Exchange and Transport

Question 1

why do single celled organisms not need a transport system

Answer 1

substances can diffuse directly into or out of the cell across the cell surface membrane

Question 2

why is diffusion across the outer membrane slow in multicellular organisms

Answer 2

long diffusion pathway, low surface area to volume ratio
high metabolic rate

Question 3

how do you calculate surface area to volume ratio

Answer 3

surface area/ volume

Question 4

give examples of special features of exchange surfaces and real life examples of where they can be found

Answer 4

large surface area- root hair cells
thin- alveoli
good blood supply- gills

Question 5

draw and label a pair of lungs

Question 6

what is the function of goblet cells and where are they found

Answer 6

line the trachea bronchi and larger bronchioles , secrete mucus which traps microorganisms to prevent them reaching alveoli

Question 7

what is the function of cilia and where are they found

Answer 7

hair-like structures lining the airways
beat mucus secreted by goblet cells no move trapped particles upwards towards the throat where it is swallowed to prevent lung infections

Question 8

what is the function of elastic fibres and where are they found

Answer 8

walls of trachea, bronchi, bronchioles and alveoli
expand when inhaling and recoil to help push air out when exhaling

Question 9

what is the function of smooth muscle in the gas exchange system and where is it found

Answer 9

walls of trachea, bronchi and bronchioles, allows diameter to be controlled (relaxes when exercising to allow more air)

Question 10

where is cartilage found in the gas exchange system and what is its function

Answer 10

rings of cartilage in the walls of the trachea and bronchi provide support, strong but flexible, stops trachea and bronchi collapsing when inhaling and pressure drops

Question 11

describe what happens during inspiration

Answer 11

external intercostal muscles and diaphragm contract
ribcage moves upwards and outwards, diaphragm flattens and volume of thorax increases
lung pressure decreases
air flows into lungs
active process

Question 12

describe what happens during expiration

Answer 12

external intercostal muscles relax and diaphragm relaxes
ribcage moves downwards and inwards
thorax volume decreases, pressure increases
air is forced out of the lungs
passive process unless forced (internal intercostal muscles contract)

Question 13

what is tidal volume

Answer 13

the volume of air in each breath

Question 14

what is vital capacity

Answer 14

max amount of air that can rebreathed in or out

Question 15

what is breathing rate

Answer 15

number of breaths per minute

Question 16

describe the structure of gill filaments

Answer 16

made up of thin plates called gill filaments/primary lamellae
gill filaments are covered in gill plates or secondary lamellae which increase surface area
each gill is supported by a gill arch
gill plates have lots of blood capillaries

Question 17

describe the counter-current system in gills and its benefits

Answer 17

blood flows through gills in one direction and water flows over gills in opposite direction
creates and maintains a steep conc. gradient so as much oxygen as possible diffuses from water into blood

Question 18

Describe the ventilation system in fish

Answer 18

the fish opens its mouth
this lowers the floor of the buccal cavity
volume of buccal cavity increases, decreasing pressure
water is then sucked into cavity
when fish closes its mouth buccal cavity is raised again
volume decreases, pressure increases and water is forced out along gill filaments
each gill is covered by an operculum, increase in pressure force this to open so water can leave gills

Question 19

describe gas exchange in insects

Answer 19

air moves into tracheae through pores called spiracles, oxygen trails down conc. gradient towards cells
CO2 from cells move down conc. gradient towards spiracles to be released
tracheae branch off into smaller tracheoles which have thin permeable walls and contain fluid which oxygen dissolves in and diffuses into the cells
use rhythmic abdominal movements to change volume of their bodies to move air in and out of specials