Control Systems

Question 1

What does cell metabolism lead to

Answer 1

build-up of waste products in the blood, including carbon dioxide and urea

Question 2

How is urea produced and removed

Answer 2

produced from the breakdown of excess amino acids in the liver and is removed by the kidneys

Question 3

Describe the structure of the urinary system

Answer 3

a) renal artery and vein - vein = carry cleaned blood back to the body, arteries = carry blood from the body to the kidneys
b) kidneys - remove substances including urea from the blood and make urine
c) ureters - carry urine from the kidneys to the bladder
d) bladder - stores urine
e) urethra - urine flows through the urethra to the outside of the body

Question 4

Describe possible treatments for kidney failure

Answer 4

kidney dialysis - blood is passed through a dialysis machine to remove waste urea and excess substances before the blood is returned to the body.
organ donation - a healthy kidney from another person is placed in the body and connected to the blood system, so that waste substances are removed from the blood

Question 5

Describe the structure of a nephron

Answer 5

a) glomerulus and Bowman’s capsule - glomerulus = small knot of capillaries, bowman’s capsule = cup shape. filtration of small molecules from blood into tubule, including water, glucose,salts and urea
b) convoluted tubules -
c) loop of Henlé
d) collecting duct

Question 6

Explain how the structure of the nephron is related to its function in filtering the blood and forming urine (osmoregulation),

Answer 6

the blood in the glomerulus is under high pressure. the walls of the glomerulus and bowman’s capsule are leaky so small molecules filter from the blood into the capsule. the large surface area of the glomerulus and capsule means filtration happens as quickly as possible. the convoluted tubule and loop of henle lie close to a capillary, so that glucose and water can be reabsorbed into the blood from the tubule

Question 7

describe the role of ADH (produced by the pituitary gland) in regulating the water content of the blood

Answer 7

to control the amount of water reabsorbed from the nephrons. this regulates the water content of the blood

Question 8

describe how ADH production is controlled by a negative feedback mechanism

Answer 8

an increase in blood water content causes the pituitary gland to be reabsorbed by the collecting duct in the kidneys so more water is excreted by the kidneys. a decrease in blood water content causes the pituitary gland to secrete more ADH, which causes less water to be excreted by the kidneys. this is a negative feedback mechanism because a change in blood water content causes can opposite change that restores the normal blood water content

Question 9

what is the menstrual cycle controlled by

Answer 9

menstrual cycle is controlled by the hormones

oestrogen and progesterone

Question 10

Describe the stages of the menstrual cycle

Answer 10

1) mensuration is the breakdown of the uterus lining. it begins on day 1 of the cycle and usually lasts between 4 and 7 days.
2) during the second week, the lining of the uterus is gradually built up
3) ovulation is the release of an egg from an ovary. this usually takes place around day 14.
4) days 14-16 are the days when fertilisation is most likely to take place
5) the lining of uterus continues to build up throughout weeks 3 and 4
6) if fertilisation occurs then the uterus lining is maintained and mensuration does not happen

Question 11

Explain why the uterus lining is maintained if fertilisation occurs

Answer 11

the embryo that develops form a fertilised egg needs to embed in the thick uterus lining, so that it can get nutrients from the mother

Question 12

Describe how oestrogen, progesterone, FSH and LH control the menstrual cycle

Answer 12

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Question 13

describe how the menstrual cycle is controlled by a negative feedback mechanism

Answer 13

changes caused by the release of of hormone inhibit the secretion of other hormones. for example, progesterone inhibits FSH and LH

Question 14

Explain how the structure of an egg is adapted to its function

Answer 14

> cytoplasm to provide nutrients that the embryo will use to grow and develop
haploid nucleus contains one set of genetic material
cell membrane changes immediately after fertilisation to block entry of other sperm

Question 15

Explain how the structure of a sperm cell is adapted to its

function

Answer 15

> acrosome containing enzymes to digest into the egg
haploid nucleus contains one set of genetic material
middle section containing mitochondria that release energy from respiration to power tail
tail for movement

Question 16

describe the advantages and disadvantages of infertility treatments

Answer 16

Egg donation:
A) used when woman of the couple has no eggs in her ovaries
D) hormones used to collect eggs may cause a bad reaction. the egg donor may want access to the child.
IVF:
A) useful if a man produces only a few healthy sperm
D) babies may be born early, which can cause problems at birth or later in life
Surrogate mother:
A) used when the woman of the couple cannot grow an embryo in her uterus
D) some surrogate mothers find it hard to hand over the baby to the couple
Hormones:
A) used when the woman’s hormones are not enough to cause ovulation
D) there is a greater risk of having several babies at the same time. these babies tend to be born earlier than normal, which can cause problems at birth or later in life

Question 17

how is the sex of a person is controlled

Answer 17

the sex of a person is controlled by one pair of

chromosomes, XX in a female and XY in a male

Question 18

Describe Edward Jenner’s contribution to the development of vaccines

Answer 18

Edward Jenner gave a boy a pathogen that causes a mild disease called cowpox. the boy developed cowpox and recovered,. later Jenner gave the boy the pathogen that causes a dangerous disease called small pox. the boy did not develop small pox - the cowpox vaccine had made him immune to smallpox

Question 19

Explain the process of immunisation

Answer 19

1) a vaccine containing a dead or weakened pathogens injected into the body. it has antigens on its surface.
2) a type of white blood cell, called a lymphocyte, with an antibody that perfectly fits the antigen is activated
3) this lymphocyte divides over and over again to produce clones of identical lymphocytes
4) some of the lymphocytes secrete large amounts of antibodies. the antibodies stick to the antigens and destroy the pathogen

Question 20

describe the advantages and risks associated with immunisation

Answer 20

risks:
> some people get a mild reaction of swelling or soreness, or a mild form of the disease
> very rarely a person has a major harmful reaction
advantage:
> immunity is produced without being ill
> immunity lasts a long time, often for life
> if most people are immune, then the few unvaccinated people are also likely to catch the disease

Question 21

Describe the role of memory lymphocytes in secondary

responses to antigen

Answer 21

memory lymphocytes are ready to respond immediately if the same antigen ever turns up again.

Question 22

explain how sex linked genetic disorders are inherited

Answer 22

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Question 23

Describe the production of monoclonal antibodies, and the use of them

Answer 23

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Question 24

Describe how the exponential growth of a population of bacteria can lead to rapid development of an infection

Answer 24

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Question 25

describe Louis Pasteur’s contribution to the development of aseptic techniques

Answer 25

Carried out experiments showing that once microorganisms are destroyed, they do. To suddenly appear again. Microorganisms can only be transferred from something that already contains them, such as the air. Led to the development of aseptic techniques that are us to destroy microorganisms. These techniques are used to prevent spoilage of food and in surgery to prevent infection of wounds.

Question 26

how do plants defend themselves against attack from pests and pathogens, how can we use them to can be used to treat human diseases, disorders or relieve symptoms

Answer 26

> poison in their cells to deter pests that try to eat them
chemicals that kill pathogens! which infect them and cause disease
humans can use them to: treat human disease, disorders, and relieve symptoms

Question 27

explain impact that attack by pests and pathogens on plants has on human food supply

Answer 27

Most of the food we eat comes from plants. Pathogens and pests that attack crop plants cause damage. This reduces the yield of the crop.

Question 28

Explain photoperiodic and it’s importance in plants

Answer 28

The response of a plant that changes as day length changes. Most noticeable where day length changes throughout the year.
> growth - plants stop growing over winter. some trees lose their leaves
> germination - some seeds germinate better in spring when day length is getting longer. This is usually when conditions for growth are getting better.
> reproduction - some produce flowers in response to days getting longer. Other plants flower when day length gets shorter.

Question 29

explain circadian rhythms in living organisms

Answer 29

Is a pattern of bah our that changes over a 24 hour period. Controlled by a biological clock. External factors such as day and night help to match the clock to changes in environment.