6.4 - Homeostasis is the maintenance of stable environment Flashcards
(34 cards)
What is homeostasis?
Internal environments is maintained within set limits around an optimum
Why is it important that core temperature remains stable?
- Maintains stable rate of enzyme-controlled reactions & prevents damage to membranes
- Temperature too loww = enzyme & substrate molecules have insufficient kinetic energy 7
- Temp to high = enzymes denature
Why is it important that blood pH remains stable?
Maintains stable rate of enzyme-controlled reactions
Acidic pH = H+ ions interact with H-bonds & ionic bonds in tertiary structure of enzymes -> shape of active site changes so no ES complexes form
Why is it important that blood glucose concentration remains stable?
- Maintains constant blood water potential: prevent osmotic lysis/crenation of cells.
- Maintains constant concentration of respiratory substrate: organism maintains constant level of activity regardless of environmental conditions.
Define negative and positive feedback.
Negative feedback: self-regulatory mechanisms return internal environment to optimum when there is a fluctuation.
Positive feedback: a fluctuation trigger changes that result in an even greater deviation from the normal level.
Outline the general stages involved in negative feedback.
Receptors detect deviation corrdinator -> corrective mechanism by effector -> receptors detect that conditions have returned to notmal.
Suggest why separate negative feedback mechanisms control fluctuations in different directions.
Provides more control, especially in case of ‘overcorrection’, which would lead to a deviation in the opposite direction from the orginal one.
Suggest why coordinators analyse inputs from several receptors before sending an impulse to effectors.
- Receptors may senf conflicting information.
- Optimum response may require multiple types of effector.
Why is there a time lag between hormone production and response by an effector?
It taked time to:
- produce hormones
- transport hormones in the blood
- cause required change to the target protein
Name the factors that affect blood glucose concentration.
- Amount of carbohydrate digested from diet
- Rate of glycogenolysis
- Rate of gluconeogenesis
Define glycogenesis, glycogenolysis and gluconeogenesis.
Glycogenesis: liver converts glucose into the storage polymer glycogen.
Glycogenolysis: liver hydrolyses glycogen into glucose which can diffuse into blood.
Gluconeogenesis: liver converts glycerol & amino acids into glucose.
Outline the role of glucagon when blood glucose concentration decreases.
- a cells in Islets of Langerhans in pancreas detect decrease & secrete glucagon into bloodstream.
- Glucagon binds to surface receptors on liver cells & activates enzymes for glycogenolysis & gluconeogenesis.
- Glucose diffuses from the liver into the bloodstream.
Outline the role of adrenaline when blood glucose concentration decreases.
- Adrenal glands produce Adrenaline. It binds to surface receptors on liver cells & activates enzymes for glycogenolysis.
- Glucose diffuses from liver into bloodstream.
Outline what happens when blood glucose concentration increases.
- B cells in Islets of Langerhans in pancreas detect increase & secrete insulin into bloodstream.
- Insulin binds to surface receptors on target cells to:
- increase cellular glucose uptake
- activate enzymes for glycogenesis (liver & muscles)
- stimulate adipose tissue to synthesise fat
Describe how insulin leads to a decrease in blood glucose concentration.
- Increases permeability of cells to glucose.
- Increases glucose concentration gradient.
- Triggers inhibition of enzymes for glycogenolysis.
How does insulin increase permeability of cells to glucose?
- Increases number of glucose carrier proteins
- Triggers conformational change which opens glucose carrier proteins
How does insulin increase the glucose concentration gradient?
- Activates enzymes for glycogenesis in liver & muscles
- Stimulates fat synthesis in adipose tissue
Use the secondary messenger model to explain how glucogon and adrenaline work.
- Hormone-receptor complex forms.
- Conformational change to receptoractivate G-protein.
- Activates adenylate cyclase, which converts ATP to cyclic AMP (cAMP).
- cAMP activates protein kinase A pathway.
- Results in glycogenolysis.
Explain the causes of Type 1 diabetes and how it can be controlled.
Body cannot produce insulin e.g. due to autoimmune response which attacks B cells of Islets of Langerhans.
Treat by injecting insulin.
Explain the causes of Type 2 diabetes and how it can be controlled.
- Glycoprotein receptors are damages or become less responsive to insulin.
- Strong positive correlation with poor diet/ obesity.
- Treat by controlling diet and exercise regime.
Name some signs and symptoms of diabetes.
- High blood glucose concentration
- Glucose in urine
- Polyuria
- Polyphagia
- Polydipsia
- Blurred vision
- Sudden weight loss
Suggest how a student could produce a desired concentration of glucose solution from a stock solution.
Volume of stock solution = required concentration x final volume needed / concentration of stock solution.
Volume of distilled water = final volume needed - volume of stock solution.
Outline how colorimetry could be used to identify the glucose concentration in a sample.
- Benedict’s test on solutions of known glucose concentration. Use colorimeter to record absorbance.
- Plot calibration curve: absorbance (y-axis), glucose concentration (x-axis).
- Benedict’s test on unknown sample. Use calibration curve to read glucose concentration at its absorbance value.
Describe the gross structure of a mammalian kidney.
- Fibrous capsule: protects kidney
- Cortex: outer region consists of Bowman’s capsules, convoluted tubules, blood vessels.
- Medulla: inner region consists of collecting ducts, loops of Henle, blood vessels.
- Renal pelvis: cavity collects urine into ureter.
- Ureter: tube carries urine to bladder.
- Renal artery : supplies kidney with oxygenated blood.
- Renal vein: returns deoxygenated blood from kidney to heart.
