IB HL Biology 11.3 The Kidney and Osmoregulation

Differences in composition between blood in the glomerulus, filtrate at various points in the nephron and urine

Blood in glomerulus:
(1) Plasma proteins present
(2) Glucose present
(3) Urea present
Glomerular filtrate:
(1) Plasma proteins absent
(2) Glucose present in same amounts
(3) Urea present in same amounts
Filtrate at start of loop of Henle:
(1) Plasma prote

Presence of abnormalities in urine tests

(1) Blood cells: infections and some cancers
(2) Glucose: diabetes
(3) Proteins: hCG and insulin in small amounts normal; large amounts sign of kidney diseases
(4) Drugs: doping; drug abuser

Treatment of kidney failure

1. Hemodialysis
Blood drawn out of the vein in the arm and passes through a kidney machine for 3/4 h, 3 times a week. Blood flows next to a semi-permiable dialysis membane with dialysis fluid on the other side. Pores allow small particles to diffuse in ei

Outline ways in which the kidney helps in homeostasis

(1) Regulation of water levels / osmoregulation
controlled by ADH
(2) Regulation of salt levels
(3) Regulation of K+ and Na+ levels
(4) Regulation of blood pH
(5) Keeping levels of metabolic waste products low
e.g. urea, ammonia

Outline the need for excretion in living organisms

(1) Removal of waste products of metabolism
(2) Removal of toxic substances that could harm us
(3) Removal of substances in excess

Explain briefly the function of the loop of Henle in the human kidney

(1) Makes the medulla hypertonic / release of sodium ions into medulla out of the ascending limb
(2) Allows the production of hypertonic, concentrated urine / more water absorption in collecting duct

Compare the composition of the blood in the renal artery and renal vein

(1) Blood in renal artery more oxygenated than the blood in the renal vein / oxygenated versus deoxygenated
(2) Blood in renal artery contains more urea than the blood in the renal vein / urea versus no urea /
(3) Blood in renal artery contains more gluco

Define osmoregulation

(1) Control of water potential /content in a cell / organism
(2) Control of osmotic potential

Discuss the relationship between the different nitrogenous waste products and the habitats of birds and amphibians

(1) Ammonia is very toxic, and soluble in water. Used by aquatic amphibia as their toxic waste. Excretion of the ammonia is easy for an aquatic animal as it dissolves in the surrounding water.
(2) Urea is quite soluble in water and not as toxic as ammonia

The walls of blood capillaries in the kidney are fenestrated. How does the fenestration of these capillaries help in the production of urine?

A larger volume of fluid can be filtered out of the blood per minute

State two reasons why a person's plasma solute concentration may increase

(1) Drink alcohol / coffee
(2) Increased salt intake

State the substances that are selectively reabsorbed by the proximal convoluted tubule

(1) Water
(2) Salts
(3) Glucose
(4) Amino Acids

State the names of the processes used to reabsorb water and salts

(1) Water by osmosis;
(2) Salts by active transport/facilitated diffusion;

Outline the need for enzymatic hydrolysis in the digestive system

(1) Large molecules cannot be absorbed;
mechanical digestion only to break down food physically;
(2) Enzymes break down large molecules into smaller ones (that can be absorbed);
need several enzymes as they are substrate specific;
(3) Enzymes speed up the

Explain how the kidney prevents the body from losing important materials absorbed from the digestive system

(1) Ultrafiltration in the glomerulus: fenestrated capillaries/ basement membrane acts as a filter/ proteins too large do not pass through
(2) Proximal convoluted tubule: selective reabsorption (salts, glucose, amino acids, vitamins, hormones, 80% of mine

Explain the presence of glucose in the urine of untreated diabetic patients

The urine of non-diabetic patients should contain no glucose as it is selectively reabsorbed from the filtrate in the proximal convoluted tubule. Diabetics have higher levels of blood glucose due to either a lack of insulin secretion (type I) or insensiti

How many barriers does a filtrate have to pass?

(1) Capillary wall of glomerulus
(2) Basement membrane of capsule wall
(3) Epithelial layer of Bowman's capsule