exchange

Question 1

how does the SA to volume ratio differ in different sized organisms?

Answer 1

larger organisms have a smaller SA to volume ratio

Question 2

Why do multicellular organisms need exchange organs and mass transport systems?

Answer 2

small SA:V so specialised systems help overcome the large diffusion pathway

Question 3

how are exchange surfaces adapted for efficient exchange?(4)

Answer 3

large SA
thin
selectively permeable
maintained concentration gradient

Question 4

what system do insects have?

Answer 4

tracheal system

Question 5

name 3 features of the tracheal system

Answer 5

spiracles
tracheae
tracheoles

Question 6

what are spiracles?

Answer 6

small openings on the surface of the insects body. They open periodically for gas exchange as having them open also causes water loss

Question 7

what is the tracheae (insects)?

Answer 7

internal network of tubes that are supported by strengthened rings

Question 8

what are tracheoles?

Answer 8

smaller tubes coming off tracheae that extend into body tissue

Question 9

explain how gas is exchanged in insects(3)

Answer 9

oxygen is used in respiration, creating concentration gradient that allows O2 to enter through spiracles

high conc of CO2 produced means it exits through spiracles

muscle contractions around tracheae help move gases

Question 10

how is the tracheal system adapted for efficient gas exchange?(4)

Answer 10

tracheoles have thin walls-short diffusion pathway

Highly branched-large surface area

Tracheae provide tubes full of air-fast diffusion

Fluid in the end of the tracheoles that moves into tissues
during exercise- faster diffusion through the air to the gas
exchange surface

Question 11

what are structures in fish gills?(2)

Answer 11

gill filaments
gill lamellae

Question 12

how are fish gills adapted for efficient gas exchange?(2)

Answer 12

many gill lamellae increase surface area

surface is thin so short diffusion pathway

Question 13

explain the counter current principle(3)

Answer 13

water and blood flow in opposite directions

this maintains a concentration gradient of oxygen as blood is always passing water with a higher conc

across the whole length of the gill filament

Question 14

how is the counter current principle more efficient than the human gas exchange system?

Answer 14

there is a greater difference in concentration in gills so
the amount of oxygen removed from water is higher

Question 15

name 9 structures of a leaf

Answer 15

waxy cuticle
upper epidermis
palisade mesophyll
spongy mesophyll
lower epidermis
stomata
guard cells
phloem
xylem

Question 16

where does gas exchange occur in a plant?

Answer 16

stomata

Question 17

what causes CO2 to diffuse into the stomata

Answer 17

CO2 is being used by the cells creating a lower conc in the leaf, this means CO2 diffuses down the conc gradient

Question 18

why are stomata more likely to stay closed at night?

Answer 18

no light for photosynthesis so no gas exchange needed

Question 19

what are xerophytes?

Answer 19

plants that are adapted to living in areas of short water supply and/or there are high rates of water loss

Question 20

what are 5 adaptations of xerophytes to limit water loss?

Answer 20

waxy cuticle
rolled leaves
hairy leaves
sunken stomata
needle-like leaves

Question 21

how does having rolled leaves /hairy leaves /sunken stomata limit water loss?(2)

Answer 21

warm still air gets trapped

gets saturated with water vapour so water potential gradient is limited

Question 22

how do needle-like leaves limit water loss?

Answer 22

limited surface area so less water lost through stomata

Question 23

what are structures of the lungs?(4)

Answer 23

trachea
bronchi
bronchioles
alveoli

Question 24

what are 2 adaptations of the trachea and bronchi?

Answer 24

rings of cartilage to support

contain ciliated epithelium lining with goblet cells to produce mucas and waft

Question 25

what is the adaptation of bronchioles?

Answer 25

walls made of muscle which can contract or relax to alter diameter of airways

Question 26

what are the 4 adaptations of alveoli?

Answer 26

one cell thick-provides short diffusion pathway

permeable walls- allows gases to diffuse

extensive blood supply and ventilation -maintains high con gradient

many alveoli-large surface area

Question 27

describe the pathway of oxygen from the alveoli to the capillaries

Answer 27

diffuses across alveolar epithelium to endothelium of capillaries

Question 28

describe inspiration(4)

Answer 28

external intercostal muscles contract, internal intercostal muscles relax, ribs are pushed up and out

diaphragm contracts, increases size of thorax

this increases volume inside lungs and decreases air pressure so that it is higher outside

causing air to flow in, down a pressure gradient

Question 29

describe expiration(4)

Answer 29

external intercostal muscles relax, internal intercostal muscles contract, ribs are pushed in and down

diaphragm relaxes, decreasing size of thorax

this decreases volume and increases air pressure so that it is higher than outside

this causes air to be forced out, down the pressure gradient

Question 30

what is pulmonary ventilation rate?

Answer 30

measure of how much air is taken in and out of the lungs in a given time.

dm3/min

Question 31

what is tidal volume?

Answer 31

volume of air taken in at each breath when at rest

dm3

Question 32

what is breathing rate?

Answer 32

the number of breaths taken in per min

Question 33

describe the process of carbohydrate digestion(5)

Answer 33

1. salivary amylase hydrolyses starch in food into maltose by breaking glycosidic bonds
2. food enters stomach which has acidic conditions, denaturing the amylase

3.after some time, the food enters intestines where it is mixed with pancreatic amylase

4.this continues to hydrolyse remaining starch to maltose

5.maltase in cell membrane of ileum lining hydrolyses maltose into a-glucose

Question 34

how is the pH maintained in the small intestine?

Answer 34

alkaline salts secreted by pancreas and intestinal wall maintain pH at neutral so enzyme can function

Question 35

what types of enzymes hydrolyse lipids?

Answer 35

lipases

Question 36

Describe the role of enzymes in the digestion of proteins(4)

Answer 36

peptidases hydrolyse the peptide bond between amino acids

Endopeptidases act in the middle of poly peptide

Exopeptidases hydrolyse bond on the terminal amino acids of polypeptides

Dipeptidases acts on dipeptides, these are membrane bound

Question 36

how is the ileum adapted for efficient absorption?(4)

Answer 36

villi increase surface area for diffusion

epithelial cells have microvilli which further increase surface area

thin walls reduce diffusion pathway

sufficient blood supply to maintain high conc gradient for molecules

Question 36

Describe the processes involved in the absorption and transport of
digested lipid molecules(6)

Answer 36

1. monoglycerides and fatty acids are associated with bile salts, forming micelles

2.the micelles are brought to the epithelial cells lining the ileum and then broken down, releasing the monoglycerides and fatty acids

3.Fatty acids/monoglycerides absorbed by diffusion

4.these are then transported to the ER where they are reformed into triglycerides

5. the triglycerides associate with cholesterol and lipoproteins, forming chylomicrons
6. chylomicrons move out epithelial cells by exocytosis, entering lymphatic capillaries(lacteals)