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A level Biology OCR A > 15.4 Excretion, Homeostasis & the Liver > Flashcards

15.4 Excretion, Homeostasis & the Liver Flashcards

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1
Q

What is excretion?

A

Removal of WASTE products

of METABOLISM from body

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2
Q

What are the main waste products in mammals?

A

CARBON DIOXIDE

BILE PIGMENTS

NITROGENOUS WASTE (UREA)

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3
Q

What are the blood vessels of the liver?

A

Hepatic artery

Hepatic vein

Hepatic portal vein

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4
Q

What are the main cells of the liver called?

A

hepatocytes

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5
Q

What are hepatocytes?

A

Main cells of the liver

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6
Q

Why do hepatocytes have large nuclei, prominent golgi apparatus and many mitochondria?

A

they are highly metabolically active

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7
Q

What are sinusoids?

A

spaces in liver lobule

brings oxygen + nutrient rich blood close to hepatocytes for diffusion.

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8
Q

What type of cells do sinusoids contain?

A

Kupffer cells

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9
Q

What are Kupffer cells?

A

macrophage-like cells found in sinusoids

which PHAGOCYTOSE foreign particles

protecting the liver from DISEASE

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10
Q

What are canaliculi?

A

channels in the liver lobule

which hepatocytes secrete bile into

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11
Q

What does bile contain?

A

bilirubin, a pigment from breakdown of haemoglobin

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12
Q

What is the bile duct?

A

vessel where bile drains into from the canaliculus

carries bile to gallbladder

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13
Q

What is a portal triad?

A

3 vessels found together in liver lobule

hepatic portal vein + hepatic artery + bile duct

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14
Q

In the liver, how is blood detoxified & removed of foreign particles, and how do hepatocytes receive nutrients?

A
  1. blood from HEPATIC PORTAL VEIN + HEPATIC ARTERY mix in SINUSOID
    - Venous blood contains TOXIC BYPRODUCTS of metabolic processes, so DETOXIFIED (using catalase + alcohol dehydrogenase)
    - Mixed blood contains high concentration of O2 + nutrients, diffuses into hepatocytes.
  2. Foreign particles phagocytosed by KUPFFER CELLS
    - lowers risk of disease
  3. Blood drains into CENTRAL VEIN + transported to heart via HEPATIC VEIN
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15
Q

Which vessels does blood enter the liver lobule sinusoid by?

A

hepatic portal vein + hepatic artery

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16
Q

Which vessel does blood leave the liver lobule by?

A

central vein

17
Q

How is bile formed, secreted + transported in the liver lobule?

A
  1. hepatocytes produce bile from BILIRUBIN
  2. SECRETED into CANALICULUS
  3. drains into BILE DUCT
  4. carried to GALLBLADDER for storage
18
Q

What is bilirubin and what is it produced from?

A

yellow pigment

produced from breakdown of haemoglobin

19
Q

What are the functions of the liver?

A

CARBOHYDRATE METABOLISM (glucoregulation)

DEAMINATION OF EXCESS AMINO ACIDS

DETOXIFICATION

20
Q

What happens when blood glucose levels rise?

A

insulin levels rise (secreted by pancreas)

stimulates hepatoctes to convert glucose to glycogen

21
Q

What happens when blood glucose levels decrease?

A

glucagon levels increase (secreted by islets of langerhans in pancreas)

stimulates hepatocytes to break down glycogen into glucose

22
Q

What is deamination?

A

removal of amine group from an amino acid

23
Q

Why are some amino acids in excess?

A

diet is unbalanced, never provides amino acids in perfect balance

24
Q

Why must excess amino acids be either transaminated or deaminated?

A

body cannot store amino acids

25
Q

What is transamination?

A

conversion of an amino acid type in excess

into an amino acid which is in short supply.

26
Q

What is the process of the detoxification of ammonia called?

A

Ornithine cycle

27
Q

What is the neutralisation of toxic products in the liver called?

A

detoxification

28
Q

What substances are detoxified in the liver and using which enzyme?

A

hepatocytes contain catalase + alcohol hydrogenase:

catalase: H2O2 ⟶ H2O + H2

alcohol hydrogenase: ethanol ⟶ ethanal ⟶ ethanoate

29
Q

Which enzymes are contained in hepatocytes?

A

catalase + alcohol dehydrogenase

30
Q

What 2 processes can excess amino acid types undergo?

A

transamination

deamination

31
Q

What is the ornithine cycle?

A

series of ENZYME CONTROLLED reactions

in the LIVER

converting AMMONIA from deamination ⟶ UREA

32
Q

What are the steps of the ornithine cycle?

A
  1. amino acid deaminated ⟶ amine group ⟶ ammonia
  2. NH3 + CO2 + Ornithine ⟶ Citrulline + H2O
  3. Citrulline + NH3 ⟶ Arginine + H2O
  4. Arganine + 2H2O ⟶ Ornithine + Urea
33
Q

What is the formula for urea?

A

CN2H4O

A level Biology OCR A (103 decks)

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