Adaptations for Gas Exchange C3

Question 1

what happens as a result of a cell increasing in size?

Answer 1

diffusion pathway gets longer
slower diffusion
diffusion will not meet the cell’s needs such as supplying nutrients like oxygen and glucose and removing waste like carbon dioxide

Question 2

define gas exchange

Answer 2

process of oxygen into cells/blood and removing carbon dioxide

Question 3

define ventilation

Answer 3

process of bringing an exchange medium like air or water to and from an exchange surface

Question 4

define respiration

Answer 4

hydrolysis of glucose to form ATP/phosphorylation of ADP

Question 5

what must happen for an organism to become larger?

Answer 5

a number of cells must come together so it becomes multicellular

Question 6

describe 5 factors of unicellular organisms such as amoebas

Answer 6

extremely large surface area to volume ratio
gas exchange occurs across the whole surface
permeable membrane allowing diffusion of gases
specialised gas exchange organs are not needed
diffusion is sufficient to meet the oxygen requirements of the organism

Question 7

describe 5 factors of a flatworm which is a simple multicellular organism

Answer 7

evolved flattened shape to overcome problem of increase in size

this increases SA:V ratio so no cell is far from surface

no specialised gas exchange organs so short diffusion pathway

exchange gases directly with environment by diffusion

diffusion across permeable membrane is sufficient to meet oxygen requirements

Question 8

describe 6 factors of an earthworm which is a simple multicellular organism

Answer 8

developed tubular shape and restricted to damp environments

worms secrete mucus to keep body surface cells moist allowing gases to dissolve and diffuse

elongated shape provides a large SA:V compared with compact organism of similar volume

exchange gases directly with environment by diffusion across moist surface since blood vessels are close to body surface so gases can diffuse in/out of blood, then across cells covering body surface

blood circulates in vessels maintaining conc. gradient for diffusion of oxygen into cells and CO2 out

blood contains respiratory pigment haemoglobin to carry oxygen to body cells

Question 9

why do multicellular organisms require a specialised gas exchange surface? give 8 points

Answer 9

as size of organism increases, SA:V decreases

diffusion across body is insufficient to provide enough oxygen for organism to survive

larger organisms more metabolically active so have higher oxygen demand

diffusion pathway across body surface too large and rate of diffusion too slow

(so larger multicellular organisms need specialised gas exchange surface between organism and external environment)

provided with a large area of gas exchange surfaces to increase surface area for diffusion

need a method of circulation to distribute gases around body

many animals have toughened body surface so have internal gas exchange surfaces e.g. lungs

Question 10

in order to achieve maximum rate of diffusion all respiratory surfaces must be: list 4 things

Answer 10

large surface area to volume ratio
thin
moist
permeable

Question 11

what 2 additional features increase efficiency of gas exchange in organisms which has a circulatory system and respiratory pigment?

Answer 11

extensive blood supply surrounding exchange surface - circulatory system maintains conc. gradient increasing rate of diffusion

respiratory pigments - haemoglobin increases oxygen-carrying capacity of blood

Question 12

why do insects need a good supply of oxygen for respiration?

Answer 12

since they fly which requires a lot of energy

Question 13

why is an insects’ gas exchange system different to other animals?

Answer 13

they don’t use blood to transport gases

Question 14

how does air go into the insect?

Answer 14

it diffuses into the insect through paired holes called spiracles running along each side of the body. these spiracles lead to a system of branched chitin-lined air tubes called trachea

Question 15

the spiracles can open and close like valves. why is this important?

Answer 15

when its open it allows oxygen in for respiration but when closed it is to reduce water loss

Question 16

how do insects ventilate during periods of activity?

Answer 16

at rest, simple diffusion of gases meets the oxygen needs of the insect, during flight movements of the abdomen ventilate the trachea with the aid of air sacs off the trachea

Question 17

describe the gas exchange surface of insects

Answer 17

the trachea branch repeatedly until they end as very fine thin-walled tracheoles. oxygen diffuses directly from the ends of the tracheoles into the cells and carbon dioxide diffuses out of the cells into the tracheoles. the surface of the tracheoles is lined with chitin which keeps the airways open during body movements while allowing some flexibility

Question 18

give 4 advantages of the tracheal system for gas exchange

Answer 18

oxygen is supplied directly to tissues

no respiratory pigment needed

oxygen diffuses faster in air than in blood

spiracles close to reduce water loss

Question 19

what is the disadvantage of the insect tracheal system?

Answer 19

only efficient in smaller organisms and chitin is heavy so it would slow the insect down if it was too large

Question 20

why are the gas exchange organs retained inside the body of all terrestrial organisms?

Answer 20

reduces water loss
reduces heat loss
protection by the ribs or exoskeleton in insects

Question 21

what problems are caused by living in water?

Answer 21

less oxygen in water than air
rate of diffusion lower than water
water is more dense so doesn’t flow as easily

Question 22

what two groups can fish be categorised in?

Answer 22

cartilaginous fish
bony fish

Question 23

describe cartilaginous fish eg sharks in 5 points

Answer 23

skeleton made of cartilage

nearly all live in sea water

5 gill clefts behind head on each side

water taken in the mouth and forced through gill slits when floor of mouth is raised

gas exchange involves parallel flow: blood in capillaries circulates in same direction as water flowing over gills

Question 24

describe bony fish eg herring in five points

Answer 24

have internal skeleton made of bone

gills covered with a flap called operculum

live in freshwater and seawater

gas exchange involves counter-current flow : blood in gill capillaries circulates in opposite direction as water flowing over gills

usually 4 gills on each side

Question 25

how does water flow into, through and out of the fish?

Answer 25

water taken in through mouth, passes over gills and expelled via operculum movement of buccal cavity floor and operculum allow one-way current of water to flow through gills for gas exchange

Question 26

describe the structure of the gills of bony fish in 4 points

Answer 26

along each gill arch there are many thin filaments on these are the gill lamellae therefore gill filaments have a large SA for gas exchange blood circulates through gill lamellae into capillaries and CO2 diffuses out into water

Question 27

describe how countercurrent works

Answer 27

water always meets blood with a higher oxygen concentration gradient for diffusion of oxygen into blood from water is maintained over the whole length of gill lamellae oxygen diffuses into blood across the whole length of gill lamellae counter-current flow more efficient than parallel flow as it results in higher blood oxygen saturation level

Question 28

describe how parallel flow works

Answer 28

water is taken into the mouth and blood flows through the gill capillaries in the same direction as the water gas exchange is very efficient at first as there is a very high concentration gradient about halfway along the gill lamellae, equilibrium is reached and diffusion of oxygen and carbon dioxide is no longer possible

Question 29

describe briefly the gas exchange in amphibian larvae

Answer 29

the larvae live in water so have gills for gas exchange the adult amphibians are terrestrial so live on land

Question 30

describe briefly the gas exchange in adult amphibians

Answer 30

when inactive, diffusion happens across their moist skin when active, it happens across lungs

Question 31

describe the lung structure of an amphibian

Answer 31

lungs have a simple structure with little folding of the gas exchange tissues

Question 32

give the names of structures in the human breathing system give 14

Answer 32

larynx, cartilage, tracheae, left lung, bronchus, heart, diaphragm, alveoli, pleural membranes, ribs, pleural cavity, inner intercostal muscles, outer intercostal muscles, bronchiole

Question 33

why do rings of cartilage support the trachea, bronchi and bronchioles?

Answer 33

prevents them from collapsing during inspiration when the pressure is low

Question 34

what is the name of the airtight compartment of the body that encloses the lungs?

Answer 34

thorax

Question 35

what is the role of goblet cells?

Answer 35

produce and secrete mucus to trap microorganisms, cilia will then waft to move the mucus up and out of the trachea.

Question 36

why is there pleural fluid in the pleural cavity?

Answer 36

lubrication prevents friction with other organs helps lungs to stick with thorax and expand with it

Question 37

what is in each bronchiole?

Answer 37

hundreds of alveoli providing a large surface area to volume ratio

Question 38

describe briefly about alveolus

Answer 38

each alveolus lined with thin film of water to allow gases to dissolve and diffuse lined with lung surfactant which prevents watery lining from creating surface tension

Question 39

describe what happens to the alveoli due to emphysema lung tissue disease

Answer 39

alveoli air sacs broken down drastically reduced gas exchange surface area, reducing surface area to volume ratio scarring thickens the walls of the alveoli reducing the efficiency of diffusion.

Question 40

describe the ventilation of the human lungs during inspiration and expiration

Answer 40

inspiration: external intercostal muscles and ribs contracts and moves out and up outer pleural membrane moves out and up with the ribcage inner pleural membrane moves out and up with the outer pleural membrane as the pressure in the pleural cavity decreases thorax increases in volume diaphragm contracts (flattens) alveoli increase in volume and lungs pulled out pressure in alveoli decreases below atmospheric pressure expiration: external intercostal muscles and ribs relaxes and moves in and down outer pleural membrane moves in and down inner pleural membrane moves in and down thorax decreases in volume diaphragm relaxes (dome shape) alveoli decrease in volume and lungs move in pressure in alveoli increases above atmospheric pressure

Question 41

describe the pressure changes during inspiration in 4 points

Answer 41

diaphragm flattens and rib cage expands pulling on outer pleural membrane, which lowers pressure in pleural cavity inner pleural membrane pulls on lungs which increases volume of lungs/alveoli this decreases pressure in alveoli pressure in alveoli is below atmospheric pressure so air moves in

Question 42

what changes would you expect to see during strenuous exercise?

Answer 42

greater/faster pressure and volume changes faster (inspiration/expiration/)breathing

Question 43

why is the alveoli suitable as a gas exchange surface? (Give 5 points)

Answer 43

large SA:V ratio due to many alveoli moist short diffusion distance due to extensive capillary network walls of alveoli and capillaries are one cell thick maintained conc. gradient - circulation of blood/ventilation of air

Question 44

describe what is surfactant

Answer 44

a chemical substance covering the surface of alveoli, reduces surface tension, prevents alveoli from sticking together and collapsing when breathing out

Question 45

why is the cellular demand for oxygen in a mammal higher compared to a fish the same size?

Answer 45

mammals are warm-blooded and have to maintain their body temp.

Question 46

list 12 structures in the breathing system and their function

Answer 46

external intercostal muscles - when these contract, the ribs are pulled up and out increasing the volume of the thorax bronchioles - bronchi branch into these smaller tubes larynx - box-shaped structure above trachea containing vocal cords alveoli - main site of gas exchange bronchi - trachea splits into 2 of these surfactant - prevents alveoli from sticking together and collapsing, reduces surface tension trachea - tube held open by rings of C-shaped cartilage ribs - bones moved by intercostal muscles and alter the size of the thorax diaphragm - dome-shaped muscle relaxes and contracts altering the volume of the thorax pleural cavity - contains pleural fluid which acts as a lubricant to reduce friction between lungs and inside wall of thorax during ventilation epiglottis - flap of skin that stops food entering the trachea when swallowing pleural fluid - acts as a lubricant providing friction-free movement against the inner wall of the thorax

Question 47

out of all organisms studied, which need haemoglobin?

Answer 47

mammal, amphibian, earthworm, fish

Question 48

where is the ventilation in the fish?

Answer 48

buccal floor movements

Question 49

which organism has water as their respiratory medium?

Answer 49

amoeba, flatworm, fish , amphibian (air also)

Question 50

what are the 4 adaptations of leaves to gas exchange?

Answer 50

flat/thin air spaces in spongy mesophyll - a lot of cell walls are in contact with air mesophyll walls wet due to transpiration structural pores

Question 51

how do plants respire?

Answer 51

they generate ATP so they respire all the time oxygen is required when light available, plants carry out photosynthesis using chloroplasts, carbon dioxide is required

Question 52

how are plant leaves adapted for photosynthesis? give 7

Answer 52

large surface area to absorb as much light as possible leaves can orientate themselves towards the sunlight leaves are thin to allow light to penetrate lower layers cuticle and epidermis are transparent to allow light to pass through the mesophyll below palisade cells are elongated and densely packed together and contain many chloroplasts chloroplasts can move and rotate within the mesophyll cells to maximise light absorption intercellular air spaces allow carbon dioxide to diffuse into cells and oxygen and water vapour to diffuse away

Question 53

where in the leaf is the stomata found and what is their role?

Answer 53

lower epidermis to allow co2 in

Question 54

how many guard cells surround each stoma?

Answer 54

2

Question 55

what is unusual about guard cells?

Answer 55

they are the only epidermal cells that contain chloroplasts they have unevenly thickened inner cell wall

Question 56

what causes the stomata to open?

Answer 56

light makes K+ ions and water to enter guard cells causing change in shape or potassium pump and entry of water causes stomata to open

Question 57

how does the structure of stomata help it to open/close?

Answer 57

inner cell wall is thick and outer wall is thin so if guard cells become turgid pore opens and if guard cell becomes flaccid pore closes in some plants inner cell wall is thin so ends of guard cells expand and stoma opens

Question 58

describe in detail the mechanism for stomatal opening (give 5 points)

Answer 58

K+ Ions actively transported from epidermal cells into guard cells stored starch, insoluble, in guard cells is converted to malate, soluble, by enzymes in cytoplasm both above processes happen due to ATP water potential in guard cells is lowered so water enters by osmosis guard cells become turgid and curve apart because outer cell walls are thinner than inner cell walls so have more stretch

Question 59

why are stomata open during the day and closed at night?

Answer 59

open - plants need co2 to diffuse into the leaf for photosynthesis close - allows plants to reduce water loss

Question 60

what do chloroplasts provide as a result of photosynthesis?

Answer 60

glucose energy ATP sugar