1
Q
Why do only small animals have an open circulatory system?
A
- Their surface area is small enough to rely on diffusion
- Diffusion is only quick enough in small animals
Because the rate of diffusion is inversely proportional to the distance travelled
2
Q
What are the advantages of a double circulatory system?
A
- Blood can pass slowly through the region where gas exchange occurs
- This maximises the transfer of of O2 and CO2
- But this causes a large pressure drop
- Therefore blood is moved back to the heart
- This allows the blood to be pumped around the body at high pressure
- Allowing the organism to be very active
3
Q
What are the disadvantages of a 3 chambered heart?
A
- Oxygenated and deoxygenated blood are mixed
4
Q
Why do animals have a heart and circulation?
A
- Diffusion is too slow because of a small SA:V ratio
- Which means materials can’t travel quick enough
- So diffusion can’t support a high metabolic rate
- Animals need to maintain a constant temperature (uses energy)
- A heartbeat means blood can reach the capillaries quickly
5
Q
What is the structure of the heart?
A
*SEE DIAGRAM
- Shown as if we were facing someone
- Left ventricle has thicker walls because a greater force is needed to push blood around the body
- Tricuspid valve has 3 flaps, preventing back flow into the right atrium
- Bicuspid valve has 2 flaps, preventing back flow into the left atrium
- Atria are smaller as they only have to collect blood
- The Vena Cava and Pulmonary Vein don’t have valves because the Vena Cava has low pressure and the right ventricle also has low pressure, as it has mostly emptied itself
6
Q
What is intermolecular bonding in water?
A
- There are strong covalent bonds between H and O
- There are weak intermolecular bonds between each atom
This creates a liquid that can be pumped around the body while carrying materials
7
Q
What is adhesion?
A
- The formation of hydrogen bonds between cellulose and water molecules
8
Q
What is cohesion?
A
Where hydrogen bonds with water molecules
9
Q
Why is water a good solvent?
A
- Water is a good solvent of sonic, charged and polar chemicals
- This is because of the attraction between particles in the chemicals and the polar water molecules (hydrophilic)
- This allows for vital biochemical reactions to occur in the cytoplasm of cells
- This allows substances to be transported around the body, as well as into it
10
Q
Do non-polar substances dissolve?
A
- No, as they are hydrophobic
11
Q
What are the thermal properties of water?
A
- Water has a high specific heat capacity
- This is because it requires a large volume of energy to break the hydrogen bonds
- This helps to avoid rapid changes in the internal temperature
- This allows organisms to maintain a steady temperature
- Water is at room temperature because the water molecule is polar
12
Q
What is mass flow?
A
- The process of materials being carried in a liquid in one direction to multiple exchange surfaces
13
Q
What is the role of skeletal muscles in blood flow?
A
- They push blood back up towards the heart
14
Q
What are the steps of the skeletal muscles assistance in blood flow?
A
- Relax - The valves are closed
- Contract - The valves open and blood is rushed upwards
- Relax - The valves close as blood falls back
15
Q
What is the structure and function of the arteries?
A
- To carry blood away from the heart at high pressure
- They have a tough outer layer to prevent bursting due to high pressure
- They have a thick layer of muscle and elastic fibres to help pump blood through after each contraction of the heart
- They have a narrow lumen to help maintain the high pressure, preventing back flow
16
Q
What is the structure and function of the capillaries?
A
- Supplies all cells with their requirements (O2) and removes their waste products (CO2)
- They have a cell wall that is one cell thick - they don’t need a strong wall as most of the blood pressure has been lost
- They have a narrow lumen - it is only just wide enough for a RBC to pass through
The thin walls and narrow lumen bring blood into close contact with body tissues - This close contact means a small diffusion pathway and a large SA
- The walls contain pores which allows WBC to enter/exit
17
Q
What is the structure and function of veins?
A
- They return blood to the heart at a low blood pressure
- Their wall is thin and mainly fibrous tissue
- They don’t require a strong wall as pressure has been lost
- They have a wide lumen which means there is less resistance to the blood flow
- They contain valves, which prevent back flow
18
Q
What is the purpose of the cardiac cycle?
A
- To flow blood from the vena cava and pulmonary veins to atria
19
Q
What is the process of Atrial Systole?
A
- The atria contracts and pumps into ventricles
20
Q
What is the process of ventricular systole?
A
- The ventricles contract and pump blood to the arteries
- The increased BP forces atrioventricular valves to shut and semi-lunar valves to open
21
Q
What is the process of ventricular diastole?
A
- Everything relaxes and the atria fills with blood
- The increased BP in the atria opens the AV valves
22
Q
Where does the left ventricle pump blood?
A
- Thick muscle walls to pump blood around the body
23
Q
Where does the right ventricle pump blood?
A
- Thinner muscle walls to pump blood to the lungs
24
Q
What is atherosclerosis?
A
- When atheroma’s form inside the arterial walls, thus narrowing the artery
- It increases the chances of blockages in arteries (thrombosis)
- This can lead to a total blockage of coronary arteries = HA
25
What are causes of Atherosclorosis?
* Damage to endothelium
- Caused by HBP, toxins or oxidised LDL (REF to free radicals)
* Inflammatory response
- WBC leaves blood vessel to artery wall accumulating chemicals from the blood - especially Cholesterol
- Calcium salts and fibrous tissue collects =ing a plaque
- Loss of artery elasticity
- Narrowing can lead to strain and +ve feedback
26
How does clotting occur at the atheroma?
- Platelets change shape when they come into contact w/ damaged blood vessel
- Stick to exposed collagen in artery wall
- Form a temporary platelet plug =ing more platelets being activated
- Blood contact w/ collagen =ing series of chemical changes
27
What is the process of atherosclerosis?
1. Artery wall damaged so inflammatory response
2. WBC enter wall bringing cholesterol which accumulates = Atheroma
3. Calcium salts and fibrous tissue accumulate = Plaque
4. Wall elasticity reduced and artery narrowed
5. Raises BP = Atherosclerosis
6. Platelets in contact w/ wall and become sticky
7. Platelet plug forms =ing chemical changes
8. Prothrombin → Thrombin → Fibrinogen → Fibrin
9. Tangled mesh traps blood clots
10. A blood clot forms which can lead to myocardial infarction
28
What are macrophages?
- Make proteins that act in 2 ways
- ‘Punch’ holes in bacteria so that they die
- Phagocytose them (eat them)
- However it can’t deal w/ one particular microorganism as some will always survive
- Also can’t remember past infections
29
What is correlation?
- When an increase/decrease can be linked to an increase/decrease in the other variable
30
Does correlation = causation?
NO
31
Why do people perceive risk wrong?
- People guess the number of deaths per risk wrong mostly b/c:
- Over/underestimate the danger
- Forget about medical advancements
- Over/underestimate the time it takes some illnesses to become fatal
32
How do you design a good study?
- Large sample size (to make it reliable)
- Use of control variable (to compare against)
- Clearly stated aim and hypothesis
- A design appropriate to the question
- Participants are representative (to make valid results)
- Knowledgeable about what to look for during study and analysing results
- Appropriate measurements are made (to be valid)
- Methods used are repeatable (to be reliable)
- Time scale is suitable
- Other variables taken into account
- Carried out by an unbiased company (to be reliable)
33
What is a cohort study?
- Follow a group of people over time to see who develops the disease
- People’s exposure to risk factors are recorded and tested for correlation
34
What is a case-control study?
- A group of people w/ a disease compared w/ a control group
- Information on risk factors is collected
35
What are monosaccharides?
- Have 2 or more hydroxyl groups
- Either contain an aldehyde group (aldoses)
- Or a ketone group (ketoses)
- Formula = (CHշO)n
- Ring formation
- In aqueous solution aldehyde/ketone groups of a sugar molecule react w/ a hydroxyl group of the same molecule
- Which closes the molecule into a ring
36
What are Isomers?
- Many monosaccharides differ only in their spatial arrangement
- Small differences = minor changes in chemical properties
- But recognised by enzymes and other proteins = important biological effects
37
What are dissaccharides?
- Carbon carrying aldehyde/ketone group can react w/ any hydroxyl group
- Disaccharide (2 sugar units) = 2x monosaccharides (2x 1 sugar units)
- Formed through a condensation reaction =ing water being released
- Formula = Cx(HշO)n
38
What are Oligosaccharides and Polysaccharides?
- Short chains of molecules are called oligosaccharides
- Long chains are called polysaccharides
- Long and linear branched molecules can be made from repeating units
- Oligosaccharides are non-digestible
- Helps feed friendly bacteria so are referred to as prebiotics
- Prebiotics in large intestine
39
What are α and β links?
- The hydroxyl group can rapidly change
- α hydroxyl group is below
- β hydroxyl group is above
- As soon as one sugar is linked to another the forms are frozen
- (1-4) glycosidic link 1 = carbon no. of first mono, 4 = carbon no. of second
40
What is starch?
- α glucose arranged in a helix
- Energy stored in plant cells
- Insoluble
- Doesn’t draw water into cells
- Doesn’t easily diffuse into cells
- Compact
- Easily transported when hydrolysed into α-
glucose
41
What is glycogen?
- Energy stored in animal cells
- Similar storage advantages to starch
- Shorter chains = more highly branched
- Even more readily hydrolysed
42
What are lipids?
- Insoluble in water
- 3 fatty acids and a glycerol
- Triglyceride = 3 fatty acids and a glycerol
(lipid)
43
What is the condensation reaction?
- Produces a fat and HշO
- 1st a monoglyceride is formed
- 2nd a diglyceride is formed
- 3rd a triglyceride is formed
- Unsaturated fats are found mainly in plants
- Ester bonds are formed b/w glycerol and
fatty acids
44
The Energy Balance
- Mass of calories needed each day depends on:
- Volume of energy body uses at rest
(basal metabolic rate)
- Energy used as a result of eating (specific
dynamic action)
- The volume of physical activity carried out
- Energy requirement < energy intake = weight
gain
- Energy requirement > energy intake = weight
loss
- Energy intake = total energy output (heat +
work + energy storage)
- RDA = recommended daily intake
- DRV = dietary reference values
- L/HRNI = lower/ higher reference nutrient
intake
45
What is Cholesterol?
- C27H46O
- w/o cholesterol body couldn’t function
- Help form/repair cell membranes and some
hormones
- Links fatty acids together to stabilise and
strengthen cell membranes
- Carried by proteins (when together called
lipoproteins)
46
What are the sources of cholesterol?
- Liver (80%)
- Food (20%)
47
What are things that affect cholesterol levels?
- Genetics
- Physical activity
- Stress
- Diet/ habits (eg. smoking
48
What are HDL's?
- Is good cholesterol
- Unsaturated
- Less likely excess will be deposited on artery
walls
- Higher % protein than LDL (more dense)
- Transport cholesterol to liver for elimination
- So ↓blood cholesterol and helps to remove
fatty plaques of atherosclerosis
49
What are LDL's?
- Carry cholesterol away from the liver
- Excess can be deposited on artery wall
- So known as bad cholesterol
- Triglyceride + cholesterol + protein = LDL
- Bind w/ receptor sites on cells
- Excess overloads membrane receptors =
↑blood cholesterol
- Saturated fats ↓activity of LDL receptors
so LDL not removed from the blood (+ve
feedback)
50
Fats in the diet
- Saturated = raise blood cholesterol (no double bonds)
- Mono-unsaturated = can ↓cholesterol and improve balance b/w HDL and LDL
- Polyunsaturated = ↑activity of LDL receptor site to actively remove them from blood
51
Free Radicals
= Any atom/molecule w/ an ‘unpaired’ electron (not a cell)
- Unpaired electron is restored to a pair by pulling a hydrogen atom from another
- Causes damage to DNA, proteins, lipids, cell membranes and mitochondria
- Produced w/n
- Mitochondria in respiration reactions
- Reactions inv. Hydrogen peroxide can = hydroxyl radicals
- The breakdown of toxic chemicals and their products
- WBC and them destroying bacteria and virus infected cells
*. Causes CHD
- LDL’s undergo oxidation b/c of free radicals - released from endothelial cells
- Attracts macrophages and initiates atherosclerosis plaque formation
- Larger no.s of free radicals mean more LDL’s are oxidised
52
Antioxidants
- Helps reduce levels of free radicals
- Sources inc. tea, red wine, fruit, veg, legumes
- They neutralise free radicals
53
Vitamin C
- An antioxidant
- Oxidised LDL is more readily taken up by the WBC involved in atherosclerosis
54
DCPIP Experiment
- DCPIP is a redox dye (blue when oxidised)
- When reduced it turns clear (OIL RIG)
- Vitamin C is ascorbic acid, reduces DCPIP to colourless slightly pink solution
Method:
1. Have 5 test tubes of the same volume of DCPIP→for validity→glass
2. Then use a pipette to place 1 drop of a substance into a test tube→to see if it goes clear→long contact w/ DCPIP = irritation // eyes
3. Keep adding one drop of the substance, till you can’t see the DCPIP, keeping record of how many drops→to see how many drops are necessary→glass // DCPIP
4. Once the DCPIP has disappeared, compare it to a calibration curve of DCPIP volume against vitamin C content→to know vitamin C content
5. Then repeat experiment w/ different substances→to compare
6. Repeat whole experiment and create an average→for reliability
* If its a solid to be tested
- Take a small section and put into a test tube to a depth of ~2cm
- Add a similar volume of distilled water and stir w/ a glass rod
- Leave for a few minutes, and then carry out normal experiment
55
Effect of Heart Rate in Daphnia
* Daphnia:
- Transparent so can easily see the heart beating
- Counting number of beats may be difficult b/c its quick and their legs
- Freezing them beforehand slows down heart rate
- Or count the rate of leg beats, which is proportional to HR
- Control Group: recording HR of Daphnia in culture solution
- Distilled water may increase HR as less O2
- Blind study may be better so counters don’t assume or bias results
* Problems
- Human error
- difficult to count HR
- making caffeine solutions
- counting for different lengths of time
- Stress on Daphnia may increase HR
* Ethical problems
- Daphnia are living creatures and don’t deserve to be put under stress
- Microscope lights may be hot, so burn Daphnia
- Many Daphnia’s may die as a result of the experiment
* Control variables
- Temperature of the solution
- Size/ age/ gender of the daphnia
- Time spent counting Daphnia
56
Effect of Heart Rate in Daphnia - Method
1. Place a few strands of cotton wool on a cavity slide→restrict flea movement→glass
2. Using a pipette transfer the Daphnia, and add pond water to the slide→for normal breathing rate→glass // water
- Use as much water as possible, to keep O2 levels high
3. Use a stopwatch and count the no. of heart beats in 10 seconds→to record heart rate
4. Repeat procedure using other Daphnia, and create an average→for validity
5. Repeat previous steps using different caffeine solutions→for reliability
6. Record results in a suitable format and present them in an appropriate graph→for validity and reliability
57
What are the habits that can increase risk of CVD?
- Smoking
- Caffeine
- Cholesterol levels (esp. LDL cholesterol)
58
What can reduce risk of CVD?
* Scientific Knowledge of:
- Diet
- Obesity indicators
- BMI
- Waist-to-hip ratio
- Exercise
- Smoking
59
Diuretics
- Increase urine volume
- Rids body of excess fluids and salts
- Blood volume falls
- Lower stroke volume
- BP drops
60
Beta Blockers
- Blocks the response the heart gives to hormones, eg. adrenaline
- Contractions less strong = lowered HR and BP
61
Diuretics and Beta Blockers - Side Effects
- General: prolonged BP = dizziness = falls/ injuries
- Which can be life threatening in elderly
- Specific: dry cough, abnormal heart rhythms, fatigue, swelling of ankles, constipation, impotence
- They can mask benefits and lead to patients dropping treatment
62
Diuretics and Beta Blockers - Benefits
- They lower BP
- Means ↓ risk of CVD, which inc. life threatening conditions (eg. heart attack)
63
Statins
- What it does:
- Inhibits cholesterol synthesis in the liver
- Increases LDL uptake
- Improves the balance of HDL:LDL
- Improves the lining of the endothelium
64
Statins - Side Effects
- Muscle pain, constipation, nausea and changes in attitude
65
Anticoagulant and Platelet inhibitory drugs
- Prevents blood clotting easily
- Prescribed after surgery from thrombosis
- Anticoagulants, eg. Warfarin
- Interfered w/ manufacture of prothrombin
- Platelet inhibitors, eg. Aspirin
- Make platelets less sticky
- Reduces blood clotting
66
Anticoagulant and Platelet inhibitory drugs - Risks
- Aspirin = irritates stomach lining, can cause bleeding
- Careful monitoring of any drug is needed to prevent internal bleeding, eg. in the brain
A Level Biology (SNAB)
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