Topic 1 Flashcards
Why do mammals and other large organisms need a circulation system?
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
How does the surface area to volume ratio affect how substances enter/leave an organism?
In organisms with a small surface area to volume ratio, substances + water can enter and leave by diffusion + osmosis
What size surface area to volume ratio might a small organism have?
What size surface area to volume ratio might a large organism have?
Small organisms have a large surface area to volume ratio
Large organisms have a small surface area to volume ratio
What 3 properties make water a good solvent for transporting susbtances + CO2 around the body?
It is a polar molecule
It is a liquid at RTP
It easily dissolves molecules held together by ionic bonds
What is a polar molecule?
A molecule with an uneven charge distribution
One end is slightly positive (𝛿+) and the other is slightly negative (𝛿-)
Explain why water is described as a dipolar molecule
Because the oxygen end is negatively charged and the 2 hydrogen ends have a positive charge
Why is water a liquid at room temperature?
Because seperate water molecules are held together by hydrogen bonds
These are formed by the electrostatic attraction between the polar molecules
Why is water able to dissolve molecules held together by ionic bonds?
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
Aside from molecules held together by ionic bonds, what other molecules can water dissolve?
Other polar molecules
e.g. Sugars + amino acids
Describe the sturcture + corresponding function of arteries
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
Describe the structures + corresponding functions of veins
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
Describe the structures + corresponding functions of capillaries
Very thin wall (1 cell thick) - allows rapid exchange between blood + tissues
How can the materials that make up arteries, veins, and capillaries be compared?
Arteries + veins are made of the same tissues but in different proportions
Capillaries only have an endothelium
Draw diagrams to show the structure of arteries, veins, and capillaries
Explain why the mammalian heart has 2 sides
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)
Label the diagram of the heart shown below
Also label the apex (bottom) of the heart + the septum (wall seperating sides)
Could also label the tendinous cords that support the semilunar valves
What are the names of the artieries that carry oxygenated blood to the neck + head?
Cartoid arteries
What is another name for the artioventricular valve in the right side of the heart?
The tricuspid valve
What is another name for the atrioventricular valve in the left side of the heart?
The bicuspid valve
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
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
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
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
What causes the formation of a blood clot?
Damage to a tissue
What is atherosclerosis?
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
Describe the possible health effects of having an atheroma
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
Describe the stages that lead to the formation of an atheroma
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!)
It’s important that a blood clot doesn’t form in the wrong place or at the wrong time.
How is this prevented?
A number of (clotting) factors have to be present for a blood clot to be able to form
Describe the sequence of the clotting cascade
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.
What is risk?
The probability of an unwanted event/outcome occuring
What can cause people to overestimate risk?
Involunatary (e.g. being a passanger in a plane as opposed to driving a car)
Dreaded
Not natural
Unfair
Unfamilliar
Very small
Why do people tend to judge the risk of heart disease poorly?
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)
Give the risk factors for CVD and explain why they increase risk
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
What does correlation mean?
That a change in one varible is accompanied by/corresponds to a change in another
Doesn’t mean there is a causation
What is causation?
When the change in one variable causes the change of another
If this is the case the variable are said to be causally linked
What is an epidemiologist?
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
What are the 2 main types of study?
Cohort studies
Case-control studies
What are the features of a cohort study?
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
What are the features of a case-control study?
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
What are the features of a good study?
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
What is ‘energy budget’?
The amount of energy a person requires (to carry out bodily functions) compared to the energy they consume through their diet
What is BMR?
Basal metabolic rate
The minimum daily energy required for basic bodily functions e.g. beating of the heart
Measured irrespective of physical activity
What can effect BMR?
Sex
Age
Body mass
What might having an energy imbalance put you at risk of?
Weight loss
Or weight gain which could lead to obesity
What is the general formula for carbohydrates?
Cx(H2O)n
What are saccharides?
The individual sugar units that make up carbohydrates
What are monosaccharides made of?
One sugar (saccharide) unit
What are disaccharides made up of?
2 sugar (saccharide) units
What are polysaccharides made up of?
Many sugar (saccharide) units
(i.e. more than 2)
Describe the structure of glucose
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
Explain how the stucture of glucose relates to its functions and makes it a useful molecule
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
Name 3 disaccharides
Maltose
Sucrose
Lactose
Describe the stucture of galactose
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)
Describe the stucture of fructose
Is a hexose sugar as it contains 6 carbons (2 not in ring)
Which monosaccharides is the disaccharide maltose made up of?
2 α-glucose molecules
Joined by 1,4 glycosidic bonds
Which monosaccharides is the disaccharide sucrose made up of?
An α-glucose molecule and a fructose molecule
Which monosaccharides is the disaccharide lactose made up of?
β-glucose and galactose
Joined by 1,4 glycosidic bonds as glucose is in β form
Describe how disaccharides are formed
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
Describe how disaccharides are split
Split by a hydrolysis reaction where a water molecule is added
The glycosidic bond is broken
The 2 monosaccharides are reformed
What type of molecule is a polysaccharide?
A polymer
What are the 2 forms/types of polysaccharide?
Branched or unbranched
What is starch?
A mixture of the polysaccharides amylose and amylopectin
Found in plants
What is glycogen?
‘Animal starch’
Polysaccharide found in animals
How monosaccharides (e.g. glucose) are stored for later use as energy for respiration
Describe the stucture of amylose
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
Describe the structure of amylopectin
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
Describe the stucture of glycogen
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
What happens to starch when it is broken down during digestion?
Enzymes catalyse a hydrolysis reaction
This causes monosaccharides to be formed again
Explain how the structure of strach relates to its function
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
Explain how the structure of glycogen relates to its function
Lots of branches (more than amylopectin) means more terminal ends. Therefore can release glucose even faster. Allows quick supply of energy needed in animals
Describe the structure of triglycerides
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
What property do all lipids have?
They are all hydrophobic
What causes fatty acids/triglycerides to be different from each other?
May be different lengths
Fatty acids can be unsaturated or saturated
What are mixed triglycerides?
Contain 3 fatty acids that are different from each other
What are the uses of lipids?
To store energy
To act as waterproofing + insulating agents
Can be used to form triglycerides
How do the properties of unsaturated fatty acids differ from those of saturated fatty acids?
Why?
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
What is cholesterol used for in the body?
Is an essential component of cell membranes where it affects their fluidity
Chloesterol is a water-insoluble lipid.
How is it carried around the body?
By proteins in complexes called lipoproteins
There are 2 types: Low density and high density
Out of LDL and HDL, which is the ‘bad’ cholesterol?
LDL
Describe the features of LDL
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
Describe the features of HDL
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
There is a correlation between the amount of cholesterol in diet and the rate of CVD.
Suggest a causal link
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
What actions can individuals take to reduce their risk of CVD?
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
What dietary strategies can an individual follow to reduce their risk of CVD?
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
What type of molecule is Vitamin C?
An antioxidant
Hence it’s a reducing agent
What role do antioxidants play in the body?
Neutralise free radicals which damage cells
How is Vitamin C destroyed?
Heat treatment
What drug treatments can be used to reduce the risk of CVD?
Diuretics (antihypertensive)
Calcium channel blockers (antihypertensive)
Angiotensin Converting Enzyme inhibitors (antihypertensive)
Statins
Anticoagulants e.g. warfarin
Platelet inhibitory drugs e.g. aspirin, clopidogrel
Describe the mode of action of diuretics + any risks/side effects
Increase the volume of urine
This lowers blood volume and hence blood pressure
Very occasional dizziness, nausea, muscle cramps
Describe the mode of action of calcium channel blockers + any risks/side effects
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
Describe the mode of action of ACE inhibitors + any risks/side effects
Blocks the producition of ACE. This reduces arterial constriction so lowers blood pressure
Cough, dizziness, abnormal heart rhythm, impaired kidney function
Describe the mode of action of statins + any risks/side effects
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
Describe the mode of action of anticoagulents + any risks/side effects
Reduce risk of clot formation
Risk of uncontrolled bleeding
Dosage control is essential
Describe the mode of action of platelet inhibitory drugs + any risks/side effects
Make platelets less sticky
- *Aspirin irritates stomach lining** + can cause bleeding
- *Clopidogrel** with aspirin increases this risk
What are the potential ethical issues of using Daphnia/invertebrates in research?
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
