Gas exchange

Question 1

Surface area to volume ratio

Answer 1

surface area divided by volume
larger the organism the smaller the ratio

Question 2

factors affecting gas exchange

Answer 2

diffusion distance
surface area
concentration gradient
temperature

Question 3

ventilation

Answer 3

inhaling and exhaling in humans
controlled by diaphragm and antagonistic interaction of internal and external intercostal muscles

Question 4

inspiration

Answer 4

external intercostal muscles contract and internal relax
pushing ribs up and out
diaphragm contracts and flattens
air pressure in lungs drops below atmospheric pressure as lung volume increases
air moves in down pressure gradient

Question 5

passage of gas exchange

Answer 5

mouth/nose > trachea > bronchi > bronchioles > alveoli
crosses alveolar epithelium into capillary endothelium

Question 5

expiration

Answer 5

external intercostal muscles relax and internal contract
pulling ribs down and in
diaphragm relaxes and domes
air pressure increases above atmospheric pressure as long volume decreases
air forced out down pressure gradient

Question 6

alveoli structure

Answer 6

tiny air sacs
highly abundant in each lung
surrounded by the capillary network
epithelium 1 cell thick

Question 7

why do large organisms need specialised exchange surface

Answer 7

they have a small surface area to volume ratio
higher metabolic rate - demands efficient gas exchange
specialised organs

Question 8

fish gill anatomy

Answer 8

fish gills are stacks of gill filaments
each filament is covered with gill lamellae at right angles

Question 9

how fish gas exchange surface provides large surface area

Answer 9

many gill filaments covered in many gill lamellae are positioned at right angles
creates a large surface area for efficient diffusion

Question 10

countercurrent flow

Answer 10

when water flows over gills in opposite direction to flow of blood in capillaries
equilibrium not reached
diffusion gradient maintained across entire length of gill lamellae

Question 11

name 3 structures in tracheal system

Answer 11

involves trachea, tracheoles, spiracles

Question 12

how tracheal system provides large surface area

Answer 12

highly branched tracheoles
large number of tracheoles
filled in ends of tracheoles moves into tissues during exercise

Question 13

Fluid-filled tracheole ends

Answer 13

adaptation to increase movement of gases
when insect flies and muscles respire anaerobically - lactate produced
water potential of cells lowered, so water moves from tracholes to cells by osmosis
gases diffuse faster in air

Question 14

how do insects limit water loss

Answer 14

small surface area to volume ratio
waterproof exoskeleton
spiracles can open and close to reduce water loss
thick waxy cuticle increases diffusion distance so less evaporation

Question 15

gas exchange in plants

Answer 15

palisade mesophyll is site of photosynthesis
oxygen produced and CO2 used created a conc gradient
oxygen diffuses through air spaces in spongy mesophyll and diffuses out stomata

Question 16

role of guard cells

Answer 16

swell - open stomata
shrink - close stomata
at night they shrink, reducing water loss by evaporation

Question 17

xerophytic plants

Answer 17

plants adapted to survive in dry environments with limited water
structural features for efficient gas exchange but limiting water loss

Question 18

adaptations of xerophyte

Answer 18

adaptations to trap moisture to increase humidity - lowers water potential inside plant so less water lost via osmosis
sunken stomata
curled leaves
hair
thick cuticles reduce water loss by evaporation
longer root network

Question 19

digestion

Answer 19

process where large insoluble biological molecules are hydrolysed into smaller soluble molecules
so they can be absorbed across cell membranes

Question 20

locations of carbohydrate digestion

Answer 20

mouth
duodenum
ileum

Question 21

location of protein digestion

Answer 21

stomach
duodenum
ileum

Question 22

endopeptidases

Answer 22

break peptide bonds between amino acids in the middle of the chain
creates more ends for exopeptidases for efficient hydrolysis

Question 23

exopeptidases

Answer 23

break peptide bonds between amino acids at the ends of polymer chain

Question 24

membrane-bound dipeptidases

Answer 24

break peptide bond between 2 amino acids

Question 25

digestion of lipids

Answer 25

digestion by lipase
emulsified by bile salts
lipases produced in liver and stored in the gall bladder

Question 26

lipase

Answer 26

produced in pancreas
breaks ester bonds in triglycerides to form
monoglycerides
glycerol
fatty acids

Question 27

role of bile salts

Answer 27

emulsify lipids to form tiny droplets and micelles
increases surface area for lipase action - faster hydrolysis

Question 28

micelles

Answer 28

water soluble vesicles formed from fatty acids, glycerol, monoglycerides and bile salts

Question 29

lipid absorption

Answer 29

micelles deliver fatty acids, glycerol and monoglycerides to epithelial cells of ileum for absorption
cross via simple diffusion as lipid-soluble and non-polar

Question 30

lipid modification

Answer 30

Smooth ER reforms monoglycerides/fatty acids into triglycerides
golgi apparatus combines triglycerides with proteins to form vesicles called chylomicrons

Question 31

how do lipids enter blood after modification

Answer 31

chylomicrons move out of cell via exocytosis and enter lacteal
lymphatic vessels carry chylomicrons and deposit them in bloodstream

Question 32

how are glucose and amino acids absorbed

Answer 32

via co-transport in the ileum