Homeostasis NCEA Level 3 Biology

Glucose Homeostasis

Homeostasis

Process of maintaining internal body environment despite external changes

Negative feedback

Reversing change from set-point to achieve homeostasis

Set point

Desired value, e.g., blood glucose = 5mM

Glucose

Carbohydrate, raw material for cellular respiration

Glycogen

Storage form of glucose in animals, a polymer of glucose

Liver

Organ responsible for storing glucose as glycogen and releasing glucose

Pancreas

Organ with endocrine cells producing insulin and glucagon

Islets of Langerhans

Groups of cells in the pancreas, including alpha and beta cells

Insulin

Storage hormone decreasing blood glucose, produced by beta cells

Glucagon

Hormone increasing blood glucose, produced by alpha cells

Hypoglycaemia

Low blood glucose levels

Hyperglycaemia

High blood glucose levels

Glycation

Glucose binding to proteins, damaging small blood vessels

Facilitated diffusion

Passive transport method for glucose in cells

GLUT protein

Plasma membrane protein allowing glucose transport in/out of cells

Concentration gradient

Difference in concentration across a plasma membrane

Hormone receptor

Protein spanning cell membrane, allowing hormone binding and signaling inside the cell

Allosterically induced change

Hormone binding causing shape change inside the cell, activating an enzyme

Glycogenesis

Process of converting glucose to glycogen for storage

Glycogen synthase

Enzyme catalyzing glucose to glycogen reaction

GLUT4 protein

Type of glucose transport protein found in muscle and fat cells

Glycogenolysis

Process of breaking down glycogen to glucose

Glycogen phosphorylase

Enzyme catalyzing glycogen to glucose reaction

HbA1C

Test measuring glucose bound to Haemoglobin, indicating Glycation levels

Diabetes (mellitus)

Disease affecting glucose homeostasis

Type 1 diabetes

Caused by autoimmune destruction of Beta cells, resulting in no insulin production

Type 2 diabetes

Progressive disease - gets progressively worse, from slight insulin resistance to more insulin resistance to such insulin resistance that glucose levels rise above the threshold to be called diabetic. Plus, eventually the Beta cells may die of overwork. Cells are so insulin resistant that lots of glucose stays in the blood and isn't used as fuel for energy.

Glucosuria

Presence of glucose in the urine

Polyuria

Excessive production of urine

Polydipsia

Excessive thirst

Polyphagia

Extreme hunger

Diabetic ketoacidosis (DKA)

Condition where fats and proteins are used to make glucose, leading to acidic blood and potential coma

Gluconeogenesis

 Fats and proteins are used to make glucose in the body so ketone bodies are made

Symptoms of diabetes

Hyperglycaemia, glucosuria, polyuria, polydipsia, muscle weakness and fatigue

Type 1 diabetes treatment

Injecting insulin

Type 2 diabetes treatment

Exercise and diet. Exercise allows GLUT4 proteins in muscle cells to join the plasma membrane so glucose can enter the muscle cells, lowering blood glucose. Also diet, less sugary and fatty foods. It can also be treated by drugs, Insulin injections to take pressure off of the beta cells, and gastric bypass. 

Type 2 diabetes beta cell

Beta cells may become so overworked that they die and now the person has no ability to make their own insulin. They will still be insulin resistant though.