Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

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

Organisms respond to changes in their internal and external environments Flashcards

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

The effects of hyperglycaemia (too much blood glucose)

A

Lowers water potential of the blood, thirst and frequent urination

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

The effects of hypoglycaemia (too little blood glucose)

A

tiredness, dizziness and lack of concertation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is Type 1 diabetes?

A

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Symptoms of Type 1

A

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What is gluconeogenesis?

A

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What is glycogenesis?

A

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

How does adrenaline increase blood glucose concertation?

A

Adrenaline activates glycogenolysis; inhibits glycogenesis; and activates glucagon secretion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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
Not at all
2
3
4
5
Perfectly
25
How water potential gradients are maintained in the loop of Henle to ensure a suitable amount of water is reabsorbed?
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
26
How body monitors and controls blood water potential?
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
27
Describe and explain how secretion of ADH affects urine produced by kidneys?
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
How does lack of insulin affect reabsorption of glucose in kidneys of a person who doesn't secrete insulin?
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
How is urea concentrated in the filtrate?
Water is reabsorbed into filtrate by osmosis; occurs at PCT, DCT and collecting duct and the interstitial space will have a low WP
30
Explain how kidneys prevent glucose appearing in the urine of a non-diabetic person?
In PCT filtrate is reabsorbed back into the blood; this includes glucose and water; this occurs by active transport
31
Definition of taxis?
a simple response where an organism's is determined by the direction of the stimulus
32
Definition of kinesis?
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
Definition of a tropism?
growth response
34
name the two features of a sensory neurone, how do they apply to the Pacinian Corpuscle?
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
How does the body respond to increase in CO2/decrease in PH?
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
How does body respond to increase in heart rate?
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
Whats the role of ATP in muscle contraction?
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
What's importance of maintaining a core body temperature?
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
How does stimulation of a Pacinian Corpuscle lead to a generator potential?
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
What happens when there is low blood water potential?
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
Name some things that a filtrate is resisted by
capillaries epithelial cells connective tissue of epithelial cells epithelial cells of renal capsule hydrostatic pressure of the fluid
42
what does filtrate of the nephron pass between
podocytes - specialised cells which have spaces in between them
43
what is actin?
a thin globular protein/filament with two strands wrapped around each other
44
what is myosin?
a thicker globular protein/filament with rod shaped head
45
what is the I band?
region in a muscle fibre where thick and thin filaments do not overlap so it appears lighter
46
what is the A band?
dark region of a muscle fibre where thick and filaments do overlap
47
what is the H zone?
where actin filaments only are present
48
what is the sarcomere?
the distance between two Z lines which shorten during muscle contraction
49
purpose of slow twitch muscle fibres
adapted for endurance and have less powerful contractions
50
purpose of fast twitch muscle fibres
adapted for intense exercise under anaerobic conditions and have more powerful contractions
51
features of slow twitch muscle fibres
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
features of fast twitch muscle fibres
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
mechanism of muscle contraction
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
What is phosphocreatine?
Regenerates ATP in anaerobic conditions by donating a phosphate
55
mechanism of neuromuscular junction stimulation
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
features of rod cells
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
features of cone cells
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
Three factors that determine the speed nerve impulse conduction
Myelin sheath Diameter of axon- larger diameter, less leakage Temperature- higher temp, faster enzume function
59
define refractory period
when after an action potential is generated the Na+ voltage gated channels are closed
60
what does the refractory period ensure?
action potentials are propagated in one direction discrete impulses are generated limited number of impulses are generated
61
features of nervous system
produces short lived responses localised responses rapid responses
62
features of hormonal system
longer lasting response less specific target cells have specific receptors stimulated by hormone concertration
63
how is resting potential is generated
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
how is an action potential generated
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
how are proteins digested in the gut?
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)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions