BIOLOGY EDEXCEL UNIT 1 DETAILED PPT FOR

BIOLOGY PPT IGCSE

1. Edexcel
Unit 1

2. Structure of the Heart
Arteries and Veins
The Cardiac Cycle
Atherosclerosis
Estimating Risk
Identifying Health Risks
Prevention and
Treatment of CVD

Blood Pressure
Carbohydrate Structure
Lipids
 Energy Budget
Cholesterol
Caffeine affecting heart
rate
Vitamin C

3. Dipole
Positive H
Negative O
Electrostatic
attraction
between water
molecules
forming Hydrogen
bonds
Water molecules
‘stick together’

4. Components:
1.Plasma
2.Erythrocytes
3.Leucocytes
4.Platelets
Functions:
1.Transports; digested food
to diff parts of the body,
food molecules from
storage areas to cells that
need them, excretory
products to e.g. kidneys or
lungs, hormones
2.Keeps body temp regular
3.Acts as a buffer to pH
changes

5. Thrombosis is used by the body to prevent lots of blood
being lost when a blood vessel is damaged. A series or
reactions occurs that leads to the formation of a blood clot.
1.Platelets releases two main substances; serotonin and
thromboplastin.
2.Serotonin causes smooth muscle of blood vessels to
contract. Blood flow cut off from damaged area.
3.Thromboplastin triggers the conversion of prothrombin
(large protein) into thrombin (an enzyme)
4.Thrombin then catalyses the conversion of fibrinogen
(soluble protein) to fibrin (solid insoluble fibres)
5.The fibrin fibres tangle together and form a mesh in
which platelets and red blood cells get trapped – forms a
blood clot.

6. Fibrin fibres
have tangled
together to form
a mesh.

7. Learn the names of the
different valves, arteries
and veins for the exam.




Also known
as Atrioventricular
valve.

8. Arteries:
Narrow lumen. Smaller the further
away from heart.
Smallest branches are ‘arterioles’
Thick muscular walls with elastic
fibres
Near heart=more elastic fibres and
collagen(for strength and flexibility)
Far from heart=more muscle tissue
Smooth lining allow easy blood flow
No valves
Pumps oxygenated blood to the body
Blood at high pressure

Veins
Wide lumen
Thinner walls (less smooth muscle
with few elastic fibres)
Less collagen than arteries, but outer
tough layer of mainly collagen fibres
Has valves to stop backflow
Pumps deoxygenated blood to the
heart
Blood at low pressure

9. Every time the heart contracts, blood is forced into
arteries and their elastic wall stretch to accommodate
the blood.
When the heart relaxes, the elasticity of the artery
walls causes them to recoil behind the blood, helping
to push the blood forward.
Pressure falls further away from heart

10. The heart has a less direct
effect on the flow of blood
through the veins.
In the veins, blood flow is
assisted by the contraction of
skeletal muscles during
movement of limbs and
breathing.
Backflow is prevented by
semi lunar valves within the
veins
The steady flow without
pulses of blood means that
the blood is under low
pressure in veins
Valves preventing backflow

11. One cell thick
No collagen, smooth muscle or elastic fibres
Allows quick diffusion of gases

12. Phase 1: Atrial Systole
(Ventricles are relaxed) The
atria contract, decreasing
the volume of the chamber
and increasing the pressure
inside the chamber This
pushes the blood into the
ventricles. AV-valves are open
There is a slight increase in
ventricular pressure and
chamber volume as the
ventricles receive the
ejected blood from the
contracting atria.

(The atria relax). The ventricles
contract, increasing their
pressure. The pressure becomes
higher in the ventricles than the
atria, which forces the
atrioventricular valves shut to
prevent back-flow.
The pressure in the ventricles is
also higher than in the aorta
and pulmonary artery, which
forces open the semi-lunar
valves and blood is forced out
into the arteries.

Phase 2: Ventricular Systole

13. The ventricles and atria both relax. The higher pressure in the
pulmonary artery and aorta closes the semi-lunar valves to
prevent back-flow into the ventricles.
Blood returns to the heart and the atria fill again due to the
higher pressure in the vena cava and pulmonary vein. This starts
to increase the pressure of the atria.
As the ventricles continue to relax, their pressure falls below
the pressure of the atria and the atrioventrivular valves
open this allows blood to flow passively into the
ventricles from the atria
The atria contract and the whole process starts again.

Phase 3: Diastole

14. Pulmonary
vein
Or
Atrioventricular
valve
Or
Atrioventricular
valve
Vena Cava
Pulmonary
Artery
Aorta

15. What is it?
Means ‘hardening of the arteries’
It is the disease process that leads to coronary heart
disease and strokes.
Fatty deposits can either block an artery directly, or
increase its chance of being blocked by a blood clot
(thrombosis) – the blood supply can be blocked
completely and cells can be permanently damaged.

16. The endothelium (smooth lining of blood vessel) becomes damaged.
result from high blood pressure which puts an extra strain on the layer of cells, or
from toxins in cigarette smoke in the bloodstream.
 Then there is an inflammatory response once the inner lining of the
artery is breached. White blood cells leave the blood vessel and move
into the artery wall accumulates chemicals e.g. Cholesterol.
A fatty deposit builds up called an atheroma
A hard swelling called a plaque occurs as fibrous tissue and calcium
salts build-up around the atheroma. Artery wall loses some of its
elasticity. THIS IS ATHEROSCLEROSIS.
Plaques cause the artery to become narrower. This makes it more
difficult for the heart to pump blood around the body and can lead to a
rise in blood pressure.
Now there is a dangerous positive feedback plaques lead to
raised blood pressure and raised blood pressure makes it more likely
that plaques will form

17. Angina: gripping pain in the chest, breathless,
narrowed coronary arteries (from a formation of a
plaque) cannot supply enough oxygenated blood and
heart muscle has to start anaerobically respiring.

Myocardial Infarction (Heart Attack): coronary artery
becomes fully blocked, heart muscle starved of oxygen.
Many as a result of atherosclerosis. A clot that forms in
a blood vessels is known as a ‘thrombosis’

18. Interruption to normal blood supply in an area of the
brain

Either from bleeding from damaged blood capillaries
or blockage of blood vessel

Symptoms: FAST: face etc.

19. Risk – ‘the probability of occurrence of some unwanted event or
outcome’
The statistical chance of something unfavourable happening is
supported by scientific research e.g. The actual risk of dying
from CVD is 60% higher for smokers than non-smokers.
People’s perception may be different from actual risk

May overestimate the risk e.g. May have known someone who
smoked and died from CVD, therefore think if you smoke you
will die of CVD. Articles and media give constant exposure which
make people worry
Underestimate risk, could be due from lack of information
making them unaware of the factors that contribute to diseases
like CVD.

20. Lifestyle risk factors for CVD:
1.Diet – high in saturated fats increases blood cholesterol
level leads to atheroma formation, which leads to
blood clots and therefore heart attack or stroke. High is
salt increases risk of high blood pressure.
2.High blood pressure – increases risk of damage to the
artery walls, which increases risk of atheroma formation
leads to CVD.
3.Smoking – CO combines with haemoglobin and reduces
amount of oxygen transported in the blood.
4.Inactivity – lack of exercise increases risk of CVD as it
increases blood pressure

21. Factors beyond your control
1.Genetics - inherit particular alleles that make them
more likely to have high blood pressure or high
blood cholesterol, more likely to suffer from CVD
2.Age – risk of developing CVD increases with age.
Arteries lose some of their elasticity
3.Gender – men are 3 times more likely to suffer from
CVD than pre-menopausal women

22. Antihypertensives
Include diuretics, beta-blockers,
Sympathetic nerve inhibitors, ACE
inhibitors
Reduce high blood pressure – less
chance of damage to artery walls.
Benefits – different
antihypertensives work in different
ways, so can be given in
combination. Blood pressure can be
monitored at home
Risks – coughs, swelling of the
ankles, impotence, tiredness,
fatigue and constipation. Not
serious compared to risks of high
blood pressure
Reduce blood cholesterol
level by reducing amount of
cholesterol abosorbed by the
gut
Block the enzyme in the liver
that is responsible for making
cholesterol
Benefits – reduce risk of
developing CVD and
atherosclerosis forming
Risks – muscle and joint
aches, nausea, constipation,
diorrhoea
Statins

23. Sold in spreads and yoghurts
Similar structure to cholesterol
Reduces amount of cholesterol being absorbed from
your gut into your blood

Makes it easier for body to deal with cholesterol and
reduces level of LDLs in your blood

24. Anticoagulants
E.g. Warfarin. Reduce blood clots
(thrombosis) – blood clots are less likely
to form at sites of damage in artery
walls. Interferes with production of
prothrombin
Benefits – used to treat people who
already have blood clots or CVD or who
have just had heart surgery. Prevent any
existing blood clots from growing any
larger and prevent any new blood clots
from forming
Risks – if person is badly injured, the
reduction of blood clotting can cause
excessive bleeding, which can lead to
fainting or even death. Other side effects
are allergic reactions, osteoporosis and
swelling of the tissues.
A type of anticoagulant
They work by making platelets
less sticky so they don’t clump
together to form a blood clot e.g.
aspirin, clopidogrel
Benefits – can be used to treat
people who already have blood
clots or CVD, (but can’t get rid of
existing blood clots)
Risks – side effects including,
irritates stomach lining, rashes,
diarrhoea, nausea, liver function
problems and excessive bleeding
Platelet Inhibitory
Drugs

25. Elevated blood pressure, known as hypertension, is
considered to be one of the most common factors in
the development of CVD.
Systolic pressure – pressure in the artery is at its
highest, ventricles have contracted and forced blood
into arteries
Diastolic pressure – pressure is at its lowest in the
artery when the ventricles are relaxed

26. A sphygmomanometer is used to measure blood
pressure
Blood pressure is reported in 2 measures


Systolic
pressure, the
max blood
pressure when
the hearts
contracts
Diastolic pressure,
the blood pressure
when the heart is
relaxed

27. What determines blood pressure?
Contact between blood and the walls cause friction, this
impedes the flow of blood – peripheral resistance
If the smooth muscles in the walls of an artery contract,
the vessels constrict , increasing resistance – blood
pressure is raised.
If the smooth muscles relax, the lumen is dilated, so
peripheral resistance is reduced and blood pressure falls.
Any factor that causes arteries or arterioles to constrict can
lead to elevated blood pressure e.g. Natural loss of
elasticity with age, adrenaline, high-salt diet.

29. Carbohydrates are the main energy supply in living
organisms.
Most carbohydrates are large, complex molecules
composed of long chains of monosaccharides
Glucose is a monosaccharide with 6 carbon atoms in
each molecule
Structure of alpha- glucose.

30. Monossaccharides are joined together by glycosidic
bonds in a condensation reaction
When 2 monosaccharides join together, they form a
disaccharide
Names of disaccarides:
1.Maltose – glucose and glucose with a 1-4 glycosidic
bond
2.Lactose – glucose and galactose, 1-4 glycosidic bond
3.Sucrose – glucose and fructose, 1-2 glycosidic bond

31. Two alpha glucose molecules can be joined
together by a CONDENSATION REACTION in
which a molecule of water is formed from two -
OH groups in the two molecules
The remaining O atom forms a link between
the carbon 1 of one glucose molecule and the
carbon 4 of the other. This is called a 1,4
glycosidic link.
The disaccharide formed from two glucose
molecules is MALTOSE.
Water is formed
in this reaction

32. A polysaccharide is formed when more than 2
monosaccharide join together
Lots of glucose molecules are joined together by 1-4 glycosidic
bonds to from amylose.

33. Animal cells get
energy from
glucose. Store excess
glucose as glycogen.
Lots of side
branches – glucose
can be released
quickly.
Very compact
molecule.
Insoluble in water,
doesn’t cause cells to
swell by osmosis.
Large molecule,
store lots of energy.

34. Starch is the main energy storage
material in plants. Plants store
excess glucose as starch
Starch is a mixture of two
polysaccharides; amylose &
amylopectin.
Long, unbranched chain of
glucose joined together
with glycosidic bonds. Has
a coiled structure to make
it compact – good for
storage as you can fit more
in to a small space
Long branched
chain of glucose .
Side branches allow
enzymes that break
down molecules to
get to the glycosidic
bonds easily.
Glucose can be
released quickly

35. Triglycerides are a type of lipid

It is made up of one molecule of
glycerol with 3 fatty acids attached to it.

The fatty acid molecules have long tails
made of hydrocarbons
The tails are hydrophobic.
These tails make lipids insoluble in
water.

All fatty acids consist of the same
structure, but the hydrocarbon tail
varies .

36. Triglycerides are formed by condensation reactions and broken up by
hydrolysis reactions
Three fatty acids and a single glycerol are joined together by ester
bonds
A hydrogen atom on the glycerol molecule bonds to a hydroxyl (OH)
group on the fatty acid, releasing a molecule of water.
Reverse happens in hydrolysis – molecule of water added to each ester
bond to break it apart, and the triglyceride splits up into 3 fatty acids
and one glycerol molecule .

37. Saturated and unsaturated lipids
Saturated – animal fats (butter)
Unsaturated – plants (olive oil). Melt at a lower temp
The difference between these 2 types is their hydrocarbon
tails.

Does not have double bonds
between carbon atoms – every
carbon is attached to at least 2
hydrogen atoms. ‘saturated’ with
hydrogen.
Has double bonds between
carbon atoms. Double bonds
cause the chain to kink. If 2 or
more, the lipid is called
polyunsaturated.

38. You need a constant supply of energy to maintain your essential body
processes which are ongoing, even when you are completely at rest.
Basal metabolic rate (BMR) is the name given to energy needed for
essential processes.
Normal weight – equal
energy input and output
Underweight - illness,
diet, eating disorder.
Excessive exercise,
stress, high BMR
Overweight – overeating
and low exercise

39. It is a lipid made in the body
Some is needed to function normally
Needs to be attached to protein to be moved around, do the body forms
lipoproteins
High density lipoproteins (HDLs)
1.Mainly protein
2.Transport cholesterol from body tissues to the liver where it’s
recycled or excreted.
3.Function is to reduce total blood cholesterol when level is too high
Low density lipoproteins (LDLs)
1.Mainly lipid
2.Transport cholesterol from liver to the blood, where it circulates until
needed by cells
3.Function is to increase total blood cholesterol when level is too low.

40. A diet high in saturated fats increase the rick of CVD.
This is because it increases blood cholesterol level.
This increases atheroma formation which can lead
formation of blood clots which can cause heart attacks
and strokes.

41. Investigation: observe daphnia through a microscope to see the
effect of caffeine on the heart rate.
1.Make up a range of caffeine solutions of different
concentrations, with control solution with no caffeine
2.Transfer one daphnia into dimple of cavity slide
3.Place slide onto the stage of a light microscope and focus on
bating of the heart
4.Place small drop of caffeine solution onto daphnia
5.Count number of heartbeats in 10 secs and multiply by 6 to
calculate beats per min.
6.Repeat with all caffeine solutions, keeping all factors constant
7.Compare results to see how caffeine concentration affects heart
rate.

42. Ethical Issues:
1.Studying animal allows scientists to study things
unethical to study using humans
2.But using animals can also be seen as unethical –
can’t give consent
3.Some believe more acceptable to perform
experiments on invertebrates than on vertebrates –
simpler organisms which have much less
sophisticated nervous system
4.Could cause distress or suffering to living organism

43. Investigation to test how much vitamin C is in fruit juices:
1.Have about 6 different fruit juices of known concentrations
2.Measure out a set volume of DCPIP into a test tube
3.Add one of the fruit juices to the DCPIP, drop by drop, using a
pipette.
4.Gently shake the test tube after each drop of fruit juice is added
5.When the solution turns colourless, record the volume of fruit juice
that has been added
6.Repeat experiment twice more, with same solution to record an
average
7.Make sure all other variables are kept constant
8.Use the results to make a line graph, showing volume of vitamin C
solution against its concentration – calibration curve
9. This means an unknown solution can be tested in same way to
find vitamin C content