3A Exchange and Transport Systems (#2)

Question 1

Why do organisms need to exchange materials with their environment?

Answer 1

to take up nutrients and O2
to release waste products of metabolism(urea and CO2)
to maintain a constant body temp (crucial for survival)

Question 2

Exchange rates in single and multi cellular organisms

Answer 2

single-celled - easier and faster due to short diffusion distance
multi-cellular- harder and slower due to larger diffusion distance

Question 3

SA:V and exchange

Answer 3

larger and organism= smaller SA:V= slower rate of diffusion

smaller organism= larger SA:V= faster rate of diffusion

Question 4

Ways to increase SA:V

Answer 4

• folding surface of cell membrane (increase SA)
• developing long, thin, elongated shaped cells
• large vacuoles, push organelles to the sides of the cell for easier diffusion

Question 5

Unicellular Organisms

Answer 5

• large SA:V

- easier exchange of materials

Question 6

Developments in Multicellular organisms for exchange

Answer 6

(provides more efficient way to exchange materials)

• exchange organs -> organs in charge of exchanging substances from outside body to inside
• mass transport system -> transports materials from exchange organs to cells in the body

Question 7

Heat exchange and size

Answer 7

larger organism -> smaller SA:V -> harder to lose heat
smaller organism -> larger SA:V -> easier and quicker heat loss -> need a higher metabolic rate to generate heat and stay warm

Question 8

Heat exchange and shape

Answer 8

compact shape -> smaller SA:V

less compact shape -> larger SA:V -> need a higher metabolic rate to produce heat and maintain body temp

Question 9

Behavioural and Physiological adaptations to facilitate exchange

Answer 9

small desert mammals- high SA:V- lose water easier-> adapted to have smaller kidneys to produce less urine
Elephants- hard to cool in summer-> large ears, stay in water a lot
small mammals in cold regions-> store nuts as energy store for high metabolic rate

Question 10

Gas exchange surface

Answer 10

boundary between outside environment and inside environment of an organism.
have a large SA
thin for a short diffusion pathway
steep concentration gradient across exchange surface

Question 11

Gas exchange in single-celled organisms

Answer 11

(absorb and release materials through cell-surface membrane)
large SA, thin surface meaning a short diffusion distance so oxygen can partake in biochemical reactions as soon as it diffuses in, no need for specialised exchange system

Question 12

Gas exchange in Fish- Gill

Answer 12

gill filaments -> thin plates that increase SA (increasing rate of gas exchange and diffusion) covered in lamellea, increase SA further
gill lamellae-> increase SA more, have blood capillaries and thin surface cells to increase diffusion between water and blood

Question 13

Gas exchange in Fish- Counter-Current System

Answer 13

blood flows through lamellae in one direction and water flows over it in the opposite direction.

• water with a higher O2 concentration always flows by blood with a lower O2 concentration
• maintains a steep concentration gradient across whole length of gill
• oxygen always flows from water to the blood

Question 14

Gas exchange in dicotyledonous plants

Answer 14

Mesophyll adapted for their function as they have a large SA

• found inside the leaf, gases move through stomata on lower epidermis of leaf and into mesophyll
• stomata opens to allow gas exchange and closes to prevent too much water loss, guard cells open and close stomata

Question 15

Gas exchange in insects

Answer 15

air enters the trachea via pores on the surface of insect called spiracles, O2 travels down it’s own concentration gradient towards the cells, trachea branch off into tiny tracheoles that have permeable cells and go into individual cells. Oxygen diffuses directly into respiring cells. CO2 diffuses out and travels down it’s own concentration gradient towards the spiracles and out.
-regular abdominal movements keep the flow of air in and out

Question 16

How insects control water loss

Answer 16

when losing too much water the spiracles are closed by muscles
waterproof waxy cuticle an hairs around the spiracles to reduce evaporation

Question 17

how plants control water loss

Answer 17

stomata are normally open in the day-> water enters guard cells and they become turgid
when plant is dehydrated, water leaves guard cell and it becomes flaccid, closing the stomata

Question 18

Xerophytic adaptations for water loss

Answer 18

• stomata in sunken pits-> traps water vapour, reducing conc gradient between the leaf and the air, reduces evaporation form leaf
• hairs around epidermis -> traps water vapour to reduce conc gradient
• curled leaves with stomata inside to protect from wind
• less stomata so less places for water loss
• thicker waxy waterproof cuticle to reduce evaporation

Question 19

Structure of the Human Gas Exchange System

Answer 19

• air travels down trachea (down pressure gradient)
• trachea splits into two bronchi (bronchus) which go into the lungs
• bronchus branches off into smaller bronchioles which end at air filled sacs called alveoli (where gas exchange takes place)

Question 20

The Intercostal Muscles

Answer 20

Layers of muscle between the ribs, 3 layers - (only need 2) - External Intercostal muscles and Internal intercostal muscles

Question 21

Ventilation- Inspiration

Answer 21

External IM and diaphragm contract. The ribcage moves outwards and upwards and diaphragm flattens

• increases thoracic cavity, decreasing the pressure in the lungs to below atmospheric pressure
• air flows down the pressure gradient down the trachea and into the lungs - active process

Question 22

Ventilation- Expiration

Answer 22

External IM and diaphragm flatten, the ribcage to moves downwards and inwards and diaphragm curves upwards.
-decreases the thoracic cavity and increases the pressure in the lungs to above atmospheric pressure, forcing air out of the lungs (as it moves down the pressure gradient) - passive process

Question 23

Ventilation- Forced Expiration

Answer 23

Internal IM contract and External IM relax, pulling the ribcage further downwards and inwards, reducing the thoracic cavity further - during this time, the opposing movement of the two IMs are Antagonistic (active process - requires energy)

Question 24

Alveoli Structure

Answer 24

• walls of each alveoli is made up of one layer of thin flat epithelial cells called - alveolar epithelium
• the capillaries that cover it have walls made up from capillary endothelium
• alveoli walls have protein elastin in them, helps them to recoil to normal shape after inhaling and exhaling air

Question 25

Movement of O2 and CO2 through GES

Answer 25

air with oxygen moves down trachea, into bronchus of each lung, into bronchioles and to alveoli (down a pressure gradient)
Oxygen diffuses across alveolar epithelium and capillary endothelium into the haemoglobin in the blood (happens down diffusion gradient)
-CO2 travels down it’s own diffusion and pressure gradient in opposite direction to be breathed out

Question 26

Factors affecting rate of diffusion - alveoli

Answer 26

thin exchange surface- alveolar epithelium is only one cell thick meaning short diff pathway (faster diff)
large SA- lots of alveoli, large surface area for gas exchange
-steep conc gradient of O2 and CO2 maintained by constant flow of blood and ventilation

Question 27

Tidal volume

Answer 27

vol of air in each breath (0.4-0.5 dm3)

Question 28

Ventilation rate

Answer 28

amount of breaths per min

Question 29

Forced Expiration Volume (FEV)

Answer 29

max vol of air that can be breathed out in 1 second

Question 30

Forced Vital Capacity (FVC)

Answer 30

max mol of air that can be breathed out after taking in a deep breath

Question 31

Pulmonary Tuberculosis

Answer 31

caused by bacteria, when in the lungs, the Immune system cells detect it and build a wall around it. This forms a hard small lump - tubercle. Infected tissue around the tubercle will die reducing the SA left for gas exchange -> reduces tidal vol, breathe more to take up more air -> increased ventilation rate (can also cause fibrosis- reduces tidal vol further)

Question 32

Fibrosis

Answer 32

formation of scar tissue in the lungs, (can happen due to subs like asbestos and dust). scar tissue is thicker and less elastic, lungs can’t expand as much to hole air-> reduced tidal vol and FVC
reduces rate of gas exchange as is slower over scarred membrane
have an increased ventilation rate to get more air into the lungs and oxygenate blood

Question 33

Asthma

Answer 33

airways become inflamed and irritated ( caused by allergic reactions), smooth lining of the bronchioles contracts and releases a large amount of mucus which constricts the airway -> hard to breathe
FEV reduced severely
can be relieved by drugs (inhalers) that cause bronchioles muscles to relax

Question 34

Emphysema

Answer 34

caused by smoking or long term exposure to air pollution
foregin particles become trapped in the alveoli causing inflammation this attracts phagocytes, they release an enzyme that breaks down elastin in the alveoli -> alveoli can’t recoil to expel air as well (remains trapped in alveoli) leads to destruction of alveoli walls reducing the SA and rate of gas exchange
may have increased ventilation rate

Question 35

Effect of lung disease on Gas exchange

Answer 35

reduces rate of gas exchange, less O2 in bloodstream, cells receive less oxygen and aerobic resp is reduced, less energy released -> may feel tired or weak