Insulin/glucagon- on liver

how does glucose enter cells

facilitated diffusion through specific carrier proteins

what creates the concentration gradient for glucose to diffuse? through facilitated diffusion)

increased rate of respiration means cells use up more glucose, or glucose converted to glycogen

what is the effect of insulin on cells? (mostly liver/muscle) (except RBCs)

• insulin binds to receptor on membrane

• chemical signal sent to vesicle carrying additional glucose carrier proteins

• vesicle fuses w membrane and additional carrier proteins join, increasing rate of glucose uptake by facilitated diffusion

• glucose diffuses into cell through carrier proteins

• insulin also causes glucose carrier proteins to alter their tertiary structure, making glucose diffusion faster

• once glucose spike over, glucose transporters removed by endocytosis

what does insulin do in muscle cells?

enzymes activated which convert glucose to glycogen

what does insulin do in adipose (fat) cells?

enzymes activated which convert glucose to fatty acids and glycerol, stored as triglycerides

when does insulin act in cells?

when blood sugar is too high, to return to normal

when does glucagon/adrenalin act in cells?

when blood sugar drops, to return to normal

explain the effect of glucagon/adrenalin on liver cells. (use glucagon in answer)

• low BSL detected by pancreas, glucagon released by alpha cells in islets of langerhans

• glucagon binds to receptor in plasma membrane of target cell e.g. liver cell

• bound receptor interacts w and activates adenylate cyclase- integral membrane protein

• activated adenylate cyclase converts ATP to cAMP

• high cAMP in cytoplasm activates protein kinase A

• activated protein kinase A phosphorylates other enzymes in cell to activate them, depolymerise glycogen and release glucose

• glucose diffuses out of cell into blood, BSL normal

what is cAMP

cyclic AMP- adenosine monophosphate

glucagon activates enzymes in the liver. what do these do?

convert glycogen to glucose, convert other substances including glycerol/amino acids to glucose by glucogenesis

what happens in the cells of someone with type 1 diabetes

cytotoxic T cells attach beta cells in islets of langerhans

what type of condition is diabetes type 1

autoimmune

what is the result of a shortage of insulin in type 1 diabetes?

insufficient glycogen stored- glucose concentration can rise too high after a meal, risk of coma/death

treatment for type 1 diabetes?

inject insulin before meals, paired with diet and exercise

how can genetic engineering help diabetes type 1?

genetically modify bacteria to make insulin

what is happening in the cells of someone with type 2 diabetes

reduced sensitivity of the liver and fat storage cells to insulin- fewer insulin receptors.

what is the result of reduced sensitivity to insulin in liver/fat cells for type 2 diabetes?

beta cells stimulated to produce larger quantities of insulin

effects of diabetes

lack of stored glycogen, BSL fluctuations

treatment for type 2 diabetes

controlled diet and exercise

what risk factors is type 2 diabetes associated with?

obesity, age sedentary lifestyle, high sugar or fat diet, ethnicity

in what age group is diabetes becoming increasingly common?

over 40

where is insulin secreted

B cells in islets of langerhans in pancreas

where is glucagon secreted

alpha cells in islets of langerhans in pancreas

where is adrenaline secreted

adrenal glands

where does insulin act upon?

liver, muscle fibres, adipose tissue

where does glucagon act upon? (to return BSL to normal)

liver

where does adrenalin act upon? (to return BSL to normal)

liver