Topic 3 - Transport systems

Question 1

What’s the definition of digestion ?

Digestion and Absorption

Answer 1

Larger biological molecules are broken down into smaller molecules which can move across cell membranes and be absorbed from the gut into the bloodstream to body cells

Question 2

How are carbohydrates broken down ?

Digestion and Absorption

Answer 2

Amylase hydrolyses startch into maltose during a hydrolysis recation by adding a water molecule, breaking the glyocosodoc bonds.
Membrane bound disachharidases hydrolyse maltose into glucose during a hydrolysis reaction which adds water to break the glycosidic bonds.

Question 3

Where is amylase produced?

Digestion and Absorption

Answer 3

salivary glands (secreted into the mouth)
pancreas (secreted into the small intestine)

Question 4

Where are membrane bound disacharidases found ?

Digestion and Absorption

Answer 4

the epithelial cells of the ileum

Question 5

How are lipids broken down ?

Digestion and Absorption

Answer 5

lipase enzyme hydrolyses the ester bonds by the addition of a water molecule in a hydrolysis reaction between lipids to form monoglycerides and fatty acids.

Question 6

Where are lipases produced and found ?

Digestion and Absorption

Answer 6

produced in the pancreas
found in the small intestine

Question 7

Where are bile salts produced and stored ?

Digestion and Absorption

Answer 7

produced in the liver and stored in the gall bladder

Question 8

How are micelles formed ?

Digestion and Absorption

Answer 8

once the lipid is brown down, the monoglycerided and fatty acids stick with the bile salts to form micelles.
Monoglycerides and fatty acids are not very soluble, so micelles aid the transport of these substances to the cell surface membrane.

Question 9

What are the two main peptidases ?

Digestion and Absorption

Answer 9

endopeptidases
exopeptidases

Question 10

What is the role of endopeptidases ?

Digestion and Absorption

Answer 10

They hydrolyse the peptide bonds within a protein to form smaller proteins.

Question 11

What are 3 endopeptidases ?

Digestion and Absorption

Answer 11

Trypsin and chymotrypsin are produced in the pancreas and secreted into the small intestine.
pepsin works in the stomach and is secreted by cells in the stomach lining, they work in acidic conditions.

Question 12

What is the role of exopeptidases ?

Digestion and Absorption

Answer 12

They hydrolyse the peptide bonds at the end of the protein molecules. To inccrease the surface area for Dipeptidades.

Question 13

What is the role of dipeptidases ?

Digestion and Absorption

Answer 13

Dipeptidades hydrolyse the peptide bond between 2 amino acids (dipeptide), they’re often located in the cell surface membranes of the epithelial cells of the small intestine.

Question 14

How are monosaccharides absorbed ?

Digestion and Absorption

Answer 14

1. Sodium ions are actively transported out of the ileum epithelial cells into the blood by the sodium potassium pump, this creates a concentration gradient as there’s a high concentration of sodium ions in the lumen compared to the epithelial cells.
2. Sodium ions diffuse from the lumen into the epithelial cells down their concentration gradient via the co transporters
3. The co transporters bonded to glucose/galactose and sodium, meaning that glucose molecule is carried into the cell causing the concentration of glucose in the epithelial cells to increase.
4. glucose diffuses out of the cells into the blood stream down it’s concentration gradient in a protein channel by facilitated diffusion.

Fructose is absorbed via facilitated diffusion

Question 15

How are amino acids absorbed ?

Digestion and Absorption

Answer 15

1. Sodium ions are actively transported out of the ileum epithelial cells into the blood by the sodium potassium pump, this creates a concentration gradient as there’s a high concentration of sodium ions in the lumen compared to the epithelial cells.
2. Sodium ions diffuse from the lumen into the epithelial cells down their concentration gradient via the co transporters
3. The co transporters bonded to amino acids and sodium, meaning that amino acid molecule is carried into the cell causing the concentration of amino acid in the epithelial cells to increase.
4. amino acids diffuses out of the cells into the blood stream down it’s concentration gradient by facilitated diffusion.

Question 16

how are monoglycerides and fatty acids absorbed ?

Digestion and Absorption

Answer 16

micelles help move them into the epithelial cells where they’re transported to the ER and the golgi apparatus to be recombined and form triglycerides.
Triglycerides combine with cholesterol and lipoproteins to form chilomicrons.
chilomicrons move out of the cell by exocytosis and enter the lacteals of the villi.

Question 17

What does blood transport ?

The Cardiac Cycle

Answer 17

Respiratory gases
products of digestion
metabolic waste
hormones

Question 18

What is the function of the coronary arteries ?

The Cardiac Cycle

Answer 18

They supply the heart muscle with oxygenated blood and glucose

Question 19

What is the pericardium ?

The Cardiac Cycle

Answer 19

It encloses the heart to protect it from over expansion and infection

Question 20

What’s the pulmonary circuit ?

The Cardiac Cycle

Answer 20

Blood is pumped to the lungs to pick up oxygen

Question 21

What is the systemic circuit ?

The Cardiac Cycle

Answer 21

oxygenated blood is pumped around the body

Question 22

What are the walls of the heart made out of ?

The Cardiac Cycle

Answer 22

Cardiac muscle with doesn’t tire however it requires oxygen

Question 23

What is systole ?

The Cardiac Cycle

Answer 23

contraction of heart muscles

Question 24

What is diastole ?

The Cardiac Cycle

Answer 24

Relaxation of the heart muscles

Question 25

Why do the ventricles have thicker muscles than the atria ?

The Cardiac Cycle

Answer 25

They pump blood across longer distances so the contraction needs to be stronger

Question 26

What are the bicuspid and tricuspid valves ?

The Cardiac Cycle

Answer 26

They link the atria to the ventricles.
They close when there’s a higher pressure in the ventricles than the atria to prevent the backflow of blood from the ventricles into the atria.
They open when there’s a larger pressure in the atria than the ventricles to allow blood to flow through to the ventricles

Question 27

What are the semi-lunar valves ?

The Cardiac Cycle

Answer 27

They are valves between the ventricles and the aorta and pulmonary artery.
They close when there’s a higher pressure in the atria than the ventricles to prevent the backflow of blood into the ventricles from the aorta and pulmonary artery
They open when there’s a higher pressure in the ventricles than the atria to allow blood to flow through the aorta and the pulmonary artery

Question 28

What are the function of cords in relation to the heart ?

The Cardiac Cycle

Answer 28

They connect the atrioventricular valves to the ventricles to stop them from being forced into the atria during contraction

Question 29

What are the 3 steps of the cardiac cycle ?

The Cardiac Cycle

Answer 29

atrial systole
ventricular systole
diastole

Question 30

Explain what happens during atrial systole

The Cardiac Cycle

Answer 30

The muscles of the atria contract and the ventricles relax.
This decreases volume and increases pressure of the atria. This causes the bicuspid and tricuspid valves to open to allow blood to flow through to the ventricles. The semi-lunar valves close to prevent the back flow of blood from the aorta and pulmonary artery to the ventricles. Pressure decreases

Question 31

What happens during ventricular systole ?

The Cardiac Cycle

Answer 31

The muscles of the ventricles contract and the atrial muscles relax. This decreases the volume and increases the pressure of the ventricles. This causes the bicuspid and tricuspid valves to close to prevent the back flow of blood from the ventricles to the atria. The semi-lunar valves open to allow blood to flow through the pulmonary artery and aorta

Question 32

What happens during diastole ?

The Cardiac Cycle

Answer 32

the ventricles and atria both relax. The high pressure in the aorta and pulmonary artery causes the semi lunar valves to close to prevent the backflow of blood from the arteries to the ventricles. Blood flows to the body and lungs. Blood starts to flow through the vena cava and pulmonary vein.

Question 33

What is the function of the arteries ?

The Cardiac Cycle

Answer 33

They transport blood to the rest of the body

Question 34

Explain the structure of the arteries

The Cardiac Cycle

Answer 34

They have thick muscular walls and have elastic tissue to allow for stretching at contraction and recoil at relaxation. This helps to maintain the high pressure.
The inner lining (endothelium) is folded allowing the artery to stretch to help maintain the high pressure. It is also smooth to be streamlined for blood flow. They have smaller lumen then veins.

Question 35

What are arterioles ?

The Cardiac Cycle

Answer 35

Arteries divide into smaller vessels called arterioles. They form a network across the body. They provide demanding cells with blood by the smooth muscle contracting to cause constriction, which restricts blood flow and decreases the diameter of the lumen. Or the smooth muscle relaxes to allow dilation, full blood flow, which increases the diameter of the lumen.

Question 36

What is the function and structure of veins ?

The Cardiac Cycle

Answer 36

Veins carry blood back to the heart at a lower pressure. They have a larger lumen. They have little muscular or elastic tissue. Veins contain valves to stop the backflow of blood. The blood flow is helped by the contraction of body muscles surrounding them.

Question 37

What is the function of capillaries ?

The Cardiac Cycle

Answer 37

Arterioles branch into capillaries.
They exchange substances such as glucose and oxygen with cells.
They have no elastic or muscular tissue. They have a small lumen which is the width of one blood cell.

Question 38

How are capillaries adapted for efficient exchange ?

The Cardiac Cycle

Answer 38

They’re always close to cells in exchange tissues to decrease the diffusion pathway.
Their walls are one cell thick to decrease the diffusion pathway.
There are a large number of capillaries to increase surface area for exchange.

Question 39

Why can veins be described as organs ?

The Cardiac Cycle

Answer 39

They’re made of different tissues.

Question 40

Explain how tissue fluid is made.

Tissue Fluid

Answer 40

At the arteriole end of the capillary there is a high hydrostatic pressure which is bigger than the osmotic effect, it causes small molecules like water to move out of the vessel to from tissue fluid.
As there is less volume of water in the capillary, at the venule end of the vessel there is a lower hydrostatic pressure.
As plasma proteins remain in the plasma, there is a low water potential causing some fluid to move back into the vessel by osmosis.
The remaining tissue fluid is drained into the lymphatic system which transports it to the circulatory system.

Question 41

What type of proteins are Red Blood cells ?

Haemoglobin

Answer 41

Globular proteins.

Question 42

Describe the structure of haemoglobin .

Haemoglobin

Answer 42

It has a quaternary structure due to its 4 polypeptide chains. Each chain has a haem group which contains 1 iron ion and gives haemoglobin its red colour. Each iron ion binds to a oxygen molecule.

Question 43

What does partial pressure of oxygen/carbon dioxide mean ?

Haemoglobin

Answer 43

the pressure it exerts in a mixture of gases

Question 44

Describe the process of haemoglobin loading oxygen.

Haemoglobin

Answer 44

At the lungs, there is high partial pressure of oxygen, causing haemoglobin to have high affinity for oxygen, so oxygen loads onto haemoglobin to form oxyhaemoglobin
At respiring tissues, there is low partial pressure of oxygen, causing haemoglobin to have low affinity to oxygen, so oxyhaemoglobin unloads to form haemoglobin.

Question 45

When is there a high saturation of oxygen with haemoglobin ?

Haemoglobin

Answer 45

When partial pressure of oxygen is high, haemoglobin has a high affinity for oxygen, so oxygen loads to it. As a result, haemoglobin has a high saturation of oxygen.
It is the opposite for low saturation.

Question 46

What does the dissociation curve show in relation to haemoglobin ?

Haemoglobin

Answer 46

It shows the saturation of oxygen in haemoglobin at any partial pressure given.

Question 47

Why is the dissociation curve an S-shape ?

Haemoglobin

Answer 47

When haemoglobin combines to the first oxygen molecule it is more difficult. But afterwards, its shape alters, making it easier for other oxygen molecules to combine (it turns into Fe3+). But as haemoglobin becomes saturated it gets harder for more oxygen molecules to combine. The shallow parts at the beginning and end show where it is harder, when the curve is steeper, that’s where it is easiest for oxygen to load to haemoglobin.

Question 48

What is the Bohr effect ?

Haemoglobin

Answer 48

When cells respire they produce carbon dioxide which increases the partial pressure of CO2.
This increases the rate of oxygen unloading (oxyhaemoglobin dissociates into haemoglobin).
So the dissociation curve shifts to the right.
The saturation of haemoglobin with oxygen is lower at a given partial pressure of oxygen, meaning more oxygen is being released.

Question 49

What adaptation do organisms that live in environments with low concentration of oxygen ?

Haemoglobin

Answer 49

They have haemoglobin with high oxygen affinity.
The dissociation curve is shifted left.

Question 50

What adaptation do organisms that are very active have ?

Haemoglobin

Answer 50

They have haemolgobin with a lower oxygen affinity.

Question 51

How do atheromas form and what do they cause ?

Cardiac Disease

Answer 51

If damage occurs to the smooth lining of the artery, white blood cells and lipids from the bloodstream clump together under the lining forming fatty streaks. Over time, more white blood cells, lipids and connective tissues build up and harden forming fibrous plaque called atheroma. This plaque partially blocks the lumen of the artery and restricts blood flow, causing pressure to increase.

Question 52

What is coronary heart disease ?

Cardiac Disease

Answer 52

The coronary arteries have lots of atheromas, which restricts blood flow to the heart muscle and can cause myocardial infraction.

Question 53

How is an aneurysm formed ?

Cardiac Disease

Answer 53

When blood travels through weakened arteries at high pressure ( due to atheroma), it may push the inner layers of the artery through the outer elastic layer to form a balloon like swelling - an aneurysm. This may burst to cause a haemorrhage.

Question 54

How is thrombosis caused ?

Cardiac Disease

Answer 54

Atheroma plaque can rupture through the endothelial lining of an artery. This damages the artery wall, leaving a rough surface. Platelets and fibrin accumulate at the site of damage and form a blood clot. This can cause complete blockage of the artery. Or it can become dislodged and block a blood vessel else where.
Debris from the rupture can cause another blood clot to form

Question 55

What is the scientific term for a heart attack ?

Cardiac Disease

Answer 55

Myocardial infarction

Question 56

How does myocardial Infarction affect the heart ?

Cardiac Disease

Answer 56

It can cause damage and death of the heart muscle.
If large areas of the heart are affected, complete heart failure can occur which is often fatal.

Question 57

What are symptoms of myocardial infarction ?

Cardiac Disease

Answer 57

Chest and upper body pain
shortness of breath
sweating

Question 58

Why can high blood cholesterol levels increase the risk of CVD ?

Cardiac Disease

Answer 58

Cholesterol is one of the main components of the fatty deposits that form atheromas, which lead to coronary heart disease and also myocardial infarction.

Question 59

What 3 things in a poor diet can increase the risk of CVD?

Cardiac Disease

Answer 59

High cholesterol levels - one of the main components of the fatty deposits that form atheromas.
High in saturated fats - associated with high blood cholesterol levels.
High in salt - increases blood pressure.

Question 60

How does smoking cigarettes increase the risk of CVD ?

Cardiac Disease

Answer 60

Nicotine causes high blood pressure which damages the artery walls and increases the chance of atheromas forming.
Carbon monoxide combines with haemoglobin in the blood and reduces the amount of oxygen in the blood and therefore less oxygen at the tissues. If the heart muscle doesn’t receive enough oxygen it can cause myocardial infarction.
Smoking also decreases the amount of antioxidants in the blood - leading to cell damage in the coronary artery walls leading to atheromas.

Question 61

What are risk factors to high blood pressure (causing CVD) ?

Cardiac Disease

Answer 61

Overweight
excessive alcohol consumption
not exercising

Question 62

What causes pH to reduce from 7.4 to 7.2 in tissues ?

Haemoglobin

Answer 62

Respiring tissues produce carbon dioxide.
This CO2 dissolves in the blood forming carbonic acid which dissociates,leaving H+ ions abd lowering the pH.

Question 63

For a fetus, the oxygen dissociation curve is to the left of the mothers, how is this an advantage for the foetus ?

Haemoglobin

Answer 63

Haemoglobin has a higher affinity for oxygen so it can load more readily at a lower partial pressure. Oyxgen moves from the mother to the fetus.

Question 64

What is the function of the Xylem ?

Xylem

Answer 64

Xylem tissue transport waster and mineral ions in a solution from the roots of the plants to the leaves.

Question 65

Describe the structure of Xylem

Xylem

Answer 65

Xylem consist of xylem vessels which are long tube like structurees which are formed from dead cells joined end to end. There are no end walls, allowing for water and mineral ions to pass through the middle easily. The walls of the cells are made of lignin which is waterproof, however pits are formed where there is no lignin, this allows water to move from one vessel to an adjacent vessel.

Question 66

What is transpiration ?

Xylem

Answer 66

Loss of water from a plant’s surface

Question 67

What is a transpiration stream ?

Xylem

Answer 67

The movement of water from the roots of the plant to the leaves where it evapourates.

Question 68

How does a transpiration stream work ?

Xylem

Answer 68

Water evaporates from the stomata when they open , it moves down the concentration gradient by diffusion. This creates tension, pulling more water up to the leaves. Water molecules are cohesive meaning the column of water in the xylem moves upwards from the roots, enters the stems and up to the leaves where it will diffuse out of. Trunk diameter decreases.

Question 69

What 4 things affect transpiration rate ?

Xylem

Answer 69

Wind
Light
Humidity
Temperature

Question 70

How does light affect transpiration rate ?

Xylem

Answer 70

The lighter it is, the faster the transpiration rate, this is because the stonata open when it gets light to let in carbon dioxide for photosynthesis - allowing for water to diffuse down its concentration gradient into the atmoshphere and evapourate . When its dark, stomata close so theres little transpiration.

Question 71

How does temperature affect transpiration rate ?

Xylem

Answer 71

as temperature increases, water molecules are given more kinetic energy , so they diffuse out of cells faster, this creates a large concntration gradient causing water to difffuse out of the stomata faster, increasing transpiration rate.

Question 72

How does humidity affect transpiration rate ?

Xylem

Answer 72

The lower the humidity, the faster the transpiration rate because dry air around the leaf increases the concentration gradient between the leaf and the atmosphere, this increases the transpiration rate.

Question 73

How does wind affect transpiration rate ?

Xylem

Answer 73

The windier it is, the faster the transpirationrate because lots of air movement blows away water molecules from the stomata, increasing the concentration gradient and therfore, the rate of transpiration.

Question 74

What does a potometer measure ?

Xylem

Answer 74

The water uptake of a plant, but it assumes that water uptake is directly linked to water loss (transpiration rate)

Question 75

How would you use a potometer ?

Xylem

Answer 75

1. Cut a shoot underwater to prevent air bubbles from entering the xylem. Cut it diagonally to increase the surface area.
   2.Assemble the potometer underwater and insert the shoot underwater so that no air can enter.
   3.Remove tha apparatus from the water but keep the end of the capillary tube submerged in water. Check tha apparatus is water tight and air tight.
   4.Dry the leaves, allow time for the shoot to acclimatise and then shut the tap.
   5.Remove the end of the capillary tube from the beaker of water until one air bubble has forme, then re submerge it in the beaker.
   6.Record the starting postion of the air bubble, start a stop eatch and record the distance of the bubble every hour for 6 hours. The rate of the air bubble movement is an estimate of the transpiration rate.

Question 76

What is the function of translocation ?

Phloem

Answer 76

The movement of solutes (amino acids and sucrose) from sources to sinks in a plant.

Question 77

What is a source ?

Phloem

Answer 77

Where the solute are loaded onto the phloem ( high concentration), for example the leaf.

Question 78

What is a sink ?

Phloem

Answer 78

Where solutes are removed from the phloem (Low concentration), for example roots.

Question 79

How is the concentration gradient of solutes between sources and sinks maintained ?

Phloem

Answer 79

Enzymes chnage the solutes at the sink by breaking them down or building them into something else. For example in potatos enzymes convert sucrose into stratch at the sinks, this maintains a low concentration of sucrose so that it can continue to move down the concentration gradient from the source to the sink.

Question 80

Explain mass flow theory

Phloem

Answer 80

Active transport is used to actively load the solutes from the companion cells into seive tubes o the phloem at the source, e.g. the leaf.

This lowers the water potential of the seive tubes so water moves in by osmosis from the xylem and companion cells.

This causes a high pressure in the sieve tubes at the source of the phloem.

At the sink end solutes are removed to be used up.

This increases the water potential causing water to move out of the cells by osmisis.

This creates a lower pressure at the seive tubes in the sink end of the phloem.

This results in a prssure gradient from the source end to the sink end.

This gradient causes a movement of solutes from the high pressure in the sources to the low pressure at the sinks.

When the solutes reach the sink, they can be used up (respiration) or stored (starch).

Question 81

How is the rate of translocation Increased ?

Phloem

Answer 81

The higher the concentration of solutes at the source, the higher the rate of translocation.

Question 82

Explain why the mass flow theory is supported

Phloem

Answer 82

If a ring of bark is removed from a tree brank, a large bludge is formed above it. This buldge has a high concentration of sugars compared to the smaller buldge below the ring. This proves that there is a downward movement of sugars.
C14 radioactive isotope can be used to track the movement of organic substances in a plant
Pressure in the phloem can be investiagated using aphins. Sap flows out quicker towards the top of the branch compared to the bottom. This porves that there is a pressure gradient from the sources to the sinks.
If a metabolic inhibitor is added, transloaction stops. This shows that it requires active transport.

Question 83

Explain why the mass flow theory is rejected

Phloem

Answer 83

Sugar travels to more than one sink, not just the one with the highest water potential.
Sieve plated will act as a barrier to solutes. High pressure and speed would be needed to over come this barrier.

Question 84

Explain how you would show mass flow theory by using a radioactive isotope.

Phloem

Answer 84

surround a plant in a container and pump the 14C radioactive isotope into the conatainer
The carbon will be incorperated into the plants organic subatsnces produced (photosynthesis sugars) and transported by translocation.
Movement of the organic substances can be tracked by tracking 14C using an autoradiograph. The plant is placed on photographic film and if there is 14C present, the film will turn black.
This demonstrates the movement of solutes from sources in the leaves to sinks towards the roots.

Question 85

Why is it a bad assumption that water uptake is equivalent to the rate of transpiration ?

Xylem

Answer 85

some water will be used to keep cells turgid, for photosynthesis and other chemical reaction.
some water will be created from aerobic respiration.