6.1 - Digestion
Definition = Enzyme
A Biological catalyst
6.1.1 Explain why digestion of large molecules is essential
• Many of the foods we ingest are too large to pass across any cell membrane.
•To get into your bloodstream, molecules must pass through the cell membrane of your intestines and then through the cell membrane of a capillary.
• Any food that we eat must therefore be chemically digested to a suitable size.
Molecular Sizes before and after digestion
• Protein --> Amino Acids
• Lipids (Triglycerides) --> Glycerol and fatty acids
3 reasons we need enzymes in digestion
1. They lower the activation energy of the reactions taking place
2. They increase reaction rate and lower the temperature at which they occur
3. They catalyse reactions
State the source, substrate products and optimum pH conditions for one amylase, one protease and one lipase.
Draw and label a diagram of the digestive system
Function of the Stomach
• The primary function of the stomach is digestion, chemical digestion by gastric juice and mechanical digestion by the churning motion of the stomach.
Function of the small intestine
• In the small intestine, digestion continues.
•Most of the absorption of essential nutrients take place, following that, assimilation occurs.
Function of the large intestine
•The primary function of the large intestine is water re-absorption.
• Any food that is undigested by the bacteria or the human is eliminated from the body as solid waste or faeces.
Distinguish between absorption and assimilation
6.2 - Transport System
Draw and label a diagram of the heart showing: the four chambers, associated with blood vessels, valves and the route of blood through the heart
Coronary arteries supply the heart muscle with oxygen and nutrients
Control of the Heartbeat (Myogenic muscle contraction)
•The majority of the tissue making up the heart is cardiac muscle. Cardiac muscle spontaneously contracts and relaxes without nervous system control. This is known as myogenic muscle contraction.
Control of the Heartbeat (role of the pacemaker)
•Myogenic muscle contraction is controlled by the pacemaker (SA Node) in the right atrium of the heart. It sends out an 'electrical' signal telling both atria to contract.
•The AV node receives a signal from the SA node and sends out another 'electrical' signal telling both ventricles to contract.
Control of the Heartbeat (Adrenaline)
• At times of excitement or danger, the sympathic nerve also stimulates the release of adrenaline from the adrenal glands. Adrenaline increases strength and speed of cardiac contractions.
- Thick elastic wall, small lumen
- Pumps blood away from the heart
- One cell thick, small lumen
- Returns deoxygenated blood to the heart. Here, valves prevent backflow.
- Thin outer wall, wide lumen, valves
Blood is composed of plasma, erythrocytes, leucocytes and platelets
Plasma: liquid portion of the blood
Erythrocytes: Red blood cells (carry oxygen and carbon dioxide)
Leucocytes: White blood cells (phagocytes, lymphocytes)
Platelets: Cell fragments (assist in clotting)
The following are transported by the blood; Nutrients, Oxygen, Carbon Dioxide, Hormones, Antibodies, Urea and Heat.
Nutrients: Glucose, amino acids, etc.
Oxygen: Reactant needed for aerobic cell respiration
Carbon Dioxide: Waste product of aerobic respiration
Hormones: Transported from gland to target cell
Antibodies: Protein molecules (immunity)
Urea: Nitrogenous Waste
Heat: Skin arterioles
6.3 - Defence against Disease
An organism or virus that causes a disease
(E.g. bacteria, viruses, protozoa, fungi and worms)
Antibiotics are effective against bacteria but not viruses
1. Antibiotics block specific metabolic pathways found in bacteria.
2. Bacteria are very different to human cells so human cells are not affected.
3. Viruses reproduce using the host cell's metabolic pathways, which are not affected by antibiotics.
4. Harming the virus would harm the human cells
Outline the role of skin and mucous membranes in defence against pathogens
•Skin provides a physical barrier to infection and protects humans from pathogens entering the living tissues.
•The acidic environment of the stomach help to eliminate most of the ingested pathogens
•The cells of mucus membranes produce and secrete a lining of sticky mucus to trap incoming pathogens to protect humans from infectious cells.
Distinguish between antigens and antibodies
•Antigens are foreign substances that stimulate the production of antibodies.
•Antibodies are proteins that recognise and bind to specific antigens.
• Many different types of lymphocytes exist. Each type recognizes ine specific antigen and responds by dividing to form a clone. This clone then secretes a specific antibody against the antigen.
Effects of HIV on the immune system
HIV (human immunodeficiency virus) causes AIDS. The virus infects a type of lymphocyte that plays a vital role in the antibody production. Over a period of years these lymphocytes are destroyed and cannot then be produced. Without a functioning immune system, the body is vulnerable to pathogens that would normally be controlled easily.
Effect on immune system
HIV can lead to various complications
- IT damages the body's immune system and makes it susceptible to infections and certain types of cancers
- It infects and destroys T-Helper cells
- Affect macrophages (large immune cells that engulf and digest, invading microorganisms)
- When cell-mediated immunity (the ability of the immune system to fight off infection) is lost, Aids develops. These are a series of conditions that do not affect people with healthily functioning immune systems, but they can have devastating effects in HIV - positive people.
6.4 - Gas Exchange
Distinguish between ventilation, gas exchange and cell respiration
• The process of filling our lungs with air, then breathing it out.
•The diffusion of certain gases in and out of the blood
•Oxygen that is diffused into the cell from the blood is used to produce energy.
Explain the need for a ventilation system
Your ventilation (respiratory) system and circulatory system function together to pick up oxygen molecules in the inner portion of the lungs and transport that oxygen to body cells deep in your body tissues.
Features of alveoli that adapt them to gas exchange
Spherical Shape: provides a large surface area for respiratory gases to diffuse through
Single Cell Flattened Thickness of each alveolus: prevents respiratory gases from having to diffuse through more cell layers
Moist inner lining of alveolus: efficient diffusion
Associate capillary bed nearby:
Respiratory gases do not have to diffuse far to reach single cell thick capillaries
Draw and label a diagram of the ventilation system including: trachea, lungs, bronchioles, alveoli
6.5 - Nerves, Hormones and Homeostasis
The nervous system consists of the central nervous system and peripheral nerves, and is composed of cells called neurons that can carry rapid electrical impulses
Draw and label a diagram of the structure of a motor neuron
•Action potential is the state of the cell membrane while conduction an impulse. (The rapid depolarisation of repolarization of the cell membrane)
•Resting potential is the membrane potential energy of a neuron membrane when not conducting an impulse.
Principles of Synaptic transmission
•Neurons communicate with each other across a synaptic gap.
•The first neuron is referred to as the pre-synaptic neuron and the second neuron is referred to as the post-synaptic neuron.
•A chemical communication called a synapse occurs between these two neurons.
The endocrine system consists of glands that release hormones that are transported in the blood.
Homeostasis is the maintenance of a constant internal environment
Homeostasis involves maintaining the internal environment between limits including:
Blood pH, Carbon dioxide concentration, blood glucose concentration, body temperature and water balance
(Homeostasis) What if these things aren't maintained?
• Carbon dioxide: Increase leads to blood poisoning
• Body Temperature: too high/low does not allow for enzymes to work as they require a specific temperature to function in
•Water balance: Necessary to provide a fluid medium for molecules
•The physiological changes that bring a value back closer to a set point
•Negative feedback functions to keep a value within the narrow range that is considered normal for homeostasis.
Control of Body Temperature
The brain monitors the temperature of the blood and compares it with a set point.
Response to chilling
• Vasoconstriction; narrowing of arterioles that reduce blood flow to the surface of the skin
•Hair: Erector-pilli muscle contracts and hair moves vertical
•Shivering: Muscle effectors produce rapid contraction/relaxation of muscles
•Sweat glands do not secret sweat
Response to overheating
• Vasodilation: Arteriols dilate sending more blood closer to the skin surface
•Sweat is released onto the surface of the skin
•Hair: Erector-pilli muscles are relaxed and hair lies flat
•Skeletal muscle stays relaxed
Control of blood glucose concentration
Cells in the pancreas monitor blood glucose levels and compare it with a set point. If the blood glucose level is higher or lower than the set point, the pancreas sends messages to target organs to make them bring the blood glucose levels back to the set point.
Response to high blood glucose levels
• β cells in the pancreatic islets produce insulin, which stimulates muscle and liver cells to take up glucose from the blood and convert it into glucagon
Response to low blood glucose levels
• α cells in the pancreatic islets produce glucagen, stimulating the liver cells to convert glycogen back into glucose and release it into the blood
Distinguish between Type I and Type II diabetes
Type I Diabetes
• An autoimmune disease
• Onset is usually early
• β cells do not produce enough insulin
• Diet by itself cannot be used to control the condition --> Insulin injections are necessary to control glucose levels
Type II Diabetes
• Lifestyle related disease
• Onset usually late, sometime after childhood
• Target cells become insensitive to insulin
• Low carb diet can control condition
6.6 - Reproduction
Outline the role of hormones in the menstrual cycle
FSH, LH (Ovaries)
- Increase production and secretion of oestrogen.
- The production of structures within the ovaries known as Graafian follicles
- A spike in the levels of FSH and LH leads to ovulation
Oestrogen + Progesterone
• When the ovary is released some follicle cells remain in the ovary, these begin to produce and secrete Progsterone.
• Progesterone maintains the thickened, highly vascular endometrium, as long as progesterone is produced the endometrium will not breakdown and an embryo can still implant.
•Assuming there is no pregnancy, the corpus luteum breaks down and there is a drop in Progesterone and Oestrogen levels. As these levels fall, the endometrium cannot be maintained in its vascular state, it ruptures and menstruation begins.
Roles of Testosterone in Males
• Pre-natal development of male genitalia
• Development of secondary sexual characteristics
• Maintenance of sex drive
Outline the process of IVF
1. A woman is usually injected with FSH for ten days.
2. Several eggs (oocytes) are then harvested surgically
3. Man ejaculates into a container to obtain the sperm cells that are needed for fertilization.
4. The harvested eggs are mixed with the sperm cells in separate culture dishes.
Ethical issues associated with IVF
- Chance for infertile couple to have children
- Decision to have children is a conscious one
- Genetic screening of embryos could decrease suffering from genetic diseases
- Spare embryos can be safely stored for future pregnancies
Ethical issues associate with IVF
- IVF is expensive (not accessible)
- Success rate is low
- Not natural (cultural,religious objections)
- Could lead to gender choice
- Inherited forms of infertility could be passed to children