6.1.1

Why is digestion of large food molecules essential?

In order for the food we ingest to be useful it has to be able to pass through our cell membranes into the cells.  As large polymers this is impossible therefore digestion is necessary.

Digestion turns large food molecules into smaller molecules.

6.1.2

Why are enzymes needed in digestion?

6.1.3

What is the source, substrate, products and optimum pH conditions for one example of an Amylase?

Eg, Salivary Amylase

Source: Salivary Glands

Substrate: Starch

Products: Maltose

Optimum pH: 7

6.1.3

What is the source, substrate, products and optimum pH conditions for one example of a Lipase?

Eg, Pancreatic Lipase

Source: Pancreas

Substrate: triglycerides (lipids)

Products: Fatty acids and glycerol

Optimum pH: 7

6.1.3

What is the source, substrate, products and optimum pH conditions for one example of a Protease?

Eg, Pepsin

Source: Stomach 

Substrate: Protein (polypeptides)

Products: amino acids

Optimum pH: 3 (acidic)

6.1.4

Draw and label the human digestive system

6.1.5

What is the function of the stomach?

Food is brought to the stomach via the oesophagus

the stomach mixes the food with a variety of secretions known as gastric juice

This begins the process of digestion

After the food has been held in the stomach it leaves via a valve in the lower end of the stomach and enters the small intestine

6.1.5

What is the function of the small intestine?

The first part of the small intestine is called the duodenum.  Here more juices are added to aid the digestive process, they include: bile, pancreatic juice and various enzymes.

As the food passes through the small intestine molecules of food become small enough to be absorbed by the intestinal lining.

Most of the molecules that are useful to the body are absorbed through the villi in the small intestine

6.1.5

What is the function of the large intestine?

most nutrients are absorbed while food is in the small intestine

the large intestine contains material that cannot be digested

the main function of the large intestine is to reabsorb any water

The large intestine is also home to E.Coli, a mutualistic bacteria that synthesizes vitamin K

6.1.6

What is the different between assimilation and absorption?

Absorption is the process of taking nutrients into the bloodstream.  This mostly occurs through the villi in the small intestine

Assimilation is the breaking down of these nutrients to their component parts so that they can be used as part of the cell.

6.1.7

How is the structure of a villus related to its role in absorption and transport of the products of digestion?

There are many microvilli. This increases the surface area and provides more place for diffusion to occur.

Villi have dense capillary networks so that absorped nutrients can immediately be transported around the body

The epithelium of the villi is one cell thick to minimize the diffusion distance

Each villus has a lacteal (branch of the lymphatic system) so that substances such as lipids can be transported around the body

Epithelial cells have lots of mitochondria and protein pumps for any facilitated diffusion that needs to occur

6.2.1

Draw and label a heart

6.2.2

What is the role of the coronary arteries?

To supply blood, and therefore a supply of oxygen and nutrients to the muscle of the heart tissue.

6.2.3

What is the action of the heart in terms of collecting blood, pumping blood and opening and closing of valves?

• Blood enters the atria via the vena cava and the pulmonary vein.
• It then passes through the open atrio-ventricular valves until the ventricles are almost full.
• The atria then contract forcing whatever blood is in the atria into the ventricles. 
• This causes high pressure in the ventricles and therefore the semi-lunar valves in the aorta and pulmonary artery open and the atrio-ventricular valves close.
• Once the ventricles are empty the pressure inside them becomes low and the semi-lunar valves close and the atrio-ventricular valves open

6.2.4

What is the role of myogenic muscle contraction in the control of the heartbeat?

Myogenic muscle contraction means that the heart muscle is capable of contracting by itself without any impulses.

6.2.4

What is the role of the pacemaker in the control of the heartbeat?

The pacemaker is also known as the sino-atrial (or SA) node.  This is a mass of tissue within the wall of the right atrium.

This node sends out an electrical impulse over the walls of the atria causing them to contract simultaneously.

This impulse then stimulates the atrio-ventricular (or AV) node (a mass of tissue at the bottom of the right atrium) to send out another electrical signal that travels along nerve fibres within the walls of the ventricles causing them to contract simultaneously.

6.2.4

What is the role of the medulla of the brain in the control of the heartbeat?

Although the pacemaker stimulates the heart to beat, the brain does have the ability to increase or decrease the frequency of the heartbeat.

For example, during exercise more oxygen is need in the muscles so the heart needs to beat more often.  The medulla senses the increase in Carbon Dioxide levels associated with increased physical activity and sends an impulse through the cardiac nerve to tell the heart to beat faster.

6.2.4

What is the role of adrenaline in the control of the heartbeat?

Chemicals can also influence heart rate

For example, adrenaline causes the SA node to send impulses out more rapidly.

6.2.5

What is the relationship between the structure and the function of arteries?

Thick elastic walls - to prevent excessive bulging as blood travels under high pressure

Thick muscle layer - also to prevent bulging but also assists in pumping the blood

Narrow lumen - to maintain the high pressure of the blood and keep is moving

6.2.5

What is the relationship between the structure and function of veins?

Thin elastic layer - no need to prevent any bulging and also allows outside muscles to press of the veins and keep the blood moving

Thin muscle layer - same as above

Semi-lunar valves - to prevent backflow of the slow moving blood

Large lumen - to cope with large amounts of blood moving at low pressure

6.2.5

What is the relationship between the structure and function of capillaries?

Wall is one cell thick - this allows efficient diffusion

Narrow lumen - so that they can fit into small spaces and between cells thus providing blood to all areas of the body

Pores - to allow larger substances and molecules (eg, macrophages) to pass through.

6.2.6

What are the main components of blood?

Erythrocytes (red blood cells)

Leucocytes

Lymphocytes

Phagocytes

Plasma

Platelets

6.2.7

What are the main things transported by the blood?

Oxygen

Carbon Dioxide

Urea

Heat

Waste

Nutrients

Hormones

Antibodies

6.3.1

What is a pathogen?

An organism (or virus) which causes disease in another organism

examples include: viruses, bacteria and fungi

6.3.2

Why are antibiotics effective against bacteria but not against viruses?

6.3.3

What is the role of skin and mucous membranes in defense against pathogens?

Skin - This provides a physical barrier for pathogens.  The skin is also slightly acidic.

Mucous membranes - the cells of mucous membranes produce and secrete a lining of sticky mucous.  This traps incoming pathogens and prevents them from reaching the cells they could infect.

6.3.4

How do phagocytic leucocytes ingest pathogens in the blood and body tissues?

Phagocytes use phagocytosis to ingest pathogens.  This is a form of endocytosis

Hydrolytic enzymes released from lysosomes are then used the digest the pathogen

6.3.5

What is the difference between antigens and antibodies?

Antigens are proteins that enter the body and is identified as being foreign

However Antibodies are proteins that recognize antigens and help to fight them

6.3.6

How are antibodies produced?

A lymphocytes will recognize a specific antigen

When a pathogen enters the organism, the specific lymphcyte recognizes the pathogen and becomes active

it then clones itself so that many are made and antibodies can be made

6.3.7

What are the effects of HIV on the immune system?

The HIV virus attacks the t helper cells. This means that the B cells can't be activated and therefore antibodies can't be made.

6.3.8

What is the cause of AIDS?

AIDS  (or acquired immune deficiency syndrome) is caused by the Human Immunodeficiency Virus (or HIV)

6.3.8

How is AIDS transmitted?

HIV is transmitted by the exchange of bodily fluids.

This can occur via the use of an unsterilized, previously used needle for injections, or during the transfer of body fluids during sexual intercourse.

It is also possible for a mother to pass HIV via the placenta to her baby.

6.3.8

What are the social implications of AIDS?

There is much discrimination against those with AIDS

Grief is experienced by people who have lost friends and family to HIV

A family may become poorer if an individual is refused life insurance or cannot find a job

Sexual activity within a population may be reduced for fear of infection

6.4.1

What is the difference between Ventilation, Gas Exchange and cell respiration.

Ventilation is the process of breathing air into and out of the lungs

Gas Exchange is the exchange of gases across a surface

Cell Respiration  is the process by which energy from food is made available.

6.4.2

Why is a ventilation system needed?

Oxygen is needed for an individual to survive because is it required for respiration.

Ventilation is required because it maintains high concentration gradients of gases in the lungs and therefore ensures that diffusion of these gases will occur efficiently and regularly.

6.4.3

What are features of alveoli that adapt them to gas exchange?

The walls are one cell thick - efficient diffusion

They are very small which means that they have a large surface area to volume ratio

They are surrounded by a dense capillary network so that oxygen can immediately be carried to the heart

the surface is moist so that the gases can dissolve - this also prevents the alveoli from sticking together

6.4.4

Draw and label a diagram of the ventilation system

6.4.5

What is the mechanism of ventilation?

(in terms of volume and pressure changes)

Inhalation

Diaphragm and external intercostal muscles contract

The ribcage moves up and out which increases the volume of the thoracic cavity and therefore decreases the pressure

This causes air to rush into the lungs because the air pressure outside is higher than inside

The mechanism of Exhalation is exactly the opposite

6.5.1

What are the two parts of the nervous system and what are the cells that they're composed of called?

Central nervous system and Peripheral nervous system

the cells are called neurons

6.5.2

Draw and Label a diagram of a Motor Neuron

6.5.3

How are impulses conducted:

a) from receptors to the CNS

b) within the CNS

c) from the CNS to effectors

a) sensory neurons

b) relay neurons

c) motor neurons

6.5.4

Define Resting Potential and Action Potential

Resting Potential - (in a polarized state) This is the voltage across the membrane of a neuron that is not conducting an impulse

Action Potential (the act of depolarization and repolarization) a self propogating change in the voltage across the membrane of a neuron that is conducting an impulse

6.5.5

How does an impulse pass along a non-myelinated neuron?

To begin with the nerve actively transports sodium ions out and potassium ions into the neuron.  This causes a relative positive charge on the outside of the neuron.

When an action potential occurs, the cell becomes depolarised, i.e. channels open and the sodium and potassium ions move down the concentration gradients so that the charges are reversed.  When the action potential is over the channels close again and the cell repolarizes by actively transporting sodium and potassium ions.

6.5.6

What are the main principles of synaptic transmission?

When the action potential reaches the end of the presynaptic neuron, calcium ions diffuse into the presynaptic neuron and cause vesicles of neurotransmitter to move to the membrane and release the neurotransmitter by exocytosis.  The neurotransmitter then diffuses across the synaptic gap and binds to receptors on the post synaptic neuron.  These receptors cause channels to open so that sodium ions can diffuse into the post synaptic neuron and cause polarization.

The Neurotransmitter is then broken down and released from the receptor.

The ion channel closes and the neurotransmitter fragments diffuse back into the presynaptic neuron.

6.5.7

What does the endocrine system consist of?

glands that release hormones that are transported in the blood

6.5.8

What does homeostasis involve?

The maintaining of the internal environment between limits

This includes:

heat

glucose levels

blood pH

Carbon Dioxide Concentration

water balance

6.5.9

How does Homeostasis correct changes in levels?

By using a negative feedback mechanism

This is a mechanism in which the products of a certain chain of events inhibits the beginning of the particular chain of events

6.5.10

How does the body control body temperature?

The hypothalamus in the brain is responsible for detecting any change in body temperature

If the body is too warm the following things happen:

Vasodilation - so that some heat can be lost to the environment

Sweating - evaporation of water has a cooling effect

metabolism decreases - energy is required and gives off heat

Behaviour may change

The opposite will happen if the body is too cold (plus shivering)

6.5.11

How does the body control levels of glucose in the blood?

When a meal has just been eaten the glucose levels are high.  This stimulates the Beta cells in the pancreas to produce insulin.  Insulin stimulates glucose to be absorbed by the body cells or stored in muscles and the liver as glycogen.  This causes the glucose level to decrease again.

6.5.12

What is the difference between type 1 and type 2 diabetes?

Type 1

Onset is usually during childhood

Beta cells do not produce enough insuling

Insulin injections are usually needed

Type 2

Onset is usually after childhood

Target cells become insensitive to Insulin - although it is still produced

Can normally be controlled by diet alon

6.6.1

Draw and Label a diagram of the adult male reproductive system.

6.6.1

Draw and label a diagram of the adult female reproductive system.

6.6.2

What is the role of FSH during the menstrual cycle?

FSH (or Follicle Stimulating Hormone) stimulates the growth of the follicle.

It also stimulates the production of Oestrogen and Progesterone.

6.6.2

What is the role of LH in the menstrual cycle?

Stimulates ovulation and the formation of the corpus luteum

6.6.2

What is the role of Oestrogen in the menstrual cycle?

Thickens the endometrium

Stimulates the growth of secondary sexual features

Inhibits the production of FSH

Stimulates the production of LH

6.6.2

What is the role of Progesterone in the menstrual cycle?

Inhibits ovulation

Maintains the endometrium

inhibits the production of LH and FSH

6.6.3

Annotate a graph showing hormone levels in the menstrual cycle, illustrating the changes in hormone levels and ovulation, menstruation and thickening of the endometrium.

[image]

1. FSH levels rise - this stimulates the follicle to be developed and the production of Oestrogen
2. Oestrogen levels rise and stimulate the repair of the endometrium
3. a peak in the Oestrogen levels stimulates LH to be produced and inhibits FSH
4. The peak in LH causes Ovulation
5. LH causes Oestrogen levels to fall and Progesterone levels to increase
6. Progesterone prepares the uterus lining for an embryo and inhibits the production of FSH and LH
7. If no embryo is implanted then Oestrogen and Progesterone levels fall completley

6.6.4

What are 3 roles of testosterone in males?

Stimulate the growth of secondary sexual features

maintain sex drive

Stimulates Sperm production

6.6.5

What is the process of In Vitro fertilisation?

1. First a drug is given to the women which stops her normal menstrual cycle
2. Large amounts of FSH are injected so that many graafian follicles are produced
3. HCG is injected 36 hours before the eggs are collected to loosen the eggs from the follicles
4. The man provides semen, and the sperm are processed to concentrate the healthiest ones.
5. The eggs are extracted with a device that enters through the wall of the vagina
6. The eggs are fertilised in a petri dish which is kept overnight in an incubator
7. The dishes are checked to see if fertilisation has occured
8. 2 or 3 embryos are chosen and entered into the uterus
9. a pregnancy test is done to see if any of the embryos have implanted
10. a scan is done to check that the pregnancy is continuing normally.

6.6.6

What are ethical issues against the use of IV fertilisation?

every embryo is a potential human and should have a chance at life - not be discarded

Inherited forms of infertility may be passed on to the children

Embryos are selected - an act of god

It is unnatural

6.6.6

What are ethical points supporting the use of IVF?

Parents who go through so much trouble to become pregnant are likely to be loving parents

any embryos that are destroyed do not feel any pain because they have not yet developed nervous systems

Infertility causes great unhappiness for some couples - this can be overcome with IVF