Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

HUBS192 > Lecture 26- chemical digestion > Flashcards

Lecture 26- chemical digestion Flashcards

1
Q

What are carbohydrates important for? What are the most common examples?

A
  • Important source of energy

- Starch, glycogen

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is the structure of carbohydrates like?

A
  • Chains of monosaccharides
  • Example of monosaccharide is glucose
  • Joined by a1-4 glycosidic bonds (at least in the case of starch + glucose)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What are disaccharides and what are some common examples?

A
  • Two monosaccharides joint together

- Sucrose, lactose, maltose

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

How do we usually ingest carbohydrates and what does this mean?

A

-Usually ingest as large indigestible molecules (many units joint together) which then have to be broken down to the smallest building block (monosaccharides) to be digested + absorbed.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are proteins important for?

A
  • Not a source of energy

- Proteins are required as they break down to amino acids (most of our body is made of proteins)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

How many amino acids are there in the body? How many can be synthesized? What does this mean?

A
  • 21 amino acids in body
  • 12 can be synthesized
  • Others essential, cannot be synthesized (or too energy expensive
  • These therefore have to be gained from our diet
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What are some amino acids that can not be produced by the body?

A

Histidine, leucine lysine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is the breakdown of where we source protein?

A
  • 50% Diet

- 50% Endogenous proteins (come from within e.g. enzymes and immunoglobins secreted in the small intestine)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is the structure of proteins?

A
  • Base unit is an amino acid
  • These form long chains via peptide bonds
  • It is these long chains that are the proteins
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What are lipids important for?

A

Not essential but…

  • Important source of energy
  • Source of fat soluble vitamins A, D, E & K
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Why do lipids slow gastric emptying?

A

Because they are complex to digest + absorb (take longer to break down)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is the main type of lipid? What is it’s structure?

A
  • Mainly triglycerides

- These consist of a Glycerol back bone with 3 fatty acids attached

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

How does the length of the fatty acids attached to the glycerol backbone vary?

A

Can be…

  • Short chain fatty acids < 6 carbons
  • Medium chain fatty acids – 6 to 12 carbons
  • Long chain fatty acids – 12 – 24 carbons
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Why do we need chemical digestion?

A

We ingest nutrients in the from of large complex molecules (carbohydrates, proteins, lipids) but can only absorb nutrients as small molecules. Therefore need first mechanical and then chemical digestion to occur so that nutrients can be absorbed and then used.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Chemical digestion utilizes

A

Digestive enzymes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

How does mechanical digestion aid chemical digestion?

A

Mechanical digestion breaks up food increases surface area available for chemical digestion as enzymes can only act at the surface of the particles.

17
Q

What are some features of digestive enzymes?

A
  • Are extracellular
  • Are organic catalysts
  • Very specific (different enzymes are needed for different substrates)
  • Have optimum pH
18
Q 
What are the optimum pH's of...
-Salivary enzymes
-Gastric enzymes
-Small intestinal enzymes
??
A
  • Salivary enzymes= 7-8 (Alkaline)
  • Gastric enzymes= 1-2 (acidic)
  • Small intestinal enzymes = 7-8 (Alkaline)
19
Q 
What are the names of the specific enzyme type that digests...
-Carbohydrates
-Proteins
-Fats
??
A
  • Carbohydrates= Amylase
  • Proteins= Proteases
  • Fats= Lipases
20
Q

How do digestive enzymes act as organic catalysts?

A
  • Enzyme combines with substrate to form enzyme-substrate complex. This then produces a product and the enzyme at the end.
  • Therefore the enzyme acts as a catalyst as you get it back in the end (is not used up)
21
Q

Can cellulose be digested? What does this prove about specifity?

A
  • Cellulose is the structural polysaccharide of plants and we have lots in our diet
  • Its made of long chains of b 1- 4 glycosidic bonds
  • We do not have the enzyme specific to breaking these bonds (only have alpha amylase) and therefore cellulose cannot be digested (acts as dietary fiber)
22
Q

What are the two general stages of digestion?

A
  • Stage one= Luminal digestion. Initial digestion involving enzymes secreted into lumen. In salivary glands/mouth, stomach, small intestine (via pancreatic enzymes)
  • Stage two= Contact digestion. Only occurs in the small intestine completing digestion before absorption. Involves enzymes produced by enterocytes and attached to brush border of enterocytes
23
Q

Describe stage 1 of carbohydrate digestion…

A

Luminal digestion:

  • Using salivary and pancreatic amylase
  • Polysaccharides converted to oligosaccharides and disaccharides (smaller components via breaking bonds)
24
Q

Describe stage 2 of carbohydrate digestion…

A

Contact digestion:

  • Disaccharides converted to monosaccharides (these can then be absorbed)
  • Involves the enzymes (bound to brush border) which are specific to the disaccharide (Sucrase, lactase, maltase)
25
Q

Why is both salivary and pancreatic amylase required for the digestion of carbohydrates?

A

Salivary amylase is denatured when it reaches the stomach (low pH) therefore, need more enzyme created by the pancreas (enters into duodenum) to complete the breakdown.

26
Q

Describe stage 1 of protein digestion…

A

Luminal digestion:

  • Pepsin in stomach
  • Trypsin, chymotrypsin, carboxypeptidase in small intestine (Secreted by pancreas)
  • Converts proteins into polypeptides
27
Q

Describe stage 2 of protein digestion…

A

Contact digestion:

  • Involves peptidases
  • Many types attached to brush border
  • Convert polypeptides into individual amino acids (which can then be absorbed)
28
Q

Where does lipid digestion occur?

A

-Lumen of small intestine

29
Q

Is there contact digestion in lipid digestion?

A

No

30
Q

What are the main and minor enzymes in lipid digestion?

A
  • Pancreatic lipase main digestive enzyme

- Lingual lipase and gastric lipase have minor role

31
Q

What is the problem with lipid digestion?

A

-Digestive enzymes exist dissolved in luminal fluid
-This is no problem for carbohydrates and
proteins as they are Soluble in water
-Lipids (fats) however are insoluble in water (this is why a more complex process is required

32
Q

What are the four stages of lipid chemical digestion?

A
  • Emulsification (via Motility)
  • Stabilization (via Bile salts)
  • Digestion (Hydrolysis via Enzymes)
  • Formation of micelles (via Bile salts)
33
Q

What happens in stage 1 (emulsification) of lipid digestion?

A
  • Motility breaks up lipid droplets into small droplets forming what is known as an emulsion
  • Droplets are 0.5 -1.0 µm
  • This breaking up into smaller droplets increases the surface area for digestion (enzymes can go in)
34
Q

What happens in stage 2 (stabilization) of lipid digestion?

Where does it occur?

A
  • Bile salts which are secreted by liver & concentrated in gallbladder are released into small intestine with the arrival of food. These have a hydrophobic (water hating) and a negatively charged hydrophilic side (water loving) and stabilize the emulsion in small intestine by the surrounding the droplets (Preventing them from recombining again). This works to reduce the size of the emulsion droplets and further increases the surface area available for enzymes to act.
  • Occurs in small intestine
35
Q

What happens in stage 3 (digestion/ hydrolysis) of lipid digestion?

A
  • Occurs in small intestine at surface of emulsion droplets
  • Involves lipase and cofactor colipase (Both secreted by pancreas)
  • Colipase anchors lipase to surface of droplet so that it can carry out its function
  • Lipase converts triglycerides to Monoglyceride + Free fatty acids
36
Q

What happens in stage 4 (formation of micelles) of lipid digestion?

A
  • Products of fat digestion are insoluble in water (Monoglycerides +Long chain fatty acids)
  • These are therefore kept in solution through the formation of micelles
  • Micelles are small droplets (4-6 nm diameter). Which consist of 20-30 molecules. Bile salts (amphipathic-2 sides) form outside with water loving side facing outwards. In the center have fatty acids and monoglycerides so they are not exposed to water.
37
Q

Where does stage 1 of lipid digestion (emulsification) occur and how does it differ in different places?

A
  • Occurs in the Stomach via retropulsion. This is simple emulsion
  • Small intestine via segmentation. This is more complex emulsion and invovled bile salts which stabilize the droplets preventing them from coming together again

HUBS192 (38 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions