Gaseos exchange, digestion and absorbtion

Question 1

what cells line the wall of the alveoli

Answer 1

flattened epithelial cells

Question 2

what cells line the wall of the blood capillaries

Answer 2

endothelial cells

Question 3

how do we breath in (inspiration)

Answer 3

1) the external intercostal muscles contract, pulling the ribs upwards and outwards whilst the internal intercostal muscles relax

2) the diaphragm muscles contract which pulls the diaphragm down so it flattens

3) both these actions increase the volume of the thoracic cavity

4) the pressure inside the lungs decreases below atmospheric pressure and air enters the lungs down a concentration gradient

Question 4

is breathing in / inspiration an active or passive process

Answer 4

active as it involves muscle contraction

Question 5

how do we breath out (expiration)

Answer 5

1) the external intercostal muscles relax

2) the diaphragm muscles relax and the diaphragm moves upwards to its dome shape

3) these actions decrease the volume of the thoracic cavity

4) the pressure increases above thoracic pressure and air is forced out the lungs

5) elastic recoil of the lung tissue helps to force air out the lungs during breathing out

5) the internal intercostal muscles may contract moving the ribcage inwards and downwards

Question 6

what happens when we exhale strongly

Answer 6

the internal intercostal muscles contract pulling the ribcage inwards and downwards, forcing air out the lungs

the external intercostal muscles relax

^ antagonistic muscles

Question 7

unicellular organisms have a large or small surface area : volume ratio

and what does this mean

Answer 7

large

this means exchange of gasses can occur directly across the cell membrane

Question 8

large organisms have a low surface area : volume ratio what does this mean

Answer 8

they require specialised gas exchange organs

Question 9

are insects active and require a high oxygen demand

Answer 9

yes

Question 10

what are insects covered with

what does this mean

Answer 10

a protective exoskeleton made of the polysaccharide chitin

this means gasses such as co2 and o2 cant pass easily through the exoskeleton

Question 11

what’s on the surface of insects exoskeleton

Answer 11

small openings called spiracles

Question 12

what do spirscles allow

Answer 12

the diffusion of co2 and o2 into the body of the insect

Question 13

what do spiracles lead to

Answer 13

lead into a network of tubes called trachea which are relatively large (1mm)

Question 14

what are the walls of tracheae reinforced with

Answer 14

they are reinforced with spirals of chitin which keeps the tracheae open during pressure fluctuations or when an insect moves

Question 15

what extends from the tracheae

Answer 15

very fine tubes called tracheoles

each tracheole is a single cell that has extended to form a hollow tube

a huge number of them extend down the insects body in between cells

unlike tracheae they are not supported by spirals of chitin

Question 16

why is there a short diffusion distance between tracheoles and cells

what does this allow

Answer 16

because the tracheoles are very narrow in diameter and are extremely close to cells

this allows the oxygen in the air of the tracheoles to diffuse rapidly into the cells

this oxygen is needed for aerobic respiration which produces co2

the co2 can also rapidly diffuse back into the air of the tracheoles

Question 17

is there a huge number of tracheoles

Answer 17

yes which provides a very large surface area for gas exchange

this allows insects to maintain a rapid rate of aerobic respiration

Question 18

what are the ends of tracheoles filled with and what happens to it during intense activity

Answer 18

the ends of the tracheoles are filled with tracheole fluid

during intense activity the cells around the tracheoles undergo anaerobic respiration which produces lactic acid. this reduces the water potential in the cells. this causes the water in the tracheol fluid to move in to the cells via osmosis

this reduces the volume of tracheol fluid , drawing air into the tracheoles

this also means more tracheole surface is available for the diffusion of co2 and o2

Question 19

in many insects is gas exchange a passive or active process

Answer 19

passive

o2 down a conc gradient from high conc in external air to tracheoles

co2 from high conc of tracheoles to low conc in air

Question 20

why is the small size of insects useful

Answer 20

reduces the diffusion distance

Question 21

how is water loss in insects controlled

Answer 21

valves around spiracles which can close when oxygen is not needed as much

Question 22

in large / very active insects what is done to increase the rate of diffusion

Answer 22

the muscles in the insect may contract which will compress the tracheae forcing air out of it

when the muscles relax the tracheae springs back into shape

fresh oxygen rich air is drawn into the tracheae, increasing the rate of diffusion

Question 23

why do fish need specialised exchange system

Answer 23

there are large and active organisms

they have low surface area to volume ratio

they are covered in scales so diffusion cannot occur

there’s a lower concentration of oxygen in water than in air

Question 24

what is the flap of tissue behind the head of the fish

what’s inside it

Answer 24

the opercolum

the opercolum cavity which has gill arches,gill filaments and gill lamellae inside it

Question 25

how does water enter the fish

Answer 25

oxygen rich water enters via the mouth

it passes through the gill lamellae and oxygen diffuses from water out of the epithelial cells of the gills and past the endothelial cells of the capillaries into the blood stream

finally water passes out through the operculum opening

Question 26

what are the structure of gills

Answer 26

gills consist of 4 pairs gill arches

extending from these gill arches are a large number of gill filaments

gill filaments are covered with numerous gill lamellae

Question 27

where does gas exchange take place in fish

Answer 27

gill lamellae

^ water flows between gill filaments

Question 28

name the adaptations in the fish for gas exchange

Answer 28

1) a large surface area due to the large number of gill filaments and the gill lamellae which cover them

2) a short diffusion pathway as the blood and water are separated by a thin barrier consisting mainly of 2 cell layer

(epithelial layer of the gill lamellae)
and
(endothelial layer of the blood capillaries)

3) the circulatory system (which consists of a large network of blood capillaries) ensures a continuous flow of blood through the respiratory surface(lamellae) to absorb o2 and remove co2 to maintain a high diffusion gradient for gaseous exchange

4) ventilation system provides a continuous flow of water over the gills bringing more o2 and removing co2 maintaining a high diffusion gradient for gas exchange

5) the counter current system!!!! ( blood and water flowing in opposite directions ) which ensures water has a higher o2 concentration than blood so that a high diffusion gradient is maintain along the whole length of the lamellae

Question 29

explain counter current exchange system in fish

Answer 29

water flows over the gills in the opposite direction to the flow of blood in the capillaries

counter current flow ensures equilibrium is not reached

this ensures a concentration gradient is maintained across the entire length of the gill lamallae

Question 30

what is pulmonary ventilation ?

what is tidal volume?

what is ventilation/breathing rate?

what’s the equation for pulmonary ventilation

Answer 30

pulmonary ventilation = the total volume of air drawn into the lungs in 1 minute

tidal volume = the total volume of air drawn into the lungs in one breath

ventilation/ breathing rate = the total number of breaths per minute

pulmonary ventilation = tidal volume x ventilation/breathing rate

Question 31

what is digestion

Answer 31

the process where large molecules are hydrolysed by enzymes to produce smaller soluble molecules

Question 32

what does complete hydrolysis of carbohydrates result in

Answer 32

monosaccharides which are small soluble molecules which can be absorbed

Question 33

explain the first stage of the digestion of carbohydrates

Answer 33

happens in the mouth:

the sight smell and taste of food stimulates the secretion of saliva from the salivary glands

saliva contains the enzyme salivary amylase

amylase hydrolyses STARCH into MALTOSE

only a small amount of starch is hydrolysed into maltose due to the short time food remains in the mouth . chewing breaks down food into smaller particles for a larger surface area so that hydrolysis by enzymes is more rapid

Question 34

explain the 2nd stage of the digestion of carbohydrates

Answer 34

it happens in the small intestine

the pancreas releases pancreatic juice into the small intestine. pancreatic juice is an alkaline fluid which contains many enzymes including pancreatic amylase. this enzyme hydrolyses the remaining starch into the disaccharide maltose

the complete hydrolysis of starch into alpha glucose occurs in the ileum (end of the small intestine)

maltase and other disaccharidases are not released into the lumen of the ileum but form part of the cell surface membrane of the epithelial cells that line the ileum (they are referred to as membrane bound disaccharidases)

Question 35

what are the disaccharidases that form part of the cell surface membrane of the epithelial cells that line the ileum

Answer 35

maltase -> hydrolyses maltose into 2 alpha glucose molecules

lactase -> hydrolyses lactose into glucose and galactose

sucrase-> hydrolyses sucrose into glucose and fructose

Question 36

what are lipids hydrolysed into

Answer 36

lipids are hydrolysed into glycerol, fatty acids and monoglycerides (glycerol and one fatty acid) by the enzyme lipase

Question 37

where is lipase secreted from and where to

Answer 37

lipase is secreted from the pancreas into the small intestine

Question 38

what does lipase specifically hydrolyse

Answer 38

the ester bonds in triglycerides

Question 39

how is the rate of hydrolysis of lipids increased and how

Answer 39

by bile salts

bile salts emulsify lipids into small droplets

this increases the surface area of the lipids which increases the rate of hydrolysis

Question 40

where are bile salts found

Answer 40

in bile (an alkaline fluid) which is made in the liver and stored in the gall bladder

bile enters the small intestine via the bile duct

Question 41

is emulsification and physical or chemical process

Answer 41

physical - there is no chemical breakdown

Question 42

explain absorption of digested lipids

Answer 42

1) bite salts emulsify large droplets of lipids into smaller droplets. this increases the surface area for lipase to hydrolyse triglycerides

2) the products of lipid digestion (monoglycerides and fatty acids) combine with bile salts to form micelles

3) the micelles are necessary as it can transport the insoluble monoglycerides and fatty acids to surface of the epithelial cell in the ileum

4) the micelles break down next to the epithelial cell releasing the fatty acids and monoglycerides.

5) these non polar molecules can diffuse past the cell membrane of the epithelial cell

6) fatty acids, monoglycerides and glycerol recombine in the smooth endoplasmic reticulum to form triglycerides

7) they are packaged by proteins and phospholipids in the golgi body to form chylomicrons

8) chylomicrons are then absorbed into the lacteals in the villi which will eventually drain into the blood

Question 43

explain absorption of digested lipids

Answer 43

1) bite salts emulsify large droplets of lipids into smaller droplets. this increases the surface area of the lip

Question 44

adaptation of ileum to absorb

Answer 44

The ileum is adapted for absorption of digested products in the following ways.

• Large surface area due to its long length and the presence of villi (singular: villus) and microvilli (on the epithelial cells).

• Villi contain blood capillaries that absorb monosaccharides and amino acids maintaining a high diffusion gradient for further absorption.

The lacteals (lymph vessels) in the villi absorb digested lipids that also maintains a high diffusion gradient for further absorption.

The wall of each villus villi consists of a single layer of epithelial cells providing a short diffusion pathway for absorption.

• A large number of mitochondria are present to supply ATP. for active transport.

• There are carrier and channel proteins in the cell-surface membrane for absorption of specific molecules by active transport (carrier proteins) and facilitated diffusion (carrier & channel proteins).