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Z A Level Biology 2 > Coordination 3 > Flashcards

Coordination 3 Flashcards

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1
Q

What are some of the advantages and disadvantages of the nervous system?

A
  1. Adv:
    - Very fast
  2. Dis:
    - Very expressive in terms of energy needing for pumping sodium and potassium ions to maintain resting potentials and in protein synthesis to make all the channel and pump proteins
    - Energy is also needed to maintain all the neurones and other cells in the nervous system such as Schwann cells
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2
Q

What is better in terms of energy usage than the nervous system?

A
  • Use hormones that are secreted in any quantities and dispersed around the body in the blood
  • Homeostatic functions such as the control of blood glucose conc and water potential of the blood need to be coordinated all the time but not in a hurry so hormones are ideal for controlling these functions
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3
Q

What are hormones?

A

A substance secreted by an endocrine gland, that is carried in blood plasma to another part of the body where it has an effect

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4
Q

What are endocrine glands?

A

A gland that secrets sites products which are always hormone, directly into the blood

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5
Q

What is secretion?

A

The release of a useful substance from a cell or gland

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6
Q

What are a group of proteins?

A
  1. Hormones with homeostasis are peptides or small proteins
  2. They are water soluble, so they cannot cross the phospholipid bilayer of cell surface membranes
  3. These hormones bind to receptors on their target cells that in turn activate second messengers to transfer the signal throughout the cytoplasm
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7
Q

What are steroid hormones?

A
  1. They are lipid soluble so they can pass through the phospholipid bilayer
  2. Once they have crossed the cell surface membrane, they bind to receptor molecules inside the cytoplasm or the nucleus and activate processes such as trasnpcrition
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8
Q

What are steroid hormones?

A
  1. They are lipid soluble so they can pass through the phospholipid bilayer
  2. Once they have crossed the cell surface membrane, they bind to receptor molecules inside the cytoplasm or the nucleus and activate processes such as transcription
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9
Q

Summarise the changes that occur during the menstrual cycle

A
  1. A potential female gamete starts to develop
  2. A primary folic is produced by development of tissues surrounding the developing gamete
  3. The primary folic becomes a secondary follicle
  4. The secondary follicle develops into an ovarian or Graafian follicle
  5. At ovulation the gamete is related
  6. The remaining tissues forms a corpus lutes
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10
Q

What happens in the middle of the cycle?

A

The female gamete is released in the oviduct

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11
Q

What is the menstrual cycle?

A

The changes than occur in the ovary and the uterus approximately every 28 days involving ovulation and the breakdown and loss of the lining of the uterus (menstruation)

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12
Q

What is the uterine cycle synchronised with?

A

The ovarian cycle so that the endometrium (lining of the uterus) is ready the receive the embryo at the right time

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13
Q

Describe the first step of the uterine cycle

A
  • Uterus: most of the endometrium lining is lost during menstruation if fertilisation did not take place in the last cycle
  • Ovary: a follicle develops
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14
Q

Describe the second step of the uterine cycle

A
  • Uterus: the endometrium develops

- Ovary: ovarian follicle is produced

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15
Q

Describe the third step of the uterine cycle

A
  • Uterus: endometrium is most developed and contains many blood vessels
  • Ovary: ovulation takes place
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16
Q

Describe the fourth step of the uterine cycle

A
  • Uterus: endometrium maintained until corpus lutes degenerates
  • Ovary: a corpus lutem develops and then degenerates
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17
Q

How is the menstrual cycle coordinated?

A

By glycoprotein hormones released by the anterior pituitary gland and by the ovaries

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18
Q

What does the anterior pituitary gland secrete?

A

follicle stimulating hormone (FSH) and luteinising hormone (LH)

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19
Q

What is the follicle stimulating hormone (FSH)?

A

Glycoprotein hormone secreted by anterior pituitary gland to stimulate the development of follicles in the ovaries

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20
Q

What is the luteinising hormone (LH)?

A

A glycoprotein hormone that is secreted by the anterior pituitary gland to stimulate ovulation and the development of the corpus lutem

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21
Q

What is oestrogen?

A

Steroid hormone secreted by follicles in the ovary; used in some contraceptive pills

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22
Q

What is progesterone?

A

A steroid hormone secreted by the corpus lutem in the ovary after ovulation; used in contraceptive pills

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23
Q

What is the corpus lutem?

A

The ‘yellow body’ that develops from an ovarian follicle after ovulation

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24
Q

What does FSH and LH do?

A

They control the activity of the ovaries

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25
Q

What is the purpose of the hormones in the menstrual cycle?

A
  1. To synchronise the development of the egg cell in the ovary and the lining of the uterus (the endometrium)
  2. It is to ensure that by the time a potential embryo arrives at the uterus the endometrium is receptive to it and therefore can successfully implant into the endometrium
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26
Q

Where does fertilisation occur?

A

In the oviduct as the incoming sperm encounter the mature ovum

27
Q

What happens at the start of the menstrual cycle and what does this entail?

A
  1. The anterior pituitary gland release FSH and LH into the bloodstream
  2. FSH causes an immature egg cell to complete its development with a Graafian follicle
  3. The follicle begins to produce oestrogen
28
Q

What are the effects of the follicle produce oestrogen?

A
  1. Inhibition of further FSH (and LH) from the pituitary gland, an example of negative feedback
  2. Further development of the follicle including the ovum
  3. Stimulates the endometrium to grow, thicken and develop numerous blood capillaries
  4. When oestrogen concentration of the blood gas reached a level around two to four times its level at the beginning of the cycle, it stimulates a surge in the secretion of LH (and to a lesser extent FSH) from the pituitary gland
29
Q

What does this surge in LH cause?

A
  • The Graafian follicle to burst and (to shed its gamete into the oviduct), releasing the ovum as well as several hundred associated nurse cells, which protect the cell on its joinery through the oviduct
  • This usually happens 14-36 hours after the LH surge
  • The release o the follicle is called ovulation
30
Q

What happens once the follicle has burst? What is this effect

A
  1. The follicle collapses to form the corpus lutem (yellow body), which secretes progesterone and some oestrogen
  2. These two hormones maintain the lining of the uterus (the endometrium) and continues to thick it and to mature it in preparation to receive a possible embryo if fertilisation occurs
31
Q

What does progesterone also do?

A

Inhibits the anterior pituitary from secreting FSH so no more follicles develop

32
Q

What happens to the high levels of oestrogen and progesterone?

A
  1. High levels of oestrogen and progesterone in the second half of the cycle inhibit the secretion of FSH and LH by the anterior pituitary
  2. This means that there is less stimulation of the corpus lutem so that it begins to degenerate the secrete less oestrogen and progesterone
  3. As the concentration of these two hormones decrease, the endometrium is not maintained and leads to the breaking down of the uterine lining and leads menstruation begins
  4. The decrease also releases the anterior pituitary from inhibition, so FSH is secreted to begin another cycle
33
Q

What does the pill contain?

A
  1. Steroid hormones that suppress ovulation
  2. Usually synthetic hormones rather than natural ones are used because they are not broken down so rapidly in the body and therefore act for longer
34
Q

Which hormones does the pill contain?

A
  • Some forms contain progesterone only
  • But most contain progesterone and oestrogen and are known as ‘combined oral contraceptives’
  • There are many different types, with slightly different ratios of the hormones, as women are not all alike in the way their bodies respond to the pill
35
Q

How is the pill usually taken?

A
  1. With most types of oral contraceptive, the woman takes one pill daily for 21 easy and then stops for seven days, during which menstruation occurs
  2. For some types she continues to take a different coloured inactive pill for these seven days
36
Q

How does the pill work?

A
  1. Both oestrogen and progesterone suppress the secretion of FSH and LH from the anterior pituitary gland (this is an example of negative feedback)
  2. In the menstrual cycle the highest concentration of FSH and LH are produced when the concentration of oestrogen starts to fall and when progesterone concentration has only just started to rise
  3. Taking the pill daily, starting at the end of menstruation, keeps oestrogen and progesterone concentrations high
  4. This suppress the secretion of FSH and LH and prevents their concentrations from reaching the levels that would stimulate ovulation
  5. This essentially mimics the natural situation during the second half of the menstrual cycle
37
Q

What happens when you stop taking the pill after 21 days?

A
  1. Stopping taking the pill after 21 days allows the concentrations of oestrogen and progesterone to fall to the point at which the uterine lining is no longer painted
  2. Menstruation occurs and this reassures the woman taking the pill that she is not pregnant
38
Q

What is the danger of taking the pill?

A

-This combined oral contraceptive is very effective at preventing conception, but the women taking it have to be careful not to mis even a single day’s pill as this might allow ovulation tot taken place, and lead to fertilisation if she has unprotected sex at that time

39
Q

How else might the combination of oestrogen and progesterone be given?

A
  • A skin patch from which the hormones are absorbed through the skin
  • By injection
  • By inserting an implant under the skin that is effective for several months
  • With these methods, no menstruation takes place
40
Q

What happens with pills containing progesterone only?

A
  1. Pills containing progesterone only may allow ovulation to occur
  2. They seem to work as contraceptives by reducing the ability of sperm to fertilise the egg and by making the mucus secreted by the cervix more viscous and so less easily penetrated by sperm
41
Q

What is the morning after pill? How does it work?

A
  • After sex
  • It works for up to 72 hours after intercourse
    1. The pill contains a synthetic progesterone like hormone
    2. If taken early enough, it reduces the chances of a sperm reaching and fertilising an egg
    3. However in most cases it probably prevents a pregnancy by stopping the embryo implanting into the uterus
42
Q

How does the loss of potassium ions from guard cells lead to closure of a stoma?

A
  1. Water potential of guard cells increases
  2. Water leaves cells
  3. By osmosis/down a waster potential gradient
  4. Guard cell becomes flaccid
43
Q

What might a plant respond to?

A
  • Changes in carbon dioxide concentration
  • Lack of water
  • Grazing by animals
  • Infection by fungi or water
    1. Some of these may be Brough about by quick changes in turgidity e.g. stomata responding to changes in humidity, CO2 conc and water availability
44
Q

Describe a Venus fly trap

A
  1. Leaf divided into two lobes separated by a midrib
  2. Each lobe have three stiff sensory hairs that respond to being deflected
  3. Outer edges of lobes have stiff hair that interlock to trap inside the insect
  4. Surface of lobes many golds that secrete enzymes for digestion of trapped insect
  5. The touch of a fly or other insect insect on the sensory hairs not he inside of the folded leaves of Venus fly trap stimulates action potentials that travel very fast across lead causing it to fold over and trap insect
45
Q

How does a Venus fly trap respond?

A
  1. Deflection of sensory hairs activates calcium ions channels in cells at base of hair to open to calcium ions flow In to create a receptor potential
  2. If two of these hairs stimulated within 20-35 seconds, or one hair touched twice within same time interval, action potentials travel across the trap
  3. When the second trigger takes too long to occur after first, new time interval starts again
  4. If a hair deflected this time then traps will still close
  5. Time between stimulus and response is 0.5s and takes trap less than 0.3s to close
46
Q

How does Venus fly trap close?

A
  1. Lobes of leaf bulge upwards when trap open and convex in shape
  2. Lobes change into concave shape bending downwards so trap snaps shut - too fast for water movement to be responsible, instead release of elastic tension in cell walls.
47
Q

When does a Venus fly trap close?

A
  1. To seal the rap requires ongoing activation of trigger hairs by trapped prey and unless it escapes the inner surface if lobes are constantly stimulates triggering further action potentials
  2. Forces edges of lobes together
  3. Further deflections of sensory hairs by trapped insects stimulate the entry of calcium ions into gland cells
  4. Calcium ions stimulate exocytosis of vesicles containing digestive enzymes
  5. Trap stays shut for up to a week
  6. Once insect is digested cells in upper surface of midrib grow slowly so lead reopens and tension builds in cells walls of of the midrib
48
Q

What are the adaptation of Venus fly traps to avoid closing unnecessarily and wasting energy?

A
  1. Stimulation of a single hair does not trigger closure
    - Prevents trap closing when it rains or when piece of debris falls on traps
  2. Gaps between stiff hairs that form the bars of the trap allow very small insects to crawl out, preventing waste of energy by digesting very small meal
49
Q

What are plant growth regulators?

A

(plant hormone) any chemical produced in plants that influences their growth and development e.g. auxins, gibberellins, cytokinins and abscisic acid

50
Q

What are auxins?

A

They influence many aspects of growth including elongation growth which determines the overall length of roots and shoots

51
Q

What are gibberellins?

A

Involved in seed germination and controlling stem elongation

52
Q

What is ABA (Abscisic acid(?

A

Controls response of plants to environmental stresses such as shortage of water

53
Q

How do plant hormones interact?

A
  1. Interact with receptor on surface if cells or in cytoplasm or nucleus
  2. Usually initiate a series of chemical or ionic signals that employ and transmit the signal within the cell
54
Q

Describe auxins

A
  1. Principle one is IAA
  2. Synthesised in growing tips (meristems) of shoots and roots, where the cells are dividing
  3. It is transported back down the shoot, or up the root by active transport for cell to cell and in phloem sap
  4. Growth in plants occurs at meristems in threes stages, cell division by mitosis, cell elongation by absorption of water and cell differentiation
  5. Auxin is involved in controlling growth by elongation
55
Q

How does auxin act?

A
  1. Auxin stimulates cells to pump hydrogen ions into the cell wall
  2. This acidifies the cells walls which leads to a loosening of the bonds between cellulose microfibrils and the matrix that surrounds them
  3. The cells absorb water by osmosis and the pressure potential causes the wall to stretch so that these cells become longer or elongate
56
Q

How do auxins work in more detail?

A
  1. Molecules of auxin bind to a receptor preteen on the cell surface membrane
  2. The binding of auxin stimulates ATPase proton pumps to move hydrogen ions across the CSF from the cytoplasm into the cell wall
  3. Proteins called expansins in the cell wall are activated by this decrease in pH and loosen the linkages between the cellulose microfibrils
  4. Expansins disrupt non-covalent interactions between the cellulose microfibrils and surrounding substances such as hemicelluloses in the cell wall and this disruption occurs briefly so microfibrils can move past each other allowing cell to expand without loosing most of overall strength of the wall
  5. K+ ions channels also stimulated leading to increase K+ conc in cytoplasm and this decreases rate potential so water enters through aquaporins
57
Q

Describe gibberellins

A

Synthesised in most parts of plants and present in high conc in young leaves and in seeds and stems where important role in determining growth

58
Q

How does gibberellins affect stem elongation?

A
  1. Height of plants controlled by genes: dominant Le then plants grow tall but if homozygous le always remains short
  2. Dominant allele of this gene regulates synthesis of last enzyme in a pathway which produces active form of gibberellin GA1
59
Q

How does gibberellins affect stem elongation?

A
  1. Height of plants controlled by genes: dominant Le then plants grow tall but if homozygous le (codes for non-functioning enzyme) always remains short
  2. Dominant allele of this gene regulates synthesis of last enzyme in a pathway which produces active form of gibberellin GA1
  3. This active form from stimulates cell division and cell elongation in stem, causing plant to grow tall
  4. Substitution mutation in gene changes Alanine to threonine in primary structure of enzyme near active site producing non-functioning enzyme, this gives isa to recessive allele le and homo lele are genetically dwarf
  5. Applying active gibberellin to plants which would normally remind short, e.g. cabbages, can stimulate them to grow tall
60
Q

What is dormancy?

A
  • Involved in control of seed germination in wheat and barley
    1. When seed shed from parent plant in dormancy (very little water and metabolically inactive) allows seed to survive cold winters and only geminating when temperature rises in spring
61
Q

Describe the embryo of a seed

A
  1. The seed contains an embryo, which will grow to form the new plant when the seed germinates
  2. The embryo is surrounded by endosperm (a tissue that stores food in some seeds, such as cereal grains), which is energy store continuing starch
  3. Outer edge of endosperm, protein rich aleurone layer (a layer of tissue around the endosperm in a cereal seed that synthesises amylase during germination)
  4. Whole seeds covered by a tough waterproof protein layer
62
Q

What happens at the beginning of germination?

A
  1. Absorption of water at beginning of germination stimulates the embryo the produce gibberellins
  2. These gibberellins diffuse to the aleurone layer and stimulate the cells to synthesise amylase
  3. The amylase mobilise energy reserves by hydrolysing starch molecules in endosperm covering them into soluble maltose molecules
  4. These maltose molecules are covered to glucose and transported to the embryo, providing a source of carbohydrate that can be respired to provide energy as the embryo begins to grow
63
Q

How does gibberellins cause these effects?

A
  1. Gibberellins cause these effects by regulating genes that are involved in the synthesis of amylase
  2. In barely seeds, it has been shown that application of gibberellins causes an increase in the transcription of mRNA coding for amylase
  3. It has this action by promoting the destruction of DELLA proteins that inhibit factors that promote transcription
64
Q

What is electrical communication in plants?

A
  1. Plant cells have electrochemical gradients across CSM in same way as animal cells and have resting potentials
  2. Plant action potentials are triggered when the membrane is depolarised
  3. Depolarisation results from outflow of Cl- ions not influx of Na) and repatriation is achieved by outflow of K_
  4. Plants not have specific nerve cells, but many of their cells transmit waves of electrical activity that are very similar to those transmitted along he neurones of animals
  5. The action potentials travel along the cell membranes of plants cell and from cell to cell through plasmodesmata that are lined by cell membrane
  6. APs last much longer and travel more slowly than in animal neurones
  7. Different stimuli e.g. chemicals in contact with plants curfew trigger APs

Z A Level Biology 2 (18 decks)

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