Brenda - Hormones and Metabolism

Question 1

What is the control centre for the endocrine system?

Answer 1

The hypothalamus

Question 2

How does the endocrine system work?
(4)

Answer 2

Hypothalamus receives and integrates signals from the nervous system

The hypothalamus then releases regulatory hormones

These pass directly to the nearby pituitary gland

Anterior and posterior pituitary gland release hormones which regulate the endocrine tissue (amplification)

Question 3

What are the two classifications of hormones?

Answer 3

Protein based hormones

Lipid based hormones

Question 4

Where are the receptors for protein based hormones?

Answer 4

Receptors for these exist on plasma membranes

Question 5

What are the receptors for lipid based hormone?

Answer 5

Receptors for these exist inside the cell

Question 6

List the three classifications of hormones

Answer 6

Peptide hormones

Amino acid derivatives

Lipid derivatives

Question 7

What are peptide hormones?
(3)

Answer 7

Relatively short

Defined amino acid chains

e.g. insulin and glucagon

Question 8

What are amino acid derivative hormones?

Answer 8

Hormones derived from tyrosine

e.g. epinephrine, norepinephrine (catecholamines) and thyroxine and triiodothyronine (thyroid hormones)

Question 9

What are lipid derivative hormones?
(2)

Answer 9

Steroid hormones derived from cholesterol

e.g. testosterone, oestradiol, progesterone, cortisol, aldosterone

Question 10

What four hormones regulate glucose?

Answer 10

Insulin

Glucagon

Adrenaline

Cortisol

Question 11

What does insulin do?

Answer 11

Signals that blood glucose levels are too high

Question 12

What does glucagon do?

Answer 12

Signals that blood glucose levels are too low

Question 13

What does adrenaline do?

Answer 13

Signals tissues that extreme bursts of activity are imminent

Question 14

What does cortisol do?

Answer 14

Cortisol mediates the response to chronic stress

Question 15

What is blood glucose maintained at?

Answer 15

4.5mM

Question 16

What are the four pancreatic cells in the islets of Langerhans?

Answer 16

a cells
B cells
Delta cells
Gamma cells

Question 17

What do alpha cells do?

Answer 17

Produce glucagon

Question 18

What do beta cells do?

Answer 18

Produce insulin

Question 19

What do delta cells do?

Answer 19

Produce somatostain

Question 20

What do gamma cells do?

Answer 20

Produce a polypeptide with unknown function

Question 21

Write a note on insulin synthesis
(3)

Answer 21

Insulin gene encodes preproinsulin (precursor of insulin)

During translation, the signal peptide is cleaved to form proinsulin

During packaging in granules by Golgi, proinsulin is cleaved into insulin and C peptide

Question 22

How does glucose control the release of insulin from Beta cells?
(4)

Answer 22

Glucose concentrations in blood rise -> GLUT2 transports glucose into beta cells -> its converted into G6P and enters glycolysis

Aerobic oxidation of glucose causes an increase in intracellular ATP which closes ATP dependent potassium ion channels

The membrane becomes depolarised and causes calcium channels in the plasma and ER membranes to open

An influx of calcium induces release of insulin stored in granules by exocytosis

Question 23

What does GLUT2 do?

Answer 23

GLUT2 transports glucose into beta cells

Question 24

What does aerobic oxidation of glucose do?
(2)

Answer 24

Causes an increase in intracellular ATP

This closes ATP potassium ion channels

Question 25

What happens when ATP potassium ion channels close?
(2)

Answer 25

The membrane becomes depolarised

This causes calcium channels in the plasma and ER membranes to open

Question 26

What happens when the calcium channels open?
(2)

Answer 26

There is an influx of calcium

This induces release of insulin stored in granules

Question 27

What is glucagon?
(2)

Answer 27

A 29 amino acid polypeptide hormone

Produced by alpha cells in the pancreas

Question 28

What does glucagon promote?
(3)

Answer 28

Glycogenolysis

Gluconeogenesis

Release of glucose to the blood from the liver cells

Question 29

What is glycogenolysis?

Answer 29

The breakdown of glycogen to glucose

Question 30

What is gluconeogenesis?

Answer 30

Synthesis of glucose from lactic acid and noncarbohydrates

Question 31

What are the two types of liver cells?

Answer 31

Kupffer cells (phagocytes)

Hepatocytes

Question 32

What do hepatocytes do?

Answer 32

Transform dietary nutrients into fuels and precursors and export them

Question 33

What do the hepatocytes do in a protein-rich diet?

Answer 33

Hepatocytes increase their synthesis of enzymes for amino acid catabolism and gluconeogenesis

Question 34

What do hepatocytes do in a carbohydrate rich diet?
(2)

Answer 34

Levels of gluconeogenesis enzymes drop

Hepatocytes increase their synthesis of enzymes for carbohydrate synthesis and fat synthesis

Question 35

How does insulin affect liver metabolism?
(7)

Answer 35

It stimulates the uptake of glucose by the muscle, liver and adipose tissue

In the liver it activates glycogen synthase and converts glucose into glycogen

Glucose is also broken down into acetyl coA

It activates enzymes responsible for converting glucose into pyruvate and pyruvate into acetyl-coA

If acetyl-CoA is not oxidised further via the TCA cycle it is used for fatty acid synthesis

Triacylglycerides are synthesised from these fatty acids in the liver and transported to muscle and adipose tissue by VLDL

Insulin also stimulates the conversion of fatty acids absorbed from the small intestine into triacylglycerides

Question 36

What does insulin stimulate fatty acids to do?

Answer 36

Stimulates the conversion of fatty acids absorbed in the small intestine into triacylglycerides

Question 37

What happens if the liver doesn’t oxidise acetyl-CoA?

Answer 37

It is used for fatty acid synthesis for muscle and adipose tissue