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Biology
Unit One

Data Definitions
(ISA/EMPA)
• Accuracy: how close the measurement is to the true value
...

• Errors: these cause readings to be different from the true value
...

• Anomalous Data: measurements that fall outside the expected
range
...

• Standard Deviation: the spread of data around the mean
...


Data Definitions
(ISA/EMPA)
• Large Sample Size: this increases reliability as anomalous data can be
identified
...

• Causal Link: a change in one variable causing a change in another
variable
...

• Confounding Variable: this affects the result so must be monitored or
kept constant
...

• Dependent Variable: the variable that is measured when the
independent variable changes
...

• Epidemiologists: they collect data and look for relationships and
patterns between the disease and the various factors in the lives of
people who have them
...

• Risk: a measure of the probability that damage to health will occur as a
result of a given hazard
...


Data & Disease
•

There needs to be a clear causal connection before a correlation can be proven
...
The impression
given is that the figure applies to everyone, this is often far from the case
...


Pathogens
•
•
•
•

Microorganism: a single celled organism
...

Example: bacteria, fungi and virus
...


•

For a microorganism to be considered a pathogen, it must: gain entry to the host, colonise
host tissues, resist host defences and damage host tissues
...
Disease
occurs when the infection leads to symptoms
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•
•
•

Transmission: the movement of a pathogen from one host to another
...

Producing toxins
...

Example: proteins on cell-surface membrane, cell walls, or diseased cells
...


•

A pathogen enters the body by penetrating an organism’s interface
...

Some interfaces exchange material between internal and external: body linings at
these points are think, moist, sticky, have a large surface area and are supplied with
blood vessels
...
g
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•

•
•
•
•
•

Non-Specific Defence Mechanisms:
These do not distinguish between one type of pathogen but respond in the same
way
...
Invasion
occurs when the skin breaks
...
E
...
In the
lungs, pathogens stick to the mucus and are transported away by cilia, up the
trachea and to the stomach
...


Defence Mechanisms
Phagocytosis
• Phagocytosis is still a non-specific defence mechanism, and goes as follows:
• Chemical products of pathogens act as attractants to the receptors and so the
phagocytes move towards the pathogen
...

• This forms a phagosome
...

• Lysozymes in the phagolysosome then break down the pathogen via
hydrolysis
...

• Soluble products of breakdown are absorbed into the cytoplasm of the
phagocyte, whereas the waste materials are discharged
...
This is the result of the
release of histamine which causes dilation of the blood vessels
...


Defence Mechanisms
T Cells and Cell-mediated Immunity
•

Specific Defence Mechanism: slower at first, but can provide long-term immunity
...


• T Cells form in the bone marrow and develop in the thymus gland
...
Pathogens invade body cells or are taken in by phagocytes
...
Phagocyte places antigens from pathogen to cell-surface membrane
...
Receptors on certain T helper cells fit on antigens
...
This activates other T cells to divide by mitosis
...
The cloned T cells can:
Develop into memory cells for long-term immunity
...

Stimulate B cells to divide
...

•
•

T cells can kill infected cells by producing a protein that makes holes in the cell-surface
membrane
...


Defence Mechanisms
B Cells and Humoral Immunity
• B Cell Response Stages:
1
...
They then process the antigens and
present them on their surface
...
T helper cells attach to processed antigen and B cells are activated
...
B cells divides by mitosis
...
Cloned plasma cells produce the specific antibody to destroy the pathogen
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5
...
This is the secondary immune response
...

There are therefore no appropriate memory cells to stimulate antibody
production
...


Antibodies
• Antibodies: proteins synthesised by B cells
...


Monoclonal Antibodies
•
•

Antibodies that are produced by B cells are known collectively as polyclonal antibodies
...


• Production of a monoclonal antibody:
1
...

2
...

3
...

4
...
This is because the tumour cell has the ability to multiply out of control
...
Then the tumour cells and b cells are fused together to form hybridomas
...
These hybridomas are then screened for the correct antibody production: some of the antibodies
may have been from memory cells which are not specific to the antigen in question
...
Once isolated, the specific hybridoma is cloned in order to produce many of the antibodies
...

•
•
•

•
•

Functions:
Separation of a chemical from a mixture
...
E
...
Pregnancy
tests, drug tests etc
...
The cancer cells are then destroyed
...
Monoclonal antibodies
can be designed to ‘knock-out’ the t cells that are rejecting the organ
...

Passive Immunity: no immunological memory
...


•

Herd Immunity is where the majority of a population are immunised and so the odd individuals
are fairly safe without vaccination
...

Few, if any, side effects
...

Means of administering vaccine properly at appropriate time
...


•
•
•

Why vaccination doesn’t eliminate a disease:
Fails to induce immunity in certain individuals
...

Pathogen may frequently mutate (antigenic variability)
...

Certain pathogens hide from immune system (within cells, within out of reach places etc
...


•
•
•
•

Digestion
•
•

Digestive system: an interface with the environment
...


•
•

Oesophagus: a thick muscular wall that transports food from the mouth to the stomach
...
The inner layer produces
enzymes
...

Small Intestine: a long muscular tube that further digests food by enzymes produced there
...

Large Intestine: absorbs water so food becomes drier and thicker in consistency to form faeces
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•
•
•
•
•

•
•
•

Salivary glands: they are near the mouth and pass secretions via the duct in the mouth
...

Pancreas: a large gland below the stomach
...


Physical breakdown: food is broken down by structures such as the teeth to increase the surface
area for chemical breakdown
...

Chemical breakdown: breaks down large, insoluble molecules into smaller ones through means of
hydrolysis carried out by enzymes
...


Carbohydrates
•
•

Carbon readily forms bonds with other carbon atoms and therefore the variety of
life is based on the versatile carbon atom
...


•
•
•

Carbohydrate monomer: monosaccharide
...

Polymer: Polysaccharide
...


• Benedict’s Test:
1
...
If not in liquid form then grind it up in
water
...
Add equal volume of Benedict’s reagent (alkaline solution of Copper(II) Sulfate)
...
Heat mixture gently for five minutes
...

No concentration of reducing sugar: remains blue
...
Low: yellow
...
High: red
...

2
...

4
...

This forms glycosidic bonds
...

Some disaccharides (e
...
Sucrose) are non-reducing sugars
...

Do Benedict’s test, if solution remains blue then a reducing sugar is not present
...

Re-test resulting solution with the Benedict’s test
...


Carbohydrates
• Polysaccharides are large molecules that are insoluble
...
g
...

• Starch is a polysaccharide found in many parts of plants in the form of small
granules or grains
...

• Test for Starch (Iodine test):
1
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2
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•

A positive result is shown by a blue/black colouration
...


• Starch Digestion:
1
...

2
...
Saliva contains mineral salts to maintain a neutral pH
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Food enters the stomach and the acid denatures the enzyme amylase
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Food passes to the small intestine where it mixes with the pancreatic juice
...
It also contains alkaline salts to
maintain a neutral pH
...
Intestine muscles push food along where the epithelial linings produce the enzyme maltase
to hydrolyse maltose to glucose
...


•

Lactose intolerance: as milk becomes a smaller part of the diet when growing up, the
production of lactase diminishes
...

When undigested lactose reached the large intestine, microorganisms break it down
resulting in a large volume of gas
...

It can be resolved by eating foods high in calcium or by adding enzyme lactase to milk
before drinking
...

There are approx
...


•
•

Monomer: amino acids
...

This forms a peptide bond between the nitrogen and carbon atom
...
The process is
called polymerisation
...
Add sample to test tube and add an equal volume of sodium hydroxide solution at R
...
P
...
Add a few drops of very dilute (0
...

•
•

Positive result: purple colouration
...


Protein Structures
• Primary structure: the sequence of amino acids in polypeptide bonds
...

• Secondary structure: hydrogen bonds form between the positive H of the –NH
group and the negative O of the –C=O group
...

• Tertiary structure: the structure twists and folds to more to give a complex and
often unique 3-D structure which is maintained by different bonds
...

• Ionic bonds: formed between any carboxyl and amino group not involved in
forming peptide bonds
...

• Hydrogen bonds: numerous but easily broken
...


Examples of Proteins
• Proteins perform different roles: the role depends on molecular shape
...
g
...

• Globular proteins (e
...
enzymes and haemoglobin) carry out metabolic
functions
...

•
•
•
•
•

Example: Collagen
Primary structure: amino acid sequence
...

Tertiary structure: chain twisted into second helix
...


• Collagen is found in the tendons (join muscle to bone)
...

• Catalysts alter the rate of reaction and can be reused repeatedly
...

• Enzyme molecules are large but only a small region is functional
...

• A substrate binds to the active site of a specific enzyme to form an enzymesubstrate complex
...

• A scientific model: scientists often try to explain their observations by
producing a representation of how something works
...

Limitation: an enzyme is considered a rigid structure as scientists have observed
that other molecules can bind to enzymes at other sites
...

Structure must therefore be flexible,
not rigid
...

• The enzyme is flexible and can mould itself around the substrate
...


Factors Affecting Enzyme Action
• Measuring enzyme-catalysed reactions:
• To measure progress, measure time-course (how long it takes for a particular
event to run its course)
...

•
•
•
•

Effect of temperature:
As temperature rises, the kinetic energy of molecules increase
...

Once the temperature rises past optimum, the hydrogen and other bonds in the
enzyme begin to break
...

• At first it’s just harder for the substrate to bind to the active site
...

• In the human body, enzymes have an optimum temperature of 40˚C so they can
work during illnesses
...

• A change in pH reduces effectiveness and can cause denaturing of the enzyme
...

• pH changes can alter the charges on amino acids and break the bonds in the
tertiary structure
...

• Intermediate substrate concentration: all active sites may be occupied at one
time
...

• High substrate concentration: addition of further molecules has no effect as all
active sites are occupied
...


Enzyme Inhibition
•
•
•

Enzyme inhibitors: substances that directly or indirectly interfere with the
functioning of the active site of an enzyme and so reduce its activity
...

Reversible: only make temporary attachments
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•
•

Competitive: binds to the active site
...
A higher substrate concentration reduces the
inhibitors effect
...


•
•
•
•

Non-competitive: binds to a different site
...
The enzyme can’t function
...


Microscopes
•
•

Magnification: how many times bigger the image is when compared to the object
...


•

Light microscopes: the light rays have a relatively long wavelength so the objects must be 0
...


•

Electron beams have very short wavelengths and a high resolution
...
Since electrons are absorbed by
molecules in the air, a near-vacuum must be created within the chamber
...
Some parts absorb the
electrons and the image appears dark and vice versa
...

The specimen mustn’t be alive as the whole system is in a vacuum, it must be extremely thin
and the image can contain artefacts
...

The electrons are scattered and it builds up a 3-D image
...


Cell Fractionation
•

Cell fractionation is the process where cells are broken up and the different
organelles they contain are separated out
...

Isotonic to prevent bursting/shrinking from osmosis
...


•
•
•
•
•
•
•
•

Homogenation: the cells are broken up and the organelles are released
...

Ultracentrifugation: fragments in the homogenate are separated in an
ultracentrifuge which spins at a very high speed to create a centrifugal force
...

The supernatant is removed, and the sediment is left
...

The next heaviest organelle (mitochondria) is forced to the bottom and the process
continues
...

• Nuclear envelope: double membrane surrounding nucleus to control entry in
and out of cell and to contain reactions
...
g
...

• Nucleoplasm: granular, jelly-like
material
...

• Nucleolus: manufactures ribosomal
RNA and assembles ribosomes
...

• Size of mitochondria and cristae increase in cells with high metabolic activity
...

• Cristae: provides large surface area for the attachment of enzymes involved in
respiration
...

Semi-rigid material containing protein, lipids and
traces of DNA: allows production of own
proteins
...

• Rough ER: has ribosomes on outer surface
...

• Smooth ER: more tubular in
appearance: synthesises, stores and
transports lipids and carbohydrates
...

2
...

4
...


Golgi Apparatus:
Compact, stack of membranes form cisternae with small, rounded, hollow
structures called vesicles
...

Proteins and lipids produced by ER pass through the Golgi Apparatus in strict
sequence:
Proteins are modified, non-protein components are often added
...

They’re sorted and sent to destination
...

Vesicles then moved to cell surface
...

They break down material digested by phagocytic cells; release enzymes to destroy
material around the cell; digest worn-out organelles so useful chemicals can be reused; completely break down cells (autolysis)
...

There are two subunits: one small and one large that contain ribosomal RNA and
protein
...

70s: in prokaryotic cells
...


•

As each organelle has its own function, its possible to deduce the possible role of
the cell by looking at number and size of the organelles it contains
...

• Roles: cell membrane, energy source, waterproofing, insulation and protection
...
T
...
fats are solids and oils are liquids
...

• The glycerol molecule is always the same, different properties come from
variations in the fatty acids (over 70 fatty acids)
...

• Single C=C bonds: monounsaturated
...


•
•
•
•

Phospholipids: two fatty acids, one glycerol and one phosphate
...

Hydrophobic ‘tail’ from the fatty acids (repels water, mixes with fat)
...


Test for Lipids
• Emulsion Test:
1
...

3
...

5
...


Take completely dry and grease-free tube
...

Shake tube to dissolve lipid
...

A cloudy-white colour indicates presence of a lipid
...


•

The cloudy colour is due to the lipid being finely dispersed in water to form an
emulsion
...


Cell-Surface Membrane
•
•
•

Phospholipids form a bi-layer sheet
...

Other layer has hydrophobic heads facing outwards
...


•

Extrinsic protein: either on surface of bi-layer or partly embedded
...

Intrinsic protein: spans the entire membrane
...
They either provide structural support, act as ion channels, form
recognition sites by identifying cells, helps cells adhere together or act as receptors
...


Diffusion
• Diffusion: the net movement of molecules or ions from a region of high
concentration to a region of low concentration
...

• Factors that affect the rate of diffusion:
• Concentration gradient: the greater the difference, the faster the rate
...

• Thickness of exchange surface: the thinner the exchange surface, the faster
the rate
...

• They’re selective and open only for a specific ion
...


Osmosis
• Osmosis: the passage of water from a region of high water potential to a region
of lower water potential through a partially permeable membrane
...


Active Transport
•
•

Active Transport: the movement of molecules or ions into or out of a cell from a
region of lower concentration to a higher concentration using energy and carrier
proteins
...


• Direct active transport:
1
...

2
...

3
...
Protein molecule changes shape and opens
...
Molecules or ions are released into the inside
...
Phosphate is released from the protein and recombines with ADP during
respiration and protein reverts to original shape
...


Absorption in Small Intestine
• Walls of small intestine are folded into finger-like projections called villi
...
Epithelial cells possess microvilli
...

1
...

3
...


•

Sodium ions are actively
transported out of cell
...

Na+ diffuse into cell through
different carrier protein after
binding with glucose molecules
...


Indirect active transport: Na+ concentration gradient powers glucose movement
...

• Symptoms: Diarrhoea and dehydration
...

• Most of the bacteria is killed by acidic stomach conditions
...

• They then produce a toxic protein: one part of it binds to specific carbohydrate
receptors on the membrane, the other part enters the cells and opens ion
channels
...
The loss of these ions raise the water
potential in cells and water flows into the lumen
...


Oral Rehydration Therapy
• Drinking water is ineffective as it is not absorbed from the intestine and doesn’t
replace lost ions
...

• A rehydration solution must be developed that uses alternative carrier
proteins
...

Sodium: to replace lost ions
...

Potassium: to replace ions and stimulate appetite
...


• Can be mixed into a powder and administered by people with minimum
training
...

• Trachea: a flexible airway supported by rings of cartilage to prevent it
from collapsing as the air pressure falls
...

• Bronchi: similar structure to the trachea, supported by cartilage
...
The walls are
made up of muscle lined with epithelial cells
...

• Alveoli: minute air-sacs lined with epithelium that contain some collagen
and elastic fibres to allow the alveoli to stretch
...
Intercostal muscles contract
...
The ribs are pulled up and outwards – increase the volume of the thorax
...
Diaphragm muscles contract and flatten – increase the volume of the thorax
...
Increased volume of thorax reduces pressure in the lungs
...
Atmospheric pressure is greater than pulmonary pressure so air is forced into the
lungs
...

2
...

4
...


Expiration/Exhalation (passive process):
Intercostal muscles relax
...

Diaphragm muscles relax and return to upwardly domed position – decrease the
volume of the thorax
...

Pulmonary pressure is greater than atmospheric pressure so air is forced out of the
lungs
...
g
...

• Tidal volume: volume of air normally taken in at each breath when the body is
at rest
...


• Pulmonary Ventilation = Tidal Volume X Ventilation Rate
(dm³/min)
(dm³)
(min)

Exchange of Gases in the Lungs
•
•

Site: epithelium of the alveoli
...


•
•
•
•
•
•

Essential features:
Large surface area to volume ratio
...

Partially permeable (allows selected materials to diffuse)
...

Movement of internal medium (blood)
...


•
•

Role of alveoli:
Around each alveolus, there is a network of pulmonary capillaries which are narrow
so red blood cells are flattened in order to squeeze through
...

Blood flow through capillaries maintains concentration gradient
...

Symptoms: persistent cough, tiredness, loss of appetite, and later, fever and coughing blood
...


•
•
•
•
•

Those at greater risk:
Close contact with infected people over long periods
...

From countries where TB is common
...


•
•
•
•
•
•
•

Course of infection:
Bacteria grows and divides in upper lungs as there’s a plentiful supply of oxygen
...

This leads to inflammation of lymph nodes that drain the area (primary infection)
...

Years later, bacteria may re-emerge to cause a second infection (post-primary tuberculosis)
...
The bacteria destroys lung tissue which results
in cavities and scar tissue
...
Can spread if not treated
...
Bovis
...

More and better housing
...

Better nutrition – strengthen immune system
...

Development of M
...


•
•

Increase in TB:
HIV spread, resistant forms, more people living in poor conditions and a larger
proportion of elderly people
...

Effects:
Shortness of breath (thickened epithelium and loss of elasticity)
...

Chest pain and discomfort (due to pressure and damage from fibrous tissue)
...

Asthma:
Cause: localised allergic reaction caused by allergens like pollen, animal fur and dust mite
faeces
...

This causes white blood cells to release the chemical histamine
...

Symptoms: breathing difficulty, wheezing sound (air passing through constricted airways),
tight feeling (not able to ventilate lungs) and coughing
...

Elastin becomes stretched – lungs are no longer able to force air out of alveoli
...

Symptoms:
Breath shortness: lungs are not emptied, difficult for new air to be inhaled – more
rapid breathing
...

Bluish skin colouration: low levels of oxygen
...

Ventricle: has a much thicker muscular wall – the right is thinner as it only pumps
blood to the lungs
...


•
•
•
•

Vessels connecting heart to lungs are the pulmonary vessels
...

Veins: pump blood towards the heart
...


•
•

Aorta: connected to the left ventricle and carries oxygenated blood to the body
...

Pulmonary artery: connected to the right ventricle and carries deoxygenated blood
to the lungs
...


•

•
•

Valves
•
•

Valves are designed so that they open whenever the difference in blood pressure on
either side of them favours the movement of blood in the required direction
...


•
•
•

Left atrioventricular (bicuspid) valves: between the left atrium and ventricle
...

These prevent backflow of blood when contraction of the ventricle means that
ventricular pressure exceeds atrial pressure
...
They prevent backflow into the ventricles when the recoil action
of the elastic walls creates greater pressure in the vessels than in the ventricles
...


The Cardiac Cycle
• Diastole (relaxation of the heart):
• Blood returns to the atria via the pulmonary vein and vena cava
...

• Relaxation of the ventricle reduces pressure – causes pressure to be lower than
in the aorta and pulmonary artery so the semi-lunar valves remain closed
...

• Ventricular systole (contraction of the ventricle):
• After filling with blood, ventricle walls contract – increases pressure, forcing
shut the atrioventricular valves
...


The Cardiac Cycle
• Cardiac muscle is myogenic – initiated by its own muscle
...

• Wave of electrical activity spreads from SAN across both atria – causes
contraction
...

• Wave passes through a second cell group called the atrioventricular node (AVN)
that lie between the atria
...

• The bundle branches into smaller fibres – wave of electrical activity is released
from the fibres and the ventricle contracts from apex upwards
...


Cardiac Output
• Cardiac output: the volume of blood pumped by one ventricle of the heart in
one minute
...

• Stroke volume: volume of blood pumped out at each beat
...

Begins as fatty streaks of white blood cells that have taken up low-density lipoproteins
...

The atheroma bulges into the lumen – narrows it and reduces blood flow
...


•
•
•
•
•
•

Thrombosis 
If an atheroma breaks through the lining of the blood vessel, it forms a rough surface that
interrupts smooth blood flow
...

A thrombus may block the blood vessel, reducing or preventing supply of blood to certain tissues
...

A thrombus can sometimes be carried to a different artery
...

Atheromas weaken artery walls – these swell to form blood-filled structures called an aneurysm
...


•
•
•

Myocardial infarction 
A heart attack which is caused by a blockage in the coronary arteries
...


Heart Disease
• Risk Factors 
• Smoking: 2-6 time more likely to suffer – due to carbon monoxide (attaches to
haemoglobin and causes heart to work harder this leads to raised blood
pressure) and nicotine (stimulates adrenaline production and platelets become
more sticky – causes thrombosis)
...

• Blood cholesterol: high-density lipoproteins remove cholesterol from tissues
and transports it to the liver whereas low-density lipoproteins transport
cholesterol from liver to tissues – leads to atheroma
...

• Food that acts as antioxidants and non-starch polysaccharides reduce the risk
of heart disease

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