Section 3 - Mass transport Flashcards

Question

How does CO2 affect haemoglobins affinity for oxygen?

Answer 1

Reduced affinity in the presence of carbon dioxide. The greater conc the more readily the haemoglobin releases its oxygen (The Bohr Effect)

Answer 2

**The Bohr Effect -** The greater the conc. of CO2 the more readily the haemoglobin releases its oxygen. **Why the behaviour of haemoglobin changes in different regions of the body.**

Answer 3

Dissolved CO2 is acidic and the low pH causes haemoglobin to change shape.

Answer 4

1. At exchange surface, **CO2** is **constantly** being **removed** 2. Low CO2 = raised pH 3. the higher pH **changes the shape of haemoglobin** into one that enables it to **load oxygen readily** 4. this shape also **increases the affinity** of haemoglobin for oxygen, so it is not released while being transported in the blood of the tissues. 5. in the tissues **carbon dioxide is produced** by respiring cells 6. carbon dioxide is acidic in solution, so the **pH** of the blood within the **tissues is lowered** 7. the lower pH changes the **shape** of haemoglobin into one with a **lower affinity for oxygen** 8. **haemoglobin releases its oxygen** onto the respiring tissues.

Answer 5

Higher rate of respiration -\> More CO2 tissues produce -\> Lower the pH -\> Greater the haemoglobin shape change -\> More readily oxygen is unloaded -\> more oxygen is available for respiration.

Answer 6

**97%** As not all haemoglobin molecules are loaded with their maximum four oxygen molecules.

Answer 7

Species with the lower partial pressure of oxygen have evolved haemoglobin that had a higher affinity for oxygen than the haemoglobin of animals that live where the partial pressure of oxygen is higher.

Answer 8

Contraction - systole Relaxation - diastole.

Answer 9

Contraction occurs separately in the ventricles and the atria and is therefore described in two stages.

Answer 10

**Diastole** 1. As atria fill the pressure rises. 2. When pressure exceeds that in the ventricles, the atrioventricular valves open allowing the blood to pass into the ventricles. 3. This passage is aided by gravity 4. Muscular walls of both atria and ventricles are relaxed at this stage. 5. Relaxation causes them to recoil and reduces the pressure within the ventricle. 6. Causes pressure to be lower than that in the aorta and pulmonary artery so semi-lunar valves in the aorta and pulmonary artery close, accompanied by the 'dud' sound of the heart beat.

Answer 11

**Atrial systole** Contraction of the atrial wallas, along with the recoil of the relaxed ventricle walls, forces the remaining blood in the ventricles from the atria. Throughout this stage, the muscle of the ventricle walls remains relaxed.

Answer 12

**Ventricular systole** 1. After a short delay to allow the ventricles to fill with blood, their walls contract simultaneously. 2. This increases the blood pressure within them, forcing shut the atrioventricular valves and preventing backflow of blood in the atria. 3. The 'lub' sound of these valves closing is the characteristic of the heartbeat. 4. With the atrioventricular valves closed, the pressure in the ventricles rises further, 5. When exceeded that of the aorta and pulmonary artery, blood forced from the ventricles into vessels. 6. Venticles contract forcefully creating high pressure.

Answer 13

So they open whenever the difference in blood pressure either side of them favours the movement of blood in the required direction. When the pressure difference is reversed the valves close.

Answer 14

Between the left atrium and ventricle and the right atrium and ventricle. Prevent backflow of blood when contraction of the ventricles mean that ventricular pressure exceeds atrial pressure. Closure of these valves ensures that when the ventricles contract blood within them moves to the aorta and pulmonary artery rather than back to the atria.

Answer 15

In the aorta and pulmonary artery. Prevent backflow of blood into the ventricles when the pressure in these vessels exceeds that in the ventricles. This arises when the elastic walls of the vessels recoil increase ng the pressure within them and when the ventricle walls relax reducing the pressure within the ventricles.

Answer 16

Blood is confined to vessels. Allows the pressure within them to be maintained and regulated.

Answer 17

In veins Occur throughout the venous system Ensure that when the veins are squeezed blood flows back towards the heart rather than away from it.

Answer 18

A number of flaps of though, but flexible, fibrous tissue, which are cusp-shaped, in other words like deep bowls. When pressure is greater on the convex side of the cusps they move apart to let blood pass between. When pressure is greater on the concave side blood collects within the 'bowl' of the cusps. Pishes them together to form a tight fit that prevents the passage of blood.

Answer 19

The volume of blood pumped by one ventricle of the heart in one minute. Measured in dm^3min^-1

Answer 20

The heart rate stroke volume

Answer 21

Cardiac output = heart rate x stroke volume

Answer 22

1. Arteries 2. Arterioles 3. Capillaries 1. Veins

Answer 23

Blood vessels that carry blood away from the heart and into arterioles

Answer 24

Smaller arteries that control blood flow from arteries and capillaries.

Answer 25

Tiny blood vessels that link arterioles to veins.

Answer 26

Carry blood from capillaries back to the heart.

Answer 27

* **Tough fibrous outer layer** - resists pressure changes from both within and outside * **muscle layer** - contract and so control the flow of blood * **elastic layer -** helps to maintain blood pressure by stretching and springing back (recoiling) * **thin inner lining (endothelium)** - smooth to reduce friction and thin to allow diffusion * **lumen** - not actually a layer but the central cavity of the blood vessel through which the blood flows.

Answer 28

Lumen Lining layer

Answer 29

To transport blood rapidly under high pressure from the heart to the tissues.

Answer 30

* **Muscle layer is thick compared to veins -** constricted and dilated in order to control the volume of blood passing through them * **Thick elastic layer** - maintain high pressure to reach extremities * **The great overall thickness of the wall -** resists the vessel bursting under pressure * **no valves -** except in arteries leaving the heart as constant high pressure due to heart pumping blood into the arteries tends to be no backflow.

Answer 31

Carry blood, under lower pressure than arteries, from arteries to capillaries. Also, control the flow of blood between the two.

Answer 32

* **Muscular layer relatively thicker than in arteries** - contraction of this muscle layer allows constrictions of the lumen of the arteriole. Restricts the flow of blood and so controls its movement into the capillaries that supply the tissues with blood. * **Elastic layer relatively thinner than arteries** - blood pressure is lower.

Answer 33

Transport blood slowly, under low pressure from the capillaries in tissues to the heart.

Answer 34

* **Thin muscle layer -** carry blood away from tissues and constriction and dilation cannot control the flow of blood to tissues * **Thin elastic layer -** low pressure of blood not prone to bursting and pressure too low to recreate recoil action * **Small overall thickness of the wall -** no risk of bursting. Also allows them to flatten easily aiding flow of blood within them. * **Valves throughout -** ensure blood doesn't flow backwards.

Answer 35

To exchange metabolic materials such as oxygen, carbon dioxide and glucose between the blood and the cells of the body. Flow of blood is much smaller allowing more time for the exchange of materials.

Answer 36

* **Wall mostly lining layer** - extremely thin so diffusion pathway small. * **Numerous and highly branched -** providing a large surface area for exchange * **Narrow diameter -** permeate tissues * **lumen is narrow -** red blood cells squeezed flat against the side of a capillary. Brings them even closer to the cells they supply oxygen. * **Spaces between the lining cells** allowing white blood cells to escape in order to deal with infections within tissues.

Answer 37

Capillaries can not serve severy cell directly. SO final journey of metabolic materials is made in a liquid solution that bathes the tissues.

Answer 38

a watery liquid containing glucose, amino acids, fatty acids, ions in solution and oxygen. Supplies all these substances to the tissues. Receives carbon dioxide and other waste materials from the tissues.

Answer 39

From **blood plasma** and the composition of blood plasma is controlled by various homeostatic systems. As a result, it provided cells with a mostly constant

Answer 40

Pumping by the heart creates a pressure at the arterial end of the capillaries.

Answer 41

Tissue fluid to move out of the blood plasma.

Answer 42

1. Hydrostatic pressure of the tissue fluid outside the capillaries which resists outward movement of liquid 2. lower water potential of the blood due to the plasma proteins, that causes water to move back into the blood within the capillaries.

Answer 43

1. Loss of tissue fluid from capillaries reduces the hydrostatic pressure inside them 2. As a result, by the time the blood has reached the venous end of the capillary network its hydrostatic pressure is usually lower than that of the tissue fluid outside it 3. Therefore, tissue fluid is forced back into the capillaries by the higher hydrostatic pressure outside them 4. in addition, the plasma has lost water and still contains proteins. It, therefore, has a lower water potential than the tissue fluid 5. As a result, water leaves the tissue by osmosis down a water potential gradient.

Answer 44

* The combined effect of all forces creates an overall pressure that pushes tissue fluid out of the capillaries at the arterial end. * This pressure is only enough to force small molecules out of the capillaries, leaving all cells and proteins in the blood because these are too large to cross the membranes. * This type of filtration under pressure is called ultrafiltration

Answer 45

Can not be pumped by the heart. * Hydrostatic pressure - of the tissue fluid that has left the capillaries * Contraction of body muscles that squeeze the lymph vessels - valves in the lymph vessels ensure that the fluid inside them moves away from the tissues in the direction of the heart.

Answer 46

Carried back via the lymphatic system. This is the system of vessels that begin in the tissues. Initially, they resemble capillaries but they gradually merge into larger vessels that form a network throughout the body. These larger vessels drain their contents back into the bloodstream via two ducts that join veins close to the heart.

Answer 47

Thick-walled tubes that transport the vast majority of water in plants. Hollow.

Answer 48

The main force that pulls water through the xylem vessels in the stem of a plant. It requires the evaporation of water from leaves. The energy for this is supplied by the sun and the process is therefore passive.

Answer 49

There is a water potential gradient from the air spaces through the stomata to the air. Provided the stomata are open, water vapour molecules diffuse out of the air spaces into the surrounding air. Water loss by diffusion from the air spaces is replaced by water evaporating from the cell walls of the surrounding mesophyll cells. Changing the shape of the stomatal pores means the plants can control their rate of transpiration.

Answer 50

By evaporation from their cell walls to the air spaces of the leaf. This is replaced by water reaching the mesophyll cells from the xylem either via cell walls or via the cytoplasm.

Answer 51

* Mesophyll cells lose water to the air spaces by evaporation due to heat supplied by the sun * These cells now have a lower water potential and so water enters by osmosis from neighbouring cells * the loss of water from these neighbouring cells lowers their water potential * they in turn take in water from their neighbours by osmosis.

Answer 52

Cohesion-tension.

Answer 53

* water evaporates from mesophyll cells due to heat from the sun leading to transpiration * Water molecules form hydrogen bonds between one another and hence tend to stick together. This is known as **Cohesion.** * Water forms a continuous, unbroken column across the mesophyll cells and down the xylem. * As water evaporates from the mesophyll cells in the leaf into the air spaces beneath the stomata, more molecules of water are drawn up behind it as a result of this cohesion. * A column of water is, therefore, pulled up the xylem as a result of transpiration. This is called the **transpiration pull.** * Transpiration pull puts the xylem under tension, that is, there is a negative pressure within the xylem, hence the name **cohesion-tension theory.**

Answer 54

Water molecules form hydrogen bonds between one another and hence tend to stick together.

Answer 55

A column of water that is pulled up the xylem as a result of transpiration

Answer 56

Easily raise water up to 100m or more of the tallest trees.

Answer 57

1. Change in the diameter of tree trunks according to the rate of transpiration. 2. If a xylem vessel is broken and air enters it, the tree can no longer draw up water. 3. When a xylem vessel is broken, water does not leak out as would be the case if it were under pressure.

Answer 58

During the day, when transpiration is at its greatest, there is more tension (more negative pressure) in the xylem. This pulls the walls of the xylem vessels inwards and causes the trunk to shrink in diameter. At night when transpiration is at its lowest, there is less tension in the xylem and so the diameter of the trunk increases.

Answer 59

As the continuous column of water is broken and so the water molecules can no longer stick together.

Answer 60

Instead air is drawn in which is consistent with it being under tension.

Answer 61

They are dead cells with no end walls. Meaning they form a series of continuous, unbroken tubes from root to leaves which is essential to the cohesion-tension theory of water flow up a stem. The energy needed for transpiration is in the form of heat that evaporates water from the leaves and it ultimately comes from the sun.

Answer 62

The process by which organic molecules and some mineral ions are transported from one part of a plant to another. IN flowering plants the tissue that transports biological molecules is the phloem.

Answer 63

In flowering plants, it is the tissue that transports biological molecules. Made up of sieve tube elements, long thin structures arranged end to end. Their end walls are perforated to form sieve plates. Associated with the sieve tube elements are cells called companion cells.

Answer 64

As sinks can be anywhere in a plant - sometimes above and sometimes below the source.

Answer 65

Organic molecules including sucrose and amino acids. Also inorganic ions such as potassium, chloride, phosphate and magnesium ions.

Answer 66

mass flow theory

Answer 67

1. Transfer of sucrose into sieve elements from photosynthesising tissue 2. Mass flow of sucrose through sieve tube elements 3. Transfer of sucrose from the sieve tube elements into storage or other sink cells

Answer 68

Transfer of sucrose into sieve elements from photosynthesizing tissue * sucrose is manufactured from the products of photosynthesis in cells with chloroplasts * The sucrose diffuses down a concentration gradient by facilitated diffusion from the photosynthesising cells into companion cells * Hydrogen ions are actively transported from companion cells into the spaces within cell walls using ATP * These hydrogen ions then diffuse down a concentration gradient through carrier proteins into the sieve tube elements * Sucrose molecules are transported along with the hydrogen ions in a process known as co-transport. The protein carriers are therefore also known as co-transport proteins.

Answer 69

The bulk movement of a substance through a given channel or area in a specified times.

Answer 70

Mass flow of sucrose through sieve tube elements. * Sucrose produced by photosynthesising cells (source) is actively transported into the sieve tubes as described above. * This causes the sieve tubes to have a lower (more -tive) water potential * As the xylem has a much higher (less -tive) water potential, water moves from the xylem into the sieve tubes by osmosis, creating a high hydrostatic pressure within them. * At the sinks, sucrose either used in respiration or converted to starch * cells have low sucrose content and sucrose is actively transported into them from the sieve tubes lowering their water potential * Due to lower water potential, water also moves into these respiring cells, from the sieve tubes by osmosis. * The hydrostatic pressure of sieve tubes in this region is therefore lowered * As a result of water entering the sieve tube elements at the source and leaving at the sink, there is high hydrostatic pressure at the source and low one at the sink * Therefore a mass flow of sucrose solution down this hydrostatic gradient in the sieve tubes.

Answer 71

Transfer of sucrose from the sieve tube elements into storage or other sink cells * The sucrose is actively transported by companion cells, out of the sieve tubes and into the sink cells.

Answer 72

Passive process A result of the active transport of sugars. Therefore the process as a whole is active which is why it is affected by for example temperatures and metabolic poisons.

Answer 73

An outer protective layer of bark on the inside of which is a layer of phloem that entends all around the stem. Inside the phloem layer is xylem.

Answer 74

* Section of the outer layers (protective layer and phloem) is removed around the complete circumference of a woody stem while it is still attached to the rest of the plant. * After a period of time, the region of the stem immediately above the missing ring of tissue is seen to swell. * Samples of liquid that has accumulated in this swollen region are found to be rich in sugars and other dissolved organic substances. * Some non-photosynthetic tissues in the region below the ring are found to wither and die, while those above the ring continue to grow.

Answer 75

* Sugars of the phloem accumulating above the ring leading to swelling in this region * The interruption of flow if sugars to the region below the ring and the death of tissues in this region.

Answer 76

That the phloem rather than xylem is the tissue responsible for translocating sugars in plants. As the ring of tissue removed had not extended into the xylem its continuity had not been broken. If it were the tissue responsible for translocating sugars you would not have expected sugars to accumulate above the ring nor tissues below it to die.

Answer 77

Radioactive isotopes are useful for tracing the movement of substances in plants. These radioactive sugars can then be traced as they move within the plant using autoradiography. Eg. 14C can be used to radioactively label 14CO2. If a plant is then grown in an atmosphere containing 14CO2 the 14C isotope will be incorporated into the sugars produced during photosynthesis. Taking cross-sections of the plant stem and placing on a piece of X-ray film. Will blacken when exposed to radiation produced by 14C in sugars. These areas found to correspond to where phloem tissue is in the time. As other tissues do not blacken it follows that they do not carry sugars and that phloem alone is responsible for their translocation.

Answer 78

* When phloem is cut a solution of organic molecules flow out * plants provided with radioactive carbon dioxide can be shown to have radioactively labelled carbon in phloem after a short time. * Aphids are a type of insect that feed on plants. They have needle-like mouthparts which penetrate the phloem. They can therefore be used to extract the contents of the sieve tubes. These contents show daily variations in the sucrose content of leaves that are mirrored a little later by identical changes in the sucrose content of the phloem. * The removal of a ring of phloem from around the whole circumference of a stem leads to the accumulation of sugars abover the ring of their disappearance from below it.

Answer 79

* Hemoglobin * Difficult to attach first Oxygen molecule * Once the first oxygen binds the **shape changed making the other binding sites of oxygen more exposed** * **Conformational change**

Answer 80

water potential = pressure potential + solute potential

Answer 81

* in capillaries * pumping of blood created hydrostatic pressure forcing fluid out of capillaries at the arteriole end * plasma proteins do not move out * outward movement is opposed by the pressure of the fluid already in the tissue fluid and by the low water potential of the blood due to the plasma proteins in the capillary * once fluid enters tissue fluid, oxygen, glucose ect passes into cell

Answer 82

* The loss of fluid decreases the hydrostatic pressure of the capillaries * The water potential of the blood in the venule end is low due to plasma proteins * Therefore water moves back into the venule end by osmosis * Dissolved waste also enters the venule end (CO2 )

Answer 83

* Supporting tissue * Forming of cell walls * Stops the cells from collapsing

Answer 84

1. Fill potometer with water making sure there are no air bubbles 2. leafy shoots fitted into potometer underwater 3. Air bubble introduced into a capillary tube 4. Distance moved by the air bubble in a given time indicates the rate of transpiration 5. Water from the reservoir can be used to push the bubble back to its starting position.

Section 3 - Mass transport Flashcards

(113 cards)