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LGS A-Level OCR Biology - Excretion, Homeostasis, and the Liver

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This deck covers key concepts from A-Level OCR Biology Unit 5, focusing on excretion, homeostasis, and liver functions, including protein metabolism, detoxification, and nephron processes.

Protein metabolism in the liver

Protein synthesis of plasma proteins; Deamination to form keto acid and NH2; Transamination to make new amino acids
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Key Terms

Term
Definition
Protein metabolism in the liver
Protein synthesis of plasma proteins; Deamination to form keto acid and NH2; Transamination to make new amino acids
Fate of keto acids
Kreb’s cycle (respration)
Portal triads
Hepatic Artery; Bile duct; Hepatic Portal Vein
Bile canaliculi
Drains bile from hepatacytes to bile duct
Where does deamination occur
In hepatocytes
Keto acid
An acid with a carboxylic acid group and a ketone group

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TermDefinition
Protein metabolism in the liver
Protein synthesis of plasma proteins; Deamination to form keto acid and NH2; Transamination to make new amino acids
Fate of keto acids
Kreb’s cycle (respration)
Portal triads
Hepatic Artery; Bile duct; Hepatic Portal Vein
Bile canaliculi
Drains bile from hepatacytes to bile duct
Where does deamination occur
In hepatocytes
Keto acid
An acid with a carboxylic acid group and a ketone group
Equation of deamination
Amino acid + oxygen ---> keto acid + ammonia
Ornithine cycle
2NH3 + ornithine + CO2 (from respiration) ---> H2O + urea (circulates in blood until filtered by kidney)
Detoxification of alcohol
Alcohol is broken down by hepatocytes by alcohol dehydrogenase to make ethanal which is further dehydrogenated by ethanal dehydrogenase to make ethanoate; NAD is needed to oxidise and breakdown fatty acids
Uses of ethanoate
Build up fatty acids | Cellular respiration
Pressures in the glomerulus
Hydrostatic pressure; Oncotic pressure; Capsular pressure
Calculating net pressure in the nephron
Hp - (Op + Cp)
Where does blood leave from the nephron
Efferent arteriole
Whats in the glomerular filtrate
Glucose; Amino acids; Ions (sodium, potassim, etc); Urea; Water
Where does ultrafiltration occur
Bowman's Capsule
Process of ultrafiltration
Blood flows through fenestrations in endothelium then basement membrane then podocytes (3 layers); Basement membrane consists of fine mesh of collagen fibres and glycoproteins, preventing proteins and rbc's leaving; Podocytes have projecting fingers that wrap around capillaries; Tiny slits are left between interlocked podocytes
How does blood reach Bowman's capsule
Diameter of afferent arteriole > diameter of efferent arteriole; Build up of hydrostatic pressure in glomerulus capillaries so blood is forced through slits of podocytes into Bowman's Capsule
Components of nephron
Glomerulus; Bowman's capsule; Loop of Henle; Proximal convoluted tubule; Distal convoluted tubule; Collecting duct
Glomerulus
High hydrostatic pressure mass of capillaries that filters blood
Function of proximal convoluted tubule
Selective reabsorption