Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

A-Level Biology > 6C - Homeostasis > Flashcards

6C - Homeostasis Flashcards

You may prefer our related Brainscape-certified flashcards:
AP® Biology flashcards Biology 101 flashcards
1
Q

What is homeostasis?

A
  • maintenance of a stable internal environment
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

How does body temperature affect enzyme activity?

A
  • if body temp is too high, becomes denatured.
  • H bonds break due to heavy vibrations.
  • Active site changes shape
  • if body is too low, activity is reduced
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is the optimum body temperature for enzyme activity?

A
  • 37 degrees celsius
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

How does blood pH affect enzyme activity?

A
  • too high or too low; become denatured

- H bonds break and active site changes shape

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

What is the optimum pH for enzyme activity?

A
  • pH 7 (neutral)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is meant by ‘negative feedback’?

A
  • receptors detect when a level is too high or too low

- effectors respond to counteract change, bringing the level back to normal

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

How does glucose concentration affect providing energy and water potential?

A
  • too high; WP is reduced to where water diffuses out of cells by osmosis. Cells shrivel up and die
  • too low; cells are unable to carry out normal activities due not enough glucose for respiration to provide energy
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Why does homeostasis involve multiple negative feedback mechanisms?

A
  • gives more control
  • you can actively increase or decrease a level so it returns to normal
  • one mechanism means a slower response and less control
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is meant by ‘positive feedback’?

A
  • effectors respond to further increase the level away from the normal level
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

How is positive feedback used to form a blood clot?

A
  • platelets become activated and release chemical - activates more platelets and so on
  • they very quickly form blood clot at injury site
  • process ends w/ negative feedback when body detects clot had been formed
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

How is positive feedback used for hypothermia?

A
  • hypothermia = low body temp, happens when heat is lost quicker than it can be produced
  • as body temp falls, brain doesn’t work properly and shivering stops
  • positive feedback takes body temp further away from normal level
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Which cells secrete insulin into the blood?

A
  • Beta cells
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Which cells secrete glucagon into the blood?

A
  • Alpha cells
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is the first two steps in insulin lowering blood glucose concentration?

A
  • insulin binds to specific receptors on membranes of liver cells and muscle cells
  • increases permeability of membranes to glucose, so cells take up more glucose. Involves increasing no. of channel proteins
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What are the 3rd and 4th steps in insulin lowering blood glucose concentration?

A
  • insulin also activates enzymes in liver and muscle cells that convert glucose into glycogen
  • cells are more able to store glycogen in cytoplasm, as an energy source
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What are the 5th and 6th steps in insulin lowering blood glucose concentration?

A
  • glycogenesis; forming glycogen from glucose

- insulin also increases rate of respiration of glucose, especially in muscle cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What are the first two steps in glucagon increasing blood glucose concentration?

A
  • binds to specific receptors on membranes of liver cells

- activates enzymes in liver cells that break down glycogen into glucose

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What are the 3rd and 4th steps in glucagon increasing blood glucose concentration?

A
  • glycogenolysis; breaking down glycogen into glucose

- also activates enzymes involved in formation of glucose from glycerol and amino acids

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

What are the 5th and 6th steps in glucagon increasing blood glucose concentration?

A
  • gluconeogenesis; forming glucose from non-carbohydrates

- glucagon decreases rate of respiration of glucose in cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

How does negative feedback respond to a rise in blood glucose concentration?

A
  • pancreas detects when its too high
  • beta cells secrete insulin, alpha cells stop secreting glucagon
  • insulin binds to receptors on liver and muscle cells
  • cells take up more glucose, glycogenesis activated, cells respire more glucose
  • less glucose in blood
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

How does negative feedback respond to a fall in blood glucose concentration?

A
  • pancreas detects when its too low
  • alpha cells secrete glucagon, beta cells stop secreting insulin
  • glucagon binds to receptors on liver cells
  • glycogenolysis activated, gluconeogenesis activated, cells respire less glucose
  • cells release glucose into blood
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

How does adrenaline increase blood glucose concentration?

A
  • binds to receptors in membrane of liver cells; activates glycogenolysis, inhibits glycogenesis
  • activates glucagon secretion and inhibits insulin secretion
  • gets ready for action by making more glucose available for muscles to respire
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

How can adrenaline and glucagon act via a second messenger?

A
  • they bind to receptors and activate adenylate cyclase
  • adenylate cyclase converts ATP into chemical signal (second messenger)
  • second messenger is called cyclic AMP (cAMP)
  • cAMP activates protein kinase A, which activates a cascade (chain of reactions) that involves glycogenolysis
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What is Type 1 diabetes?

A
  • immune system attacks beta cells in islets of Langerhans so they can’t produce any insulin
  • after eating, blood glucose level rises and stays high (hyperglycaemia) and can result in death if untreated
  • kidneys can’t absorb all this glucose, so some its excreted in urine
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What is used to treat Type 1 diabetes?

A
  • insulin therapy (regular injections, insulin pump

- eating regularly and controlling simple carbohydrate intake helps avoid sudden rise in glucose

26
Q

Why must insulin therapy has to be carefully controlled?

A
  • too much insulin can produce a dangerous drop in blood glucose levels (hypoglycaemia)
27
Q

What is Type 2 diabetes?

A
  • when beta cells don’t produce enough insulin or when body’s cells don’t respond properly to insulin
  • cells don’t respond properly due to insulin receptors not working properly
28
Q

What can cause Type 2 diabetes?

A
  • linked w/ obesity and more likely in people w/ family history
  • lack of exercise
  • age
  • poor diet
29
Q

What is used to treat Type 2 diabetes?

A
  • eating a healthy, balanced diet
  • losing weight (if necessary)
  • regular exercise
  • glucose-lowering medication
  • insulin injections
30
Q

What do health advisors recommend that people do in order to reduce risk of Type 2 diabetes?

A
  • eat a diet that’s low in fat, sugar and salt, w/plenty of whole grains, fruit and vegetables
  • take regular exercise
  • lose weight if necessary
31
Q

What else have health advisors challenged the food industry to do?

A
  • reduce advertising of junk food
  • improve nutritional value of products
  • use clearer labelling on products
32
Q

How have some food companies attempted to make their products more healthy?

A
  • using sugar alternatives to sweeten food/drinks

- reducing the sugar, fat and salt content of products

33
Q

What is one issue on food companies’ response to criticism?

A
  • some people believe that diet varieties aren’t as good for health as they’re claimed to be
  • e.g some evidence suggests artificial sweeteners are linked to weight gain
34
Q

What are nephrons?

A
  • long tubules along with the bundle of capillaries where blood is filtered
  • around one million in the kidney
35
Q

What happens first in the filtration of blood?

A
  • blood from renal artery enters smaller arterioles in cortex of kidney
36
Q

What is the structure and function of a Bowman’s capsule?

A
  • hollow ball containing a glomerulus (bundle of capillaries looped)
  • where ultrafiltration takes place
37
Q

What is the difference between afferent arterioles and efferent arterioles?

A
  • afferent - takes blood into glomerulus
  • efferent - takes filtered blood away from glomerulus
  • efferent is smaller in diameter, so blood in glomerulus in under high pressure
38
Q

What does this high pressure in glomerulus do?

A
  • forces liquid and small molecules in blood out of capillary and into Bowman’s capsule
39
Q

The liquid and small molecules enter what after getting into the Bowman’s capsule?

A
  • capillary wall; a basement membrane and epithelium of Bowman’s capsule
40
Q

What happens to the larger molecules?

A
  • can’t pass through, so they stay in blood
41
Q

What are the substances that enter the Bowman’s capsule called?

A
  • glomerular filtrate
42
Q

What are the last 2 stages of the filtration of blood?

A
  • glomerular filtrate passes along rest of nephron and useful substances are reabsorbed along the way
  • filrate flows through collecting duct and passes out of kidney along the ureter
43
Q

Where does selective reabsorption take place?

A
  • glomerular filtrate flows along proximal convoluted tubule (PCT), through loop of Henle, and along distal convoluted tubule (DCT)
44
Q

What property does the microvilli in the epithelium of the wall of the PCT give?

A
  • large SA for reabsorption of useful materials from filtrate into the blood
45
Q

How are useful solutes e.g. glucose reabsorbed along PCT?

A
  • active transport

- facilitated diffusion

46
Q

Why does the water enter the blood by osmosis?

A
  • because water potential of blood is lower than that of the filtrate
47
Q

What is urine usually made of?

A
  • water and dissolved salts
  • urea
  • other substances such as hormones and excess vitamins
48
Q

What doesn’t urine usually contain?

A
  • proteins and blood cells; too big to be filtered out of blood
  • glucose; actively reabsorbed back into blood
49
Q

What is osmoregulation?

A
  • kidneys regulate WP of the blood (and urine), so the body has just the right amount of water
50
Q

What happens when the water potential in blood is too low?

A
  • more water is reabsorbed by osmosis into the blood from tubules of nephrons
  • means urine is more concentrated, less water is lost through excretion
51
Q

What happens when the water potential in blood is too high?

A
  • less water is reabsorbed by osmosis into blood from tubules of nephrons
  • urine is more dilute, so more water is lost during excretion
52
Q

Where does the regulation of water potential mainly take place?

A
  • loop of Henle, DCT and collecting duct
53
Q

What is the first stage of control of movement of sodium ions for water absorption by loop of Henle?

A
  • near top of ascending limb, Na+ ions pumped out into medulla using active transport
  • ascending limb is impermeable to water, so water stays inside tubule
  • creates low WP in medulla due to high concentration of ions
54
Q

What is the second stage of control of movement of sodium ions for water absorption by loop of Henle?

A
  • water moves out of descending limb into medulla by osmosis
  • makes filtrate more concentrated
  • water in medulla is reabsorbed into blood through capillary network
55
Q

What is the third stage of control of movement of sodium ions for water absorption by loop of Henle?

A
  • near bottom of ascending limb, Na+ ions diffuse out into medulla, further lowering WP in medulla
  • ascending limb is impermeable to water, so it stays in tubule
56
Q

What is the fourth stage of control of movement of sodium ions for water absorption by loop of Henle?

A
  • water moves out of distal convoluted tubule (DCT) by osmosis and reabsorbed into blood
57
Q

What is the fifth stage of control of movement of sodium ions for water absorption by loop of Henle?

A
  • the first 3 stages massively increase ion concentration in medulla, which lowers WP
  • causes water to move out of collecting duct by osmosis
  • water in medulla is reabsorbed into blood through capillary network
58
Q

What monitors the water potential of the blood?

A
  • osmoreceptors in the hypothalamus
59
Q

What happens when the water potential in the blood decreases?

A
  • water will move out of osmoreceptor cells by osmosis
  • causes cells to decrease in volume
  • sends signal to hypothalamus, which send signal to posterior pituitary gland
  • causes it to release antidiuretic hormone (ADH)
60
Q

What does ADH do?

A
  • makes walls of DCT and collecting duct more permeable to water
  • means more water is reabsorbed from tubules into medulla and blood by osmosis
  • small amount of concentrated urine is produced, less water is lost from body
61
Q

How does ADH change water content of the blood when its too low?

A
  • water content of blood drops, so WP drops
  • detected by osmoreceptors in hypothalamus
  • posterior pituitary gland releases more ADH into blood
  • more ADH means DCT and collecting duct are more permeable, so more water is reabsorbed into blood
  • highly concentrated urine produced, less water lost
62
Q

How does ADH change water content of the blood when its too high?

A
  • water content in blood rises, so WP rises
  • detected by osmoreceptors in hypothalamus
  • posterior pituitary gland releases less ADH into blood
  • less ADH means DCT and collecting duct are less permeable, so less water is reabsorbed into blood
  • large amount of dilute urine produced, more water lost

A-Level Biology (19 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions