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A2 Biology > Organisms respond to changes in their internal and external environments > Flashcards

Organisms respond to changes in their internal and external environments Flashcards

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1
Q

Explain how some substances are ultrafiltrated into the Bowman’s capsule, and why others are not?

A

-Blood has a high hydrostatic pressure;
filtered substances passes through endothelium and epithelium of capillaries and Bowman’s capsule;
RBC and proteins are too large to pass through and so remain the blood

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2
Q

Explain how the structure of PCT is adapted to reabsorb glucose?

A

LSA;
lots of mitochondria which produces ATP which can used for active transport of glucose
glucose is absorbed by diffusion and active transport along the PCT

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3
Q

How water potential gradients are maintained in the loop of Henle to ensure a suitable amount of water is reabsorbed?

A

Descending limb is permeable to water and impermeable to ions;
WP of DL decreases as water moves out of limb by osmosis into interstitial space;
Na+ diffuse out of the bottom;
actively transported out of ascending limb and lowers of WP in the tissue fluid of the kidney

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4
Q

How does body increase blood water potential?

A

Osmoreceptors in the hypothalamus detect the WP osmoreceptors stimulate the PPG to release MORE ADH;
walls of collecting duct made more permeable to water; (aquaporins +phosphrylase)
so more water is reabsorbed into the blood
Urine is more concertrated and smaller volume

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5
Q

Describe and explain how secretion of ADH affects urine produced by kidneys?

A

-Secretion of ADH changes permeability of collecting duct; this means more water is reabsorbed in the blood; more concentrated the urine is; smaller the volume of urine

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6
Q

How does lack of insulin affect reabsorption of glucose in kidneys of a person who doesn’t secrete insulin?

A

high conc of glucose in the blood; high conc of glucose in filtrate; co transport carrier proteins becomes saturated with glucose so not all glucose is reabsorbed

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7
Q

How is urea concentrated in the filtrate?

A

Water is reabsorbed into filtrate by osmosis; occurs at PCT, DCT and collecting duct and the interstitial space will have a low WP

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8
Q

Explain how kidneys prevent glucose appearing in the urine of a non-diabetic person?

A

In PCT, filtrate is reabsorbed back into the blood; this includes glucose and water; this occurs by active transport

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9
Q

What is the second messenger model?

A

Peptide hormones bind to receptor; more than one cyclic AMP is formed from ATP; this activates more than one enzyme (cascade effect); activates reactions

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10
Q

How do lipid hormones work?

A

They bind to a receptor in the cytoplasm; this complex passes into nucleus and affects gene expression

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11
Q

The effects of hyperglycaemia (too much blood glucose)

A

Lowers water potential of the blood, thirst and frequent urination

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12
Q

The effects of hypoglycaemia (too little blood glucose)

A

tiredness, dizziness and lack of concertation

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13
Q

How body responds to high blood sugar levels (1st)

A

Beta cells detect this; secrete insulin; acts through 2nd messenger model for glycogenesis

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14
Q

How body responds to high blood sugar levels (2nd)

A

Insulin is secreted; fits into receptor proteins, extra glucose carrier channels open; allowing glucose to travel from blood into the cells

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15
Q

What is Type 1 diabetes?

A

They cannot make insulin; as a result blood glucose levels rise

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16
Q

Symptoms of Type 1

A

Weight loss;
Thirst;
Glucose in the urine;
Excess Urine

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17
Q

Why does glucose go into urine as a result of type 1 diabetes?

A

Because when blood glucose levels are too high, the kidney cannot reabsorb all the glucose

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18
Q

How body responds to low blood sugar levels ?

A

Alpha cells detect this; secrete glucagon; acts through 2nd messenger model for gluconeogenesis or glycolysis

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19
Q

What is gluconeogenesis?

A

Glucagon causes formation of glucose from non-carbohydrate substances (eg: AA, glycerol and fatty acids)

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20
Q

What is glycogenolysis?

A

Glucagon causes the breakdown of glycogen in the liver and the release of glucose into the bloodstream
occurs in liver and muscle cells

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21
Q

What is glycogenesis?

A

Liver takes up glucose and stores it as glycogen in response to high glucose levels

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22
Q

How does adrenaline increase blood glucose concertation?

A

Adrenaline activates glycogenolysis; inhibits glycogenesis; and activates glucagon secretion

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23
Q

Explain how some substances are ultrafiltrated into the Bowman’s capsule, and why others are not?

A

-Blood has a high hydrostatic pressure; filtered substances passes through endothelium and epithelium of capillaries and Bowman’s capsule;
blood cells and proteins are too large to pass through and so remain the blood

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24
Q

Explain how the structure of PCT is adapted to reabsorb glucose?

A

LSA;
Lots of mitochondria which produces ATP which can used for active transport of glucose;
Glucose is absorbed by diffusion and active transport along the PCT

How well did you know this?
1
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2
3
4
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25
Q

How water potential gradients are maintained in the loop of Henle to ensure a suitable amount of water is reabsorbed?

A

Descending limb is permeable to water and impermeable to ions;
WP of DL decreases as water moves out of limb by osmosis into interstitial space; Na+ diffuse out of the bottom;
actively transported out of ascending limb and lowers of WP in the tissue fluid of the kidney

How well did you know this?
1
Not at all
2
3
4
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26
Q

How body monitors and controls blood water potential?

A

Osmoreceptors in the hypothalamus detect the WP decrease; person loses water thorough exercise; BWP decreases; osmoreceptors stimulate the PPG to release MORE ADH; walls of collecting duct made more permeable to water; so more water is reabsorbed into the blood

How well did you know this?
1
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27
Q

Describe and explain how secretion of ADH affects urine produced by kidneys?

A

Secretion of ADH changes permeability of collecting duct; this means more water is reabsorbed in the blood; more concentrated the urine is; smaller the volume of urine

28
Q

How does lack of insulin affect reabsorption of glucose in kidneys of a person who doesn’t secrete insulin?

A

high conc of glucose in the blood; high conc of glucose in filtrate; co transport carrier proteins becomes saturated with glucose so not all glucose is reabsorbed

29
Q

How is urea concentrated in the filtrate?

A

Water is reabsorbed into filtrate by osmosis; occurs at PCT, DCT and collecting duct and the interstitial space will have a low WP

30
Q

Explain how kidneys prevent glucose appearing in the urine of a non-diabetic person?

A

In PCT filtrate is reabsorbed back into the blood; this includes glucose and water; this occurs by active transport

31
Q

Definition of taxis?

A

a simple response where an organism’s is determined by the direction of the stimulus

32
Q

Definition of kinesis?

A

a form of responses where an organism changes speed or rate of it changes direction in order to spend a minimum amount of time in an unfavourable environment

33
Q

Definition of a tropism?

A

growth response

34
Q

name the two features of a sensory neurone, how do they apply to the Pacinian Corpuscle?

A

Is specific to a single type of stimulus- in the case of the PC only to mechanical pressure
Converts one type of energy to another

35
Q

How does the body respond to increase in CO2/decrease in PH?

A

Increase in CO2 detected by chemoreceptors in aorta and carotid arteries
Send IMPULSES to medulla
Send MORE impulses to the SAN via the sympathetic route to increase heart rate

36
Q

How does body respond to increase in heart rate?

A

Rise in heart PRESSURE detected by baroreceptors in aorta and carotid arteries
Send impulses to medulla
Send FEWER impulses to the SAN
via the parasympathetic route

37
Q

Whats the role of ATP in muscle contraction?

A

Hydrolysis allows for the binding of myosin head to actin binding site
Provides energy for movement of the myosin head in the ‘power stroke’ movement

38
Q

What’s importance of maintaining a core body temperature?

A

Allows for enzymes to work at optimum rate and provides high metabolic rate
If temp too high, enzymes denature
If temp too lower, fewer e-z complexes form

39
Q

How does stimulation of a Pacinian Corpuscle lead to a generator potential?

A

Applying pressure deforms the membrane and it leads to the opening of the stretch mediated Na+ channels
Opens Na+ channels which leads to influx of Na+
Leads to depolarisation of membrane

40
Q

What happens when there is low blood water potential?

A

Osmosreceptors in hypothalamus detect this change
less ADH is released from PPG
The collecting duct has less permeability to water
Urine has a smaller volume and is more concentrated

41
Q

Name some things that a filtrate is resisted by

A

capillaries epithelial cells
connective tissue of epithelial cells
epithelial cells of renal capsule
hydrostatic pressure of the fluid

42
Q

what does filtrate of the nephron pass between

A

podocytes - specialised cells which have spaces in between them

43
Q

what is actin?

A

a thin globular protein/filament with two strands wrapped around each other

44
Q

what is myosin?

A

a thicker globular protein/filament with rod shaped head

45
Q

what is the I band?

A

region in a muscle fibre where thick and thin filaments do not overlap so it appears lighter

46
Q

what is the A band?

A

dark region of a muscle fibre where thick and filaments do overlap

47
Q

what is the H zone?

A

where actin filaments only are present

48
Q

what is the sarcomere?

A

the distance between two Z lines which shorten during muscle contraction

49
Q

purpose of slow twitch muscle fibres

A

adapted for endurance and have less powerful contractions

50
Q

purpose of fast twitch muscle fibres

A

adapted for intense exercise under anaerobic conditions and have more powerful contractions

51
Q

features of slow twitch muscle fibres

A

lots of myoglobin to carry oxygen
lots of mitochondria to produce ATP during aerobic respiration
large store of blood vessels to deliver oxygen and glucose for aerobic respiration

52
Q

features of fast twitch muscle fibres

A

large store of glycogen
large store of phosphocreatine to produce ATP under anaerobic conditions
thicker and more numerous myosin fibres
high concertation of enzymes involved in anaerobic respiration present

53
Q

mechanism of muscle contraction

A

AP stimulates Ca2+ channels to open and influx of Ca2+
Ca2+ binds to a protein which stimulates tropomyosin to change shape and expose actin binding sites
ATP molecule is hydrolysed which provides energy for myosin head to bind to actin binding site and forms a cross bridge
Myosin head bends and forms a ‘powerstroke’ movement and pulls actin fibre along
An ATP molecule is resynthesised and myosin head detaches

54
Q

What is phosphocreatine?

A

Regenerates ATP in anaerobic conditions by donating a phosphate

55
Q

mechanism of neuromuscular junction stimulation

A

Action potential stimulates opening of Ca2+ channels
Ca2+ cause the synaptic vesicles to move to the presynaptic membrane and fuse with it
Acetylcholine diffuses across synaptic cleft and binds to receptors on post synaptic membrane
Binding of acetylcholine stimulates opening of Na+ channels and influx of Na+ depolarises the membrane

56
Q

features of rod cells

A

Retinal convergence- several rod cells attached to single bipolar cells, breaks down rhodopsin so you can see in low intensity light
Low visual acuity- because many cells attached to single bipolar cell

57
Q

features of cone cells

A

Good visual acuity- one cone cell attached to one bipolar cell
Can detect colour- three different types; each respond to a different wavelength of light

58
Q

Three factors that determine the speed nerve impulse conduction

A

Myelin sheath
Diameter of axon- larger diameter, less leakage
Temperature- higher temp, faster enzume function

59
Q

define refractory period

A

when after an action potential is generated the Na+ voltage gated channels are closed

60
Q

what does the refractory period ensure?

A

action potentials are propagated in one direction
discrete impulses are generated
limited number of impulses are generated

61
Q

features of nervous system

A

produces short lived responses
localised responses
rapid responses

62
Q

features of hormonal system

A

longer lasting response
less specific
target cells have specific receptors stimulated by hormone concertration

63
Q

how is resting potential is generated

A

3 Na+ is actively transported out of the axon
2 K+ actively transported in of the axon
Creates electrochemical gradient so Na+ naturally diffuses in and K+ diffuses out

64
Q

how is an action potential generated

A

Once a stimulus is detected, Na+ diffuse into axon membrane, this causes some voltage- gated Na+ channels to open
This causes influx of Na+ and this causes more channels to open
Once the threshold is reached, action potential is generated and Na+ channels shut whilst K+ channels open

65
Q

how are proteins digested in the gut?

A
  1. peptide bonds are hydrolysed
  2. endopeptidases break polypeptides into smaller peptide chains
  3. exopeptidases remove terminal amino acids
  4. dipeptidases hydrolyse dipeptides into amino acids

A2 Biology (5 decks)

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