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biology > 9.1 > Flashcards

9.1 Flashcards

1
Q

homeostasis

A

maintenance of a constant internal environment
involves an optimum point
-temp
-pH
-water potential

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2
Q

processes of life

A

metabolism
response
homeostasis
growth
reproduction
excretion
nutrition

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3
Q

optimal conditions external

A

temp
toxins
humidity
light intensity

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4
Q

optimal conditions internal

A

temp
water potential
pH
metabolic substrate

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5
Q

if not optimum conditions

A

enzymes denature
tertiary structure changed
can no longer make substrate complexes
or not enough successful collisions

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6
Q

water potential changes

A

change in the volume of cells due to osmosis-expand and shrink
influenced by glucose concentration
glucose conc affects supply of glucose for respiration

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7
Q

controlling homeostasis

A

1-optimum
2-receptor
3-coordinator
4-effector

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8
Q

positive feedback

A

amplifacation of a response
-conditions change
-change detected
-response reinforces change
so conditions are changed and cycle continues

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9
Q

positive feedback example

A

stretch in the cervix from the baby
nerve impulse to the brain
brain stimulates the release of oxytocin
causes the uterus to contract
stretching the cervix

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10
Q

negative feedback

A

restoration of set point
ideal conditions
increase/decrease detected
decrease/increase occurs

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11
Q

example of negative feedback

A

oven
heat goes over set temp
fan turns off
heat goes under set temp
fan goes on

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12
Q

hormones release

A

endocrine glands can be stimulated to release hormones by nerves or other hormones
pituitary gland particularly secretes hormones that affect other glands

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13
Q

pituritry and hypothalomus

A

found in brain
hypothalamus often controls pituitary
hypothalomus contains neurosecretry cells
a group of which stimulate or inhibit the release of hormones from the anterior pituitary
-release factors or release inhibiting factors
another group of neurosecretery produce secretions that are stored in the posterior pituitary and released as hormones /

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14
Q

anterior lobe hormones x6

A

thyroid stimulating hormone
-secretion of thyroxin
growth hormones (GH)
-stimulates growth
adrenocorticotrophic hormone (ACTH)
-controls adrenal cortex
follicle stimulating hormone (FSH)
-stimulates oestrogen and sperm
leueinising hormone (LH)
-stimulates ovulation
prolactin
-milk production

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15
Q

posterior lobe hormones x2

A

antidiuretic hormone (ADH)
-decreases urine volume
oxytocin
-stimulates muscle contraction in the uterus

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16
Q

second messenger

A

-hormones bind to receptors on target cells
-triggers intracellular membrane bound reactions
-stimulates the release of second messenger
-which activates enzymes to alter the metabolism of a cell

17
Q

second messenger e.g

A

adrenaline binds to a receptor
activating to an enzyme- adenyl cyclase which converts atp to cyclic AMP
the cAMP acts as second messenger
triggers different responses e.g increased respiration

18
Q

hormone enters through cell

A

hormones pass through the membrane and bind to a receptor inside the cell
they form a hormone-receptor complex which passes into the nucleus and acts as a transcription factor to regulate gene expression

19
Q

oestrogen

A
20
Q

tropisms

A

growth of a plant in response to a stimulus
plant grows towards or away from stimuli
e.g
positive phototropism - plant grows towards light
negative gravitropism - plant grows away from light
hydrophobic - water

21
Q

plant hormones

A

auxins
cytokinins
gibberellins

22
Q

auxins

A

produced in young shoots (e.g IAA)
plant growth factor
released from terminal bud
move down plant - active transport + calcium ions
control gravitropism and photo
inhibit growth of side plants- apical dominance (growth only in stem)
control the amount of cytokines

23
Q

cytokinins

A

promote bud growth
produced from base of shoot
promote cell devision in the meristems and cambium
work with ethene in the abcisiion of leaves flowers and fruits

24
Q

how does IAA work

A

iaa diffuses to zone of elongation
bind to specific receptor sites on the cell membrane -active pumping of H+ ions into the cell wall spaces
changes pH to 5 which is the optimum for enzymes that break myofibrils bonds
so more water can be absorbed by osmosis causing cell walls to stretch elongating the cell

25
Q

giberellins

A

growth regulators
stimulate elongation
break dormancy of seeds
stimulate enzymes in germination

26
Q

phytochromes

A

blue green pigment in plants
2 forms
Pr-inactive absorbs red light
Pfr- active absorbs far red light
red light germinates
far red light inhibits germination
final flash is the determining factor
once the light is absorbed it becomes the other form reversibly

27
Q

photoperiod

A

amount of time an organism is exposed to light during 24 hour period

28
Q

short day plants

A

plants flowering when days are short and nights long
e.g strawberries
Pfr inhibits flowering

29
Q

long day plants

A

plants flowering in long days and short nights
e.g cabbage
Pfr stimulates flowering

30
Q

day neutral plants

A

unaffected by the length of day
e.g cucumbers

31
Q

day time

A

Pfr rise
more red than far red
so conversion from Pr to Pfr occurs more rapidly in daytime than Pfr to Pr

32
Q

night time

A

Pr levels rise
red not available in darkness
so Pfr converts slowly to Pr

33
Q

etiolation

A

occurs in plant shaded from light
grow rapidly using up reserves to find the light
form tall and thin
-thin stems
-lack of chlorophyll (yellowish)
once light is reached growth slows as chlorophyll forms

34
Q

Pfr as a transciption factor

A

-Pr converted into Pfr in light moves into nucleus through pores
it binds to a nuclear protein- phytocrome interacting factor 3 (PIF3)
- a known transcription factor
-only binds to Pfr nit Pr
-actives gene transcription and formation of mRNA when bound to Pfr

35
Q

axins and expansin growth

A

as ph falls elongation increases
expansin activated by lower ph
weakening intermolecular bonds between cellulose
cell takes in water causing it to expand

36
Q

adh

A

increase in adh increases permeability of the collecting duct to water - more concentrated urine

biology (33 decks)

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