5.4: Hormones

Question 1

Where in the pancreatic cell insulin molecules are synthesised?

Answer 1

RER

Question 2

Outline the events that occur after the synthesis of an insulin molecule until it is ready to be secreted from the pancreatic cell:

Answer 2

Transported to Golgi; modified/ processed in Golgi; packaged into Golgi vesicles; vesicles transported towards plasma membrane; detail of modification
(splitting / recombining, polypeptide); role of cytoskeleton; use of ATP (in context of, modification / movement)

Question 3

Describe the events leading to secretion of insulin from beta cell:

Answer 3

Glucose is phosphorylated/ respired/ metabolised to produce ATP (glucokinase); ATP blocks/closes K+ channels ; K+ build up (inside cell); (voltage-gated) Ca2+ channels open Ca2+ enter (cell by diffusion); (more) Ca2+ resulting in movement of vesicles to membrane/ exocytosis

Question 4

Why does insulin secretion continue even when there is no further glucose intake:

Answer 4

(Continues to be secreted) as long as blood glucose conc higher than normal; (sufficient) ATP is still present so K+ channels remain closed; exocytosis still being triggered by Ca2+ (continues until Ca removed)

Question 5

Describe how negative feedback is used to control blood glucose concentration:

Answer 5

1) beta cells/ alpha cells/ receptors detect change in bgc;
2) if higher gc, beta cells release insulin;
3) (increased) absorption of glucose by liver/ muscle/ effector;
4) enters through glucose transport proteins (in cell surface membrane);
5) glucose converted to glycogen/ glycogenesis;
6) increased (use of glucose in) respiration: ATP production;
7) if lower gc, alpha cells release glucagon;
8) (increased) conversion of glycogen to glucose/ glycogenolysis;
9) (increased) conversion of other compounds, (amino acid/ lipids), to glucose/ gluconeogenesis;
10) glucose leaves cell by facilitated diffusion/ through glucose channels

Question 6

Define homeostasis:

Answer 6

Maintaining (relatively) stable internal environment within (narrow) limits/ range; even though environment is changing

Question 7

Describe the changes that take place to make sure that the blood glucose concentration does not fall to a dangerous level:

Answer 7

Fall detected by pancreas; fall inhibits insulin secretion; stimulates secretion of glucagon (by alpha cells); into blood; binds to receptors on hepatocytes; glycogenolysis; gluconeogenesis; glucose into blood stream

Question 8

Endocrine gland:

Answer 8

Ductless gland; secretes hormones; (directly) into the blood

Question 9

Exocrine gland:

Answer 9

Enzymes/ pancreatic juice/ HCO3-; amylase/ trypsin/ chymotrypsin/ lipase/ carboxylpeptidase; into duct

Question 10

Explain the advantages of using GM in treatment of diabetes:

Answer 10

Insulin produced by, microorganisms/ bacteria; cheaper source of insulin/ more reliable supple/ large scale production; more rapid response; less chance of immune/ allergic response; better for people who have developed a tolerance for animal insulin; acceptable to people who have ethical objections; vegetarians; no risk of infection/ contamination

Question 11

After long periods of fasting, explain how the liver can still produce glucose by the process of gluconeogenesis:

Answer 11

Deamination of amino acids; pyruvate/ carbon skeleton; triose phosphate/ TP; condensation/ increasing no of C atoms
OR
Breakdown of lipid/ triglyceride; glycerol; TP; condensation

Question 12

Describe how glucagon is involved in the regulation of blood glucose concentration in a healthy person: June 14 3dii 5mks

Answer 12

The alpha cells in the IoL detect low bgc and secrete glucagon in the blood; leads to glycogenolysis; gluconeogenesis; conversion of triglycerides to (free) fatty acids/ lipolysis/ increased use of fatty acids in respiration; glucagon inhibits insulin secretion; negative feedback;

Question 13

What might happen if liver did not break down insulin:

Answer 13

Bcg would fall too low/ below normal; glucose would continue to be taken up by cells -> low bcg/ store too much glucose as glycogen; mitochondria can’t relapse enough energy/ ATP; coma/ death

Question 15

How is type 1 diabetes caused:

Answer 15

Unable to produce sufficient/ effective insulin; beta cells not functioning correctly/ damaged/ attacked; by immune system/ antibodies/ autoimmune disease; triggered by virus/ environmental factor

Question 15

Explain what is meant by the term hormone:

Answer 15

Can be steroids/ peptides/ amides; released in minute quantities; from endocrine glands; travels in blood; affects target organs; by binding to protein receptor sites on membranes

Question 16

Treatment for type 1 diabetes:

Answer 16

Insulin injections; insulin pump therapy: permanent needle in skin; islet cell transplant (stem cells)

Question 17

Describe the different ways in which the pancreas acts as both an endocrine and an exocrine gland:

Answer 17

endocrine:
H1 hormone(s) released directly into blood ;
H2 beta / β , cells , secrete / produce / release , insulin ;
H3 alpha / α , cells , secrete / produce / release , glucagon ;
H4 islet /  and  , cells , detect / monitor ,
blood glucose concentration ;
exocrine:
E1 fluid / juice / secretion / enzymes , released into duct ;
E2 (release triggered by) nervous / hormonal , stimulation ;
E3 pancreatic secretions into ,
gut / small intestine / duodenum ;
E4 alkaline / pH 8 / (sodium) hydrogen carbonate ;
E5 containing 2 named enzyme(s) ;

Question 18

State two advantages of treating Type 1 diabetes by using insulin that has been produced by genetically modified bacteria rather than insulin that has been extracted from pigs:

Answer 18

idea of plentiful / dependable , supply ;
2 cheap ;
3 not cruel to pigs / more ethical ;
4 no religious objections / can be used by vegetarians ;
5 reliable , quality / standard ;
6 (exact match to) human insulin / no allergic reaction ;

Question 19

Factors that increase risk of type 2 diabetes:

Answer 19

Ageing (>40); genetic; more common in males; obese; ethnic groups; high intake of processed food/ high GI food/ sugars; lack of physical activity; high BP; excessive alcohol intake

Question 20

Secondary messenger for insulin:

Answer 20

Tyrosine kinase (causes phosphorylation of inactive enzymes to activate them to catalyse fusion of vesicles containing glucose transporter proteins into membrane)

Question 21

Secondary messenger for glucagon:

Answer 21

Adenyl cyclase

Question 22

A potential treatment for Type 1 diabetes is the use of stem cells. State an advantage of this form of treatment compared to treatment using insulin.

Answer 22

1 (has the potential to) cure / do more than manage ,
the condition ;
2 long term effect / permanent /
no need for repeated treatments ;
e.g. no need to restrict diet
2 e.g. no need to inject insulin (regularly)

Question 23

Name the part of the adrenal gland that releases aldosterone. [F214 jan 13 6ci]

Answer 23

cortex;

Question 24

Suggest and explain what effect the action of aldosterone will have on the secretion of ADH. (2mks) [F214 jan 13 q6cii]

Answer 24

water potential of, plasma/ blood , will , decrease/ become more negative ; [concentration of Na+ in, plasma / blood, will increase]
(ADH secretion) will increase;

Question 25

Glycogenolysis

[f214 Jan 11 q5aii]

Answer 25

Hydrolysis
Protein kinase/ (activates) glycogen phosphorylase kinase OR glycogen phosphorylase (stimulates conversion of glycogen) OR inhibition of glycogen synthase (preventing glucose conversion to glycogen)

Question 26

70.​Treated rats were given a glucose meal and the concentration of blood glucose measured immediately and at intervals for eight hours. The results of this investigation are shown in the figure below.

​With reference to the figure, discuss the possible benefits and problems of using this gene therapy in the treatment of diabetes in humans, rather than taking insulin.

Answer 26

70.​benefits
avoids injections / pain of injections / children’s fear of injections;
mimics normal pancreatic behaviour;
more stable homeostasis / reduced highs and lows in blood sugar;
less chance, hypoglycaemia / hyperglycaemia;
less restriction on lifestyle;
no need to measure blood sugar;
AVP;​max 3
​problems
rejection;
cells could lodge elsewhere;
may take longer to act;
AVP; e.g. rat data may not be applicable to humans,
​transgene may have unforeseen effect​max 3​max 4

Question 27

3 differences between in the ways in which plant and mammalian hormones operate: f215 June 13

Answer 27

1 (M) made in endocrine glands versus
(P) made in many plant tissues ;
2 (M) move in blood versus
(P) move, in xylem / in phloem / from cell to cell ;
3 (M) act on, a few / specific / target, tissues versus
(P) act on most tissues / can act in cells where produced ;
4 (M) act more rapidly ; ORA