Digestion And Absorption

Question 1

Once food has reached the gut, where does it go?

Answer 1

The blood

Question 2

What happens to the large food molecules so that they can be absorbed from the gut into the blood?

Answer 2

They are digested by different enzymes to break them down into smaller pieces so they can be absorbed.

Question 3

What are large food molecules known as?

Answer 3

Polymers

Question 4

During digestion, what reaction takes place when breaking down the large food molcules?

Answer 4

Hydrolysis

Question 5

Do you add or remove water in a hydrolysis reaction?

Answer 5

You add water as a molecule is removed during the condensation reaction when they are built up.

Question 6

During hydrolysis what are carbohydrates broken down into?

Answer 6

Disaccharides and then monosaccharides

Question 7

What are lipids broken down into during hydrolysis?

Answer 7

Fatty acids and glycerol

Question 8

What are proteins broken down into during hydrolysis?

Answer 8

Amino acids

Question 9

What bonds are broken when carbohydrates lipids and proteins are digested?

Answer 9

Glycosidic, Ester bond and peptide bond

Question 10

Where are digestive enzymes produced?

Answer 10

They are produced by specialist cells in the digestive system in mammals

Question 11

What does amylase break down?

Answer 11

Starch, which is a polysaccharide made up of amylose and amylopectin both alpha glucose chain, then broken into disaccharides then monosaccharides.

Question 12

What is the disaccharide that is formed when starch is broken down?

Answer 12

Maltose

Question 13

What is the monosaccharide made when starch is broken down?

Answer 13

Glucose and glucose

Question 14

Where is amylase made?

Answer 14

The salivary glands in the mouth and pancreas which releases it into the ileum

Question 15

What happens in the mouth?

Answer 15

• The first part of digestion, the food is chewed undergoing physical digestion, this breaks the molecules into smaller pieces increasing the SA so exposed to more enzymes.
• It begins to digest sugars and starch using amylase released in the salivary gland.
• The starch is a polysaccharide which is broken down into disaccharides, by hydrolysing the starch breaking the glycosidic bond.
• Produces a bolus of food, which travels down the oesophagus once swallowed

Question 16

What is a membrane bound disaccharide?

Answer 16

They are enzymes that are attached to cell membranes of epithelial cells lining the ileum last part of small intestine. They help beak down disaccharides into monosaccharides.

Question 17

Brief outline of digestion of starch

Answer 17

Digested in mouth via chemical digestion from salivary starch, polysaccharide—> disaccharides
Final stage in ileum the pancreatic amylase and membrane bound disaccharidase break down disaccharides into monosaccharides.

Question 18

What part Des the oesophagus play in digestion?

Answer 18

The food pipe, have muscles that push bolus down into stomach

Question 19

What part does the liver play in digestion?

Answer 19

Produces bile, this neutralises the digested food that has been broken down in the stomach as has low pH, and the small intestine has an alkaline condition so needs to be neutralised otherwise digestive enzymes will denature.
The Bile also emulsifies large fat droplets in the small intestine so have increased SA so lipase so have larger surface to bind and break down

Question 20

What does else other than bile does the liver produce?

Answer 20

Lysosomes that contain lysozymes which break down toxins like alcohol.

Question 21

What role does the pancreas have in the digestive system?

Answer 21

It produces protease and peptidases, as well as amylase and lipase this is sent to the small intestine to finish digestion then sent into the into the bloodstream.

Question 22

What is the duodenum?

Answer 22

The first 12 inches of the small intestine

Question 23

What is the ileum?

Answer 23

The last part of the small intestine that has membrane bound disaccharidase attached to the epithelial cells. Breaks down maltose, lipids and proteins

Question 24

What is the monosaccharide of sucrose?

Answer 24

Glucose and fructose

Question 25

What are lipids broken down into once digested?

Answer 25

Fatty acids and monoglycerides

Question 26

What is a monoglyceride?

Answer 26

A glyceride molecule with one fatty acid attached

Question 27

Once lipids have been broken down, many fatty acids are attached?

Answer 27

Two fatty acids and one fatty acid attached to a glycerol

Question 28

Where in the body are lipids digested?

Answer 28

Liver where bile which emulsifies.
Pancreas just produce lipase.
Small intestine lipase work and digest

Question 29

What’s the difference between alpha and beta glucose?

Answer 29

Alpha glucose has the H or OH on the same level.

H \ /——-O \ / H Alpha glucose
\ / / \
OH / -——-/ \ OH

Question 30

Where is food absorbed into once digested?

Answer 30

The gut

Question 31

What does the Benedict test test?

Answer 31

The presence of reducing sugars

Question 32

Explain how to do a Benedict test.

Answer 32

Get solution you want to test, add Benedict reagent.

Heat up.

Question 33

Findings of the Benedict test.

Answer 33

After heating, if reducing sugar present solution goes red/orange/yellow/green.
If non reducing sugar present it stays blue.

Question 34

If solution stays blue what do you do next?

Answer 34

You add hydrochloric acid to break down the glycosidic of the disaccharides into monosaccharides which is a reducing sugar.
Add sodium hydrocarbonate.
Reheat if stay blue there’s no non-reducing sugars present
If go red then non reducing sugar is present.

Question 35

What are micelles?

Answer 35

When lipids have been broken down by bile, the fatty acids and monoglyceride attached to bile salts to form micelles

Question 36

What digests proteins?

Answer 36

Peptidases

Question 37

What do endopeptidases do?

Answer 37

They hydrolyse peptide bonds in the peptide chain.

[]-[]-[]-[]-[]-[]-[] ——> []-[]-[]-[]-[] + []-[]
^
Endopeptidases

Question 38

What do exopeptides do?

Answer 38

They hydrolyse peptide bonds at the end of the peptide chain

Question 39

What are dipeptidases?

Answer 39

They are exopeptidases that work specially on dipeptides, they separate two amino acids that make up a dipeptide by hydrolysising peptide bond.

Question 40

Where are dipeptidases found?

Answer 40

Located in the cell surface membrane of epithelial cells in the small intestine

Question 41

What is the test for starch and what are the results?

Answer 41

Iodine, drop of iodine in solution,coif stay orange no starch present and if go purple then starch present.

Question 42

How is sucrose digested?

Answer 42

Sucrose, the enzyme that breaks down sucrose is a membrane bound disaccharidase attached to the cell membrane of epithelial cell in small intestine helping hydrolyse glycosidic bonds. Breaking down into glucose and fructose

Question 43

How is lactose digested?

Answer 43

The small intestine produces lactase which breaks down glycosidic bonds from membrane bound disaccharidase in lining of ileum. To form monosaccharides which are glucose and galactose.

Question 44

What is lactose intolerance?

Answer 44

The inability to digest lactose found in sugar and diary products, occurs when body doesn’t produce enough lactase on ileum to break down lactose into glucose and galactose. This means lactose stays in the bloodstream causing it to be broken down by colon releasing fatty acids and CO2 lead to bloating and diahorrea.

Question 45

Draw and label an amino acid.

Answer 45

R (variable group) 
              |
H2N -  C  - COOH (carboxyl group) 
              | 
             H 
Amino 
 group

Question 46

What test tests for proteins?

Answer 46

The Biruet test

Question 47

What do you do in the Biruet test?

Answer 47

Add a few drops of sodium hydroxide to substance make it alkali. Add copper sulphate II
If proteins present go purple
If no proteins present stay blue

Question 48

What two atoms bond together in a peptide bond?

Answer 48

C and N

Question 49

What is the primary structure of a protein?

Answer 49

The sequence of amino acids in a polypeptide chain

Question 50

What is the secondary structure?

Answer 50

When hydrogen bonds form between the chain causing it coil into an alpha helix or fold into beta pleated sheets.

Question 51

What the tertiary structure?

Answer 51

The coiled or folded chains coil and fold further, disulphide bonds are formed when two of the cysteine amino acids join together by their sulphur atoms. STRONGER AS THEY ARE COVALENT BONDS. Hydrogen and ionic bonds are also formed.
3D structure.

Question 52

What is the quarternary structure?

Answer 52

The quaternary structure is the way several different polypeptide chains are assembled.

Question 53

What is induced fit?

Answer 53

When a substrate first binds to the active site of the enzyme forming an enzyme-substrate complex, the active site changes shape to fit around the substrate and stays that way to fit other substrates that shape

Question 54

How does the enzyme’s structure relate to its function?

Answer 54

Its tertiary structure makes it specific meaning it fits certain substrates complimentary to the shape of the active site

Question 55

How can enzyme controlled reactions be measured?

Answer 55

Measure how fast the product is being produced- measure the substance initially and throughout and time increase of mass.
Measure how fast substrate broken down- measure the amount of substrate left throughout reaction. Then calculate rate of reaction.

Question 56

How does the temperature affect the rate of reaction?

Answer 56

By increasing the temp it gives more kinetic energy to enzymes and substrates meaning more frequent and vigorous collisions causing an increase in the formation of enzyme-substrate complexes increasing the rate of reaction. If temp too high, too much kinetic received collided to harsh,y causing bonds in enzyme to break causing change in shape of active site.. Denatures and not e-s complex not increase rate.

Question 57

How does the pH affect enzyme controlled reaction?

Answer 57

If right pH the rate is increased as optimum pH for enzymes they work best then. If wrong pH the H+ or OH- disrupt the ionic bonds on the tertiary structure causing a change on shape in the tactile site causing it to denature and no enzyme substrate complex formed

Question 58

How does the substrate concentration affect the rate of an enzyme controlled reaction?

Answer 58

By increasing the substrate concentration it increases rate of reaction as more likely to collide with enzymes and form enzyme substrate complexes. After the saturation point when all if the active sites are used up, the rate does no increase anymore so additional enzymes substrate complexes can be formed.

Question 59

How do competitive inhibitors affect reactions?

Answer 59

• Competitive inhibitors are similar shapes to the substrate and compete complimentary bond with the active site. This decreases the rate of reaction as it makes it less likely for enzyme substrate complexes to be made.
  By increasing the concentration of substrates it will increases the rate of reaction to a certain point.

Question 60

How do non competitive inhibitors affect reactions?

Answer 60

Non competitive inhibitors don’t compete with substrate to bind to the active site as it bonds away from the active site but it changes the shape of the active site causing it to denature meaning that substrates can’t bind to it. So enzyme substrate complexes not formed and decrease rate of reactions. By increasing the concentration of substance will not increase the rate of reaction.

Question 61

Complete the equation:

Lactose+ _____________ —> Glucose + ___________

Answer 61

Water and Galactose