IGCSE BIOLOGY SECTION 2 LESSON 6

Content Section 2 Structures and functions in living organisms a) Levels of organisation b) Cell structure c) Biological molecules d) Movement of substances into and out of cells e) Nutrition f) Respiration g) Gas exchange h) Transport i) Excretion j) Coordination and response

Content Lesson 6 i) Excretion Flowering plants 2.67 understand the origin of carbon dioxide and oxygen as waste products of metabolism and their loss from the stomata of a leaf Humans 2.68 recall that the lungs, kidneys and skin are organs of excretion 2.69 understand how the kidney carries out its roles of excretion and osmoregulation 2.70 describe the structure of the urinary system, including the kidneys, ureters, bladder and urethra 2.71 describe the structure of a nephron, to include Bowman’s capsule and glomerulus, convoluted tubules, loop of Henlé and collecting duct 2.72 describe ultrafiltration in the Bowman’s capsule and the composition of the glomerular filtrate 2.73 understand that water is reabsorbed into the blood from the collecting duct 2.74 understand that selective reabsorption of glucose occurs at the proximal convoluted tubule 2.75 describe the role of ADH in regulating the water content of the blood 2.76 understand that urine contains water, urea and salts.

Content Lesson 6 i) Excretion Flowering plants 2.67 understand the origin of carbon dioxide and oxygen as waste products of metabolism and their loss from the stomata of a leaf Humans 2.68 recall that the lungs, kidneys and skin are organs of excretion 2.69 understand how the kidney carries out its roles of excretion and osmoregulation 2.70 describe the structure of the urinary system, including the kidneys, ureters, bladder and urethra 2.71 describe the structure of a nephron, to include Bowman’s capsule and glomerulus, convoluted tubules, loop of Henlé and collecting duct 2.72 describe ultrafiltration in the Bowman’s capsule and the composition of the glomerular filtrate 2.73 understand that water is reabsorbed into the blood from the collecting duct 2.74 understand that selective reabsorption of glucose occurs at the proximal convoluted tubule 2.75 describe the role of ADH in regulating the water content of the blood 2.76 understand that urine contains water, urea and salts.

Waste products in plants

1. Carbon dioxide

Waste products in plants 1. Carbon dioxide Glucose + oxygen  carbon dioxide + water + energy C 6 H 12 O 6 + 6O 2  6CO 2 + 6H 2 O + energy

Waste products in plants 1. Carbon dioxide Glucose + oxygen  carbon dioxide + water + energy C 6 H 12 O 6 + 6O 2  6CO 2 + 6H 2 O + energy

Waste products in plants 1. Carbon dioxide Glucose + oxygen  carbon dioxide + water + energy C 6 H 12 O 6 + 6O 2  6CO 2 + 6H 2 O + energy 2. Oxygen

Waste products in plants 1. Carbon dioxide Glucose + oxygen  carbon dioxide + water + energy C 6 H 12 O 6 + 6O 2  6CO 2 + 6H 2 O + energy 2. Oxygen 6CO 2 + 6H 2 O + energy  C 6 H 12 O 6 + 6O 2 carbon dioxide + water + energy  Glucose + oxygen

Waste products in plants 1. Carbon dioxide Glucose + oxygen  carbon dioxide + water + energy C 6 H 12 O 6 + 6O 2  6CO 2 + 6H 2 O + energy 2. Oxygen 6CO 2 + 6H 2 O + energy  C 6 H 12 O 6 + 6O 2 carbon dioxide + water + energy  Glucose + oxygen

Waste products in plants 1. Carbon dioxide Glucose + oxygen  carbon dioxide + water + energy C 6 H 12 O 6 + 6O 2  6CO 2 + 6H 2 O + energy 2. Oxygen 6CO 2 + 6H 2 O + energy  C 6 H 12 O 6 + 6O 2 carbon dioxide + water + energy  Glucose + oxygen From respiration From photosynthesis

Stomata and excretion Cross section through a leaf Lower epidermis – note the presence here of stomata (tiny pores surrounded by guard cells). Inter-cellular air spaces

Stomata and excretion Cross section through a leaf CO 2 O2O2 Both gases diffuse out through the stomata

Content Lesson 6 i) Excretion Flowering plants 2.67 understand the origin of carbon dioxide and oxygen as waste products of metabolism and their loss from the stomata of a leaf Humans 2.68 recall that the lungs, kidneys and skin are organs of excretion 2.69 understand how the kidney carries out its roles of excretion and osmoregulation 2.70 describe the structure of the urinary system, including the kidneys, ureters, bladder and urethra 2.71 describe the structure of a nephron, to include Bowman’s capsule and glomerulus, convoluted tubules, loop of Henlé and collecting duct 2.72 describe ultrafiltration in the Bowman’s capsule and the composition of the glomerular filtrate 2.73 understand that water is reabsorbed into the blood from the collecting duct 2.74 understand that selective reabsorption of glucose occurs at the proximal convoluted tubule 2.75 describe the role of ADH in regulating the water content of the blood 2.76 understand that urine contains water, urea and salts.

Organs of excretion

Organs of excretion The lungs excrete carbon dioxide from respiration and also water vapour.

Organs of excretion The kidneys excrete urea, water and other metabolic waste

Organs of excretion The skin secretes sweat, maintaining levels of salt, and controlling body temperature

Kidneys The kidneys regulate the amount of water and ions in the blood and remove all UREA

What is urea? In the liver, excess proteins are broken down into amino acids. These amino acids are further broken down to form toxic ammonia, which is immediately converted to urea and carried to the kidneys in the bloodstream.

Kidneys The kidneys are involved in the process of OSMOREGULATION - This is the control of water concentration in the blood and body fluids.

Kidneys The kidneys are involved in the process of OSMOREGULATION - This is the control of water concentration in the blood and body fluids. The water levels in the blood are controlled by ADH, a hormone secreted by the pituitary gland in the brain

Kidneys The NEPHRON is the basic structural unit of the kidney.

Kidneys The NEPHRON is the basic structural unit of the kidney. Each kidney normally contains between 800,000 and 1.5 million nephrons.

Kidneys The NEPHRON is the basic structural unit of the kidney. Each kidney normally contains between 800,000 and 1.5 million nephrons. The nephrons are often referred to as the kidney tubules.

Kidneys In the nephron nearly everything is squeezed out of the blood.

Kidneys In the nephron nearly everything is squeezed out of the blood. The substances we need to keep are reabsorbed back into the blood.

Kidneys In the nephron nearly everything is squeezed out of the blood. The substances we need to keep are reabsorbed back into the blood. Unwanted substances are released as urine.

Kidneys In the nephron nearly everything is squeezed out of the blood. The substances we need to keep are reabsorbed back into the blood. Unwanted substances are released as urine.

The Kidney Nephron

GLOMERULUS – a coiled capillary.

The Kidney Nephron GLOMERULUS – a coiled capillary. BOWMAN’S CAPSULE – a cup-shaped structure where ultra- filtration occurs

The Kidney Nephron ULTRAFILTRATION occurs in Bowman’s Capsule. Lots of water plus all the smaller molecules are squeezed out of the blood, under high pressure, into the tubules. Only red blood cells and larger proteins are left in the capillary.

The Kidney Nephron GLOMERULUS – a coiled capillary. BOWMAN’S CAPSULE – a cup-shaped structure where ultra- filtration occurs PROXIMAL CONVOLUTED TUBULE – selective reabsorption occurs here back into the blood.

The Kidney Nephron Glucose, amino acids, vitamins and water diffuse into the cells surrounding the PCT, and are then actively transported into surrounding blood capillaries.

The Kidney Nephron GLOMERULUS – a coiled capillary. BOWMAN’S CAPSULE – a cup-shaped structure where ultra- filtration occurs PROXIMAL CONVOLUTED TUBULE – selective reabsorption occurs here back into the blood. LOOP OF HENLE – (descending and ascending).

The Kidney Nephron Adjustments are made to the urine concentration if necessary, with water and salts being transferred according to the needs of the body

The Kidney Nephron Adjustments are made to the urine concentration if necessary, with water and salts being transferred according to the needs of the body Permeable to water

The Kidney Nephron Adjustments are made to the urine concentration if necessary, with water and salts being transferred according to the needs of the body impermeable to water

The Kidney Nephron GLOMERULUS – a coiled capillary. BOWMAN’S CAPSULE – a cup-shaped structure where ultra- filtration occurs PROXIMAL CONVOLUTED TUBULE – selective reabsorption occurs here back into the blood. LOOP OF HENLE – (descending and ascending). DISTAL CONVOLUTED TUBULE – final adjustments to the urine.

The Kidney Nephron In the DCT, the final concentration of the urine depends upon the amount of anti-diuretic hormone (ADH). If ADH is present then the DCT becomes permeable to water, and more water is reabsorbed back into the blood

The Kidney Nephron GLOMERULUS – a coiled capillary. BOWMAN’S CAPSULE – a cup-shaped structure where ultra- filtration occurs PROXIMAL CONVOLUTED TUBULE – selective reabsorption occurs here back into the blood. LOOP OF HENLE – (descending and ascending). DISTAL CONVOLUTED TUBULE – final adjustments to the urine. COLLECTING DUCT – takes urine to the ureter and on to the bladder

The Kidney Nephron The collecting duct is also under the influence of ADH, and further water / salt re-adjustments will take place here.

The Kidney Nephron The collecting duct is also under the influence of ADH, and further water / salt re-adjustments will take place here. Excess water, ions and all the urea now pass to the bladder in the form of urine and are eventually released from the body.

ADH and the control of water content

Anti-diuretic hormone (ADH) is a hormone released from the pituitary gland in the brain. It controls the amount of water reabsorbed by the kidneys and directly affects the permeability of the kidney tubules to water

ADH and the control of water content Blood water level TOO HIGH Detected by Pituitary Gland Less ADH released into the blood Less water reabsorbed into the blood Large volume of dilute urine Normal blood water level

ADH and the control of water content Blood water level TOO HIGH Detected by Pituitary Gland Less ADH released into the blood Less water reabsorbed into the blood Large volume of dilute urine Normal blood water level Blood water level TOO LOW Small volume of concentrated urine More water reabsorbed into the blood More ADH released into the blood Detected by Pituitary Gland

Composition of blood plasma and urine Blood plasma %Urine % Water90 – 9395 Urea0.032 Uric acid Ammonia Sodium Potassium Chloride Phosphate In a healthy person, all glucose will be reabsorbed back into the blood. If glucose is found in the blood then this is indicative of diabetes, a metabolic disease.

Content Lesson 6 i) Excretion Flowering plants 2.67 understand the origin of carbon dioxide and oxygen as waste products of metabolism and their loss from the stomata of a leaf Humans 2.68 recall that the lungs, kidneys and skin are organs of excretion 2.69 understand how the kidney carries out its roles of excretion and osmoregulation 2.70 describe the structure of the urinary system, including the kidneys, ureters, bladder and urethra 2.71 describe the structure of a nephron, to include Bowman’s capsule and glomerulus, convoluted tubules, loop of Henlé and collecting duct 2.72 describe ultrafiltration in the Bowman’s capsule and the composition of the glomerular filtrate 2.73 understand that water is reabsorbed into the blood from the collecting duct 2.74 understand that selective reabsorption of glucose occurs at the proximal convoluted tubule 2.75 describe the role of ADH in regulating the water content of the blood 2.76 understand that urine contains water, urea and salts.

End of Section 2 Lesson 6 In this lesson we have covered: Excretion