Topic 5 - Homestasis and Response

Question 1

What is auxin and where is it found?

Answer 1

Auxin is a plant hormone found in the tips of roots and shoots. It controls the growth of plants in response to light and gravity. If auxin is only on one side of a shoot or root, it will cause it to elongate fast and turn.

Question 2

How does auxin work in a shoot?

Answer 2

When a shoot is exposed to light more auxin accumulates on the shaded side. This makes the plant grow faster on the shaded side so the shoot bends toward the light.

If the shoot is growing sideways. Gravity will push auxin down which will stimulate growth to point the shoot upwards out the ground.

Question 3

How does auxin work in the root?

Answer 3

When a root is growing sideways, gravity means more auxin accumulates in the lower side, this will inhibit growth and chase the tip to bend down as the upper part grows faster.

Question 4

What are some commercial uses of auxin?

Answer 4

Weed killers - auxin disrupts normal growth patterns which kills the plant.
Growing cuttings - means cuttings rapidly produce roots
Growing cells in tissue culture - tissue culture grows clones of a plant and auxin will be added to stimulate cell division.

Question 5

What is Gibberellin?

Answer 5

Gibberellin is a plant hormone that stimulates seed germination, stem growth and flowering.

Question 6

How is gibberellin used commercially?

Answer 6

Controlling dormancy - by stimulating germination seeds can germinate out of season when normally the conditions are not met
Inducing flowering - some plants require certain conditions to flower, gibberellin means the they can flower anyway.
Growing larger fruit - fruit can grow large no matter there type or season.

Question 7

What is ethene as a plant hormone?

Answer 7

A gas produced by aging plants. It causes plants to ripen.

Question 8

How is ethene used commercially?

Answer 8

Speed up ripening - either on the plant or during transport meaning a fruit can be picked while unripe to avoid damage.

Question 9

What is the ‘male’ hormone and its function?

Answer 9

Testosterone- produced in testes - triggers secondary sec characteristics and stimulates spermicide production

Question 10

What is the ‘female’ hormone and its function?

Answer 10

Oestrogen - made in ovaries - triggers secondary sex characteristics and is involved in menstrual cycle

Question 11

What four hormones are involved in the menstrual cycle?

Answer 11

FSH
LH
Oestrogen
Progesterone

Question 12

What is the menstrual cycle?

Answer 12

A sequence of events that happens about every 28days.

Question 13

When does the menstrual cycle start?

Answer 13

During puberty when eggs are matured

Question 14

What does FSH do?

Answer 14

Produced in pituitary gland
Causes eggs to mature
Stimulates ovaries to produce oestrogen

Question 15

What does oestrogen do?

Answer 15

Produced in the ovaries
Causes the uterus lining to grow
Stimulates the release of LH and inhibits FSH

Question 16

What does LH do?

Answer 16

Produced in pituitary gland
Stimulates release of an egg

Question 17

What does progesterone do?

Answer 17

Produced by ovaries
Maintains the uterus lining
Inhibits the release of LH and FSH

Question 18

Outline the 4 stages of the menstrual cycle.

Answer 18

Stage 1 - menstruation starts
Stage 2 - uterus lining builds up
Stage 3 - egg develops and releases
Stage 4 - uterus wall is maintained

Question 19

What is a detailed description of stage 1 of the menstrual cycle?

Answer 19

The uterus lining breaks down for four days

Question 20

What is a detailed description of stage 2 of the menstrual cycle?

Answer 20

From day 4 to 14 FSH matures an egg and stimulates oestrogen to build the uterus lining back up

Question 21

What is a detailed description of stage 3 of the menstrual cycle?

Answer 21

At around day 14 oestrogen inhibits the release of FSH an stimulates the release of LH which releases the egg

Question 22

What is a detailed description of stage 4 of the menstrual cycle?q

Answer 22

From around day 14 to 28 the uterus lining is maintained by progesterone, if the egg isn’t fertilised by day 28 progesterone levels fall and the process begins again

Question 23

What are the two types of contraception?

Answer 23

Hormonal and non- normal methods

Question 24

Describe some non-hormonal methods of contraception.

Answer 24

No hormonal methods or barrier methods stop sperm reaching the egg.
- condoms cover the penis to prevent sperm entering the vagina - only form of contraceptive that protects against stis
- diaphragm fits over the cervix and is covered with spermicide
- Spermicide can be used alone but it isn’t effective

Question 25

Describe hormonal methods of contraception.

Answer 25

• the pill contains oestrogen and progesterone - stops egg maturing and creates thick mucus to prevent egg reaching uterus
• patch - contains oestrogen and progesterone - lasts for 1 week
• implant - lasts for three years. Contains progesterone
• iud - copper kill sperm and progesterone

Question 26

What hormones are used in normal contraceptives?

Answer 26

Oestrogen - if taken daily stops eggs maturing
Progesterone - stimulates thick mucus production that prevents sperm reaching the egg

Question 27

What hormones are used to increase fertility?

Answer 27

FSH and LH can be given to stimulate ovulation.

Question 28

What could be the reason women can’t get pregnant?

Answer 28

Low FSH levels - no eggs maturing - no eggs released

Question 29

What does IVF stand for?

Answer 29

In Vitro Fertilisation

Question 30

What is homeostasis?

Answer 30

The regulation of internal conditions to maintain optimum conditions for enzyme action and cell function.