BIOLOGY UNIT 1 REVISION (STUDY AREA 2 AND 3)
SECTION B: SHORT ANSWER QUESTIONS
Question 1 (Total 5 marks)
Homeostasis controls breathing rate and depth. The rate and depth of breathing alters the
concentrations of oxygen and carbon dioxide in the blood.
a. Name the division of the nervous system that usually regulates breathing.
Autonomic nervous system
(1 mark)
b. Name the section of the brain responsible for regulating breathing and heart rate.
Control Centre - Medulla oblongata
(1 mark)
c. Explain why it is so important to regulate breathing as part of homeostasis.
To ensure there is sufficient oxygen supply for body to carry out aerobic respiration and
to remove excess carbondioxide which can become toxic to our body.
(1 mark)
d. The diagram below shows the main structures of the human lungs. It includes the
generalised structure of an alveolus. Alveoli are the functional units of the lungs.
Relate the structure of alveoli to their function.
Alveoli has large surface area which allow for faster rate of gas exchange.
Alveoli walls is only one cell thick and this shortens the distance for the simple diffusion to occurs.
(1 mark)
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e. The diagram below shows the main structures of the human heart. Chemoreceptors that
detect CO2 concentration in the blood are located in the aorta.
Explain why the chemoreceptors are in the aorta, rather than in the vena cava.
Chemoreceptors will detect the increase in carbondioxide more accurately in the aorta compared to
vena cava as vena cava carries deoxygenated blood
(1 mark)
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Question 2 (Total 5 marks)
Receptors in both the skin and the hypothalamus are involved in thermoregulation in humans. The
diagram below shows the position of the hypothalamus in the brain.
a. Briefly describe the main way in which the human body increases core temperature.
The main way is through metabolic reaction such as cellular respiration which release heat energy.
(1 mark)
b. Explain why stimuli received directly by the hypothalamus can override information from skin
thermoreceptors.
Internal core temperature will affect metabolic functions in the cells as they required enzymes to function at its
optimum temperature
(1 mark)
c. Describe how a person can reduce their core temperature using a stimulus-response model.
Stimulus: High core temperature
Receptor: _____________________________________________________________
Thermoreceptors of hypothalamus
Control centre: ____________________________________________________________
Hypothalamus
Effector: _____________________________________________________________
Sweat glands,
Hair will lie flat
Response: _____________________________________________________________
(2 marks)
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d. Explain why a person is more likely to die from extreme hyperthermia than from extreme
hypothermia.
Extreme (hyperthermia)increase in temperature will cause the enzyme to denature and the enzyme wil
lose its shape permanently. Hypothermia will make the enzyme inactive but it won’t lose its function.
(1 mark)
Question 3 (Total 5 marks)
A bacterial pathogen infects a person. The infection triggers the third line of defence against
disease. Both B cells and T cells are activated and work together to fight the infection.
a. Define the term adaptive immunity.
Adaptive immunity is an immunity that
Develop overtime memory cells and its specific to a pathogen and stores immunological memory of
that pathogen
(1 mark)
b. The variable regions of T cell and B cell antigen receptors are composed of protein. Name
TWO types of bonds that are involved in the formation of a functional 3D protein.
Hydrogen bonds, disulphide bonds, ionic bonds
(1 mark)
c. Explain how B cells can tell the difference between a pathogen and a 'self' cell.
B cells receptor will only bind to antigen and not to ‘self’ cells MHC markers
(2 marks)
d. Briefly describe ONE difference in either structure or function between T cell receptors and B
cell antigen receptors.
- B cell receptors are wide shape while T cell receptors are straight
- B cell receptor can bind to antigen or pathogen directly. T cells must bind to MHC markers not to the
antigen directly
- B cell receptos are made up of 4 chains. T cells receptor are made up of 2 chains.
(1 mark)
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Question 4 (Total 5 marks)
Influenza is caused by a virus. The symptoms of the flu include muscle aches, headaches, fever,
coughing and a blocked or runny nose. Influenza can be fatal in young children, the elderly or people
with weakened immune systems.
a. Identify whether antibiotics would be an effective treatment for influenza.
No, antibiotic is not effective against influenza because influenza is a virus
(1 mark)
b. Doctors recommend that the elderly get a vaccination against influenza every year. Explain
how a vaccination helps prevent a person from getting influenza.
The body will response as if there is a real pathogen
The third line of defense is activated, it will produce immunity.
It will produce memory cells.
In the future, the body will be able to fight off the influenza virus.
(2 marks)
c. Identify the type of immunity that results from a vaccination.
Artificial active immunity.
(1 mark)
d. Write a testable hypothesis for an experiment that will investigate the effectiveness of a new
vaccine against influenza.
Dependent Variable - effectiveness, Independent Variable
If most people in the community is vaccinated, then there will be herd immunity
(1 mark)
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Question 5 (Total 5 marks)
The neuron is the basic cellular unit of the nervous system. The diagram below shows the
generalised structure of a motor neuron.
a. Name the structure labelled A and state its function.
Structure A is dendrites. It received the impluses from cells. or stimulus/information/impulses
(1 mark)
b. Explain why structure A is shaped the way it is.
Structure A is in branches and it is elongated.
It increases the surface area and increases the speed of transmissions of information between the
cells
(2 marks)
c. Identify which of the structures, labelled B-E, is responsible for producing and releasing
neurotransmitters and name this structure.
Structure E Synaptic
(1 mark)
d. Briefly describe the role of a motor neuron in the nervous system.
It carries the response signals from the CNS to the effector.
(1 mark)
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Question 6 (Total 5 marks)
Blood glucose is one variable that is tightly controlled by homeostasis in the human body. Blood
glucose concentration typically increases after eating a meal.
a. Describe the function of the pancreas and liver in restoring the optimum glucose level after
eating. Refer to the specific cells, hormones and other substances involved.
After eating, high blood glucose level and when insulin is released B cell are involved.
It stimulates the liver which absorb the glucose and storing in a form of glycogen.
(2 marks)
b. Suggest why blood glucose must be so tightly controlled.
Glucose is vital for cellular respiration and therefore there is a need to ensure that there is constant
supply.
(1 mark)
c. Identify one similarity of and one difference between Type 1 and Type 2 diabetes.
Both are failure of the body in responding to high blood glucose level.
Both can lead to hyperglucemia due to the lack of responding to the insulin.
Type 1 diabetes is when beta cells are destroyed so the body cannot produce insulin.
Type 2 is when the receptors
(2 marks)
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Question 7 (Total 5 marks)
Chicken pox is a highly infectious virus that causes an itchy rash. Before a vaccine was developed
against chicken pox, it was estimated that around 80% of the Australian population contracted the
disease at some stage in their childhood. The common cold is a disease that is also caused by a
highly contagious virus. Tens of thousands of people in Australia are infected every year.
a. A person that suffered from chicken pox in their childhood is usually immune from the
disease for the rest of their life. Describe the role of cytotoxic T cells in fighting the initial
chicken pox infection.
Cytotoxic T cells must have a complementary receptor that can bind to the virus infected cell
Release cytotoxins and destroy the infected cell.
(2 marks)
b. Explain why the person becomes immune to the chicken pox virus.
Some of the cells will become memory T cells so they have immunological memory cells.
(1 mark)
c. What type of immunity is this?
Natural Active
(1 mark)
d. Explain why it is common for the same person to catch a cold every year.
cold virus - mutate very fast , antigen changes , immunological memory cells cannot be able to identify the
mutated cells.
(1 mark)
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Question 8 (Total 5 marks)
Peanuts are a common food that can cause anaphylaxis - an extreme allergic reaction that causes
swelling of the throat and respiratory passages - in some people.
a. Describe the role of immunoglobulin E when a person is exposed to an allergen, such as
peanuts, for the first time.
Plasma cells will produce the immunoglobin E (IgE)
IgE will bind with the mast cell
When the allergen bind with the two IgE at the same time on the mast cell, the mast cell will trigger and release
histamine and cytokines
inflammatory response is triggered. So, it causes swelling of throat.
(2 marks)
b. Describe how the human immune system reacts when that person is exposed to peanuts
again.
Peanuts allergen will binds on the IgE,
it will bind with the mast cell and histamine will be released
This time response will be much stronger
(2 marks)
c. Explain how antihistamine medications work to reduce the symptoms of allergies.
Antihistamine blocks the histamine receptors on the cell.
(1 mark)
THE END
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