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Flashcards in Lecture 13 Deck (41):
1

What are the functions of carbohydrates?

- Energy stores, fuels, metabolic intermediates
- Protein sparing
- Prevents ketosis
- Ribose and deoxyribose sugars are part of the structural framework of RNA and DNA
- Cellulose makes up most of plant cell walls
- Carbs are linked to many proteins and lipids, where they are vitally involved in cell interactions

2

What are the two basic compounds that carbohydrates consist of?

Aldehydes and ketones

3

Give examples of 3 monosaccharides and what food they are found within.

Glucose
Galactose: milk and dairy products
Fructose: vegetable and fruit

4

Give three examples of disaccharides

Lactose: glucose and galactose
Maltose: glucose and glucose
Sucrose: glucose and fructose

5

Are starches water soluble?

NO

6

What are sources of starch for humans?

Potatoes, rice, wheat

7

What is another name for dietary fibre?

Non-starch polysaccharides

8

Why isn't dietary fibre digestible?

Their glucose links can't be broken

9

What are the properties of soluble fibre?

Dissolves in water to form gel and easily digested by bacteria in the colon (fermentable)

10

What are the properties of insoluble fibre?

Does no dissolve in water. Does not form gel and is less readily fermented

11

What happens to starch in the mouth?

Salivary enzyme amylase begins digestion
Starch is broken down to small polysaccharides and maltose

12

What happens to starch in the stomach?

Stomach acid inactivates salivary enzymes, halting starch digestion.

13

What happens to starch in the small intestine?

Starch is broken down to small polysaccharides and maltose by pancreatic amylase
Disaccharide enzymes (maltase, sucrase, lactase) hydrolyse the disaccharides to monosaccharides

14

What is another name for disaccharidase?

Oligosaccharidase

15

Where are disaccharidases found?

On the microvilli of enterocytes

16

What happens in coeliac disease?

Microvilli are sloughed off and flattened. No brush border so can't produce disaccharidases. Consumption of milk will result in inability to digest. Severe gastroenteritis from bacteria can also cause temporary lactase deficiency.

17

What are final products of complete alpha-amylase digestion?

Maltose
Maltotriose
Alpha-limit dextrins

18

What is related to total activity of oligosaccharidase and total transport capacity?

Surface area of small intestine

19

What are glucose and galactose absorbed by?

The same Na+ linked transport protein: the sodium-glucose co-transporter 1. (Active transport)

20

How is fructose absorbed?

By facilitated transport down a conc. gradient

21

What are the symptoms of lactose intolerance?

Bloating, abdominal discomfort (bacteria ferment undigested lactose, producing gas), diarrhoea

22

What are the causes for primary and secondary lactase deficiency?

Primary: genetic predisposition
Secondary: caused by bacteria (gastroenteritis) or autoimmune disease (coeliac)

23

What are the management options for lactase deficiency?

- Remove milk products
- Increase consumption gradually (secondary lactase deficiency)
- Spreading dairy intake throughout the day
- Use of enzymes

24

Where does the absorption of carbs primarily take place?

Small intestine

25

What can high consumption of fructose lead to ?

Fatty liver

26

What do proteins and fats require more of for digestion than carbs?

Water

27

What is the most common source of energy for most humans?

Carbds

28

How long do glycogen stores in the liver last for?

Hours, so dietary carbs are required on a regular basis

29

How can fat stores be used for energy? What is an issue that arises from this?

Fat stores can be converted to ketones. Ketones can be utilised as an alternative energy source but when production exceeds their use they accumulate in the blood causing ketosis, a condition which disturbs the body's normal acid-base balance.

30

What percentage of energy should be consumed from carbs?

40-65%
10-15% from simple carbs

31

What are the two types of sugar?

1) intrinsic sugars found inside fruit and vegetables (mainly fructose) and milk (lactose)
2) added free sugars (mainly sucrose)

32

How does insoluble fibre prevent constipation?

Provides mass to the faeces making elimination easier. Plant fibres attract water ensuring the stools are large and soft.

33

What can constipation lead to?

Haemorrhoids due to the exertion of excessive pressure in the large intestine during defecation

34

What are the benefits of soluble fibre?

Inhibits absorption of cholesterol and cholesterol rich bile acids form the small intestine so lowers total cholesterol and LDL cholesterol. Bacteria in the large intestine degrade soluble fibre producing by-products which are beneficial for bowel health. Binds with fatty acids. Prolongs stomach emptying time. Regulates blood sugar.

35

What foods is soluble fibre found in?

Apples, oranges, lentils,

36

What foods is insoluble fibre found in?

Wholemeal bread, weetbix, skin on sweet potatoes, potatoes and courgettes

37

What do micriobiota in the large bowel thrive on?

Dietary fibre

38

How is our microbiota determined?

The microbiome that we are contaminated with at birth and breast feeding stays with us for the rest of our lives. Can change with diet, illness or radiotherapy but is reversible.

39

How does out microbiota affect us?

Lives with us synergistically. Affects our immune system, bowel health, regulates enterocyte turnover in bowel and DNA methylation in large bowel.

40

What are the recommended servings of carbs?

Pre-schoolers: 4
Children: 5
Adults: 6

41

What is the Glycaemic Index?

How much a food will raise the blood glucose by relative to glucose