Homeostasis and blood glucose control and adrenaline

Define Homeostasis (1 mark)

The physiological control systems that regulate the stable internal environment with restricted limits.

Suggest 5 things that are regulated by homeostasis

Body temperature, blood pH, blood glucose, blood water potential, concentration of respiratory substrates,

Why is homeostasis important?

It’s important in maintaining optimum efficiency to perform metabolism

Explain how a high rate of enzyme function could lead to an increased body temperature

High rate of enzyme functions causes metabolic imbalance.

This causes blood vessels to expand in order to transport the products

The fast rate of transport causes more het to be given off

Blood pressure decreases so oxygen supply to the brain decreases.

How does maintaining a constant body temperature allow metabolic reactions in cells to proceed with maximum efficiency? (5 marks)

When body temperature is above the optimal temperatures, enzymes denature. Causing. Change in the enzymes active site. Therefore substrate cannot bind and the rate of metabolism decreases.

when the body temperature is below optimal temperatures, enzymes and substrates Do not have enough KE to collide. Therefore the frequency of enzyme substrates collisions decreases.

So the body maintains an optimal temperature of 37 degrees for maximum efficiency

What is meant by an endotherm?

An organism that is warm blooded

What is meant by an ectotherm?

An organism that is cold blooded

And their body fluctuates with the environment.

Describe what is meant by negative feedback?

A mechanism which ensures the conditions remain stable

Explain what happens when the body detects a rise in blood glucose levels (6 marks)

Beta cells in the islets of Langerhans detect a rise in blood glucose.

Causing them to secrete insulin into the blood

Insulin increases the rate at which cells absorb glucose by facilitated diffusion

Glycogenesis occurs

And glucose is converted into glycogen

Beta cells detect the fall in blood glucose levels and stop releasing insulin

Explain what happens when the body detects a fall in blood glucose levels (6 marks)

Alpha cells in the Islets of Langerhans detect a fall in blood glucose

Causing them to secrete glucagon into the blood

Glucagon binds to specific glucagon receptor proteins, activating enzymes

causing glycogenolysis to occur

Where glycogen is converted into glucose

Glucose then diffuses into the blood, increasing blood glucose levels

Alpha cells will detect the increase in blood glucose and will stop releasing glucagon

Scientists noted that children in rural areas have much less muscle mass due to severe starvation.

Suggest what happens in starvation in terms of glucose production which has lead to children having decreased muscle mass (2 marks) Include the names of relevant processe/s

Glucose stores have runout so proteins are hydrolysed into amino acids.

To form Pyruvate which is converted into glucose

Via glyconeogenesis

Leading to a decrease in muscle mass.

Which hormone inhibits glycogenesis?

Glucagon

Which hormone promotes glycogenesis?

Insulin

Which hormone inhibits glycolysis?

Insulin

Which hormone promotes glycolysis?

Glucagon

What process occurs when glucagon converts pyruvate into glucose?

Glyconeogenesis

Prolonged Glyconeogenesis is usually caused, due to….

Starvation

Explain how insulin lowers the concentration of blood glucose (3 marks)

Insulin binds to insulin receptors which send insulin signals.

These signals cause vesicles containing glucose transport proteins

To fuse with the cell membrane

Allowing glucose to diffuse out of the cell via facilitated diffusion into the cell

Where does most glycogenolysis occur?

In the Skeletal muscles, adipose tissue

Where does most glycogenesis occur?

In the Liver and skeletal muscle

Explain how adrenaline works (6 marks)

Adrenaline binds to adrenaline receptors

This causes a change in shape in the protein

which activates Adenylyl cyclase

this causes ATP to be converted into cyclic AMP

Clyclic AMP activates protein kinase A

Protein kinase A activates enzymes that hydrolyse glycogen

Suggest why a second messenger is used in process before glycolysis (1 mark)

Adrenaline is not lipid soluble and cannot pass through the phospholipid bilayer

To amplify signals-efficiency

To activate specific enzymes

Hyperglycaemia

Condition caused by high blood glucose levels

Hypoglycaemia

Condition caused by low blood glucose

Diabetic ketoacidosis

Where prolonged ketosis occurs and fats are broken down into fuel.

Leading to a build up of ketones which are acidic

high levels of ketones are dangerous.

Give the difference between type 1 and type 2 diabetes

Type 1- inadequate production of glucose

Type 2- inefficient production of glucose

Explain how chronic high blood glucose can lead to hypertension (high blood pressure) and blood vessels to have reduced elasticity. (6 marks)

• High glucose lowers blood water potential (1)

• Causes water to move into blood by osmosis (1)

• Increases blood volume (1)

• Increased blood volume raises blood pressure (1)

• Glucose damages endothelium of blood vessels (1)

• Leads to reduced elasticity / increased peripheral resistance (1)

Explain why individuals with untreated diabetes may experience fatigue.

• Insulin is absent (Type 1) or ineffective (Type 2) (1)

• Glucose cannot enter cells via GLUT transport proteins (1)

• Reduced glucose availability for aerobic respiration (1)

• Less ATP produced (1)

• Cells lack energy for metabolic processes (1)

• Leads to feelings of tiredness/fatigue (1)

Explain why a diet low in sugar and carbohydrates is recommended for people wanting to lose weight (4 marks)

• Cells cannot use glucose for respiration (1)

• Body switches to alternative substrates (1)

• Fats from adipose tissue/proteins from skeletal muscle are hydrolysed into glucose by glucagon (1)

• Gluconeogenesis occurs instead of glucogenesis

• Loss of body mass → weight loss (1)

Explain why individuals with diabetes may experience polyphagia (excessive hunger)

• Glucose remains in the blood (1)

• Cells do not receive sufficient glucose (1)

• Cells are effectively in a state of starvation (1)

• Satiety centres in the brain are not stimulated (1)

• Hunger response persists → increased food intake (1)

Explain why untreated diabetes can lead to the production of ketone bodies and metabolic acidosis. (7 marks)

• Lack of glucose uptake by cells (1)

• Increased reliance on fats for respiration (1)

• Fats from adipose tissue is hydrolysed (5)

• Produces ketone bodies (e.g. acetoacetate) (1)

• Ketones are acidic (1)

• Accumulation lowers blood pH → metabolic acidosis (DKA) (1)