Brainscape's Knowledge GenomeTM

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


See full index

Sustainable Agriculture, Food & Nutrition > Carbohydrates 1 > Flashcards

Carbohydrates 1 Flashcards

Basics, glucose/glycogen/insulin/glucagon etc.

1
Q

What is the general formula for carbohydrates?

A

(CH2O)x - e.g. glucose is C6H12O6.

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

What does DP stand for in relation to the classification of carbohydrates?

A

Degree of polymerisation - this is the length of the carbon chain, which is used to classify carbohydrates.

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

What is the DP of the following?:

Monosaccharides
Disaccharides
Oligosaccharides
Polysaccharides

A

Monosaccharides - 1
Disaccharides - 2
Oligosaccharides - 3-9
Polysaccharides - 9+.

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

Monosaccharides and disaccharides are both…?

A

…sugars.

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

C6H12O6 can be three different monosaccharides - name them.

A

Glucose, galactose and fructose.

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

Pairs of what are shared in covalent bonds?

A

Electrons.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Monosaccharides are linked by what type of bond, in what sort of reaction?

A

Covalent glycosidic bonds, formed in dehydration reactions.

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

What does alpha and beta mean, in relation to the bonds between monosaccharides?

A

It shows whether the bond faces ‘up’ or ‘down’ (alpha = up, beta = down).

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

Which bonds between monosaccharides can mammals digest - alpha or beta?

A

Mammals can only digest alpha bonds between monosaccharides.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What do the ‘numbers’ tell us about a bond between monosaccharides - e.g. sucrose is alpha-1,2 linked glu-fru.

A

Which carbon atoms form the glycosidic bond between the two molecules, when counted from the functional group.

Therefore sucrose has an alpha bond between carbon atom 1 of glucose and carbon atom 2 of fructose.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What are the two subgroups of oligosaccharides? How do they differ?

A

Glycaemic and non-glycaemic.

GLYCAEMIC / ALPHA-GLUCANS
Digested into simple sugars and absorbed in the small intestine, potentially raising blood sugar levels. They are mostly derived from starch and have alpha-1,4 or alpha-1,6 bonds.

NON-GLYCAEMIC / NON-ALPHA-GLUCANS
Not susceptible to brush-border or pancreatic enzymes, therefore cannot be digested by enzymes in humans. Fermented in large intestine.

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

Polysaccharides can be split into what two sub-groups? Give an example of each.

A

Glycaemic (starch) and non-glycaemic (cellulose).

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

Are carbohydrates essential to sustain life?

A

No! The recommendations for dietary intake are for optimal health, a low intake of carbohydrates can cause an absence of glycogen stores and hypocholesterolaemia.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What did SACN recommend the % of total energy intake should come from free sugars in 2015? What are free sugars?

A

5%. Free sugars are added sugars including fruit juice and honey, but not lactose or sugars found in cellulose structure (i.e. whole fruits).

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

What is the SACN (2015) recommended daily intake of total carbohydrates, as a % of total energy intake?

A

50%.

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

SACN (2015) recommend how much non-starch polysaccharides (fibre) should be consumed daily?

A

30g.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Which enzyme is produced by salivary glands and the pancreas and works in the mouth and small intestine to hydrolyse polysaccharides and oligosaccharides into maltoses, maltotriose and dextrins?

A

Alpha-amylase.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is the optimal pH for alpha-amylase activity? Where is it inhibited by conditions with a very low pH?

A

The optimal pH is 6.6-6.8, its activity is inhibited by the very low pH in the stomach.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Alpha-amylase breaks which links in amylose and amylopectin? Which bonds can’t it hydrolyse?

A

Alpha-1,4 linkages are broken by alpha-amylase. I cannot hydrolyse bonds at the ends of molecules or next to 1,6 branch points in amylopectin.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Why is it helpful that further digestion of carbohydrates accurs at the brush-border of the small intestine?

A

The brush-border is close to transporter proteins which take the monosaccharides into the blood of the portal vein.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Which cells in the pancreas produce alpha-amylase?

A

Acinar cells.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

The intestinal ……………….. ………..-………… enterocytes lining the ……… of the small intestine contain various enzymes in the …………… membrane.

Name the (3) enzymes.

A

Epithelial, brush-border, villi, apical, glucosidases, disaccharidases, oligosaccharidases.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Why can’t we digest non-glycaemic carbohydrates?

HINT: there are four reasons.

A
  1. None of the enzymes in the small intestine can digest them.
  2. The enzymes to digest them do exist, but they cannot access the carbohydrate, for example when starch is locked away in a plant cell wall.
  3. Enzymes digest these carbohydrates too slowly for them to be absorbed.
  4. Monosaccharide transporters with do not exist, or function too slowly.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Which three monosaccharides are the end product of carbohydrate digestion? What happens to them after the small intestine?

A

Glucose, galactose and fructose are transported by transporter proteins across the epithelial cells of the small intestine into the blood of the portal vein, which takes them to the liver.

20
Q

What are the transport proteins associated with moving monosaccharides out of the small intestine and into the blood? Which side of the membrane are they located on and which specific monosaccharides do they transport?

A

SGLT1 - on the apical membrane of enterocytes, actively transports glucose and galactose.

GLUT5 - on the apical membrane of enterocytes, facilitates passive transport of fructose.

GLUT2 - on the basolateral membrane of enterocytes, used by glucose galactose and fructose to pass into the blood.

20
Q

What are the products of anaerobic microbial metabolism in the small intestine?

A

Hydrogen, carbon dioxide and methane - released in the breath and as flatus.

Short chain fatty acids - acetate, proprionate and butyrate - enter the blood.

Microbial biomass - waste faeces.

20
Q

Is the rate of uptake of glucose limited by the rate of absorption, or the capacity to absorb the glucose?

A

The rate of absorption.

20
Q

The rate of glucose uotake is dependent on the rate of…?

A

the rate of hydrolysis of oligosaccharides and polysaccharides susceptible to brush-border enzymes.

21
Q

What happens to the non-glycaemic carbohydrates that aren’t broken down and absorbed in the small intestine?

A

They are digested by bacteria living in the large intestine. The resulting monosaccharides are internalised by the bacteria and converted to pyruvate via the glycolytic pathway in an anaerobic reaction.

21
Q

Approximately how much glucose is taken up per day, in humans?

A

10kg.

21
Q

Which carbohydrates are fermented by bacteria in the large intestine?

A

Some sugars (e.g. lactose), non-alpha-glucan oligosaccharides, non-alpha-glucan/non-starch polysaccharides and resistant starch.

21
Q

In a typical Western diet, how much energy comes from fermentation in the large intestine?

A

5% - 10%.

22
Q

Which animals have a unique digestive system which has evolved to allow them to eat a diet rich in roughage and plant material, consisting mainly of beta-linked polysaccharides?

A

Ruminants - sheep, cattle and goats.

23
Q

Describe the specialist digestive system of ruminants.

A

Foods eaten by ruminants are exposed to microbial digestion in the rumen PRIOR to exposure to the animal’s own digestive enzymes, so food is already digested to short chain fatty acids. Anything which does make it to the large intestine is fermented.

24
Q

How much energy is provided by microbial digestion in the rumen?

A

70%-80%.

25
Q

After a meal, what level can glucose reach in the blood (in mmol)?

A

10mmol.

26
Q

After being absorbed in the small intestine, which monosaccharides enter the peripheral circulation, and which are converted into glycolytic intermediates in the liver?

A

Glucose enters peripheral circulation and is taken up by ALL tissues for metabolism.

Fructose and galactose are converted into glycolytic intermediates which can then go on to enter glycolysis.

27
Q

Blood glucose is tightly contolled in what range?

Why is it necessary to control blood glucose levels?

A

3.0-5.5mmol.

The brain and nervous system are heavily dependent on glucose and red blood cells are entirely dependent on glucose.

28
Q

What % of free energy form glycolysis is released as ATP? What % is released as heat?

A

40% ATP, 60% heat.

29
Q

Excessively high blood glucose can cause a ………………… coma. Conversely, excessively low blood glucose levels can cause a …………………… coma.

A

Excessively high - HYPERglycaemic coma.
Excessively low - HYPOglycaemic coma.

30
Q

What are the consequences of moderately high blood glucose levels?

A

The rate of glomelura filtration in the kidneys exceeds tubular respiration (glucose in urine)

Osmotic diuresis resulting in excessiive urination (polyuria) and excessive thirst (polydipsia).

Oer a long period unmanaged blood glucose levels can lead to microvascular damage to eyes, limbs etc.

31
Q

What ensures that the body has a constant supply of food and blood glucose levels to return to normal after a meal?

A

Metabolic regulation.

32
Q

Glucose is stored as ……………….. in ………. and muscle tissues.

A

Glycogen, liver.

33
Q

Glycogen stored in the liver and adipose tissue can be converted to ……… ……….. and ……………….. when required for energy.

A

Fatty acids, triacylglycerol.

34
Q

Glycogen stored in the …………. and ……………. can be converted to non-essential amino acids.

A

Liver, kidneys.

35
Q

Which molecules are synthesised into RNA, DNA, ATP, GTP, NAD and NADPH in all tissues? Which tissues is this especially high in?

A

Ribose and deoxyribose.

Liver and adipose tissue.

36
Q

In a fed state, where is glycogen synthesised from? What is the name for the synthesis of glycogen?

A

From glucose, in liver and muscle tissue.
Glycogenesis.

37
Q

Describe the structure of glycogen.

A

Long, straight glucose chains (alpha-1,4 bonds) branching every 4-8 glucose molecules (alpha-1,6 bonds).

38
Q

Which enzyme needed for glycogenesis is insulin-dependent?

A

Glycogen synthase.

39
Q

What is the name for the mobilisation of glycogen stores in a fasted state?

A

Glycogenolysis.

40
Q

Which enzyme catalyses glycogenolysis?

A

Phosphorylase.

41
Q

Which is simpler? Glycogenolysis through the liver, or muscle?

A

Liver.

42
Q

Long periods of fasting or starvation can trigger energy being obtained from non-carbohydrate sources. What is this process called, and what stimulates and inhibits it?

A

Gluconeogenesis, stimulated by glucagon and inhibited by insulin.

43
Q

What is the main site of gluconeogenesis and what are the main sources? It often happens at the same time as what process, to try and increase blood glucose levels?

A

In the liver, from pyruvate, lactate, glycerol and amino acids. Tends to happen at the same time as gluycogenolysis.

44
Q

In a fed state, excess glucose can be converted into which intermediate, which can enter the citric acid cycle and synthesise amino acids and fatty acids?

A

Acetyl CoA.

45
Q

When blood glucose levels rise in a fed state, what happens to insulin and glucagon production?

A

Insulin production stimulated in beta-cells of pancreatic islets.

Glucagon production suppressed in alpha-cells of pancreatic islets.

46
Q

In a fed state, what actions does blood glucose take? Why?

A

Increased glucose uptake in muscle and adipose tissue.

Glycogen synthesis in liver and muscle.

Increased fatty acid synthesis in adipose tissue.

Increased rate of amino acid uptake and protein synthesis.

All to reduce blood glucose levels.

47
Q

What happens to glucagon and insulin in a fasted state?

A

Glucagon is stimulated in the alpha-cells of pancreatic islets, stimulating glycogen breakdown and glyconeogenesis.

Insulin is suppressed in the beta-cells of the pancreatic islets, reducing the rate of glucose uptake in muscles and protein synthesis and increasing the release of non-esterified fatty acids.

Sustainable Agriculture, Food & Nutrition (8 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions