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AS Biology > Topic 3B (part 2) - More exchange and transport systems > Flashcards

Topic 3B (part 2) - More exchange and transport systems Flashcards

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1
Q

Look at questions about interpreting data on the cardiac cycle

A

IN BOOK

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2
Q

How are atheromas formed?

DIAGRAM

A
  1. The wall of an artery is made up of several layers
  2. The endothelium (inner lining) is usually smooth and unbroken
  3. If damage occurs to endothelium (by high blood pressure), white blood cells (mostly macrophages) and lipids from blood, clump together under lining to form fatty streaks
  4. Over time, more white blood cells, lipids and connective tissue build up and harden to form a fibrous plaque called an atheroma
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3
Q

Why are atheromas harmful?

A

They partially block lumen of artery and restrict blood flow, which causes blood pressure to rise

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4
Q

When does CVD occur?

A

When the coronary arteries have too many atheromas, which restricts blood flow to the heart muscle. This can lead to myocardial infarction

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5
Q

What do atheromas increase the risk of?

A
  1. Aneurysm - balloon like swelling of the artery

2. Thrombosis - formation of a blood clot

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6
Q

How can atheromas increase the risk of an aneurysm?

A
  1. Atheroma plaques damage, weaken and narrow arteries, increasing blood pressure
  2. When blood travels through weakened artery at high pressure, it may push the inner layers of the artery through the outer layer to form a balloon-like swelling - an aneurysm
  3. This aneurysm may burst, causing a haemorrhage
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7
Q

How can atheromas increase the risk of thrombosis?

A
  1. Atheroma plaque can rupture artery’s endothelium, damaging artery walls and leaving a rough surface
  2. Platelets and fibrin (a protein) accumulate at site of damage and forms a blood clot (a thrombus)
  3. This blood clot can cause total blockage of artery, or it can become dislodged and block a blood vessel elsewhere in the body
  4. Debris from the rupture can cause another blood clot to form further down the artery
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8
Q

How does a myocardial infarction (heart attack) occur?

A
  1. Heart is supplied with blood by coronary arteries
  2. Blood contains O2 needed for heart muscle cells to carry out respiration
  3. If coronary artery is blocked,area of heart muscle will be totally cut off from blood supply, receiving no O2
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9
Q

What can a heart attack lead to?

A

Heart failure, which can be fatal

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10
Q

What are symptoms of a heart attack?

A
  1. Shortness of breath

2. Sweating

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11
Q

What are the 2 most common risk facts for CVD?`

A
  1. Lifestyle factors e.g. smoking, bad diet.

2. Genetic predispositions e.g. age/sex Diabetes type 1

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12
Q

How can high blood cholesterol increase the risk of CVD?

A
  1. Cholesterol is one of main constituents of fatty deposits that form atheromas
  2. Atheromas can lead to increased blood pressure and blood clots
  3. This can block flow of blood to coronary arteries, which can cause a myocardial infarction
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13
Q

How can a poor diet increase the risk of CVD?

A
  1. It is associated with high blood cholesterol levels

2. A diet high in salt increases risk of CVD as it increases the risk of high blood pressure

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14
Q

How can cigarette smoking increase the risk of CVD?

A
  1. Nicotine and CO, in cigarette smoke, increase risk of CVD
    - Nicotine increases risk of high blood pressure
    - CO combines with Haemoglobin and reduced amount of O2 transported in blood, and so reduces the amount of 02 available to tissues Not enough O2 = heart attack
  2. Smoking decreases amount of antioxidants in blood - these are important in protecting cells from damage. Fewer antioxidants means cell damage in coronary artery walls is more likely, which can lead to atheroma formation
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15
Q

How can high blood pressure increase the risk of CVD?

A

It increases risk of damage to artery walls - so increases risk of atheroma formation and blood clots
- A blood clot could block flow of blood to heart muscle, leading to myocardial infarction. Therefore, anything that increases blood pressure, ,increases risk of CVD (e.g. being overweight, drinking too much, not exercising)

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16
Q

How can age/sex increase the risk of CVD?

A

Age - risk naturally increases with age

Sex - men are more at risk than women

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17
Q

What risk factors are in/out of our control?

A
  • In our control: smoking, poor diet
  • Out of our control: Genetic predispositions to CVD or having high blood pressure as result of another condition e.g. diabetes
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18
Q

Do questions on intepreting data on risk factors and cardiovascular disease

(DIAGRAM)

A

question of pg 77

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19
Q

What are the 2 different mass transport systems in plants?

A
  1. Xylem

2. Phloem

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20
Q

What is the function of the xylem tissue?

A

The xylem tissue transports water and mineral ions in solution
- These substances move up the plant from roots to leaves

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21
Q

What is the function of the phloem tissue?

A

The phloem tissue transports organic substances like sugars both up and down the plant

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22
Q

What is a mass transport system?

A

A system that allows substances to travel over large distances

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23
Q

What are xylem vessels?

DIAGRAM

A

They are very long, tube-like structures (within the xylem tissue) formed from dead cells joined end to end, with no end walls between them, to allow water and ions to pass through the middle easily and without being interrupted

24
Q

Describe the cohesion-tension theory of water transport?

A

Cohesion and tension help move water up plants, against the force of gravity

  1. Water evaporated from leaves at ‘top’ of xylem
  2. This creates tension (suction), pulling more water into leaf
  3. Water molecules are cohesive, so when some are pulled into leaf, others follow. Thus, whole column of water in xylem, from leaves down to roots, moves up
  4. Water enters stem through roots
25
Q

What is transpiration?

A

The loss of water from a plants surface

26
Q

How does transpiration occur in the leaves?

A
  1. Water evaporates from moist cell walls and accumulates in spaces between cells in a leaf
  2. When stomata open, it moves out of leaf down the conc gradient
27
Q

What 4 main factors affect transpiration rate?

A
  1. Light
  2. Temp
  3. Humidity
  4. Wind
28
Q

How does light affect transpiration rate?

A

The lighter it is, the faster the transpiration rate as the stomata are open when it gets light to let CO2 in for photosynthesis. If stomata are open, water can escape

29
Q

How does temp affect transpiration rate?

A

The higher the temp, the faster the transpiration rate as warmer water molecules have more energy so they evaporate from cells inside the leaf faster
- This increases conc gradient between inside and outside of leaf, making water diffuse out of leaf faster

30
Q

How does humidity affect transpiration rate?

A

The lower the humidity, the faster the transpiration rate. - If air around plant is dry, the conc gradient between leaf and air is increased, which increases transpiration

31
Q

How does wind affect transpiration rate?

A

The windier it is, the faster the transpiration rate. Lots of air movement blows away water molecules from around stomata, increasing conc gradient, and thus, increasing rate of transpiration

32
Q

What does phloem tissue do?

A

It transports solutes round plants

33
Q

Describe the structure of phloem tissue

A
  1. They are formed from cells arranged in tubes
  2. They contain sieve tube elements: Living cells that form the tube for transporting solutes, with no nucleus and few organelles
  3. They contain companion cells for each sieve tube element: to carry out living functions for sieve cells e.g. providing energy needed for active transport of solutes
34
Q

Define translocation

A

A process that moves solutes from ‘sources’ to ‘sinks’

35
Q

What is another name for solutes

A

Assimilates

36
Q

Is translocation an active or passive process?

A

An active process

37
Q

Where does translocation take place?

A

In the phloem

38
Q

What is a ‘source’ of a solute and a ‘sink’?

A

Source: Where its made (so at high conc here)
Sink: Where its used up (so its at low conc there)

39
Q

Give an example for a ‘source’ and a ‘sink’

A

Sucrose

Source: leaves
Sink: Other parts of plant e.g. food storage organs and meristems in roots, stems and leaves

40
Q

What is the role of enzymes in translocation?

A

They maintain a conc gradient from source to sink by changing solutes (by breaking them down or making them into something else) so that there is always a lower conc at sink than source

41
Q

Give an example of enzymes carrying out their role in translocation?

A

In potatoes, sucrose *** (how is sucrose converted to starch) is converted to starch in the sink areas, so theres always a lower conc at the sink than in the phloem. This makes sure a constant supply of new sucrose reaches the sink from the phloem

42
Q

What hypothesis best explains phloem transport?

A

The Mass Flow Hypothesis

43
Q

Describe step 1-2 of the Mass Flow Hypothesis

DIAGRAM

A
  1. Active transport is used to actively load solutes from companion cells into sieve tubes of phloem at the source
  2. This lowers water potential in sieve tubes, so water enters tubes by osmosis from xylem and companion cells, creating high pressure in sieve tubes at source end of phloem
44
Q

Describe step 3-4 of the Mass Flow Hypothesis

DIAGRAM

A
  1. At sink end, solutes are removed from phloem to be used up
  2. This increases water potential in sieve tubes, so water also leaves tubes by osmosis, lowering pressure in sieve tubes
45
Q

Describe step 5-7 of the Mass Flow Hypothesis

DIAGRAM

A
  1. This creates pressure gradient from source end to sink end
  2. This gradient pushes solutes along tubes to sink end
  3. When they reach sink,the solutes will be used
46
Q

Which process makes sucrose and in which process is it used?

A

Photosynthesis makes sucrose and sucrose is used in respiration

47
Q

What is the correlation between conc of sucrose at source, and the rate of translocation?

A

The higher the conc of sucrose at the source, the higher the rate of transpiration

48
Q

Where else, in the phloem, can sucrose be transported through?

A

Through the cell walls of the phloem

49
Q

Give supporting evidence for mass flow

A
  1. If ring of bark (only including phloem, not xylem) is removed from woody stem, a bulge forms above ring. The fluid from bulge has higher sugar conc than fluid below ring (evidence of downwards flow of sugars)***
  2. A radioactive tracer such as radioactive carbon (14C) can track movement of organic substances in plant
  3. Pressure in phloem can be investigates using aphids. Their sap flows out quicker nearer leaves than further down stem - evidence of pressure gradient
  4. If metabolic inhibitor, which stops ATP inhibition, is put into phloem, then translocation stops - evidence that active transport is involved
50
Q

What do aphids do to phloem?

A

They pierce the phloem, then their bodies are removed leaving the mouthparts behind, which allowed the sap to flow out

51
Q

Give objections to mass flow

A
  1. Sugar travels to many sinks, not just one with highest water potential, as model suggests
  2. Sieve plates would create barrier to mass flow. A lot of pressure would be needed for solutes to get through at reasonable rate
52
Q

LOOK AT QUESTIONS INVOLVING CORRELATIONS AND CASUAL RELATIONSHIPS IN DATA RELATING MASS TRANSPORT

A

book

53
Q

How can the translocation of solutes be demonstrated experimentally?

A

Using radioactive tracers

Supply part of plant (leaf) with organic substance that has radioactive label (CO2 containing 14C), by pumping into a container completely surrounding leaf

  • Radioactive carbon is then incorporated into organic substances produced by leaf (e.g. sugars produced by photosynthesis), which will then be moved around plant by translocation
54
Q

How can you track the movement of substances during translocation?

A

Autoradiography

To reveal where tracer has spread to in plant, plant is killed (by freezing in nitrogen) and then whole plant is placed on photographic film - radioactive substance is present where film turns black

55
Q

What do the results of autoradiography demonstrate?

A

They demonstrate translocation of substances from source to sink over time - e.g., autoradiographs of plants killed at different times show an overall movement of solutes from leaves towards roots

56
Q

What substance does photosynthesis produce?

A

Glucose

57
Q

In what form is glucose transported around a plant?

A

In the form of sucrose

AS Biology (12 decks)

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