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A Level Biology (Edexcel Salters-Nuffield) > Topic 1 > Flashcards

Topic 1 Flashcards

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1
Q

Why do mammals and other large organisms need a circulation system?

A

Because they are too large for diffusion alone to be an effective method of supplying the molecules needed to stay alive (e.g. glucose for respiration) + removing waste

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2
Q

How does the surface area to volume ratio affect how substances enter/leave an organism?

A

In organisms with a small surface area to volume ratio, substances + water can enter and leave by diffusion + osmosis

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3
Q

What size surface area to volume ratio might a small organism have?

What size surface area to volume ratio might a large organism have?

A

Small organisms have a large surface area to volume ratio

Large organisms have a small surface area to volume ratio

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4
Q

What 3 properties make water a good solvent for transporting susbtances + CO2 around the body?

A

It is a polar molecule

It is a liquid at RTP

It easily dissolves molecules held together by ionic bonds

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5
Q

What is a polar molecule?

A

A molecule with an uneven charge distribution

One end is slightly positive (𝛿+) and the other is slightly negative (𝛿-)

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6
Q

Explain why water is described as a dipolar molecule

A

Because the oxygen end is negatively charged and the 2 hydrogen ends have a positive charge

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7
Q

Why is water a liquid at room temperature?

A

Because seperate water molecules are held together by hydrogen bonds

These are formed by the electrostatic attraction between the polar molecules

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8
Q

Why is water able to dissolve molecules held together by ionic bonds?

A

Because they are ‘pulled apart’ by the water molecules which then surround them

This is able to happen as water molecules are charged because they are polar so are attracted to the charged ions

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9
Q

Aside from molecules held together by ionic bonds, what other molecules can water dissolve?

A

Other polar molecules

e.g. Sugars + amino acids

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10
Q

Describe the sturcture + corresponding function of arteries

A

Relatively thick walls - withstands high bp

Smooth muslce - alters diamter of lumen to vary blood flow

Elastic fibres - Allow walls to stretch when blood is pumped into the artery then recoil behind it, smoothing blood flow

Lined with smooth layer of endothelial cells - low friction surface to ease flow of blood

Narrow lumen - maintains high bp

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11
Q

Describe the structures + corresponding functions of veins

A

Relatively thin wall - blood under low pressure (so thick wall not needed)

Very little smooth muscle/elastic fibres - no pulse of blood so no need to stretch + recoil

Wide lumen - carries large volume of blood + acts as ‘blood reservoir’

Valves - stop backflow

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12
Q

Describe the structures + corresponding functions of capillaries

A

Very thin wall (1 cell thick) - allows rapid exchange between blood + tissues

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13
Q

How can the materials that make up arteries, veins, and capillaries be compared?

A

Arteries + veins are made of the same tissues but in different proportions

Capillaries only have an endothelium

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14
Q

Draw diagrams to show the structure of arteries, veins, and capillaries

A
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15
Q

Explain why the mammalian heart has 2 sides

A

2 sides allow oxygenated and deoxygenated blood to remain seperate. This allows as much oxygen as possible to be carried to cells

Having 2 sides also allows having a different amount of muscle on each side. This means there can be a higher pressure on one side (pumping blood around the body) compared to the other (puming blood to the lungs)

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16
Q

Label the diagram of the heart shown below

A

Also label the apex (bottom) of the heart + the septum (wall seperating sides)

Could also label the tendinous cords that support the semilunar valves

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17
Q

What are the names of the artieries that carry oxygenated blood to the neck + head?

A

Cartoid arteries

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18
Q

What is another name for the artioventricular valve in the right side of the heart?

A

The tricuspid valve

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19
Q

What is another name for the atrioventricular valve in the left side of the heart?

A

The bicuspid valve

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20
Q

Describe the events of the cardiac cycle in the left side of the heart

N.B. the events are the same on the right side and happen at the same time. The only difference is where the blood comes from/goes

A

Blood drains into the left atrium from the lungs along the pulmonary vein

Raising of the blood pressure in the left atrium forces the left atrioventricular valve open

Left atrial systole forces more blood through the valve

As soon as left atrial systole is over, the left ventricular systole begins

This forces the left atrioventricular valve closed + the left semilunar valve open. Blood then leaves the left ventricle though the aorta

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21
Q

Describe what is happening in terms of the contraction of the heart at each point shown on the image.

Explain how the pressure in the heart also changes at these points

A

B: Ventricle starts to contract, ventricular pressure greater than aortic pressure so atrioventricular valve clsoes

C: Pressure in ventricles now greater than in aorta so semilunar valve opens

D: Ventricular pressure now lower than aorta so semilunar valve closes

E: Ventricular pressure now lower than atrial pressure so atrioventricular valve opens + blood flows into ventricle

F: Blood still draining into atria + moving into ventricle

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22
Q

What causes the formation of a blood clot?

A

Damage to a tissue

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23
Q

What is atherosclerosis?

A

Disease than leads to CHD + strokes

Caused by fatty deposits (atheroma) that either directly block artery or increase its chance of being blocked by a blood clot

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24
Q

Describe the possible health effects of having an atheroma

A

Increased blood pressure - causes damage to kidneys, retina, + can cause strokes

Aneurysm - Increase bp caused by atheroma can lead to bursting of artery + internal bleeding

Angina - Chest pain felt during excerise. Caused by reduced blood flow to heart due to narrowing of coronary arteries

Heart attack - Blockage of coronary artery, usually by a clot, causing part of the heart to become starved of oxygen + die

Stroke - Interruption to blood supply of brain which can cause paralysis or death

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25
Q

Describe the stages that lead to the formation of an atheroma

A

Endothelial damage/dysfunction (e.g. caused by smoking or high bp)

Leads to an increased risk of blood clotting in artery but also an inflammatory response. White blood cells move into the artery wall.

Cholesterol builds up, leading to the formation of an atheroma

The build-up of calcium salts + fibres leads to plaque formation

This causes the narrowing of the artery + loss of elasticity

Blood pressure is raised (thus increasing risk of endothelial dysfunction!)

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26
Q

It’s important that a blood clot doesn’t form in the wrong place or at the wrong time.

How is this prevented?

A

A number of (clotting) factors have to be present for a blood clot to be able to form

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27
Q

Describe the sequence of the clotting cascade

A

When platelets come into contact with the damaged tissue they stick together forming a ‘plug’

Thromboplastin (a protein) is released from the damaged tissue + platelets

This causes insoluble prothrombin in the plasma to be converted into soluble thrombin if there are Ca2+ and vit. K present

Thrombin triggers the conversion of soluble fibrinogen to insoluble fibrin which forms a mesh trapping more platelets + red blood cells, thus forming a clot.

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28
Q

What is risk?

A

The probability of an unwanted event/outcome occuring

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29
Q

What can cause people to overestimate risk?

A

Involunatary (e.g. being a passanger in a plane as opposed to driving a car)

Dreaded

Not natural

Unfair

Unfamilliar

Very small

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30
Q

Why do people tend to judge the risk of heart disease poorly?

A

Their own experience carries more weight than statistics

Inability to assess risks well

Peer pressure - e.g. alcohol consumption + smoking when young

The idea that if something is destined to happen then its unpreventable (karma…)

The remoteness of the likely consequences (e.g. having a stroke is hard to imagine)

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31
Q

Give the risk factors for CVD and explain why they increase risk

A

Diet - correlation between dietart habits + CVD levels. e.g. lipoprotein + salt levels. Could be causal, especially for blood cholesterol levels

Smoking - chemicals in smoke physically damage artery linings + cause them to constrict

Sex - oestrogen gives some protection before menopause

Age - Elasticity + width of arterues decreases with age

Inactivity - Regular exercise decreases CVD risk by reducing bp + raising HDL levels

Genetics - can inherit high bp, poor cholesterol metabolism, easily damaged arteries, relative HDL:LDL levels in blood

High blood pressure - makes damage to endothelium + atherosclerosis more likely

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32
Q

What does correlation mean?

A

That a change in one varible is accompanied by/corresponds to a change in another

Doesn’t mean there is a causation

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33
Q

What is causation?

A

When the change in one variable causes the change of another

If this is the case the variable are said to be causally linked

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34
Q

What is an epidemiologist?

A

A scientist who carries out research on patterns of disease/health risks in populations to determine what the risk factors are

Also establish whether there are any correlations in data sets + if there might be a causation as well

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35
Q

What are the 2 main types of study?

A

Cohort studies

Case-control studies

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36
Q

What are the features of a cohort study?

A

Follow a large number of people over an extended period of time

Subjects are monitored to see if they develop the condition

Cohort then divided into groups - those with + without condition

Subjects interviewed to assess their risk factors

Correlation between risk factors + development of condition looked for

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37
Q

What are the features of a case-control study?

A

A group with the condition (cases) is compared to a group without it (control)

Past histories of the two groups are investigated

The study will only have validity if the two groups are matched for other factors such as age and sex

38
Q

What are the features of a good study?

A

Variables should be controlled when selecting cohorts/control groups to ensure validity + reliability. This is difficult because humans are very variable…

Measurement techniques/questions must be standardised

Sample size is important - for many diseases only a small % of population is affected, so a large sample size might only contain a small no. individuals with condition

The studied sample should be representative of the whole population to avoid bias

39
Q

What is ‘energy budget’?

A

The amount of energy a person requires (to carry out bodily functions) compared to the energy they consume through their diet

40
Q

What is BMR?

A

Basal metabolic rate

The minimum daily energy required for basic bodily functions e.g. beating of the heart

Measured irrespective of physical activity

41
Q

What can effect BMR?

A

Sex

Age

Body mass

42
Q

What might having an energy imbalance put you at risk of?

A

Weight loss

Or weight gain which could lead to obesity

43
Q

What is the general formula for carbohydrates?

A

Cx(H2O)n

44
Q

What are saccharides?

A

The individual sugar units that make up carbohydrates

45
Q

What are monosaccharides made of?

A

One sugar (saccharide) unit

46
Q

What are disaccharides made up of?

A

2 sugar (saccharide) units

47
Q

What are polysaccharides made up of?

A

Many sugar (saccharide) units

(i.e. more than 2)

48
Q

Describe the structure of glucose

A

Is a hexose sugar as it contains 6 carbons

Is a monosaccharide

Has the formula C6H12O6

Is nearly always in the form of a ring

Has 2 forms - α-glucose (in picture) and β-glucose

49
Q

Explain how the stucture of glucose relates to its functions and makes it a useful molecule

A

Is the source of the most readily available energy from respiration in living things

Its solubility in water helps it fulfil this role as it can easily be carried to where it is needed

It’s also a relatively small molecule makes it easier to move into cells

50
Q

Name 3 disaccharides

A

Maltose

Sucrose

Lactose

51
Q

Describe the stucture of galactose

A

Is a hexose sugar as it contains 6 carbons

Has the formula C6H12O6

Has almost the same structure of glucose except the -H and -OH on the 5th carbon are swapped (as shown in pic)

52
Q

Describe the stucture of fructose

A

Is a hexose sugar as it contains 6 carbons (2 not in ring)

53
Q

Which monosaccharides is the disaccharide maltose made up of?

A

2 α-glucose molecules

Joined by 1,4 glycosidic bonds

54
Q

Which monosaccharides is the disaccharide sucrose made up of?

A

An α-glucose molecule and a fructose molecule

55
Q

Which monosaccharides is the disaccharide lactose made up of?

A

β-glucose and galactose

Joined by 1,4 glycosidic bonds as glucose is in β form

56
Q

Describe how disaccharides are formed

A

By a condensation reaction between 2 monosaccharides

Results in a water molecule being produced

Forms a glycosidic bond

Bond named depending on which carbons the bonds formed between e.g. 1,4

57
Q

Describe how disaccharides are split

A

Split by a hydrolysis reaction where a water molecule is added

The glycosidic bond is broken

The 2 monosaccharides are reformed

58
Q

What type of molecule is a polysaccharide?

A

A polymer

59
Q

What are the 2 forms/types of polysaccharide?

A

Branched or unbranched

60
Q

What is starch?

A

A mixture of the polysaccharides amylose and amylopectin

Found in plants

61
Q

What is glycogen?

A

‘Animal starch’

Polysaccharide found in animals

How monosaccharides (e.g. glucose) are stored for later use as energy for respiration

62
Q

Describe the stucture of amylose

A

Is a straight chain (unbranched) polysaccharide

Made of α-glucose monomers joined with α 1,4 glycosidic bonds

Straight chain coils up due to hydrogen bonding

63
Q

Describe the structure of amylopectin

A

A branched polysaccharide

Made of α-glucose monomers

Monomers joined by both 1,4 and 1,6 glycosidic bonds

The 1,6 glycosidic bonds cause it to be branched

64
Q

Describe the stucture of glycogen

A

A branched polysaccaride

Structure very similar to amylopectin but with more frequent branches

Formed from α-glucose monomers

Monomers joined by both 1,4 and 1,6 glycosidic bonds

1,6 glycosidic bonds cause branching

Has more 1,6, glycosidic bonds than amylopectin hence more branched

65
Q

What happens to starch when it is broken down during digestion?

A

Enzymes catalyse a hydrolysis reaction

This causes monosaccharides to be formed again

66
Q

Explain how the structure of strach relates to its function

A

Its coiled shape (due to the presence of amylose) makes it compact so it can store lots of glucose monomers, and thus energy, in a small space

It is insoluble so doesn’t affect the osmotic potential of cells

Amylopectin is more easily broken down than amylose due to the fact it has more branches and thus more terminal ends. The difference in breakdown speed gives a mix of slow- and fast- glucose/energy release

67
Q

Explain how the structure of glycogen relates to its function

A

Lots of branches (more than amylopectin) means more terminal ends. Therefore can release glucose even faster. Allows quick supply of energy needed in animals

68
Q

Describe the structure of triglycerides

A

Contain 3 fatty acids joined to a glycerol molecule by an ester bond

The formation of the ester bond is a condensation reaction

The glycerol molecule loses 1 H and each fatty acid loses an -OH. So 3 H2O molecules formed in total

Triglycerides have a hydrophobic tail and a hydrophilic head

69
Q

What property do all lipids have?

A

They are all hydrophobic

70
Q

What causes fatty acids/triglycerides to be different from each other?

A

May be different lengths

Fatty acids can be unsaturated or saturated

71
Q

What are mixed triglycerides?

A

Contain 3 fatty acids that are different from each other

72
Q

What are the uses of lipids?

A

To store energy

To act as waterproofing + insulating agents

Can be used to form triglycerides

73
Q

How do the properties of unsaturated fatty acids differ from those of saturated fatty acids?

Why?

A

Membranes containing unsaturated fatty acids are more fluid

Unsaturated fatty acids have lower melting/boiling points and are generally more flexible

This is because they have a kink at each double bond

74
Q

What is cholesterol used for in the body?

A

Is an essential component of cell membranes where it affects their fluidity

75
Q

Chloesterol is a water-insoluble lipid.

How is it carried around the body?

A

By proteins in complexes called lipoproteins

There are 2 types: Low density and high density

76
Q

Out of LDL and HDL, which is the ‘bad’ cholesterol?

A

LDL

77
Q

Describe the features of LDL

A

Formed from saturated fats, protein, and cholesterol

Binds to cell surface receptors which can become saturated, leaving LDLs in the blood

Associated with the development of atherosclerosis

Should be maintained at a low level

78
Q

Describe the features of HDL

A

Formed from unsaturated fats, protein, and cholesterol

Transports cholesterol from body tissues to the liver where it is broken down

Reduces blood cholesterol levels hence discourages the development of atherosclerosis

Should be maintained at a high level

79
Q

There is a correlation between the amount of cholesterol in diet and the rate of CVD.

Suggest a causal link

A

A high cholesterol diet leads higher blood choleserol levels

This could cause an increase in LDLs in the blood, meaning choleserol is harder to remove

There may be too much cholesterol for HDLs in the blood to quickly remove

Hence the higher blood cholesterol levels resulting lead to the formation of more plaques in the endothelium of arteries

80
Q

What actions can individuals take to reduce their risk of CVD?

A

Stop smoking

Maintain resting blood pressure below 140/90mm Hg

Maintain low blood cholesterol levels

Maintain a normal BMI/low wait-to-hip ratio

Take regular physical exercise

Moderate/no consumption of alcohol

Reduce stress

81
Q

What dietary strategies can an individual follow to reduce their risk of CVD?

A

Reduce saturated fat intake (reduces total cholesterol but LDL:HDL more)

Consume more polyunsaturated fats (reduced LDL:HDL)

Reduce salt (lowers fluid levels in blood so reduces blood pressure)

Eat more fruit + veg (antioxidants + non-starch carbs lower blood cholesterol)

Eat more oily fish (linked to slight reduction in blood pressure + risk of clotting)

Eat more non-starch polysaccharides

82
Q

What type of molecule is Vitamin C?

A

An antioxidant

Hence it’s a reducing agent

83
Q

What role do antioxidants play in the body?

A

Neutralise free radicals which damage cells

84
Q

How is Vitamin C destroyed?

A

Heat treatment

85
Q

What drug treatments can be used to reduce the risk of CVD?

A

Diuretics (antihypertensive)

Calcium channel blockers (antihypertensive)

Angiotensin Converting Enzyme inhibitors (antihypertensive)

Statins

Anticoagulants e.g. warfarin

Platelet inhibitory drugs e.g. aspirin, clopidogrel

86
Q

Describe the mode of action of diuretics + any risks/side effects

A

Increase the volume of urine
This lowers blood volume and hence blood pressure

Very occasional dizziness, nausea, muscle cramps

87
Q

Describe the mode of action of calcium channel blockers + any risks/side effects

A

Disrupts calcium ion movement through calcium channels in the cell membrane.
This reduces muscle contaction, so increases the diameter of arteries. Also reduces the force + frequency of heart beats. Hence lowers blood pressure

Heaches, dizziness, swollen ankles, constipation, flushing of face

88
Q

Describe the mode of action of ACE inhibitors + any risks/side effects

A

Blocks the producition of ACE. This reduces arterial constriction so lowers blood pressure

Cough, dizziness, abnormal heart rhythm, impaired kidney function

89
Q

Describe the mode of action of statins + any risks/side effects

A

Inhibit an enzyme in the liver that produces LDL cholesterol

Tiredness, disturbed sleep, nausea, diarrhoea, headache, mucle weakness
People may depend wholly on statins + not change their diet/lifestyle

90
Q

Describe the mode of action of anticoagulents + any risks/side effects

A

Reduce risk of clot formation

Risk of uncontrolled bleeding
Dosage control is essential

91
Q

Describe the mode of action of platelet inhibitory drugs + any risks/side effects

A

Make platelets less sticky

  • *Aspirin irritates stomach lining** + can cause bleeding
  • *Clopidogrel** with aspirin increases this risk
92
Q

What are the potential ethical issues of using Daphnia/invertebrates in research?

A

Can’t give consent

No way of knowing if they’re in pain or not (or if they feel pain like we do)

Don’t use pregnant Daphnia to reduce harm/potential death

Minimise time spent on microscope slide as heat from lamp can kill them

Only use once to reduce exposure (to caffeine solution) and thus harm

Keep in cool water to prevent overheating/death

A Level Biology (Edexcel Salters-Nuffield) (10 decks)

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