OCR A2 Biology: Excretion

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A-Level Biology Flashcards on OCR A2 Biology: Excretion, created by hannawin98 on 17/05/2016.
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Flashcards by hannawin98, updated more than 1 year ago
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Question Answer
What is excretion? The removal of the waste products of metabolism from the body
What is the function of the liver? 1. Break down metabolic waste products into less harmful products
What does the hepatic artery do? Supply the liver with oxygenated blood from the heart
What does the hepatic vein do? Takes deoxygenated blood away from the liver
What does the hepatic portal vein do? Brings blood from the duodenum and ileum (parts of the small intestine), to the Liver, so it can break down ingested and harmful substances.
What does the bile duct do? Takes bile to the gall bladder to be stored
What is bile? A substance produced by the liver to emulsify fats
What is deamination? The process which removes nitrogen-containing amino acids from excess amino acids
What does deamination produce? Ammonia and organic acids
What happens to the organic acids? 1. Respired to give ATP 2. Converted to a carbohydrate and stored as glycogen
Why does ammonia enter the ornithine cycle? It is too toxic to excrete directly
What in the ornithine cycle combines with ammonia? Carbon Dioxide
What does this produce? Citrulline
What happens to the Citrulline next? It is combined with more Ammonia
What does ammonia and citrulline produce? Arginine
What combines with Arginine? Water
What does water and Arginine produce? Urea and ornithine
What is detoxification? The process in which harmful substances, such as alcohol, are broken down into less harmful compounds in order to be excreted
What is alcohol broken down into? Acetic acid
What can excess alcohol lead to? Cirrhosis of the Liver (The cells die and scar tissue blocks the blood flow)
What can excess paracetamol lead to? Liver and Kidney failure
What can excess insulin lead to? A lack of blood glucose
What is ultrafiltration? The filtering of the blood into the Kidneys
How does ultrafiltration work? 1.Blood enters the glmoerulus from the wide afferent arteriole. 2. The narrow efferent arteriole that take blood away causes the glomerulus to be under high pressure 3. This forces small substances like urea out of the blood capillaries.
What three layers do filtered substances pass to enter the Bowman's capsule? 1. Capillary endothelium 2. Basement membrane 3. Podocytes, epithelium of the Renal Capsule
What is selective reabsorption? The reabsorption of useful substances from the kidney nephrons back into the blood
What is selectively reabsorbed in the PCT? 1. Amino acids 2. Glucose 3. Vitamins 4. Salts 5. (Some) Urea
How do these get reabsorbed back into the blood? Active transport (Urea is by diffusion)
Where is water reabsorbed? The Loop of Henle, DCT and the Collecting Duct
What do the descending limb and ascending limb form? A counter-current multiplier mechanism
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