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A Level Biology Paper 1 > Digestion > Flashcards

Digestion Flashcards

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1
Q

What is the digestive system

A

A tube extending from the mouth throughout the body to the anus
With glands that produce enzymes
Consists of organs with specialised functions to perform in the breakdown and absorption of food molecules and water

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2
Q

Digestion

A

Process of hydrolysing large, insoluble polymers into small soluble molecules with enzymes
That can then be assimilated into biological molecules once absorbed into the blood

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3
Q

5 steps to digestion

A 
Ingestion; Eating, mechanical breakdown
Digestion; Hydrolysis, smaller molecules
Absorption; Small intestine into blood
Assimilation; Integrating into body for function
Egestion; Removal of waste
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4
Q

4 glands and their enzymes

A

Salivary; salivary amylase
Stomach; Endopeptidases and exopeptidases
Pancreas; Pancreatic amylase, lipase, exopeptidases
Ileum; Membrane bound dipeptidases and disaccharidases

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5
Q

Salivary gland function

A

Secretes saliva containing amylase

Hydrolyses starch into amylase

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6
Q

Ileum function

A

Chemical digestion of carbs, fats, proteins by enzymes
Absorption of most digested food
Maltase embedded in epithelium cell membrane to hydrolyse maltose into glucose for rapid absorption

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7
Q

Oesophagus function

A

Carriage of food to stomach by peristalsis of the walls

contraction and relaxation of muscle cells and tissues to push food along

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8
Q

Pancreas function

A

Secretes pancreatic juices (amylase, carbohydrase’s, endopeptidases, exopeptidases, lipases)

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9
Q

buccal purpose

A

Mechanical digestion of food due to crushing of food by teeth
Chemical digestion by salivary amylase

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10
Q

Rectum function

A

Stores faeces

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11
Q

Function of stomach

A

Muscular sac
Contraction of wall muscles churn up food (mechanical)
Secretion of hydrochloric acid to kill microorganisms and maintain optimum pH for enzymes
Chemical digestion of proteins by proteases

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12
Q

Function of colon

A

Absorption of water from food

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13
Q

Function of anus

A

Site of egestion

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14
Q

Explain the digestion of starch

A

Food is ingested
Undergoes mechanical digestion by teeth in the mouth
Then mixed with salivary amylase in saliva
Which hydrolyses the glycosidic bonds to produce maltose (chemical digestion)
Salivary amylase denatured in the stomach due to the acidic pH
In small intestine the pancreatic amylase continues to hydrolyse starch into maltose
Maltose hydrolysed into glucose by maltase enzymes embedded in epithelial cell membrane
Glucose can then be absorbed

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15
Q

Describe the role of digestive enzymes in the complete breakdown of starch

A

Amylase:
Synthesised and secreted from salivary gland and pancreas
Hydrolyses glycosidic bonds in starch into maltose

Maltose:
Embedded in membrane of epithelial cells of ileum
Hydrolyses glycosidic bonds in maltose into glucose

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16
Q

Co transport of glucose/AA across the epithelial cell membrane structure for easy recall

A
  1. Sodium potassium pump
  2. Concentration gradient
  3. Theory of co transport
  4. Facilitated diffusion
  5. Sodium gradient
  6. Glucose gradient
  7. Facilitated diffusion into blood
17
Q

Co transport of glucose across the epithelial cell membrane

A

Na+ actively transported out of epithelial cell into blood by Na+/K+ pump
Creating a concentration gradient of sodium between lumen of ileum and epithelial cell
Co-transporter protein has 2 binding sites complementary to Na+ and glucose. Moved across when both bind
Both enter by facilitated diffusion
Na+ diffuses in down its concentration gradient
Glucose actively transported in against its concentration gradient
Glucose moves from the epithelial cell into the blood by facilitated diffusion

18
Q

Advantage of stomach wall muscle churning up food

A

Mechanical digestion
Increases the rate of digestion by increases the number of successful collisions per second between enzymes and substrates

19
Q

Purpose of the sodium potassium pump

A

Maintains a concentration gradient of sodium between the lumen of the ileum and the epithelial cell
So both Na+ and glucose can enter by facilitated diffusion
Keeps Na+ low inside the cell
3Na+ out and 2K+ in creates an electrochemical gradient

20
Q

Why does the hydrolysis of triglycerides make solutions acidic

A

Hydrolysed into glycerol and fatty acids

Fatty acids are acidic so lowers pH

21
Q

Lipid digestion

A

Only occurs in lumen of ileum
In the stomach, lipids are churned up into fat droplets
Bile produced in the liver, stored in the gall bladder and released into the small intestine with food
Bile salts in bile emulsify fat droplets
Not digestion but increases the surface area for faster rate of digestion
Increased surface area for lipase to hydrolyse lipids for efficient digestion
Into glycerol, fatty acids, monoglycerides
Bile salts activate lipase

22
Q

How do chlomicrojs leave the epithelial cell and why

A

Exocytosis
Bulk transport because very large
Too big to leave otherwise

23
Q

Explain the tole of the golgi body in lipid absorption

A

Modifies triglycerides
Combines triglycerides with proteins to form lipoproteins
Packages chylomicrons for exocytosis

24
Q

Give examples of endopeptidases

A

Trypsin
Pepsin
Chymotrypsin

25
Q

Examples of exopeptidases

A

Dipeptidases
Carboxypeptidases
Aminopeptidases

26
Q

Why must chylomicrons be water soluble

A

Chylomicrons transport triglycerides into a lymph vessel by exocytosis
They then enter the blood so must be water soluble to be carried in the blood

27
Q

What are all disaccharided and what does this mean

A

Soluble so they lower water potential

28
Q

Bile salts

A

Produced in the liver

Stored in the gall bladder

29
Q

Explain protein digestion

A

Polypeptides hydrolysed in the stomach by proteases (enzymes)
Endopeptidases hydrolyse the peptide bonds within the polypeptide
Producing smaller shorter polypeptide chains
That increase the surface area for next enzyme to make digestion faster and more efficient
Exopeptidases hydrolyse the peptide bonds at the terminal ends of protein, removing 1 or 2 AA at a time
Specific, one group complementary to N terminal and the other C terminal
AA and dipeptides produced
Dipeptidases embedded in the cell surface membrane of epithelial cells
Which hydrolyse dipeptides into AA so they can be absorbed by co-transport

30
Q

Co-transport of amino acids across the epithelial cell membrane into blood

A

Na+ actively transported out of epithelial cell into blood by Na+/K+ pump
Creating a concentration gradient of sodium between lumen of ileum and epithelial cell
Co-transporter protein has 2 binding sites complementary to Na+ and amino acids. Moved across when both bind
Both enter by facilitated diffusion
Na+ diffuses in down its concentration gradient
Amino acids actively transported in against its concentration gradient
Amino acids move from the epithelial cell into the blood by facilitated diffusion

31
Q

Lipid absorption

A

Lipid droplets mixed with bile salts and emulsified to form smaller droplets
Which increases the surface area for the action of lipase
Triglycerides hydrolysed into glycerol, fatty acids and monoglycerides
Glycerol and fatty acids form micelles
Micelles enter epithelial cell by simple diffusion
At the S.E.R fatty acids and glycerol recombine to form triglycerides
At the Golgi apparatus triglycerides are modified and proteins added to form the lipoproteins chylomicrons and packaged into vesicles
Chylomicrons are water soluble so can be carried in the blood
Chylomicrons are transported into a lymph vessel by exocytosis then enter the blood

32
Q

Define absorption

A

Moving of products of digestion from the small intestine into the blood

33
Q

Why can’t humans digest cellulose

A

Do not produce cellulase

Unable to hydrolyse the glycosidic bonds

34
Q

Adaptation of the epithelial cell

A

Large surface area for the absorption of products of digestion from microvilli (finger like projections)
Enzymes embedded in membrane so products available for absorption rapidly once hydrolysed
Lots of mitochondria to produce the large amount of ATP needed for active transport

35
Q

Advantage of endopeptidases and exopeptidases hydrolysing at the same time

A

The endopeptidases produce many short polypeptide chains
More ends for action of exopeptidases
To produce amino acids
For faster absorption

A Level Biology Paper 1 (16 decks)

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