer 41

1. insect is acitve and carries out a higher rate of respiration 2. muscle cells produce lactic acid 3. lactic acid makes water potential i muscle cells lower than in tracheoles 4. water moves out the tracheole and into muscle cells by osmosis 5. less water in the tracheole so larger surface area for gas exchange and faster diffusion through the air to the gas exchange surface