transport and exchange

Question 1

gas exchange in fish

Answer 1

-blood and water flows across the gill lamellae in a counter current direction
-this is called counter-current flow
-this ensures that the diffusion gradient is maintained so that the maximum amount of oxygen is diffusing into the deoxygenated blood from the water

Question 2

gas exchange in insects

Answer 2

-spiracles (small openings of tubes on the surface of the insect) open and close allowing the correct amount of oxygen to be allowed into the insect
-the oxygen then goes through the trachea and into the tracheoles, where there is a small amount of water where gas exchange occurs
-carbon dioxide is then released through the spiracles

Question 3

gas exchange in plants

Answer 3

-the leaves have stomata (small holes), which allow gases to enter and leave
-there is a large amount of stomata meaning that no cell is fair away from a stomata
-this reduces the diffusion pathway

Question 4

gas exchange in mammals

Answer 4

-oxygen enters through the mouth or the nose and goes down the trachea, than the bronchi and into the bronchioles
-the bronchioles split off into alveoli, which are tiny sacs filled with air
-alveoli have a folded membrane, meaning that the surface area is increased so more respiration can occur
-alveoli are also one cell thick so respiration can happen at a faster rate
-carbon dioxide then leaves the alveoli and goes through the bronchioles, bronchi, trachea and then leaves via the nose or the mouth

Question 5

what happens during inspiration?

Answer 5

-the external intercostal muscles contract and the internal intercostal muscles relax
-the ribs move upwards and outwards
-the diaphragm contracts and flattens
-the volume inside the thorax increases, which lowers the pressure
-this means that oxygen is forced into the lungs

Question 6

what happens during expiration?

Answer 6

-the internal intercostal muscles contract and the external intercostal muscles relax
-the ribs move downwards and inwards
-the diaphragm relaxes and raises upwards
-this decreases the volume inside of the thorax, which increases the pressure
-this means carbon dioxide is forced out of the lungs

Question 7

what a spirometer?

Answer 7

-it is used to measure the volume of air in the lungs
-a person using a spirometer breathes in and out of the airtight chamber
-this causes it to move up and down, leaving a trace on a graph which can then be interpreted

Question 8

what is vital capacity?

Answer 8

-the maximum volume of air that can be inhaled or exhaled in a single breath

Question 9

what is tidal volume?

Answer 9

-the volume of air we breathe in or out at each breath rest

Question 10

what is breathing rate?

Answer 10

-the number of breathes per minute

Question 11

lipid digestion

Answer 11

-lipids are hydrolysed by lipase
-they hydrolyse the ester bonds between triglycerides
-they are then spilt into micelles by bile salts
-this increases the surface area of lipids
-further hydrolysis forms fatty acids and monoglycerides

Question 12

lipid absorption

Answer 12

-monoglycerides and fatty acids remain with the bile salts in the ilium and turn into micelles
-micelles break back down into monoglycerides and fatty acids when they come into contact with the epithelial cells on the ilium lining
-they then diffuse across the cell surface membrane into the epithelial cells
-they are then transported to the endoplasmic reticulum where they are remade back into triglycerides

Question 13

starch digestion

Answer 13

-the food containing a carbohydrate is eaten
-in the mouth amylase hydrolyses starch into maltose
-amylase is denatured in the stomach by stomach acid
-the maltose then travels into the ilium where its hydrolysed by maltase into glucose
-glucose is then absorbed into the bloodstream by cotransport

Question 14

protein digestion

Answer 14

-hydrolysis of proteins starts in the stomach
-endopeptidase hydrolyses the middle of the polypeptide chain
-exopeptidase hydrolyses the ends of the polypeptide chain
-dipeptidase hydrolyses dipeptides into single amino acids
-the amino acids are then absorbed via co-transport

Question 15

oxygen disassociation

Answer 15

-haemoglobin in red blood cells bind to oxygen and carry it
-the loading of oxygen in the lungs occurs in high partial pressure of oxygen
-oxygen is unloaded at the respiring tissues at low partial pressure of oxygen
-unloading occurs due to high concentrations of carbon dioxide

Question 16

blood circulation in the kidney

Answer 16

-blood flows from kidney along renal vein to vena cava
-it then travels along the vena cava and into the right side of the heart into the atria and ventricles and then into the pulmonary artery
-it then goes into the lungs and into the capillaries where carbon dioxide is unloaded and oxygen is loaded
-the travels along pulmonary vein and into the left side of the heart, down the aorta to the renal artery and then to the kidney

Question 17

one way flow of blood in the heart

Answer 17

-atrium has higher pressure than ventricle due to filling so atrioventricular valve opens
-ventricle has higher pressure than atrium due to filling. atrioventricular valve closes
-ventricles has higher pressure than aorta
-semi lunar valve opens
-higher pressure in aorta than ventricle as heart relaxes
-semi lunar valve closes-ventricular contraction causes increase in pressure

Question 18

cardiac diastole

Answer 18

-atria and ventricles relax
-the elastic recoil of the heart lowers the pressure inside the heart chambers
-blood returns to the heart from the vena cava and the pulmonary vein and fill the atria
-pressure increases in the atria until the atrioventricular valves open
-blood flows into the ventricles
-the relaxed aria and ventricles means that the semi-lunar valves are closed

Question 19

atrial systole

Answer 19

-the atria then contract forcing any remaining blood into the ventricles

Question 20

ventricular systole

Answer 20

-contraction of the ventricles causes the atrioventricular valves to close
-the semi-lunar valves to open
-this allows blood to leave the left ventricle through the aorta and right ventricle through the pulmonary artery

Question 21

structure and function of artery

Answer 21

-they have thick walls to withstand high blood pressures
-they contain an elastic tissue which allows them to stretch and recoil, smoothening the flow of blood
-they also contain smooth muscle which enables them to vary blood flow, lined with smooth endothelium to reduce friction and ease the flow of blood

Question 22

structure and function of arteriole

Answer 22

-they branch off of arteries
-they have thinner and less muscular walls
-they feed blood to the capillaries

Question 23

structure and function of capillaries

Answer 23

-they are the smallest blood vesicle
-they are where metabolic exchange occurs
-they are only one cell thick for a faster diffusion rate

Question 24

structure and function of venule

Answer 24

-they are larger than capillaries but smaller than veins

Question 25

structure and function of veins

Answer 25

-they carry blood from the body to the heart
-they have a wide lumen to maximise the capacity of blood carried to the heart
-they have thin walls as there is low blood pressure
-they contain valves to prevent the back-flow of blood

Question 26

tissue fluid formation

Answer 26

-high blood hydrostatic pressure forces water out
-the large proteins remain in the capillaries
-low ψ in the blood due to plasma proteins
-water enters the blood via osmosis and enters the lymphatic system

Question 27

movement of water in the xylem

Answer 27

-in the root active transport of ions and salts occur by endodermis
-there is a lower water potential in the xylem, water enters via osmosis down the concentration gradient
-water moves from xylem to leaves
-transpiration occurs from leaves
-this creates cohesion tension due to hydrogen bonding in water
-adhesion of water molecule binds to xylem
-this creates a continuous water column

Question 28

translocation

Answer 28

-translocation occurs when sucrose is actively transported into phloem via companion cells
-this lowers the water potential in the phloem, so water moves into the phloem via osmosis
-this produces high hydrostatic pressure
-mass flow occurs towards sink
-at sink sugars ar removed via co-transport

Question 29

evidence for mass transport

Answer 29

-translocation occurs when sucrose is actively transported into phloem via companion cells
-this lowers the water potential in the phloem, so water moves into the phloem via osmosis
-this produces high hydrostatic pressure
-mass flow occurs towards sink
-at sink sugars ar removed via co-transport

Question 30

evidence against mass transport

Answer 30

-the function of the sieve plates is unclear as they would appear to hinder mass flow (some suggest though they have a structural function to help prevent bursting under pressure)
-not all solutes move at the same speed, they should do if it is mass flow
-sucrose is delivered at more or less the same rate to all regions, rather than going more quickly to the ones with the lowest sucrose concentration, which the mass flow theory would suggest