(s3-7) Mass Transport

Question 1

Haemoglobin

What is haemoglobin, and what is its role of it in the transport of oxygen?

Answer 1

Haemoglobin is a protein with a quaternary structure found in red blood cells.

Haemoglobin binds to oxygen and carries it in the blood from the lungs to tissues where it’s needed. It then releases the oxygen for cells to use.

Question 2

Haemoglobin

What does the cooperative nature of oxygen binding mean?

Answer 2

The cooperative nature of oxygen binding means that the binding of the first oxygen molecule to haemoglobin makes it easier for subsequent oxygen molecules to bind.

Question 3

Haemoglobin

Compare the partial pressures of oxygen in the lungs and in respiring tissues, including reference to haemoglobin binding to or releasing oxygen.

Answer 3

In the lungs, the partial pressure of oxygen is high, so haemoglobin binds to oxygen.

In respiring tissues, the partial pressure of oxygen is low, so haemoglobin releases oxygen.

Question 4

Haemoglobin

What is the Bohr effect?

Answer 4

The Bohr effect, or Bohr shift, refers to the rightward shift in the oxygen dissociation curve in response to increased carbon dioxide concentration.

Higher carbon dioxide levels make haemoglobin release oxygen more readily, enhancing oxygen unloading when it’s needed.

Question 5

Haemoglobin

What is the oxygen dissociation curve?

Answer 5

The oxygen dissociation curve is a graph showing how the saturation of haemoglobin with oxygen changes when the partial pressure of oxygen changes.

It is sometimes called the oxyhaemoglobin dissociation curve.

Question 6

Haemoglobin

What is the significance of diffusion affinities for oxygen in fetal and adult haemoglobin?

Answer 6

Fetal haemoglobin has a higher affinity for oxygen than adult haemoglobin, allowing it to draw oxygen from the mother’s blood supply.

Question 7

Circulatory System

Name the major blood vessels that enter and leave the kidneys and state their functions.

Answer 7

Renal artery - transports oxygenated blood to the kidneys
Renal vein - transports deoxygenaed blood away from the kidneys

Question 8

Circulatory System

Name the major vessels that enter and leave the heart, what they transport, and where transport it to.

Answer 8

1. Pulmonary veins - transports oxygenated blood from the lungs to the heart
2. Pulmonary arteries - transports deoxygenated blood from the heart to the lungs
3. Aorta - transports oxygenated blood from the heart to the body
4. Vena cava - transports deoxygenated blood from the body to the heart

Question 9

Circulatory System

What do we mean by systemic circulation and pulmonary circulation?

Answer 9

1. Systemic circulation transports blood between the heart and the body cells
2. Pulmonary circulation transports blood between the heart and the lungs

Question 10

Circulatory System

What factors increase an organism’s need for a circulatory system with a pumping mechanism?

Answer 10

1. Large size
2. Low surface area to volume ratio
3. High metabolic activity

Question 11

Circulatory System

Why do large, complex organisms require transport systems?

Answer 11

Large organisms tend to have a small surface area to volume ratio, so diffusion is too slow to transport required materials.

Question 12

Heart Structure

What are the key functions of the atria and ventricles in the mammalian heart?

Answer 12

Atria recieves blood returning to the heart, and pump it into the ventricles:
1. The right atrium recieves deoxygenated blood from the body
2. The left atrium recieves oxygenated blood from the lungs

Ventricles pump blood out of the heart:
3. The right ventricle pumps deoxygenated blood from the lungs.
4. The left ventricle pumps oxygenated blood to the body.

Question 13

Heart Structure

Compare the structure of the atria and ventricles in a mammalian heart, and explain these differences.

Answer 13

Atria are smaller and have thinner walls as they only need to pump blood to the ventricles.

Ventricles have thicker muscular walls to pump blood out of the heart to the lungs and rest of the body, which requires more force.

Question 14

Heart Structure

Compare the structure and function of the left and right ventricles in the mammalian heart, and explain these differences.

Answer 14

The left ventricle has a thicker muscular wall as it pumps oxygenated blood to the entire body, requiring more force.
The right ventricle has a thinner wall as it only pumps deoxygenated blood to the lungs, which are close by.

Question 15

Heart Structure

Why does blood need to return to the heart after being oxygenated by the lungs, before being transported to the rest of the body?

Answer 15

Blood needs to return to the heart because, after the reduction in pressure that occurs when blood travels through the pulmonary capillaries, the pressure needs to increase again.
Blood needs to be pumped to the rest of the body under high pressure to ensusre efficient delivery of oxygen and nutrients to all cells.

Question 16

Heart Structure

State the names of the valves between the atria and ventricles on each side of the heart.

Answer 16

Valve between the right atrium and right ventricle: tricuspid valve or right atrioventricular valve.
Valve between the left atrium and left ventricles: bicuspid valve or left atrioventricular valve.

Question 17

Heart Structure

What is the function of the valves between the atria and the ventricles?

Answer 17

The valves between the atria and ventricles ensure one-way flow of blood from the atria to the ventricles, preventing backflow when the ventricles contract.

Question 18

Heart Structure

Which blood vessels are connected to the left and right atria, and where do they transport blood from/to?

Answer 18

1. The right atrium is connected to the vena cava - transports deoxygenated blood from the body into the heart
2. The left atrium is connected to the pulmonary vein - transports oxygenated blood from the lungs into the heart

Question 19

Heart Structure

Which blood vessels are connected to the left and right ventricles, and where do they transport blood from/to?

Answer 19

1. The right ventricle is connected to the pulmonary artery - transports deoxygenated blood from the heart to the lungs
2. The left ventricle is connected to the aorta - transports oxygenated blood from the heart to the body

Question 20

Heart Structure

What is the septum, and what is its function?

Answer 20

The septum is a muscular wall that seperates the left and right sides of the heart.
The septum prevents oxygenated and deoxygenated blood from mixing.

Question 21

Heart Structure

What are the semilunar valves, and what is their function?

Answer 21

The semilunar valves are located between each of the ventricles and the pulmonary artery and aorta, respectively.
The semilunar valves prevent backflow of blood into the heart after it has been pumped out.

Question 22

Cardiac Cycle

What is diastole

Answer 22

Diastole is the phase of the cardiac cycle where the heart relaxes.

Blood flows into the atria through the pulmonary vein and the vena cava, pushing open the atrioventricular valves and filling the ventricles.

Question 23

Cardiac Cycle

What happens during atrial systole?

Answer 23

During atrial systole, the atrial walls contract, forcing the remaining blood into the ventricles.

Throughout this stage, the muscle of the ventricle walls remains relaxed.

Question 24

Cardiac Cycle

What happens during ventricular sytole?

Answer 24

During ventricular systole, the ventricular walls contract simultaneously, increasing blood pressure within them.

This closes the atrioventricular valves and forces blood into the aorta and pulmonary artery.

Question 25

# Cardiac Cycle Describe the role of valves in the heart, including a reference to pressure.

Answer 25

Valves in the heart ensure blood flows in one direction. Valves open when pressure difference favour movement in the required direction and close when pressure differences would cause blood to flow in the opposire direction.

Question 26

# Cardiac Cycle What are the 3 main stages of the cardiac cycle?

Answer 26

1. Atrial systole 2. Ventricular systole 3. Diastole

Question 27

# Cardiac Cycle What is cardiac output?

Answer 27

The volume of blood pumped by one ventricle of the heart in 1 minute.

Question 28

# Cardiac Cycle How is cardiac output calculated?

Answer 28

cardiac output = heart rate × stroke volume

Question 29

# Cardiac Cycle What is stroke volume in relation to cardiac output?

Answer 29

The volume of blood that is pumped out of the left ventricle during ventricular systole.

Question 30

# Cardiac Cycle Which valves open during atrial systole?

Answer 30

Atrioventricular valves

Question 31

# Cardiac Cycle During which stage of the cardiac cycle do the semi-lunar valves open?

Answer 31

Ventricular systole

Question 32

# Cardiac Cycle What is the definition of heart rate in the context of cardiac output?

Answer 32

The number of heart beats per minute.

Question 33

# Blood Vessels What are the 5 main types of blood vessels and their functions?

Answer 33

1. Arteries - carry oxygenated blood away from the heart 2. Arterioles - control blood flow from arteries to capillaries 3. Capillaries - allows the exchange of gases and nutrients between blood and body cells 4. Venule - collect blood from capillaries and channel it into veins 5. Veins - carry deoxygenated blood back to the heart

Question 34

# Blood Vessels State the basic structural layers in arteries, arterioles, veins, and venules and the key functions of these layers.

Answer 34

From the outside inwards, the layers are: 1. Collagen - provides structural support to maintain shape and provides strength to prevent bursting 2. Muscle layer - smooth muscle allows constriction and dilation of certain blood vessels 3. Elastic layer - elastin fibres contains elastin to provide flexibility and minimise changes in pressure 4. Endothelium - thin inner lining 5. Lumen - the central cavity of the blood vessel through which the blood flows

Question 35

# Blood Vessels Describe how the structure of a capillary is adapted for its function

Answer 35

1. Narrow lumen - slows the flow of blood, allowing more time for the exchange of material between the blood and the body cells 2. Thin walls - reducing the diffusion distance for rapid exchange of materials 3. Numerous and highly branched - provides a large surface area to increase the rate of exchange 4. Permeate tissues, ensuring no cell is far from a capillary - reduces the diffusion distance

Question 36

# Blood Vessels Describe how the structure of an artery is adapted for its function.

Answer 36

1. Thick collagen wall - resists bursting 2. Thick elastic layer - stretches and recoils to maintain pressure 3. Thick smooth muscle layer - contracts/relaxes to constrict/dilate the lumen to control blood flow

Question 37

# Blood Vessels Describe how the structure of a vein is adapted for its function.

Answer 37

1. Thin walls (including muscle and elastic layers) - as they carry blood under low pressure 2. Valves - ensure blood does not flow backwards as the pressure is low 3. Large lumen - reduce resistance for blood flow

Question 38

# Blood Vessels Compare the structure of an artery and an arteriole.

Answer 38

Arteriole have a relatively thicker muscle layer and relatively larger lumen compared to arteries. Arteries have a thicker elastic layer to withstand higher pressure.

Question 39

# Blood Vessels What is the difference between vasoconstriction and vasodilation?

Answer 39

Vasoconstriction is the narrowing of blood vessels like arteries and arterioles due to contraction of the smooth muscle in their walls, which reduces blood flow. Vasodilation is the widening of these blood vessels due to relaxation of the smooth muscle in their walls, which increases blood flow.

Question 40

# Blood Vessels What adaptations allow the movement of deoxygenated blood to the heart, despite its low pressure and movement against gravity?

Answer 40

1. Veins have valves that prevent backflow of blood 2. Contraction of skeletal muscles surrounding the veins when the body moves pushes blood towards the heart 3. Thin walls of veins allow them to be easily compressed, aiding the flow of blood

Question 41

# Blood, Tissue Fluid & Lymph What do the terms of hydrostatic pressure and oncotic pressure mean in the context of the human circulatory system?

Answer 41

1. Hydrostatic pressure - pressure exerted by the force of the heart pumping on blood 2. Oncotic pressure - a form of osmotic pressure exerted by proteins in blood plasma that tends to pull water into the circulatory system

Question 42

# Blood, Tissue Fluid & Lymph What is tissue fluid, and how is it formed from plasma in a capillary network?

Answer 42

Tissue fluid is the fluid that surrounds the cells in tissues. Tissue fluid is formed when high hydrostatic pressure at the arteriole end of a capillary forces plasma out of the capillary and into the interstitial spaces surrounding cells.

Question 43

# Blood, Tissue Fluid & Lymph How does tissue fluid return to the circulatory system?

Answer 43

1. Tissue fluid returns to the circulatory system at the venule end of the capillary where the hydrostatic pressure is lower and oncotic pressure is higher 2. The lymphatic system collects excess fluid that cannot be absorbed by the capillaries, forming lymph that is eventually returned to the bloodstream

Question 44

# Blood, Tissue Fluid & Lymph What are the differences in the composition of blood, tissue fluid, and lymph?

Answer 44

Blood contains red blood cells, white blood cells, platelets, and plasma. Tissue fluid is like plasma but with fewer proteins, and it does not contain red blood cells but may contain some white blood cells. Lymph is similar to tissue fluid, but contains less oxygen and nutrients and contains many fatty acids and white blood cells (lymphocytes).

Question 45

# Blood, Tissue Fluid & Lymph What are the functions of tissue fluid?

Answer 45

Tissue fluid provides cells with nutrients and oxygen and removes waste products. It also helps fight infection as it forms part of the immune response.

Question 46

# Blood, Tissue Fluid & Lymph What is the main component of blood and tissue fluid?

Answer 46

Water is the main component of both blood and tissue fluid

Question 47

# Blood, Tissue Fluid & Lymph What is the role of proteins in the movement of water out of tissue fluid?

Answer 47

Proteins in the blood plasma exert an oncotic pressure that pulls water back into the capillaries from the tissue fluid.

Question 48

# Blood, Tissue Fluid & Lymph What is the difference between the arteriole and venule end of a capillary in terms of hydrostatic pressure and movement of fluid?

Answer 48

The arteriole end of a capillary has high hydrostatic pressure due to the force exerted by the pumping out of the heart, forcing fluid out. The venule end of a capillary has lower hydrostatic pressure, allowing fluid return to the capillaries.

Question 49

# Xylem & Phloem Why do multicellular plants needs transport systems?

Answer 49

Multicellular plants need transport systems due to their size, metabolic rate and sur+face area to volume ratio. They need to transport substances like water, nutrients, and sugars across long distances.

Question 50

# Xylem & Phloem What are two main tissues in the vascular system of plants and their key roles?

Answer 50

The vascular system in plants consists of the xylen and phloem tissues: 1. The xylem transports water and dissolved minerals from the roots to them stem and leaves 2. The phloem transports substances like sugars and amino acids from where they are made (e.g., in the leaves) to where they are needed (e.g. in the roots)

Question 51

# Xylem & Phloem Describe the structure of the xylem.

Answer 51

The xylem is made up of xylem vessels, which are long, continuous tube-like structures.

Question 52

# Xylem & Phloem Describe the structure of the phloem.

Answer 52

The phloem contains sieve tube elements and companion cells: 1. Sieve tube elements - these cells are stacked vertically to form long tubes with sieve-like structures between adjacent cells 2. Companion cells - these are specialised cells attached to sieve tube elements

Question 53

# Xylem & Phloem How does the structure of companion cells relate to their function?

Answer 53

Companion cells have a large number of mitochondria and ribosomes, which provide energy and proteins for the active transport of substances.

Question 54

# Xylem & Phloem What is the importance of companion cells in the phloem?

Answer 54

Companion cells assist the sieve tube elements in the phloem by providing energy for active transport of substances.

Question 55

# Xylem & Phloem How are mineral ions transported within plants?

Answer 55

Mineral ions dissolve in water and are transported via the xylem in plants

Question 56

# Water Transport in Plants What factors increase the transpiration rate?

Answer 56

1. High light intensity - higher rate of photosynthesis so more stomata open to obtain more carbon dioxide 2. High temperature - more kinetic energy means water evaporates faster, and there will also be a higher rate of photosynthesis 3. High wind speed - maintains a steed water vapour diffusion gradient between the air spaces in the leaf and environmental air 4. Low humidity - maintains a steep water vapour diffusion gradient between the air spaces in the leaf and environmental air

Question 57

# Water Transport in Plants Why is transpiration considered a consequence of gaseous exchange?

Answer 57

Transpiration is a consequence of gaseous exchange because in order for plants to take in carbon dioxide, they have to open their stomata, which water vapour can diffuse out of.

Question 58

# Water Transport in Plants What is a potometer?

Answer 58

A potometer is a device used to estimate transpiration rate. It does this by measuring the rate of water uptake of a leafy shoot, which is almost equal to the water loss by transpiration.

Question 59

# Water Transport in Plants What are the steps in using a potometer?

Answer 59

1. Fill the potometer with water 2. Cut a shoot underwater and fix it to the potometer 3. Dry the leaves, allow time for the shoot to acclimatise and then shut the tap 4. Record the starting position of the air bubble 5. Calculate the rate of transpiration: volume of water uptake / time taken

Question 60

# Water Transport in Plants What is transpiration?

Answer 60

Transpiration is the evaporation of water from aerial parts of plants, especially leaves.

Question 61

# Water Transport in Plants Explain why transpiration occurs in plants.

Answer 61

1. Water evaporates from moist surfaces of mesophyll cells. 2. Stomata open to absorb carbon dioxide for photosynthesis. 3. This provides a pathway for water vapours loss through open stomata. 4. Water vapour moves down a water potential gradient from leaf air spaces into the atmosphere.

Question 62

# Water Transport in Plants What is the cohesion-tension theory of water transport in the xylem?

Answer 62

The cohesion-tension theory explains the movement of water from roots to leaves in xylem vessels in plants. It suggests that water is pulled up through the plant under tension, due to the transpiration pull and the cohesive and adhesive properties of water.

Question 63

# Water Transport in Plants What is adhesion in the context of water transport in plants?

Answer 63

Adhesion is the attraction of polar water molecules to the non-polar cellulose in xylem vessel cell walls. This helps water to rise through the plant against gravity.

Question 64

# Water Transport in Plants What is cohesion in the context of water tranport in plants?

Answer 64

Cohesion is the attraction between polar water molecules due to hydrogen bonding. This helps water molecules stick together and move up the plant as a continuous column in the xylem vessels.

Question 65

# Water Transport in Plants What is the transpirational pull?

Answer 65

The transpirational pull is the upward movement of water from the roots to the aerial parts of a plant, driven by the evaporation of water from the leaves.

Question 66

# Water Transport in Plants Summarise how water moves from the soil to the leaves of a plant.

Answer 66

1. Water enter's a plant's root hair cells via osmosis 2. It moves through cell cytoplasm or cell walls towards the xylem 3. The xylem transports water from the roots up to the leaves

Question 67

# Mass Flow Hypothesis How do tracers help in understanding the process of translocation?

Answer 67

Tracers, such as radioactive isotopes, can be used to track the movement of organic substances in the plant, providing evidence for translocation.

Question 68

# Mass Flow Hypothesis What are ringing experiments, and how is the mass flow hypothesis supported by them?

Answer 68

Ringing experiments involve removing a ring of bark, which includes the phloem, from a stem. This disrupts the phloem and this translocation, which affects the plant's growth and provides evidence that the phloem is necessary for the mass flow of sugars.

Question 69

# Mass Flow Hypothesis What is the mass flow hypothesis?

Answer 69

The mass flow hypthesis proposes that translocation occurs due to pressure gradients: 1. Solutes are actively transported into sieve tube elements, causing a high hydrostatic pressure at the source 2. Solutes are moved by the phloem to respiring cells where they are removed from the sieve tube elements for use or storage, creating a low hydrostatic pressure at the sink 3. This hydrostatic pressure difference results in the mass flow of solutes through the phloem

Question 70

# Mass Flow Hypothesis Describe the processes in translocation that require energy.

Answer 70

1. Active loading at source cells - actively transporting sucros from source cells into companion cells, and subsequent into phloem sieve tube elements for translocation 2. Active unloading at sink cells - actively transporting sucros from the phloem sieve tube elements into companion cells, and subsequent into sink cells where it is used or stored

Question 71

# Mass Flow Hypothesis What are sources and sinks in the context of plant translocation?

Answer 71

Sources are areas where sucros is produced, like leaves. Sinks are areas where sucros is used or stored, like roots or meristems. ## Footnote Other substances that are transported in the phloem, like amino acids, are also moved from sources to sinks. The location of sources and sinks may change depending on the substance transported and the time of year.

Question 72

# Mass Flow Hypothesis What is the role of water in the translocation of sugars?

Answer 72

Water provides the medium in which sugars, specifically sucrose, dissolves for transport in the phloem.

Question 73

# Mass Flow Hypothesis Describe translocation in the context of plants.

Answer 73

Translocation is mass flow of sucrose and amino acids from one part of a plant (the source) to another part of the plant (the sink)