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Biology GCSE Paper 2 > Topic 5c- Animal and Plant Hormones > Flashcards

Topic 5c- Animal and Plant Hormones Flashcards

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1
Q

What happens at puberty?

A

At PUBERTY, your body starts releasing SEX HORMONES that trigger off SECONDARY SEXUAL CHARACTERISTICS.

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2
Q

What are the secondary sexual characteristics caused by sex hormones in puberty for men?

A

The development of FACIAL HAIR in men.

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3
Q

What are the secondary sexual characteristics caused by sex hormones in puberty for women?

A
  • Women develop BREASTS.

- Sec hormones also cause EGGS to MATURE in women.

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4
Q

What is the main reproductive hormone in men?

Where is this hormone produced and what does it do?

A

In MEN, the main reproductive hormone is TESTOSTERONE.

It’s produced by the TESTES and stimulates SPERM PRODUCTION.

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5
Q

What is the main reproductive hormone in women?

Where is this hormone produced and what does it do?

A

In WOMEN, the main reproductive hormone is OESTROGEN.

It’s produced by the OVARIES.

As well as bringing about PHYSICAL CHANGES, oestrogen is also involved in the MENSTRUAL CYCLE.

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6
Q

What is the menstrual cycle?

A

The menstrual cycle is the monthly sequence of events in which the female body releases an egg and prepares the uterus (womb) in case it receives a fertilised egg.

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7
Q

Describe the four stages of the menstrual cycle.

A

Stage 1 = Day 1- MENSTRUATION (bleeding) STARTS. The uterus lining breaks down for about four days.

Stage 2- The UTERUS LINING BUILDS UP AGAIN, from day 4 to 14, into a thick spongy layer full of blood vessels, ready to receive a fertilised egg.

Stage 3- An EGG DEVELOPS and is RELEASED from the ovary at day 14- this is called OVULATION.

Stage 4- The WALL is then MAINTAINED for about 14 days until day 28. If no fertilised egg has landed on the uterus wall by day 28, the spongy lining starts to break down and the whole cycle starts again.

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8
Q

What is the menstrual cycle controlled by?

A

The menstrual cycle is controlled by four HORMONES.

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9
Q

What are the four hormones that control the menstrual cycle called?

A

The four hormones are:

  1. FSH (Follicle-Stimulating Hormone)
  2. LH (Luteinising Hormone)
  3. Oestrogen
  4. Progesterone
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10
Q

Where is FSH produced?

What is the role of FSH (follicle-stimulating hormone) in the menstrual cycle?

A

FSH (Follicle-Stimulating hormone)

  • Produced in the PITUITARY GLAND.
  • Causes an EGG TO MATURE in one of the ovaries, in a structure called a FOLLICLE.

Stimulates the OVARIES to produce OESTROGEN.

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11
Q

Where is oestrogen produced?

What is the role of oestrogen in the menstrual cycle?

A

Oestrogen

  • Produced in the OVARIES
  • Causes the lining of the uterus to GROW.
  • STIMULATES the release of LH (which causes the release of an egg) and INHIBITS release of FSH.
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12
Q

Where is LH produced?

What is the role of LH (Luteinising Hormone) in the menstrual cycle?

A

LH (Luteinising Hormone)

  • Produced by the PITUITARY GLAND.
  • STIMULATES the RELEASE of an EGG at day 14 (ovulation).
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13
Q

Where is progesterone produced?

A

Progesterone

  • Produced in the OVARIES by the remains of the FOLLICLE after ovulation.
  • MAINTAINS the lining of the uterus during the SECOND HALF of the cycle. When the level of progesterone FALLS, the lining BREAKS DOWN.
  • INHIBITS the release of LH and FSH.
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14
Q

How can you predict the level of certain hormones?

A

Levels of FSH, LH oestrogen and progesterone change throughout the menstrual cycle.

So the change in the level of one hormone can be used to predict the change in the level of another hormone.

E.g. FSH stimulates the ovaries to produce oestrogen, so if the FSH level rises you’d expect the oestrogen level to rise too. The increasing oestrogen level will then inhibit FSH release, causing the FSH level to drop.

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15
Q

What does the inhibition of FSH by oestrogen do?

A

The inhibition of FSH by oestrogen makes sure that no more eggs mature during that month’s cycle.

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16
Q

What is the main female reproductive hormone produced?

A

Oestrogen is the main female reproductive hormone produced in the ovary.

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17
Q

When do eggs begin to mature in a woman?

What is ovulation?

A

At puberty eggs begin to mature and one is released approximately every 28 days. This is called ovulation.

The release of an egg-ovulation.

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18
Q

When does pregnancy occur?

A

Pregnancy can happen if sperm reaches the ovulated egg.

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19
Q

What is fertility?

A

Fertility is the ability to get pregnant.

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20
Q

Why are contraceptives used?

A

Contraceptives can be used to prevent pregnancy.

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21
Q

Why is progesterone and oestrogen taken as contraceptives?

A

The hormones oestrogen and progesterone can be taken by women to reduce fertility and so are often used as contraceptives.

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22
Q

Why is oestrogen used to reduce fertility (getting pregnant)?

A

Oestrogen can be used to PREVENT the RELEASE of an EGG- so it can be used as a method of CONTRACEPTION.

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23
Q

How does oestrogen prevent ovulation?

A

This may seem odd (since naturally oestrogen helps stimulate the RELEASE of eggs). But if oestrogen is taken EVERY DAY to keep the level of it PERMANENTLY HIGH, it INHIBITS the production of FSH, and after a while EGG DEVELOPMENT and PRODUCTION STOP and stay stopped.

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24
Q

How does progesterone reduce fertility?

A

Progesterone also reduces fertility, e.g. by stimulating the production of THICK CERVICAL MUCUS which prevents any SPERM getting through and reaching an egg.

It can inhibit egg MATURATION and therefore the RELEASE of an egg too.

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25
Q

What is the pill?

A

The PILL is an oral contraceptive containing OESTROGEN and PROGESTERONE, this inhibits FSH production so that no eggs mature

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26
Q

What is the pill known as?

A

It’s known as the COMBINED ORAL CONTRACEPTIVE PILL).

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27
Q

When was the first oral contraceptive made?

What was wrong with it?

A

The first version known as the COMBINED ORAL CONTRACEPTIVE PILL was made in the 1950s.

It contained HIGH levels of OESTROGEN and PROGESTERONE. There were concerns about a link between oestrogen in the pill and side effects like blood clots.

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28
Q

How was the pill improved to ensure it was safe?

A

The pill now contains LOWER doses of oestrogen and has FEWER side effects.

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29
Q

What are the benefits of the combined oral contraceptive pill?

A

Advantages:
- The pill is over 99% EFFECTIVE at preventing pregnancy.

  • It’s also been shown to REDUCE the RISK of getting some types of CANCER.
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30
Q

What are the problems with the combined oral contraceptive pill?

A

Disadvantages:
-It isn’t 100% effective at preventing pregnancy.

  • It can cause SIDE EFFECTS like headaches and nausea.
  • It DOESN’T PROTECT against STDs (sexually transmitted diseases).
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31
Q

How many types of oral contraceptive are there?

A

There are two types:

  1. The combined oral contraceptive pill.
  2. There’s also a PROGESTERONE-ONLY PILL.
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32
Q

What are the advantages of a progesterone only pill?

A

The progesterone only pill has fewer side effects than the pill, and is just as effective.

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33
Q

What are the other methods of contraception that use hormones?

A
  • The CONTRACEPTIVE PATCH
  • The CONTRACEPTIVE IMPLANT
  • The CONTRACEPTIVE INJECTION
  • An IUD (intrauterine device)
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34
Q

How does the contraceptive patch work?

A

The contraceptive patch contains OESTROGEN and PROGESTERONE (the same as the combined pill).

It’s a small (5cm x 5cm) patch that’s stuck to the SKIN.

Each patch lasts ONE WEEK.

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35
Q

What is the contraceptive implant?

A

The contraceptive implant is inserted UNDER THE SKIN of the arm. It releases a CONTINUOUS amount of PROGESTERONE, which stops the ovaries releasing eggs, makes it hard for sperm to swim to the egg, and stops any fertilised egg implanting in the uterus. An implant can last for THREE YEARS.

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36
Q

What is the contraceptive injection?

A

The contraceptive injection also contains PROGESTERONE. Each dose lasts 2 to 3 months.

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37
Q

What is an IUD (an intrauterine device)?

A

An intrauterine device is a T-shaped device that is inserted into the UTERUS to KILL SPERM and PREVENT IMPLANTATION of a fertilised egg. There are TWO main types- PLASTIC IUDs that release PROGESTERONE and COPPER IUDs that prevent the sperm SURVIVING in the uterus.

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38
Q

What are barrier methods?

A

Non-hormonal barrier forms of contraception are designed to STOP the SPERM from getting to the egg.

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39
Q

What are the 2 types of barrier methods?

A
  • Condoms

- A diaphragm

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40
Q

What are condoms?

A

Condoms are worn over the penis during intercourse to prevent the sperm entering the vagina.

There are also FEMALE CONDOMS that are worn inside the VAGINA.

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41
Q

What is a benefit of using condoms over other forms of contraception?

A

Condoms are the only form of contraception that will protect against SEXUALLY TRANSMITTED DISEASES.

42
Q

What is a diaphragm?

A

A DIAPHRAGM is a shallow plastic cup that fits over the CERVIX (the entrance to the uterus) to form a barrier.

It has to be used with SPERMICIDE (a substance that DISABLES or KILLS the sperm).

43
Q

Is spermicide an effective form of contraception?

A

Spermicide can be used alone as a form of contraception, but it is NOT AS EFFECTIVE (only about 70-80%).

44
Q

What is the most effective barrier method?

A

Male condoms are the most effective barrier method at 98%.

45
Q

What is sterilisation?

A

Sterilisation involves CUTTING or TYING the FALLOPIAN TUBES (which connect the ovaries to the uterus) in a female, or the SPERM DUCT (the tube between the test and penis) in a male.

This is a PERMANENT procedure.

46
Q

Is sterilisation an effective form of contraception?

A

This is a permanent procedure. However, there is a VERY SMALL chance that the tubes can rejoin.

47
Q

What are natural methods of contraception?

A

Natural methods:

Pregnancy may be avoided by finding out WHEN in the menstrual cycle the woman is most FERTILE and AVOIDING having SEXUAL INTERCOURSE on those days.

It’s popular with people who think that hormonal and barrier methods are UNNATURAL.

48
Q

Are natural methods of contraception effective?

A

It’s NOT VERY EFFECTIVE.

49
Q

What is abstinence?

A

The only way to be COMPLETELY SURE that sperm and egg don’t meet is to NOT HAVE INTERCOURSE.

50
Q

How can you increase fertility?

A

Hormones can be taken by women to increase their fertility.

Some women have levels of FSH (follicle-stimulating hormone) that are TOO LOW to cause their EGGS to MATURE. This means that NO EGGS are RELEASED and the women CAN’T GET PREGNANT.

51
Q

What hormones are given to women in fertility treatments?

A

The hormones FSH and LH can be injected by these women to stimulate egg maturation and OVULATION in their ovaries.

52
Q

What are the benefits of fertility drugs?

A

It helps a lot of women to GET PREGNANT when previously they couldn’t.

53
Q

What are the problems of fertility drugs?

A

It DOESN’T ALWAYS WORK- some women may have to do it many times, which can be EXPENSIVE.

TOO MANY EGGS could be stimulated, resulting in unexpected multiple pregnancies (twins, triplets etc).

54
Q

What is IVF?

A

IVF (in vitro fertilisation) is a process that can be used to help women/couples who are having difficulty having children.

55
Q

What does IVF involve?

A

1) FSH and LH are given to the woman to STIMULATE MATURATION of MULTIPLE EGGS.
2) Eggs are then collected from the woman’s ovaries.
3) The eggs are fertilised in a LAB using the man’s SPERM.
4) The fertilised eggs then grow into EMBRYOS (small balls of cells) in a laboratory incubator.

5) Once the embryos have formed, one or two of them are TRANSFERRED to the woman’s uterus .
Transferring more than one IMPROVE’S the chance of pregnancy.

56
Q

What is ICSI (Intra-Cytoplasmic Sperm Injection)?

When is this technique useful?

A

IVF treatment can also involve a technique called
Intra-Cytoplasmic Sperm Injection, where the sperm is INJECTED directly into an egg.

It’s useful if the man has a very low sperm count.

57
Q

What are the advantages of IVF?

A

Fertility treatment can give an infertile couple a CHILD.

58
Q

What are the 3 disadvantages of IVF?

A
  • MULTIPLE BIRTHS can happen if more than one embryo grows into a baby- these are RISKY for the mother and babies (there’s a higher risk of miscarriage, stillbirth etc).
  • The success rate of IVF is LOW- the average success rate in the UK is about 26%. This makes the process incredibly STRESSFUL and often UPSETTING if it ends in MULTIPLE FAILURES.
  • As well as being EMOTIONALLY STRESSFUL, the process is also PHYSICALLY STRESSFUL for the woman. Some women have a strong REACTION to the hormones-e.g. ABDOMINAL PAIN, VOMITING, DEHYDRATION.
59
Q

How have developments in microscopy helped to improve the techniques (and therefore success rate) of IVF?

A
  • Specialised MICRO-TOOLS have been developed to use on the eggs and sperm under the microscope. They’re also used to REMOVE single cells from the embryo for GENETIC TESTING (to check that it is HEALTHY).
  • More recently, the development of TIME-LAPSE IMAGING (using a microscope and camera built into the incubator) means that the growth of the embryos can be CONTINUOUSLY MONITORED to help identify those that are more likely to result in a SUCCESSFUL PREGNANCY.
60
Q

What are the social and ethical issues regarding IVF?

A

1) The process of IVF often results in UNUSED embryos that are eventually destroyed. Because of this, some people think it is UNETHICAL because each embryo is a POTENTIAL HUMAN LIFE.
2) The GENETIC TESTING of embryos before implantation also raises ethical issues as some people think it could lead to the selection of PREFERRED CHARACTERISTICS, such as gender or eye colour.

61
Q

What is thyroxine?

Where is thyroxine released from?

A

Thyroxine is a hormone. It’s made from IODINE and AMINO ACIDS.

Thyroxine is released by the THYROID GLAND, which is in the NECK.

62
Q

What is the role of thyroxine?

A

It plays an important role in regulating the BASAL METABOLIC RATE- the speed at which chemical reactions in the body occur while the body is at REST.

Thyroxine is also important for loads of processes in the body, such as stimulating PROTEIN SYNTHESIS for GROWTH and DEVELOPMENT.

63
Q

When is thyroxine released?

A

Thyroxine is released in response to THYROID STIMULATING HORMONE (TSH), which is released from the PITUITARY GLAND.

64
Q

What is negative feedback?

A

When the levels go above or below a normal level, the body triggers responses that help to bring these levels back into a normal range. This is called negative feedback.

65
Q

What regulates the amount of thyroxine in the the blood?

A

A NEGATIVE FEEDBACK SYSTEM keeps the amount of thyroxine in the blood at the right level.

66
Q

What happens when the level of thyroxine is higher than normal?

A

When the level of thyroxine is HIGHER than NORMAL, the secretion of TSH (thyroid stimulating hormone) from the pituitary gland is INHIBITED (stopped). This reduces the amount of THYROXINE released from the thyroid gland, so the level in the blood FALLS back towards normal.

The opposite happens when the level of thyroxine is lower than normal.

67
Q

What is adrenaline?

A

Adrenaline is a hormone.

68
Q

Where is adrenaline released from?

A

Adrenaline is released by the ADRENAL GLANDS, which are just ABOVE the KIDNEYS.

69
Q

When is adrenaline released?

A

Adrenaline is released in times of STRESS or FEAR- your brain detects fear or stress and sends NERVOUS IMPULSES to the adrenal glands, which respond by secreting adrenaline.

70
Q

What is the role of adrenaline?

A

It INCREASES the HEART RATE and INCREASES the SUPPLY of OXYGEN and GLUCOSE to the cells in the BRAIN and MUSCLES, preparing the body for ‘FIGHT or FLIGHT’.

71
Q

Why do plants produce hormones?

A

*Plants produce hormones to coordinate and control growth and responses to light (phototropism) and gravity (gravitropism or geotropism).

72
Q

Why must plants be able to respond to stimuli?

A

Plants need to be able to respond to stimuli (changes in the environment) in order to survive.

E.g. Plants need light to make their own food. Plants can sense light, and grow towards it in order to maximise the amount of light they receive.

73
Q

What is auxin?

A

Auxin is a PLANT HORMONE that controls GROWTH near the TIPS of SHOOTS and ROOTS.

74
Q

What is the role of auxin?

A

Auxin controls:

1) PHOTOTROPISM- plant growth in response to LIGHT.
2) GRAVITROPISM or GEOTROPISM- plant growth in response to gravity.

75
Q

Where is auxin produced?

A

Auxin is produced in the TIPS and MOVES BACKWARDS to stimulate the CELL ELONGATION (ENLARGEMENT) PROCESS which occurs in the cells JUST BEHIND the tips.

76
Q

Why does a plant stop growing?

A

If the tip of a shoot is REMOVED, no auxin is available and the shoot may STOP GROWING.

77
Q

What happens if there is extra auxin in the plant?

A

Extra auxin PROMOTES growth in the SHOOT but INHIBITS growth in the ROOT.

78
Q

How do shoots grow in response to light and why?

A

SHOOTS GROW TOWARDS LIGHT

1) When a SHOOT TIP is exposed to LIGHT, MORE AUXIN accumulates on the side that’s in the SHADE than the side that’s in the light.
2) This makes the cell grow (elongate) FASTER on the SHADED SIDE, so the shoot bends TOWARDS the light.

79
Q

How do shoots grow in response to gravity and why?

A

SHOOTS GROW AWAY FROM GRAVITY

1) When a SHOOT is growing sideways, GRAVITY produces an unequal distribution of auxin in the tip, with MORE AUXIN on the LOWER SIDE.
2) This causes the lower side to grow FASTER, bending the shoot UPWARDS.
3) The distribution of auxin in response to gravity means that the shoot should always grow in the right direction (i.e. upwards), even in the absence of light.

80
Q

How do roots grow in response to gravity?

A

When a ROOT is growing sideways, more auxin will accumulate on its LOWER SIDE.

But in a root the EXTRA auxin INHIBITS growth. This means the cells on TOP elongate faster, and the root bends DOWNWARDS.

81
Q

What is the method to investigate the effect of gravity on plant growth?

A
  1. Put 10 cress seed into three different petri dishes, each lined with MOIST FILTER PAPER. (Remember tolerable your dishes, e.g. A, B, C).
  2. Shine a LIGHT onto one of the dishes from ABOVE and two of the dishes from DIFFERENT DIRECTIONS.
  3. Leave the cress seeds alone for ONE WEEK until you can OBSERVE their RESPONSES- you’ll find the seedlings GROW TOWARDS the LIGHT.
  4. You know that the GROWTH RESPONSE of the cress seeds is due to LIGHT only, if you CONTROL all other variables.
82
Q

What are the control variables in the experiment to investigate gravity on plants?

A
  1. Number of seeds- use the same number of seeds in each dish.
  2. Type of seed-use seeds that all come from the same packet
  3. Temperature- keep your Petri dishes in a place where the temperature is stable (i.e. away from heat sources and draughts).
  4. Water- use a measuring cylinder to add the same amount of water.
  5. Light intensity- keep the distance between the bulb and the dish the same.
83
Q

What is the method to investigate gravity on the growth of plants?

A
  1. Put four cress seedlings into a Petri dish that’s lined with damp cotton wool. The roots of each cress seedling should be pointing in a different direction.
  2. Store the Petri dish vertically for a few days in the dark.
  3. You should find that the roots of each seedling grow downwards (towards gravity) and the shoots grow upwards (away from gravity).
84
Q

Why is it important to store the petri dish in the dark when investigating the affect of gravity on plant growth?

A

By storing the Petri dish in the dark, you’ll know that the result of the experiment won’t have been affected by light.

85
Q

Why are plant hormones extracted?

A

Plant hormones can be EXTRACTED, or ARTIFICIAL COPIES can be made.

They can then be used to do all kinds of useful things, including KILLING WEEDS, GROWING CUTTINGS and RIPENING FRUIT.

86
Q

Auxins are plant hormones responsible for plant growth.

How are auxins used commercially?

A

Auxins can be used for:

  1. Killing weeds
  2. Growing from cuttings with rooting powder
  3. Growing cells in tissue culture
87
Q

How are auxins used to kill weeds?

A

Killing weeds-
Most WEEDS growing in fields of crops or in a lawn are BROAD-LEAVED, in contrast to GRASSES and CEREALS which have very NARROW LEAVES.

SELECTIVE WEEDKILLERS have been developed using auxins, which only affect the BROAD-LEAVED plants.

88
Q

What is an advantage of using auxins to kill weeds?

A

They totally DISRUPT their normal growth patterns, which soon KILLS them, whilst leaving the grass crops UNTOUCHED.

89
Q

How are auxins used to grow cuttings with rooting powder?

A

Growing cuttings with rooting powder-
A CUTTING is a part of a plant that has been CUT OFF IT, like the end of a branch with a few leaves on it.

Normally, if you stick cuttings in the soil they WON’T GROW, but if you add ROOTING POWDER, which contains AUXINS, they will PRODUCE ROOTS rapidly and start growing as NEW PLANTS.

90
Q

What is a benefit of using auxins to grow cuttings?

A

This enables growers to produce lots of CLONES (exact copies) of a really good plant VERY QUICKLY.

91
Q

How are auxins used in growing cells in tissue culture?

A

Growing cells in tissue culture:
TISSUE CULTURE can be used to grow CLONES of a plant from a few of its cells. To do this, hormones such as auxins need to be added to the GROWTH MEDIUM (along with NUTRIENTS) to stimulate the cells to DIVIDE to form both roots and shoots.

92
Q

What is gibberellin?

A

Gibberellin is another type of PLANT GROWTH HORMONE.

It stimulates SEED GERMINATION, STEM GROWTH and FLOWERING.

93
Q

What are the commercial uses of gibberellin?

A
  1. Controlling dormancy
  2. Inducing flowering
  3. Growing larger fruit
94
Q

What is dormancy?

A

Lots of seeds WON’T GERMINATE until they’ve been through CERTAIN CONDITIONS (e.g. a period of COLD or of DRYNESS). This is called DORMANCY.

95
Q

How is gibberellin used to control dormancy?

A

Controlling dormancy-
SEEDS can be treated with GIBBERELLIN to ALTER DORMANCY and make them GERMINATE at TIMES OF THE YEAR that they WOULDN’T normally.

It also helps to make sure ALL the seeds in a batch germinate at the SAME TIME.

96
Q

How is gibberellin used to induce flowering?

A

Inducing flowering-
Some plants require CERTAIN CONDITIONS to FLOWER, such as LONGER DAYS or LOW TEMPERATURES. If these plants are treated with GIBBERELLIN, they will flower WITHOUT any change in the environment.

Gibberellin can also be used to grow BIGGER FLOWERS.

97
Q

How is gibberellin used to grow larger fruit?

A

Growing larger fruit-

SEEDLESS VARIETIES of fruit (e.g. seedless grapes) often DO NOT GROW AS LARGE as seeded fruit. However, if GIBBERELLIN is added to these fruit, they will grow LARGER to match the normal types.

98
Q

What is ethene?

A

Ethene is a GAS produced by AGEING parts of a plant.

99
Q

What is the role of ethene?

A

It influences the GROWTH of the plant by controlling CELL DIVISION.

It also STIMULATES ENZYMES that cause FRUIT TO RIPEN.

100
Q

How is ethene used commercially?

A

Commercially, it can be used to SPEED UP THE RIPENING of fruits-either while they are still on the plant or during TRANSPORT to the shops.

101
Q

What are the benefits of using ethene?

A

1) this means fruit can be picked while it;s still UNRIPE (and therefore firmer and LESS EASILY DAMAGED). The gas is then added to the fruit on the way to the supermarket so that it will be PERFECT just as it reaches the shelves.
2) RIPENING can also be DELAYED while the fruit is in STORAGE by adding chemicals that BLOCK ethene’s effect on the fruit or reduce the amount of ethene that the fruit can PRODUCE.

Alternatively, some chemicals can be used that REACT WITH ETHENE to remove it from the air.

Biology GCSE Paper 2 (3 decks)

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