Topic 6

Question 1

(1) Enzymes used to digest macromolecules and where they are at work/environment they are found in (pH)

Answer 1

salivary amylase
salivary glands
mouth; ph 7
starch, glycogen
maltose (disacharide)

Question 2

(2)Enzymes used to digest macromolecules and where they are at work/environment they are found in (pH).

Answer 2

pancreatic amylase
pancreas
small intestine (8)
starch, glycogen
maltose

Question 3

(3)Enzymes used to digest macromolecules and where they are at work/environment they are found in (pH).

Answer 3

carbohydrases
- sucrase
-maltase
-lactase
small intestine
small intestine; ph 8
sucrose
maltose
lactose
glucose +fructose
glucose
glucose+galactose

Question 4

(4)Enzymes used to digest macromolecules and where they are at work/environment they are found in (pH).

Answer 4

pancreatic lipase
pancreas
small intestine; ph 8
lipids
fatty acids and glycerol

Question 5

(5)Enzymes used to digest macromolecules and where they are at work/environment they are found in (pH).

Answer 5

proteases
-pepsin
-trypsin
-chymotrypsin
stomach
pancreas
pancreas
stomach; ph 1/2
small intestine; ph 8
small intestine; ph 8
protein
small polypeptides
small polypeptides
peptides
smaller peptides
smaller peptides

Question 6

(6)Enzymes used to digest macromolecules and where they are at work/environment they are found in (pH).

Answer 6

peptidases
pancreas and small intestine
small intestine; ph 8
peptides
smaller peptides and amino acids

Question 7

Blood flow through a heart (oxygenated vs deoxygenated)

Answer 7

1. Blood passes through the heart twice on one circuit of the body.
2. Deoxygenated blood (low O2, high CO2) returns to the heart via the right atrium. It is pumped from the right ventricle to the lungs, where carbon dioxide is offloaded and oxygen is picked up. It is now oxygenated blood (high O2, low CO2).
3. Oxygenated blood enters the left atrium and is pumped from the left ventricle to the body, where oxygen is used for respiration and carbon dioxide is collected as a waste product.
4. And now it’s deoxygenated, it makes its way back to the right atrium and the cycle continues.
5. Deoxygenated blood circles from the right side and oxygenated blood circles from the left side.

Question 8

Heart rate and control of the heart rate

Answer 8

1. The beating of the heart is due to myogenic muscle contraction. This means the myocyte (muscle cell) itself is the origin of the contraction and is not controlled externally.
2. A region of myocytes called the sinoatrial node (peacemaker) controls the rate of the heartbeat. A wave of excitations is sent from the sinoatrial node, causing the atria to contract.
3. This excitation is conducted to the atrioventricular node, where it is passed through nerves to the muscles of the ventricles, causing them to contract.
4. Myogenic initiation of the contraction means that the heart does not stop beating - it is not a conscious process. Heart rate can be controlled by the autonomic nervous system - the part of the nervous system that responds automatically to changes in body conditions.
5. Where myocardial contraction maintains the beating of the heart, we may need to speed up or slow down the heart rate.
6. When exercising, more CO2 is present in the blood. This is detected by chemoreceptors in the brain’s medulla oblongata, resulting in a nerve signal being sent to the SA node to speed the heart rate.
7. When CO2 levels fall, another nerve (Vagus) reduces the heart rate. The hormone adrenalin causes a rapid increase in heart rate fight-or-flight responses, preparing the body for action. This effect can be mimicked by stimulant drugs.

Question 9

What are the three layers of defense the body has?

Answer 9

The immune system can be divided into 3 basic lines of defense against pathogenic infection:
- The first line of defense against infection is the surface barriers that prevent the entry of pathogens into the body (skin, mucous membranes, secretion of skin and mucous membranes)
- The second line of defense is the non-specific phagocytes and other internal mechanisms that comprise innate immunity (antimicrobial protein, phagocytic leukocytes, inflammatory response, and fever)
- The third line of defense is the specific lymphocytes that produce antibodies as part of the adaptive immune response (memory cells, lymphocytes, antibodies)

Question 10

How does the body defend against blood loss? (order of events that stop blood flow in an injury)

Answer 10

1. Wounds such as cuts to the skin cause opening through which pathogens can potentially enter the body.
2. Blood clots at the site of a wound prevent blood loss and the entry of pathogens. Platelets (small cell fragments) along with damaged tissue release clotting factors in response to a wound.
3. Clotting factors cause a series of reactions that end with fibrin (a protein) fibers forming a mesh across the wound site.
4. The fibrin fibers capture blood cells and platelets forming a clot that dries to form a scab that shields the healing tissues underneath.

Question 11

Production of antibodies and how they provide specific immunity in the body

Answer 11

1. An antigen is a substance or molecule, often found on a cell or virus surface, that causes antibody formation (characteristic of the surface of a cell/cell type).
2. An antibody is a globular protein that recognizes a specific antigen and binds to it as a part of an immune response. Antibodies are specific to certain antigens.
3. An immune response is triggered by non-self cells, which is why matches are crucial in transplants and blood transfusions - and why stem cell technologies are so promising.
4. Many different lymphocytes exist. Each type recognizes one specific antigen. When the immune system is challenged by the invasion of a pathogen, the corresponding lymphocyte responds.
5. It makes many clones of itself, each of which produces antibodies to the pathogen. This process is called clonal selection, as the right lymphocyte is selected and then cloned. Some clones cells remain as memory cells, ready for a second invasion by the pathogen. This is immunity.

Question 12

Differences between eukaryotic and prokaryotic cells and how they are affected by antibiotics/vaccines

Answer 12

1. Antibiotics are drugs used in the treatment and prevention of prokaryotic bacteria (prokaryotes are always unicellular and eukaryotes are multi-celled).
2. They are designed to disrupt structures or metabolic pathways in bacteria and fungi:
   cell walls and membranes
   protein synthesis (translation)
   DNA/RNA synthesis
   other metabolic processes (e.g. enzyme function)
3. These do not exist or are very different from viruses so antibiotics have no effect on them.
4. Eukaryote (e.g. human) cells are also very different in structure and function from prokaryotes. Therefore drugs that inhibit prokaryotes often have little or no effect on eukaryotes.
5. There is no point in taking antibiotics for colds and the flu. Viruses use the (eukaryotic) host cell metabolism. Viruses are protected by the host cell structure.
6. Viruses have a very different structure from prokaryotes, just a protein capsid, and genetic material - no cell wall or membrane to attack.

Question 13

How is HIV transferred?

Answer 13

1. HIV gradually attacks the immune system, which is our body’s natural defence against illness. If a person becomes infected with HIV, they will find it harder to fight off infections and diseases.
2. There is no risk of HIV transmission from skin contact, toilet seats, and mosquitoes.
3. There is a low risk of HIV transmission from saliva/kissing, ingestion, childbirth, breastfeeding
4. A higher risk of HIV transmission from oral sex, sexual intercourse, and blood-to-blood contact.

Question 14

Difference between type I and II pneumocytes.

Answer 14

Type I pneumocytes
a single layer of cells from the walls of an alveolus
extremely thin - short diffusion distance
permeable - aids diffusion

Type ll pneumocytes
secrete fluid to moisten the inner surface of the alveolus
fluid aids the diffusion of gases
the fluid contains a surfactant to prevent the walls from sticking together - maintains the lumen
can divide to form Type l pneumocytes - repair damage

Question 15

Outline the processes of inspiration

Answer 15

pressure change: decrease (draws air in)
volume change: increase
ribcage movement: up and out
external intercostal muscles: contract
internal intercostal muscles: relax
diaphragm: contract (flattens, moves down)
abdominal muscle: relax

Question 16

Outline the processes of expiration

Answer 16

pressure change: increase (pushes air out)
volume change: decrease
ribcage movement: down and in
external intercostal muscles: relax
internal intercostal muscles: contract
diaphragm: relax
abdominal muscle: contract

Question 17

What is the purpose of the myelin sheath and how is it used in saltatory conduction?

Answer 17

1. Myelin Sheath is an insulating layer of fatty white tissue around an axon; allows impulses to travel quickly.
2. As myelin acts as an insulator myelinated axons only allow action potentials to occur at the unmyelinated nodes of Ranvier. This forces the action potential to jump * from node to node (saltatory conduction).
3. The result of this is the impulse travels much more quickly (up to 200 m/s) along myelinated axons compared to unmyelinated axons (2 m/s).
4. Saltatory conduction from node to node also reduces degradation of the impulse and hence allows the impulse to travel longer distances than impulses in unmyelinated axons.
5. The myelin sheath also reduces energy expenditure over the axon as the quantity of sodium and potassium ions that need to be pumped to restore resting potential is less than that of an un-myelinated axon.

Question 18

Label a neuron and explain how nerve impulses are transmitted

Answer 18

The neuron is the basic functional unit of the nervous system. It’s a specialized cell that uses electrical signals called impulses to communicate with other cells. A bundle of neurons is called a nerve.

Dendrite: projection of cytoplasm that carries signals from outside the neuron toward the cell body

Axon: part of the neuron that carries impulses away from the cell body and toward other cells

Myelin Sheath: an insulating layer of fatty white tissue around an axon; allows impulses to travel quickly

Terminal knob: part of the neuron that attaches it to another cell

Synapse: the connection between the terminal knob of a neuron’s axon and a dendrite of an adjacent neuron

Nodes of Ranvier: areas between sections of my; nerve impulses jump from one node to another; increases the speed of transmission

A nerve impulse is transferred from one neuron to another at either an electrical or chemical synapse. A synapse is the “connection” between 2 neurons and is made up of 3 parts: pre-synaptic neuron; synaptic cleft; and post-synaptic neuron. An electrical synapse is a synapse in which the presynaptic cell makes direct contact with the postsynaptic cell, allowing the flow of electrical current via gap junctions. A chemical synapse is when a neurotransmitter moves from a presynaptic cell to post-synaptic cells through a synaptic cleft (the narrow gap between pre and post-synaptic cells).

Question 19

Identify and explain depolarization and repolarization

Answer 19

Depolarization is caused when positively charged sodium ions rushed into a neuron with the opening of voltage-gated sodium channels. Repolarization is caused by the closing of sodium ion channels and the opening of potassium ion channels.

Question 20

Identify and explain the 4 stages of an action potential

Answer 20

1. Action potential is the reversal (depolarization) and restoration (repolarization) of the membrane potential as an impulse travels along it.
2. The sodium-potassium pump (Na+/K+ pump) maintains the electrochemical gradient of the resting potential. Some K+ leaks out of the neuron (making the membrane potential negative, -70mv)
3. In response to a stimulus (e.g. change in membrane potential) in an adjacent section of the neuron some voltage-gated Na+ channels open and sodium enters the neuron by diffusion.
4. If a sufficient change in membrane potential is achieved (threshold potential) all voltage-gated Na+ channels open.
5. The entry of Na+ causes the membrane potential to become positive (depolarization)
   The depolarization of the membrane potential causes the voltage gated Na+ channels to close and the voltage gated K+ channels open.
6. K+ diffuses out of the neuron rapidly and the membrane potential becomes negative again (repolarisation)
7. Before the neuron is ready to propagate another impulse the distribution of Na+ (out) and K+ (in) needs to be reset by the Na+/K+ pump, returning the neuron to resting potential.
8. This enforced rest (refractory period) ensures impulses can only travel in a single direction

Question 21

Summarize synaptic transmission

Answer 21

1. Nerve impulse reaches terminal end of pre-synaptic neuron
2. Depolarisation causes voltage-gated calcium channels to open. Ca2+ rushes in.
3. Ca2+ causes synaptic vesicles to move to the membrane and fuse
4. Neurotransmitters (NTs) that were stored in the synaptic vesicle now diffuse across the synaptic gap
5. Nts bind with post-synaptic receptors (Nts are specific to the receptor
6. Sodium channels open, causing Na+ to enter, leading to depolaristaion of the post-synaptic neuron. An action potential is initiated. The nerve impulse is then propagated along the post-synaptic neuron by active transport (hence the large number of mitochondria)
7. Enzymes in the synaptic gap then breakdown the NT.

Question 22

Explain the use of acetylcholine as a neurotransmitter at synapses

Answer 22

Acetylcholine is a neurotransmitter used in many synapses through the nervous system. Acetylcholine (ACh) is made from choline and acetyl CoA. In the synaptic cleft ACh is rapidly broken down the enzyme acetylcholinesterase. Choline is transported back into the axon terminal and is used to make more ACh. One use is at the neuromuscular junction, i.e. it is the molecule the motor neurons release to activate muscles. Interfering with the action of acetylcholine can cause a range of effect from paralysis to convulsions.

Question 23

Explain how insulin and glucagon work to maintain blood glucose levels.

Answer 23

Blood glucose is maintained through the actions of the pancrease and liver. Pancreatic cells monitor blood glucose; absorption of glucose from digestion in the intestine increases blood sugar/fasting reduces blood sugar; glucoregulation is an example of negative feedback; uses hormones insulin and glucagon;

If blood glucose is too high B-cells of pancreas produce insulin; insulin stimulates uptake of glucose to cells, e.g. muscle; insulin stimulates liver/fat cells to store glucose as glycogen; leading to decrease in blood glucose;

If blood glucose is too low a-cells of pancreas produce glucagon; glucagon stimulates liver to break glycogen into glucose; leads to increased blood sugar;

Diabetes is the recued ability to control blood glucose through insulin. Type 1: early onset diabetes is hereditary and has a weak relationship. It requires an illness to trigger it. Beta cells are destroyed and insulin production is stopped. Type 2: Adult Onset diabetes is hereditary and has a strong relationship. It is related with obesity and poor diet. Fewer insulin receptors in liver and less sensitivity to insulin (insulin does not work as well)

Question 24

Understand the importance/actions of thyroxine, leptin, and melatonin.

Answer 24

Thyroxin is secreted by the thyroid gland to regulate the metabolic rate and help control body temperature. It targets most body cells and effects the rate of protein synthesis, increases metabolic rate, increases heat production (e.g. increased respiration). Leptin is secreted by cells in adipose tissue and acts on the hypothalamus of the brain to inhibit appetite. It is produced by adipose cells (fat storage cells) and targets appetite control centre of the hypothalumus (in brain). It affects the increase in adipose tissue, resulting in the increase of leptin secretions into the blood, causing appetitw inhibation and hence reduced food intake. Melatonin is secreted by the pineal gland to control circadian rhythms. It is produced by pineal gland in darkness and targets the pituitary gland and other glands. Melatonin effects the synchronization of the circadian ehythyms including sleep timing and blood pressure regulation.

Question 25

What is the role of testosterone before and during puberty?

Answer 25

The testes develop from the embryonic gonads when the embryo is becoming a fetus. The testes secret testosterone which causes the male genitalia to develop. At puberty the secretion of testosterone increases causing:
the primary sexual characterstic of sperm production in the testes
development of secondary sexual characterstics such as enlargement of the penis, growth of the pubic hair and deepining of the voice.

Question 26

What is the role of estrogen and progesterone before and during puberty?

Answer 26

Estrogen and progesterone are present. At first they are secreted by the mother’s ovaries and later by her placenta. At puberty the secretion of estorgen and progesterone increases causing:
primary sexual characterstic of egg release
development of female secondary sexual charcterstics such as enlargement of the breasts and growth of pubic hair.
In the absence of fetal testosterone and the prescence of maternal estorgen and progesterone, female reproductive organs develop (ovaries develop from the embryonic gonads) due to:
estrogen and progesterone
no testerone

Question 27

What is the role of LH and FSH in the female menstrual cycle?

Answer 27

The menstrual cycle is controlled by negative and postive feedback mechanisms involving ovarian and pituitary hormones (controlled by the endocrine system). FSH stimulates oocyte development and LH matures oocyte and causes release (ovulation)

Question 28

Identify the hormones involved in the menstrual cycle on a graph.

Answer 28

Day 1-4 (Follicular phase):
Menstruation. Endometrium shed.
FSH increases, stimulating follicle development
Day 5-14 (Ovulatory phase):
FSH and follicle stimulate oestrogen release.
Oestrogen stimulates endometrium development. Oestrogen stimulates LH.
Peak in LH causes ovulation (day 14)
Day 14-28 (Luteal Phase):
Fall in LH. Corpus luteum forms from now-empty follicle
Corpus luteum releases progesterone
Progesterone maintains the endometrium and inhibits FSH and LH
If no fertilisation and implantation occurs progesterone and oestrogen drop, triggering menstruation and FSH release.

Question 29

Identify the steps involved in IVF.

Answer 29

IVF is formally known as In vitro fertilization.
It begins after determining suitability for IVF, FSH and LH are given to stimulate multiple egg releases.
These eggs are collected.
Eggs are fertilised with father’s sperm, in a dish, and incubated. This is ‘IVF.’ After incubation, viable (fertilised) blastocysts are selected and developed into embryos.
Guidelines state that up to 3 embryos can be selected for implantation. Hopefully one or more will ‘take.’ There is risk of multiple preganacy.
After bedrest and a month or so, a preganacy test is administered. If positive, pregnancy continues as normal. If not, a woman may wait a few months and attempt another cycle.