Homeostatsis

Question 1

What is homeostasis ?

Answer 1

Maintenance of a stable internal environment

Question 2

Why is blood ph and body temp important to keep constant

Answer 2

Temp and pH affect enzy activity and enzymes control rate of metabolic reactions

Question 3

What’s the pH equation

Answer 3

-log(H+)

Question 4

Why use a logarithmic scale

Answer 4

Easier to plot very small and very large values on same axis of a graph

Question 5

What is the effect of too high/ low blood glucose

Answer 5

Too high - water potential of blood is reduced so water molecules diffuse out of cells into blood by osmosis which causes cell to shrivel and die
Too low- cells can’t carry out normal activities as there isn’t enough glucose for respiration

Question 6

What is the negative feedback mechanism

Answer 6

Normal level - level changes from normal - receptors detect change - communications via nervous or hormonal system - effectors respond

Question 7

Does negative feedback always work ?

Answer 7

No there are limits if change is too big effectors may not be able to counteract

Question 8

What is the positive feedback mechanism ?

Answer 8

Amplified a change
Normal level - level changes - receptors detect change - communication via nervous or hormonal system - effectors respond

Question 9

What are the islets of Langerhan and what do they do

Answer 9

Clusters of cells in the pancreas which contain beta and alpha cells. Beta cells secrete insulin into the blood alpha cells secret glucagon into the blood. Insulin and glucagon both act on effectors which respond to restore blood glucose concentration

Question 10

What does insulin do

Answer 10

Lowers blood gluc levels by binding to specific receptors on cell membranes of muscle cells and liver cells and increases permeability of muscle cells to glucose by increasing no of channel proteins on cell membrane.
Insulin also activated enzymes in muscle and liver cells that convert glucose to glycogen (glycogenesis) so it is stored in cytoplasm.
Insulin also increases rate of resp of glucose especially in muscle cells.

Question 11

What does glucagon do

Answer 11

Raises blood glucose conc by binding to specific receptors on cell membranes of liver cells and activated enzymes that break down glycogenesis. It also activated enzymes that are involved in formation of glucose from glycerol and amino acids ( glucogenesis) glucagon decreased rate of resp of glucose in cells

Question 12

What are adv/ disadv or honeonal responses

Answer 12

They travel in blood to target cells so responses are slowe but they can occur all over body if target is wide spread unlike nervous impulses which are localized. Hormones are not broken down as quickly as neurotransmitters so effects last longer

Question 13

What happens when there is a rise in blood glucose conc

Answer 13

Beta cells secrete insulin and alpha cells stop secreting glucagon , insulin binds to receptors on liver and muscle cells . Liver and muscle cells respond eg cells take up more glucose , glycogenesis is activated , cells report more glucose

Question 14

What happens when there is a fall in blood glucose levels

Answer 14

Pancreas defects blood glucose is too low, alpha cells secrete glucagon and beta cells stop averting insulin. Glucagon binds to receptors on liver cells and increase blood glucose conc ( glycogenolysis is activated

Question 15

How is glucose transported

Answer 15

Channel proteins which allow glucose to be transported across cell membrane, skeletal and cardiac muscle cells contain GLUT4 transporter , when insulin binds to receptors it triggers movement of GLUT4 to membrane so glucose can move via facilitated diffusion

Question 16

What is adrenaline what does it do

Answer 16

Hormone secreted fro maternal glands it’s secreted when there’s low conc of glucose in bloods, it binds to receptors on cell memb of liver cells and activated glycogenolysis and inhibits glycogenesis
Also activates glucagon secretion and inhibits insulin secretion ( which increases glucose conc) it makes body ready for action by making glucose for muscles to respire

Question 17

What are second messengers

Answer 17

Second messenger model- binding ofbthe hormone to cell receptors activated an enzyme on inside of cell membrane which produces second messenger chemical which activates other enzymes which bring on a response

Question 18

How is glycogenolysis activated

Answer 18

Adrenaline and glucagon bind to their receptors and activate an enzyme( adenylate cyclase) which converts ATP to cyclic AMP( a second messenger ) it activates an enzyme called protein kinase A which activates a cascade taht causes glycogenesis

Question 19

What’s type 1 diabetes

Answer 19

Immune system attacks beta cells on islets of langerhan so they can’t produce insulin. After eating blood glucose levels stay high so the kidneys can’t reabsorb all the glucose so some is secreted into urine, it is treated with insulin injections and controlled eating. Most people have genetic predisposition to this disease .

Question 20

What’s type 2 diabetes

Answer 20

Acquired later in life , linked to obesity and is more likely if family have it. Risk factors - age, diet , exercise. Occurs when beta cells don’t produce enough insulin or body doesn’t respond to insulin. Cells don’t respond because insulin receptors don’t work. Blood glucose is higher than normal. Treated with healthy eating and exercise. Glucose lowering meds may be usedb, type 2 diabetes is getting more common and can lead to kidney failure

Question 21

What is the quantitative Benedict’s test

Answer 21

Heated with glucose , initial blue colour is lost no precipitation is formed. More glucose - more blue - less absorbance

Question 22

What are nephrons

Answer 22

Long tubules with bundles of capillaries where the blood is filtered there are around Q million per kidney

Question 23

What is ultrafiltration

Answer 23

Blood from renal artery enters smaller arterioles which then go to glomerulus ( a bundle of capillaries looped within the Bowman’s capsule ) . The afferent arteriole takes blood to the glomerulus the efferent arteriole takes takes filtered blood away ( efferent is smaller in diameter so blood in glomerulus is under high pressure ) this forced small molecules of blood out of capillary into Bowman’s capsule and enter nephron tubules. From capillary glomerular filtrate diffuses through pores in capillary endothelium , basement membrane , epithelium of Bowman’s capsule . Filtrate passes along rest of nephron and useful substances are reabsorbed and filtrate flows through collecting duct and passes out of kidney by ureter.

Question 24

What is selective reabsorption

Answer 24

Glomerular filtrate flows along proximal convoluted tubule through loop of henle along distal convoluted tubule useful substances leave the tubules of the nephrons and enter the capillary network thats wrapped around them , epithelium wall of PCT has microvilli that provide large surface area for reabsorption of useful