topic 8 exchange and transport

Question 1

why can single celled organisms diffuse directly in/out the cell membrane

Answer 1

large surface area compared to their volume

Question 2

why CAN’T multicellular organisms diffuse directly in and out across the cell membrane

Answer 2

smaller surface area to volume ratio
difficult to exchange enough substances

Question 3

what’s the job of the lungs?

Answer 3

transfer oxygen to the blood and remove waste (carbon dioxide) from it

Question 4

how do the lungs exchange gases

Answer 4

happens in the alveoli
blood arriving at the alveoli has lots of CO2, little O2.
O2 diffuses out of the air in the alveoli (where concentration of O2 is high) and into the blood (where it is low)
CO2 diffuses in the opposite direction to be breathed out.

the membranes are partially permeable.

Question 5

how is the alveoli adapted to exchange gases?

Answer 5

moist lining to dissolve gases

good blood supply to maintain concentration gradient of O2 and CO2

very thin walls - short diffusion distance

Question 6

rate of diffusion depends on three main things. what is it.

Answer 6

distance
concentration difference
surface area

Question 7

what’s fick’s law equation?

Answer 7

rate of diffusion ∝ surface area * concentration difference / thickness of membrane

(∝ means ‘is proportional to’)

Question 8

fick’s law explained

Answer 8

rate of diffusion will DOUBLE if:
surface area or the difference in concentration doubles
OR
if the thickness of the membrane HALVES

Question 9

what is respiration

Answer 9

process of transferring energy from the breakdown of organic compounds (like glucose) into energy

Question 10

aerobic respiration equation

Answer 10

glucose + oxygen -> carbon dioxide + water

C6H12O6 + 6O2 -> 6CO2 + 6H2O

Question 11

what’s anaerobic respiration

Answer 11

respiration with NO OXYGEN

Question 12

anaerobic respiration in humans

Answer 12

less efficient due to less energy being transferred

glucose is only partially broken down, and lactic acid is produced

Question 13

equation for anaerobic respiration in ANIMALS

Answer 13

glucose -> lactic acid

Question 14

anaerobic respiration in PLANTS

Answer 14

plants can respire without oxygen, but they produce ethanol instead of lactic acid

Question 15

word equation for anaerobic respiration in plants

Answer 15

glucose -> ethanol + carbon dioxide

Question 16

red blood cells are also known as

Answer 16

erythrocytes

Question 17

adaptions of a red blood cell

Answer 17

biconcave disc shape to give a large surface area for absorbing oxygen
no nucleus for more room to carry oxygen
has haemoglobin to bind to oxygen to release oxygen into cells

Question 18

name two different types of white blood cells

Answer 18

phagocytes and lymphocytes

Question 19

what do phagocytes do

Answer 19

engulf unwelcome microorganisms

Question 20

what do lymphocytes do

Answer 20

produce antibodies against microorganisms

Question 21

adaptations of a white blood cell

Answer 21

can multiply to fight infection off

irregular shape to squeeze out of blood vessels to travel to the infection

lymphocytes have a large nucleus to help them receive signals from the brain

Question 22

what does plasma carry

Answer 22

red blood cells
white blood cells
platelets
urea
carbon dioxide
hormones
proteins
antibodies and antitoxins

Question 23

what are the three types of blood vessels

Answer 23

arteries - away from heart
capillaries - exchange of materials
veins - to heart

Question 24

what are arteries like

Answer 24

thick layers of muscle to make them strong and elastic fibres to allow them to stretch and spring back

the walls are strong and elastic because the blood pumps blood out at a high pressure

Question 25

what are capillaries like

Answer 25

really small

narrow to squeeze into gaps between cells to carry blood really close to every cell to exchange substances

permeable walls so substances can diffuse in and out

take away waste

one cell thick - short diffusion distance

Question 26

what are veins like

Answer 26

lower pressure than arteries so thinner walls

bigger lumen (hole down the middle) to help blood flow despite the lower pressure

valves to keep blood flowing in the right direction

Question 27

how does blood pump through the heart

Answer 27

1. right atrium receives deoxygenated blood from the body through the vena cava.
2. deoxygenated blood moves through to the right ventricle which pumps it to the lungs via the pulmonary artery
3. the left atrium receives oxygenated blood from the lungs through the pulmonary vein
4. oxygenated blood then moves through the left ventricle which pumps it out to the whole body via the aorta

Question 28

what’s cardiac output equation

Answer 28

cardiac output = heart rate x stroke volume

Question 29

cardiac output formula triangle

Answer 29

cardiac output
——————————
heart rate x stroke volume