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UNIT 1 REVISION
Chapter 1 – Causes of Disease
• What is a pathogen?
• A micro-organism that causes disease
• How do pathogens enter the body?
• Through the skin/gas-exchange system/digestive system
• How do pathogens cause disease?
• Damage host tissues, produce toxins
• What is the difference between a correlation and a cause?
• A correlation is when a change in one variable is reflected
by a change in another variable. A cause is when we have
experimental evidence that one thing causes another.
Chapter 1 – Causes of Disease
• What is risk?
• A measure of the probability that damage to health will
occur as the result of a given hazard
• List risk factors for cancer
• Smoking, diet, obesity, physical activity, sunlight
• List risk factors for CHD
• Smoking, high blood pressure, high blood cholesterol,
obesity, diet, physical activity
Chapter 2 – Enzymes and the Digestive
System
• Label the parts of the
digestive system and
explain the function
of each part:
• State what chemical
and physical digestion
are and where take place
Chapter 2 – Enzymes and the Digestive
System
Tongue
Salivary glands –
secrete amylase
Oesophagus – for transport of
food from the mouth to the
stomach
Liver
Large intestine (transverse limb)
Large intestine (ascending limb)
– absorbs water, faeces form
Physical Digestion – breaking
food into smaller pieces (teeth,
stomach)
Chemical Digestion – breaking
down molecules into small, soluble
ones. (Enzymes)
Stomach – muscular sac,
produces enzymes. Stores
and digests food.
Pancreas – gland that
produces enzymes
Large intestine (descending limb)
Small intestine – produces enzymes,
has villi to increase surface are for
absorption of digestion products
Rectum – stores faeces
before egestion
Chapter 2 - Enzymes
• What do enzymes do?
• Break down large insoluble molecules into small soluble
ones by hydrolysis (splitting of molecules by adding water
to them)
• Name the enzymes that break down carbohydrates,
proteins and lipids
• Carbohydrases, proteases, lipases
Chapter 2 - Carbohydrates
Draw the monomer α-glucose:
Explain how to carry out the Benedict's
test:
Grind up your sample with water (if it is not
already a liquid. Add an equal volume of
Benedict’s and boil for about 5 minutes.
Label the tubes below to show the result:
How are large molecules like carbohydrates
made?
Made from a chain of smaller monomers. The
longer chain is called a polymer. In carbohydrates,
a single monomer is called a monosaccharide. A
pair of monomers are called a disaccharide and a
long chain of monomers is called a
polysaccharide.
None
Very low
Low
Medium
High
Chapter 2 - Carbohydrates
Draw the formation of maltose, name the bond formed
and the type of reaction:
Glycosidic bond, condensation reaction
Glucose links to glucose to form:
Maltose
Glucose links to fructose to form:
Sucrose
Glucose links to galactose to form:
Lactose
What is the test for non-reducing
sugars, and what results would
you expect?
How is sucrose digested?
The small intestine produces sucrase which hydrolyses the
glycosidic bond in sucrose, forming glucose and fructose.
How is lactose digested?
The small intestine produces lactase which hydrolyses the
glycosidic bond in lactose. This forms glucose and galactose.
Lactose intolerant people cannot produce sufficient lactase.
This results in bloating, nausea, diarrhoea and cramps.
Add HCl to the food sample and boil for
5 minutes. Slowly add sodium
hydrogencarbonate solution and check
with pH paper that it has neutralised the
HCl. Test by boiling with Benedict’s for 5
minutes.
What is the test for starch, and
what results would you expect?
Add iodine solution and it will turn blueblack is starch is present.
Chapter 2 – Proteins
Draw and label an amino acid:
What is the test for proteins and what
results would you expect?
Add sodium hydroxide to the food
sample. Add a few drops of copper
sulphate solution. It will turn purple if a
protein is present.
What is the primary structure of a protein?
The sequence of amino acids in a polypeptide chain.
What is the secondary structure of a protein?
The formation of hydrogen bonds which causes the polypeptide chain to twist
into a 3D shape.
What is the tertiary structure of a protein?
Further twisting and folding of the chain to give a complex 3D structure. Bonds
hold the structure in place – disulphide, ionic, hydrogen.
What is the quaternary structure of a protein?
Linking of more than one polypeptide chain (and often non-protein groups e.g.
haem)
Chapter 2 - Enzymes
• How do enzymes speed up reactions?
• They act as catalysts by lowering the activation energy
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needed for a reaction to occur.
How does an enzyme work?
The substrate fits into the active site and forms an enzymesubstrate complex.
Explain the lock and key model of enzyme action
Each key (substrate) has a specific shape that is only
complementary to its lock (active site of the enzyme). The
limitation of this model is that the enzyme is considered to be
a rigid structure, but it is not, it can be flexible.
Chapter 2 - Enzymes
• Explain the induced fit model of enzyme action
• The enzyme changes shape slightly to fit the substrate.
• List the factors that affect enzyme action
• Temperature, pH, substrate concentration, inhibitors
• Explain how temperature will affect an enzyme
• As temperature increases molecules have more kinetic
energy, so move faster and collide more. This speeds up the
rate of reaction (more enzyme-substrate complexes form). At
some point the enzyme will become denatured – the higher
temperature causes bonds holding the enzyme together to
break. The active site changes shape and can no longer fit the
substrate.
Chapter 2 - Enzymes
• Explain the effect of a changing substrate concentration on
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the rate of enzyme action
As you increase substrate concentration then the rate of
reaction increases (more enzyme-substrate complexes form).
At a certain point all the active sites will be filled so adding
more substrate will not increase the rate of reaction further.
Explain the difference between competitive and noncompetitive inhibitors.
Competitive inhibitors have a shape similar to the substrate.
They compete with the substrate for the active sites. This is
not permanent.
Non-competitive inhibitors attach to the enzyme at a place
other than the active site. This alters the shape of the active
site so the substrate cannot fit in, E-S complexes can’t form,
the enzyme can’t function.
Chapter 3 – Investigating Cells
Fill in the formula triangle for magnification
Label the diagram to summarise cell
fractionation
Image
size
Magnification
Actual
size
Tissue is cut up and
kept in an isotonic,
buffer solution
What is magnification?
How many times bigger the image is compared
to the actual size of the object.
What is resolution?
The minimum distance apart two objects must
be in order to be able to distinguish them as
separate points.
Tissue is
further broken
down by a
homogeniser.
Tissue is spun at
increasing speeds.
After each spin the
supernatant (liquid) is
removed and spun
again.
Tissue is spun
at low speed
for 10 mins.
Chapter 3 – Investigating Cells
The transmission electron microscope:
How it works:
A beam of electrons focused onto the
specimen by an electromagnet.
What are its limitations:
Cannot use living specimens, only a
black an white image produced,
specimen must be very thin, image may
contain artefacts.
The scanning electron microscope:
How it works:
A beam of electrons directed onto the
specimen from above. The beam passes
back and forth in a regular pattern. This
creates a 3D image.
What are its limitations:
Cannot use living specimens, black and white
image produced, image may contain
artefacts, lower resolving power than a TEM.
Chapter 3 - Cells
Chapter 3 - Cells
Organelle
Explanation
Nucleus
Contains the DNA. Has a nuclear envelope (double membrane to control
the entry and exit of materials), nuclear pores (holes in the envelope to
allow exit of large molecules) and nucleolus (manufactures ribosomal
RNA and assembles ribosomes)
Mitochondrion
Site of respiration. Has a double membrane, cristae and matrix.
Rough Endoplasmic
Reticulum
Has ribosomes for synthesis of proteins and glycoproteins. Provides a
pathway for transport of materials out of the cell.
Smooth Endoplasmic
Reticulum
Lacks ribosomes. Synthesises, stores and transports lipids. Synthesises,
stores and transports carbohydrates.
Golgi Apparatus
Stacks of flattened stacks of cisternae. Adds carbohydrates to proteins to
form glycoproteins, produces secretory enzymes, secretes carbohydrates,
transports, modifies and stores lipids and forms lysosomes.
Lysosomes
Contain enzymes. Break down material in phagocytes, release enzymes to
the outside of the cell, digest worn out organelles and break down cells
after they have died.
Ribosomes
80s (eukaryotic) or 70s (prokaryotic). Important for protein synthesis.
Chapter 3 - Lipids
• List the roles of lipids
• Energy source, waterproofing, insulation, protection.
• How does a triglyceride form?
• Glycerol joins to 3 fatty acids in a condensation reaction.
• Describe a phospholipid
• They have a hydrophilic head (phosphate molecule) that
attracts to water and a hydrophobic tail (fatty acids) that
orients itself away from water.
• How do we test for lipids?
• Add ethanol to the food sample and shake. Add water and
shake. A cloudy-white colour indicates a lipids is present.
Chapter 3 – The Cell-Surface Membrane
• Label the diagram to show the structure of the cell surface membrane and the function
of it’s components:
Glycoprotein – has a
branching CHO part
that acts as a
recognition site for
chemicals (such as
hormones)
Extrinsic Protein – on
the surface or partly
embedded. Can give
support to the
membrane or help to
act as receptors for
chemicals.
Phospholipid bilayer
– allow lipid-soluble
substances through
and prevent watersoluble substances
passing.
Intrinsic Protein –
protein spanning the
bilayer. Can act as
carriers for watersoluble substances.
What is the model of the cellsurface membrane known as
and why?
Fluid-Mosaic Model.
Fluid because the
phospholipids can move
relative to one another
making it flexible. Mosaic
because the proteins in
the membrane vary in
shape, size and pattern.
Chapter 3 - Diffusion
• Definition of diffusion?
• The net movement of molecules or ions from a region of
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high concentration to a region of lower concentration
What affects the rate of diffusion?
Concentration gradient, area of the exchange surface and
thickness of the exchange surface
What is facilitated diffusion?
Diffusion through protein channels in the plasma
membrane. These channels are selective. Alternatively, it
can be through carrier proteins that change shape in the
presence of a particular molecule and release it to the
inside. It is a passive process that occurs down a
concentration gradient.
Chapter 3 - Osmosis
• Definition of osmosis?
• The passage of water from a region of higher water potential to
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a region of lower water potential through a partially permeable
membrane (less negative to more negative water potential).
Describe how an animal cell changes when placed in solutions
of different water potential
In a solution with a higher (less negative) water potential the
animal cell will take in water and burst. In a solution with a
lower (more negative) water potential the animal cell will lose
water and shrink/shrivel up.
Describe how a plant cell changes when placed in solutions of
different water potential
In a solution with a higher (less negative) water potential the
plant cell will take in water and become turgid. In a solution
with a lower (more negative) water potential the plant cell will
lose water and become plasmolysed.
Chapter 3 – Active Transport
• Definition of active transport?
• The movement of molecules or ions into or out of a cell
from a region of lower concentration to a region of higher
concentration using energy and carrier molecules
• Explain how the carrier molecules help a molecule to
enter the cell
• The molecule binds to a receptor on the carrier protein.
Inside the cell ATP binds to the protein and splits into ADP
+ Pi, this changes the shape of the carrier protein. The
carrier protein now opens to the inside of the membrane
and releases the molecule to the inside.
Chapter 3 – Absorption in the Small
Intestine
• How is the small intestine adapted for absorption?
• Villi and microvilli increase the surface area, very thin walls,
good blood supply
• Explain how absorption occurs in the small intestine
• Na+ ions are actively transported out of epithelial cells
• The epithelial cell has a much lower Na+ concentration than inside the
lumen of the intestine
• Na+ ions diffuse into epithelial cells down a concentration gradient
through a carrier protein
• As Na+ ions diffuse in they couple with glucose molecules and carry
them into the epithelial cell too.
• Glucose passes into the blood by facilitated diffusion.
Chapter 3 - Cholera
Label the structures of a bacterial cell
and describe their role
Flagellummovement
Capsuleprotection
Nuclear
material –
circle of
DNA
Cytoplasm –
contains
enzymes and
soluble
materials
Ribosomes
– protein
synthesis
Cell Wall –
barrier
How does the cholera bacterium cause disease?
They use their flagellum to corkscrew through the
mucus lining of the intestinal wall. They produce a
toxic protein. Part of this toxin binds to CHO
receptors on epithelial cells, the other part enters
the epithelial cells and causes ion channels to
open and Cl- ions enter the intestine. This lowers
the water potential and water floods in, causing
diarrhoea.
What is oral rehydration therapy and how does it
work?
Cell-surface
membrane entry and
exit of
materials
Plasmid – genes
to aid survival
ORT is used to treat diarrhoeal diseases. You cannot just
drink water, as you need to replace the ions too. ORT
contains: water (rehydrate tissues), sodium (replace Na+
ions and use the alternative sodium-glucose carrier
proteins), glucose (stimulate Na+ ion uptake and for
energy), potassium (replace lost K+ ions and stimulate
appetite) and other electrolytes (maintain ion balance).
Chapter 4 - Lungs
• Use the diagram to describe and explain the structure of
the lungs
Bronchioles –
branching subdivisions
of the trachea, walls of
muscle and epithelial
cells
Diaphragm –
muscle
important in
breathing.
Trachea – flexible airway, rings of cshaped cartilage to stop it collapsing,
walls of muscle with cilia and goblet
cells
Bronchi – divisions of the trachea,
larger bronchi supported by
cartilage, contain cilia and goblet
cells
Alveoli – air-sacs, contain collagen
and elastic fibres and lined with
epithelium, site of gas-exchange
Chapter 4 - Lungs
• Describe inspiration
• External intercostal muscles contract, pulling the ribs up and out.
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Diaphragm contracts, flattening it. This increases the volume of the
chest, decreasing pressure. Air moves in.
Describe expiration
Internal intercostal muscles contract, pulling the ribs down and in.
Diaphragm relaxes and returns to its domed shape. This decreases
the volume of the chest, increasing pressure. Air moves out.
What is tidal volume?
The volume of air normally taken in in each breath.
How are the alveoli adapted for efficient diffusion?
Large surface area to volume ratio, very thin (short diffusion
pathway), partially permeable (allow selected material through
easily), movement of air (maintain diffusion gradient), movement of
blood (maintain diffusion gradient.
Lung Disease
Lung Disease
Problems Caused
TB
Alveoli destroyed
Scar tissue forms
Pulmonary Fibrosis
Scar tissue forms
Loss of elasticity
Asthma
Linings become inflamed
Excess mucus
Emphysema
Alveoli burst
Loss of elasticity
Problem
How does this reduce diffusion?
Scar tissue forms
This thickens the epithelium of the lungs.
Makes a longer diffusion pathway.
Alveoli destroyed/burst
Surface area is reduced, slowing down
diffusion.
Loss of elasticity
Harder to ventilate the lungs. The diffusion
gradient is not maintained.
Chapter 5 - The Heart Structure
11
Aorta
2
Pulmonary vein
Vena cava
10
Pulmonary artery
9
Semi-lunar valve
8
1
Left atrium
3
Right atrium
4
7
Tricuspid valve
5
6
Bicuspid
valve
Right ventricle
Left ventricle
Chapter 5 – The Cardiac Cycle
The Cardiac Cycle
What is diastole?
Relaxation of the heart. Blood returns to the atria
and they fill. Atria pressure rises, forcing open the
AV valves and some blood passes into the
ventricles. Ventricles pressure is lower, SL valves
closed.
What is atrial systole?
Atria contract, forcing the rest of the blood into the
ventricles. The ventricles stay relaxed.
What is ventricular systole?
A short delay allows the ventricles to fill with blood.
Their walls now contract. The pressure rises in the
ventricles, forcing the AV valves to close (to
prevent backflow). The pressure now increases
further and the SL valves are forced open, pushing blood into the
pulmonary artery and aorta.
Control of the cardiac cycle
The SAN
___ sends out a wave of
electrical activity. This causes
atria to contract. The wave
both _____
ventricles
cannot pass to the __________
due to a layer of _____________
non-conductive
tissue, but is picked up by the
AVN After a short delay this
___.
sends a wave of electrical activity
down the ___________
bundle of His between
the ventricles. The ventricles now
apex
contract from the ______of
the
heart upwards.
Cardiac Output Equation
Cardiac Output = Heart Rate x
Stroke Volume
Chapter 5 – Heart Disease
• What is an atheroma?
• A fatty deposit that forms within the wall of an artery. It narrows
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the artery, reducing blood flow.
What is thrombosis?
If an atheroma breaks through the lining of the blood vessel
then it forms a rough surface that disrupts blood flow. This may
result in a blood clot (thrombus) which may block the artery,
depriving tissues of oxygen.
What is an aneurysm?
Atheromas may weaken the artery walls. Weakened points
may swell and burst leading to haemorrhage.
What is a myocardial infarction?
A heart attack. Reduced supply of oxygen to the heart muscle
resulting from a blockage in the coronary arteries.
Chapter 6 – Defence Mechanisms
HCl in the
Stomach
Epidermis of
the skin
Barriers to
Disease
Mucus
membranes
Ciliated
epithelia
What is an antigen?
• A molecule on the
surface of an organism
that is recognised as
foreign and triggers an
immune response.
What are the differences between specific and
non-specific mechanisms?
• Non-specific mechanisms do not distinguish
between types of pathogens, specific
mechanisms do. Specific mechanism are
slower but provide long-lasting immunity.
Chapter 6 - Phagocytosis
Chapter 6 - T Cells
• Cell mediated immunity
• Activated by antigen-
presenting cells (e.g.
Phagocyte)
• Mature in the thymus
• Clone by mitosis
Do 4 main things:
• Produce memory cells
• Stimulate B cells to
divide
• Stimulate
phagocytosis
• Kill infected cells (by
making holes in the
cells)
Chapter 6 - B Cells
• Humoral immunity
 Produce memory cells
• Activated by T cells
 Produce plasma cells
(these secrete
antibodies)
• Clone by mitosis
Chapter 6 - Structure of an antibody
Chapter 6 - Monoclonal Antibodies
• The response of the immune system to any pathogen is
polyclonal. That is, the system manufactures antibodies of a
range of structures (due to pathogens having a range of
antigens).
• Isolating a single type of antibody and cloning it creates
monoclonal antibodies
• Uses?
• Separating a chemical from a mixture
• Cancer treatment (antibodies only attach to cancer cells and activate a
drug that kills cells)
• Immunoassay (e.g. pregnancy tests)
• Transplant surgery (help to prevent rejection)
Chapter 6 - Vaccination
• What is passive immunity?
• The introduction of antibodies from an outside source. Short•
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lived.
What is active immunity?
Stimulation of the production of antibodies by the individual’s
own immune system. Long-lasting.
What is vaccination?
Introduction of a substance into the body (dead or attenuated
pathogen) to stimulate active immunity.
List features of a successful vaccination programme.
Vaccine is cheap and readily available, few side effects, easy
to produce, store and transport, easy to administer, able to
vaccinate most of the population (Herd Immunity).