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A Level Biology > Digestion > Flashcards

Digestion Flashcards

1
Q

What is digestion?

A

The process which large (insoluble) molecules are hydrolysed by enzymes into small, soluble molecules which can be absorbed

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2
Q

Which organs are involved in digestion?

A

Mouth
Salivary glands
Oesphagus
Stomach
Liver
Gall bladder
Pancreas
Small intestine (ileum)
Large intestine
Rectum
Anus

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3
Q

What is the function of the mouth?

A

Food is ingested and teeth physically/mechanically digest the food

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4
Q

What is the function of the salivary glands?

A

Produces salivary amylase which begins the chemical digestion of starch

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5
Q

What is the function of the oesophagus?

A

Tube connecting the mouth to the stomach

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6
Q

What’s the function of the stomach?

A

A muscular bag that churns food (mechanical/physical break down) adds acid and pepsin to start the digestion process

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7
Q

What’s the function of the ileum?

A

A long tube with villi, site of final stages of digestion and absorption of monomers

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8
Q

What’s the function of the liver?

A

Produces bile (for emulsification of fats) that is stored in the gall bladder

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9
Q

What’s the function of the pancreas?

A

Produces many digestive enzymes which are released into the duodenum

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10
Q

What is the function of the large intestine?

A

Where water and ions are absorbed

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11
Q

What is the function of the rectum?

A

Storage of faeces before being expelled from the anus

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12
Q

What is ingestion?

A

When food is taken in through the mouth

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13
Q

What is absorption?

A

Where small soluble molecules are absorbed through the ileum into the blood

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14
Q

What is egestion?

A

Any food that can’t be digested is eliminated from the body (eg, cellulose, aka fibre -plant cell walls)

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15
Q

What are proteins broken down into?

A

Protestases hydrolyse the peptide bonds to form AMINO ACIDs

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16
Q

What are the different types of peptidases?

A

Endopeptidase
Exopeptidase
Dipeptidase

17
Q

What is the purpose of ENDOpeptidases?

A

Work in the stomach along the chain to produce MULTIPLE SHORTER POLYPEPTIDES

18
Q

What is the purpose of EXOpeptidases?

A

Removal terminal (ends of chain) amino acids to form DIPEPTIDES AND AMINO ACIDS

19
Q

What is the purpose of DIpeptidases?

A

They are membrane bound in the duodenum and ileum and the hydrolyse the peptide bonds between dipeptides to produce amino acids which can be absorbed via contransport

20
Q

How are carbohydrates broken down into monosaccharides?
Give an example

A

Starch is hydrolysed by amylase to form Maltose
Maltose is hydrolysed by Maltase to form alpha glucose - which can be absorbed

21
Q

Which enzymes hydrolysed lactose?

A

LactASE

22
Q

Which enzyme hydrolysed sucrose?

A

SucrASE

23
Q

How are lipids digested?

A

Lipases hydrolyse the ester bond in triglycerides to form glycerol, fatty acid and monoglycerides

24
Q

What is peristalsis?

A

Waves of muscular contractions which move food boluses into the stomach

25
Q

Give an example of an endopeptidase?

A

Pepsin
Tripsin

26
Q

What is the purpose of bile?

A

Emulsifies large lipid droplets into micelles to increase its surface area for lipases to work on

27
Q

How is the ileum adapted to increase the efficiency of absorption?

A
  • Lining of ileum folded into villi - increase the surface area
  • Villi have thin walls for short diffusion pathway
  • Epithelial cells have micro Lili
  • Inside is a rich blood supply which can carry away absorbed molecules to maintain the concentration gradient
  • Villi waft/move so we can ,is food to maintain the concentration gardient
28
Q

How are monosaccharides and amino acids absorbed into the blood?

A

Co-transport

29
Q

Describe the process of co-transport?

A

Na+/K+ pump is used on the basal membrane of epithelial cells
Na+ actively pumped out of epithelial cells into blood by active transport
Simultaneous K+ transported into epithelial cells
This creates a low Na+ ion concentration in epithelial cells
Low concentration of glucose in the lumen of the intestine compared to epithelial cell (much smaller)
Na+ diffuses down its concentration gradient by facilitated diffusion taking glucose with it
This provides energy and drives transport of glucose into the cell with it - against its concent gradient by co-transport
The glucose then moves out of epithelial cells into the blood by facilitated diffusion (using a carrier protein)

30
Q

Lipids are digested by which two chemicals?

A

Lipase
Bile salts

31
Q

Where are bile salts produced?

A

In the liver

32
Q

What is the purpose of bile salts?

A

Emulsify lipids to form tiny droplets called micelles

33
Q

What is the purpose of micelles?

A

Increase the surface area of lipids for lipase to act on

34
Q

What is a micelle?

A

A vesicle that contain fatty acids, glycerol, monoglycerides and bile salts

35
Q

How do micelles aid lipid absorption?

A

Make fatty acids more soluble in water (allows simple diffusion - lipid soluble molecules )
They carry the fatty acids to epithelial cells of the ileum
They help to maintain a higher concentration of fatty acids compared to the epithelial cells of the ileum

36
Q

What happens to fatty acids (micelles) once they enter cells?

A

Fatty acids and monoglycerides are modified into triglycerides inside the endoplasmic reticulum and Golgi body
If a protein is added to the lipid it makes chylomicron

37
Q

How do modified lipid leave the epithelial cells?

A

Vesicle containing the chylomicron are released and move towards the cell membrane
They are released by exocytosis
They are absorbed/enter the lacteal (lymphatic system)

A Level Biology (15 decks)

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