3.1 exchange surfaces and breathing

Question 1

what do cells need to survive

Answer 1

supply of oxygen
nutrients
remove waste products so they don’t build up and become toxic

Question 2

what does and doesn’t need a specialised exchange system

Answer 2

small organisms don’t need one because their cytoplasm is close to the environment so diffusion is sufficient

large organisms need one because they have multiple layers of tissues so diffusion is not sufficient

Question 3

what factors affect the need for a exchange system

Answer 3

size
surface area to volume ratio
level of activity

Question 4

how does size affect the need for a transport system

Answer 4

small organisms cytoplasm is close to the environment so diffusion is sufficient

multicellular organisms have multiple layers of cells so the diffusion pathway is too long and too slow for supply to the inner cells

Question 5

how does surface area to volume ratio affect the need for a transport system

Answer 5

small organisms have large SA/V ratio- SA is larger than V so diffusion is sufficient
Large organisms have small SA/V ratio- SA not sufficient for diffusion

Some organisms can adopt shapes to increase SA
Animals can’t bc they have a range of tissues and larger volume

Question 6

how does level of activity affect the need for a exchange system

Answer 6

metabolic energy uses energy from food and oxygen
cells of active organisms need a good supply of O2 and nutrients for movement
energy is also needed to keep warm
some organisms are more active than others

Question 7

what makes a good exchange surface

Answer 7

large surface area- space for molecules to pass thru
thin barrier- decrease diffusion distance
good blood supply- steep conc. gradient, diffusion fast

Question 8

what is gas exchange like in animals

Answer 8

lungs and airways carry air in and out

AIR- NOSE-TRACHEA-BRONCHI-BRONCHIOLE-LUNGS
gas exchange takes place at alveoli (tiny air filled sacs)
lungs are protected by rubs and ribcage
intercostal muscles and diaphragm help produce breathing movements

Question 9

how does gas exchange happen in the lungs

Answer 9

gas passes by diffusion through thin walls of alveoli
O2 passes from alveoli to blood in capillaries
CO2 passes from blood to air in alveoli
lungs maintain steep conc. gradient to continue diffusion

Question 10

why are lungs a good exchange surface

Answer 10

surface area- alveoli is small but lots of them (high SA)

permeability- plasma membrane of alveolus and capillaries allow diffusion

Thin barrier- alveolus and capillary are 1 cell thick, squamous cells

Blood supply- blood system transports CO2 from tissues to lungs (CO2 in blood diffuses into alveoli) , blood transports oxygen away from lungs (lower than alveoli so O2 diffuses into blood)

Question 11

Describe mammalian ventilation

Answer 11

breathing ventilates lungs and replaces old air w fresh air
gets rid of CO2 and brings in more O2
Conc of O2 is higher in alveoli than in blood
Conc of CO2 is lower in alveoli than in blood
conc gradient maintained

Question 12

describe airways

Answer 12

large enough for sufficient air flow
supported to prevent collapse when air pressure is low
flexible for movement
goblet cells in epithelium release mucus to trap pathogens

Question 13

describe trachea and bronchi

Answer 13

similar structure but bronchi are smaller
supported by C-shaped rings of cartilage- prevent collapse and allow flexibility and space for food to move down oesophagus

Question 14

describe bronchioles

Answer 14

narrower than bronchi
they have a wall of smooth muscle and elastic fibres
smallest ones end in cluster of alveoli

Question 15

describe alveoli

Answer 15

squamous epithelium
surrounded by blood capillaries
contain elastic fibres which stretch in inspiration and recoil in expiration
alveolus wall is thing

Question 16

describe smooth muscle and elastic tissue

Answer 16

action of smooth muscle constricts the airway as lumen narrows which restricts flow or air
contraction of smooth muscle not voluntary (allergy)
smooth muscle elongated again by elastic fibres
muscle contraction deforms elastic fibres but when it relaxes, they recoil to their original shape and size

Question 17

describe inspiration

Answer 17

diaphragm contracts and moves down and flatter
external intercostal muscles contract and raise ribs
volume of thoracic cavity increases

Question 18

describe expiration

Answer 18

diaphragm relaxes and is pushed up
externcostal muscles relax and ribs fall
volume of thoracic cavity decreases

Question 19

what do you measure lung volume with

Answer 19

spirometer

Question 20

how does a spirometer work

Answer 20

consists of chamber of air floating on a tank of water

CO2 ruch air is passed through the chamber of soda lime which absorbs it- allows measurement of O2 consumption

Question 21

what precautions should you take when using a spirometer

Answer 21

subject is healthy, free of asthma

soda lime fresh

nor air leave in apparatus

mouthpiece sterilised

water chamber not overfilled

Question 22

what direction does the graph on a spirometer go

Answer 22

inspiring- down

expiring- up

Question 23

why does the overall trace of the spirometer graph go down

Answer 23

soda lime absorbs CO2

when breathing we use up the O2 from the tank and the CO2 we breathe out is absorbed by the soda lime

gas volume of tank decreases over experiment by participant

Question 24

explain tidal volume

Answer 24

volume of air that moves in and out of lungs with each resting breath

500cm3 in average adult

15% of vital capacity

Question 25

explain vital capacity

Answer 25

the maximum volume of air that can be moved by the lungs in one breath

Question 26

what factors does vital capacity depend on

Answer 26

size of person
age and gender
level of regular exercise

Question 27

explain residual volume

Answer 27

volume of air that remains in lungs after forced expiration

approximately 1.5dm3

Question 28

what does increased oxygen uptake result from

Answer 28

increased breathing rate

deeper breaths

Question 29

describe fish ventilation

Answer 29

mouth opens (operculum closed)
buccal cavity floor is lowered- increases volume + decreases pressure of buccal cavity
water rushes into mouth down pressure gradient
opercular cavity expands
buccal cavity floor is raised- pressure in buccal cavity higher than opercular cavity
water moves from buccal cavity over gills into opercular cavity
mouth closes and operculum opens
sides of opercular cavity move inwards- increase pressure
water rushes out fish through operculum

Question 30

what is the operculum

Answer 30

bony flag that covers and protects gills

Question 31

define countercurrent flow

Answer 31

where two fluids flow in opposite directions and this maintains a favourable concentration gradient

Question 32

define tracheal system

Answer 32

system of air filled tubes in insects

Question 33

describe ventilation in insects

Answer 33

air enters system via spiracle (external opening)
air is transported into body via tracheae (series of tubes)
tracheae divined into smaller tubes- tracheoles which are open and filled w fluid called tracheal fluid
gaseous exchange happens between air in the tracheole and tracheal fluid

Question 34

how can larger insects also ventilate their tracheal system

Answer 34

movements of the body

Question 35

examples of how insects ventilate through movements of their body

Answer 35

• some have sections of their tracheal system which is expanded and flexible and repetitive expansion and contraction ventilates the system
• movements of the wings alter the volume of the thorax and when it increases the pressure drops so air is pushed in
• some can alter the volume of their abdomen by opening and closing valves in the spiracles which causes air to enter the tracheal system