B3 Topic 1 - Control Systems

Question 0

What are the three main functions of the kidney?

Answer 0

Removal of urea from the blood.
Adjustment of ion levels of the blood.
Adjustment of water content of the blood.

Question 1

What is the main component of the kidney responsible for filtration?

Answer 1

The nephron.

Question 2

What are the three steps in urine production in the nephrons?
Explain each one.

Answer 2

1. Ultrafiltration - high pressure is built up in the Bowman’s Capsule to squeeze out water, urea, ions and glucose. The glomerulus acts like a filter, so that bigger molecules such as proteins and blood cells stay in the blood.
2. Selective Reabsorption - glucose is reabsorbed though active transport, against the concentration gradient. Water is reabsorbed according to the levels of ADH (Anti-Diuretic Hormone) in the blood.
3. Release of Waste - excess water that is not reabsorbed and urea carry on, out of the nephron, into the ureter and out of the bladder as urine.

Question 3

Name the components of the body that urea travels though to get to the urethra, starting with the blood.

Answer 3

Renal Artery -> Kidney -> Ureter -> Bladder -> Urethra

Question 4

Which hormone controls the amount of water in the blood?

Answer 4

ADH or Anti-Diuretic Hormone

Question 5

How is water content controlled by negative feedback?

Answer 5

1. The brain notices a decrease/increase in water in the blood.
2. It instructs the pituitary gland to release/stop releasing ADH into the blood.
3. The increase/decrease in levels of ADH cause the kidney to absorb more/less water in the nephrons.
4. Water levels return to normal.

Question 6

How do dialysis machines filter blood mechanically?

Answer 6

• Dialysis machines are used to filter the blood of people who have had kidney failure and therefore cannot filter their own blood.
• Dialysis must be done regularly so that waste such as urea does not build up in the blood.
• Dialysis fluid must have the same concentration of salts and glucose as blood so that they are not removed from the blood
• The barrier must be permeable so that ions and other waste substances can pass through, but not large enough for big molecules like proteins.

Question 7

What is the only cure for kidney failure?

What can go wrong and how can these be prevented?

Answer 7

Kidney transplant

Could be rejected by body - donor with similar tissue type to patient has kidney taken, patient is treated with drugs that suppress immune system
Complications with surgery

Question 8

What are the main functions of an egg cell?

What special features do egg cells have?

Answer 8

• To carry the female DNA and to supply the developing embryo in it’s early stages
• Contain nutrients in cytoplasm to feed embryo
• After fertilisation, egg’s membrane changes structure to prevent any more sperm from entering
• Has a haploid nucleus, so it has half the number of chromosomes of a normal cell (diploid)

Question 9

What are the main functions of a sperm cell?

What special features do sperm cells have?

Answer 9

• Function is to transport the male’s DNA to the egg so that the DNA can combine
• Sperm are small and have long tails so that the can swim to the egg
• Have many mitochondria in their middle section to provide energy (from respiration) to swim
• Head contains acrosome, enzyme which helps digest through membrane of the egg
• Has a haploid nucleus, so it has half the number of chromosomes of a normal cell (diploid)

Question 10

What are the four stages of the menstrual cycle?

Answer 10

1. Menstruation - Uterus lining breaks down and is released. (Day 1)
2. Build up - Lining of the uterus builds up into a thick and spongy layer of blood vessels for a fertilised egg (Day 4 to 14)
3. Ovulation - Egg is released from ovary (Day 14)
4. Lining is maintained - If no fertilised egg lands on uterus wall by day 28, spongy lining breaks down again and cycle starts over (Day 15 to 28)

Question 11

What are the four hormones that control the menstrual cycle?

What is each one responsible for?

Answer 11

FSH:
Causes an egg and it’s surrounding cells to mature in one of the ovaries.
Increases production of oestrogen

Oestrogen:
Causes the lining of the uterus to thicken and grow
Sharply increases the production of LH

LH:
Stimulates ovulation, cells surrounding egg rupture and egg is released
Remains of cells surrounding egg become corpus luteum, which secrete progesterone

Progesterone:
Maintains lining of uterus
Inhibits production of LH and FSH
If levels of progesterone and oestrogen fall, lining of the uterus breaks down
If levels of progesterone fall, FSH is produced and cycle starts again

Question 12

What happens if a fertilised egg implants in the uterus?

Answer 12

The level of progesterone remain high to maintain the uterus lining during pregnancy.

Question 13

What is the purpose of the placenta?

Answer 13

It provides the baby with oxygen, nutrients and glucose, and removes waste like urea and carbon dioxide.

Question 14

Give an example of how negative feedback controls the levels of hormones in the menstrual cycle.

Answer 14

FSH stimulates the ovary to release oestrogen.
Oestrogen inhibits the release of FSH from the pituitary gland.
After FSH causes the follicle (an egg and it’s surrounding cells) to mature, negative feedback keeps FSH low to prevent more follicles from being released.

Question 15

Name four different types of fertility treatment and explain them.
What are the benefits and problems with these treatments?

Answer 15

Hormones:
If the levels of FSH are too low in a woman, eggs may not mature at all. FSH and LH can be injected to stimulate egg release in the ovaries.
Pros - women who previously could not get pregnant now can
Cons - does not always work and therefore may have to be repeated which is expensive; more than one egg could be released, resulting in twins or triplets

IVF:
In vitro fertilisation involves collecting eggs from the ovaries and fertilising them with sperm. They are then grown in labs. Once they become embryos, one or two are transferred into the womb to improve the chances of pregnancy.
Pros - infertile couples can have children
Cons - some women have strong reactions to the treatment: abdominal pains, vomiting, dehydration; there are reports that suggest a higher risk of cancer; there is a chance of multiple births if more than one embryo is successful

IVF with donated eggs:
Women who can’t produce eggs can use eggs from a donor and then use IVF to conceive the baby.
Pros - allows women who can’t produce eggs to have children; use of donated eggs prevents genetic disorders being passed down from the mother
Cons - can be emotionally difficult for family knowing that baby comes from a different genetic mother

Surrogate mother:
If a woman cannot become pregnant, she can ask another woman to have her baby for her. IVF is used to produce the embryo by either egg and sperm from the couple or by donated eggs and sperm. The embryo is then transferred into the surrogate mother. After giving birth to the baby, the surrogate mother gives the baby to the couple.
Pros - allows a couple who can’t have a baby due to medical problems preventing pregnancy
Cons - surrogate is legally the mother and can decide to keep the baby if she doesn’t want to give it up

Question 16

Which combination of X and Y chromosomes cause male and female characteristics?

Answer 16

XX - Female

XY - Male

Question 17

What is pasteurisation and who discovered it?

Answer 17

Pasteurisation is a process where you heat something up to around 70°C before cooling it. This kills most harmful bacteria, making the product safe to handle, eat, drink etc. this was discovered by Louis Pasteur.

Any process involving reducing the contamination of germs is called an aseptic technique.

Question 18

How does immunisation prevent infections?

Answer 18

Immunisation involves injecting dead or inactive micro-organisms into the body. The antigens on these organisms trigger the body’s defence mechanism and antibodies attack. The production of memory lymphocytes is also triggered. If live pathogens with the same antigens enter the body later on, it is killed immediately because there are already antibodies for that pathogen.

Question 19

Name some advantages and disadvantages of immunisation.

Answer 19

Pros - epidemics can be prevented if a large portion of the population is immunised. Some diseases can be wiped out entirely by immunisation, such as the Black Plague and small pox.

Cons - immunisation doesn’t always work. Some people have bad reactions to vaccines, such as seizures or swelling.

Question 20

What are monoclonal antibodies, how are they made and what are they used for?

Answer 20

Monoclonal antibodies are identical antibodies and are produced by fusing a B-lymphocyte, which makes the antibody, and a tumour cell, which divides very quickly, to create a hybridoma. These divide very quickly to produce many monoclonal antibodies. This is used for vaccination to get a large number of antibodies for a patient.

Question 21

How are monoclonal antibodies used in pregnancy tests?

Answer 21

There is a hormone found in urine, but only when a woman is pregnant.
1) Hormone sticks to antibodies attached to blue beads.
2) If woman is pregnant, urine moves up stick, carrying hormone and beads.
3) Beads bind to antibodies stuck onto test strip, turning it blue.
…
2) If woman is not pregnant, beads carry on past test strip and colour doesn’t change.

Question 22

How are monoclonal antibodies used in the treatment of cancer?

Answer 22

Different cells have different antigens on their surface, so scientists can make monoclonal antibodies that bind to specific antigens to target cells. Cancerous cells have antigens that aren’t found in the body so monoclonal antibodies can be made to target the tumours.

Diagnosis:

1) Antibodies are labelled with a radioactive element.
2) These antibodies are injected or given to the patient with a drip.
3) The antibodies travel around the bloodstream until they come into contact with the tumour.
4) The antibodies bind to the cancerous cells.
5) A picture of the patient is taken using a camera that detects radiation.
6) Doctors can see what size the cancer is, it’s location and whether it is spreading.

Treatment:

1) An anti-cancer drug is attached to the monoclonal antibodies.
2) The antibodies are given to the patient.
3) The monoclonal antibodies target only the cancer cells due to the antigens on the surface of the cells.
4) The drug kills the cancer cells but none of the normal cells.
5) This method of treatment is better than other cancer treatments, like radiotherapy, because they kill the cancer cells as well as some normal cells.

Question 23

What is Taxol®, and where does it come from?

Answer 23

Taxol® is an anti-cancer drug and it comes from the Pacific Yew Tree.

Question 24

How are plants photoperiodic?

Answer 24

Photoperiodicy means that an organism responds to changes in day length. For example, during the summer, the days are long and the nights are short, and in the winter, this is the opposite.
Some plants only germinate, grow or flower when the days are a certain length.

Question 25

Give some examples of photoperiodicy in plants.

Answer 25

Seeds of Arctic plants only germinate when the days are long so that they only germinate in the middle of the summer when temperatures are warmer.

Some plant buds use the increasing day length to tell them when the winter is over so that they don’t sprout and get killed by frost.

Different plants use the different day lengths to make sure that they germinate, flower or grow at different times of the year.

Question 26

What is the definition of a circadian rhythm?

Answer 26

A Circadian Rhythm is a biological process that follows a 24hr cycle.
This can include chemical patterns; such as hormone production; physiological patterns; such as body temperature; and behavioural patterns; such as sleeping and eating.
They are controlled internally but can still be affected by environmental changes, such as light intensity in plants.

Question 27

Give examples of circadian rhythms in animals.

Answer 27

Sleep pattern: the body clock gets information about light intensity from your eyes. It uses this information to control the release of melatonin, which induces sleep. As it gets darker, melatonin production is increased. The opposite happens with nocturnal animals.

Urine production: the body clock also controls the production of ADH. At night, ADH production increases so that sleep is not interrupted.

Question 28

Give examples of circadian rhythms in plants.

Answer 28

Stomata opening: stomata respond to light intensity. During the day, they open to allow the CO2 and O2 to go in and out of the plant for photosynthesis, and during the night they close to decrease the amount of water loss from evaporation.

Flower opening: plants respond to light intensity by opening and closing their flowers during the day and night, respectively. They open during the day because this is the time when pollinating insects are active.