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Human Nutrition > Carbohydrates > Flashcards

Carbohydrates Flashcards

1
Q

What percentage of the energy in our diet does carb make up?

A

45-65% total calories

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2
Q

What are carbs made of?

A

Carbon
Hydrogen
Oxygen

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3
Q

How can simple carbs be classified?

A

Monosaccharide (one sugar)
Disaccharide (two sugars)
Oligosaccharide (more than 3, less than 10)
Polysaccharide (more than 10)

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4
Q

What are the 3 monosaccharides?

A

Glucose
Fructose
Galactose

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5
Q

What are the 3 disaccharides

A

Maltose
Sucrose
Lactose

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6
Q

What are the 3 complex carbs?

A

Starch
Glycogen
Fiber

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7
Q

What is glucose commonly known as?

A

Blood sugar
Essential energy source for all body’s activity

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8
Q

What is fructose?

A

Sweetest sugar
Occurs naturally in fruits
In desserts/soft drinks, etc

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9
Q

Does galactose naturally occur in foods?

A

No, rarely as a single sugar

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10
Q

How do disaccharides form?

A

Putting together two monosaccharides through condensation (water removed)

Hydrolysis (water added) will cause them to seperate again

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11
Q

What is maltose made of

A

2 glucose

Produced when starch breaks down (human digestion of carbs, fermenting alcohol)

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12
Q

what is sucrose?

A

One fructose, one glucose

Table sugar

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13
Q

What is lactose?

A

Galactose and glucose

Principle carb of milk/milk products

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14
Q

How much should complex carbs form your plate

A

50%, should be the majority of what you eat

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15
Q

What is glycogen?

A

Human body stores glucose unit as glycogen in highly branched chains

Arrangement permits rapid hydrolysis

Can only store 24hrs of it

Found in limited meats, not plants

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16
Q

How is glucose released?

A

When message to release energy arrives as glycogen storage sites (liver, muscles), enzymes respond by attacking branches to make surge of glucose avaliable

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17
Q

What is a starch?

A

Long chains of thousands of glucose molecules linked, stored in plant cells

Molecules packed side by side, body hydrolyses into glucose for energy

Wheat, grains, rice, tubers, root crops

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18
Q

What is the difference between an alpha and beta bond starch?

A

Alpha - easily digested (amylose)

Beta - are not broken down (amylopectin)

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19
Q

What is dietary fibre made of?

A

Non-starch polysaccharides - cannot be broken down by enzymes in body

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20
Q

What is the difference between soluble and insoluble fibre

A

Soluble - dissolves in water to forms a gel, lowers blood cholesterol, fermentable in colon, balances blood sugar levels, lowers risk of diabetes, satiety

Insoluble - fibres that do not dissolve in water, not very fermentable, adds bulk and soften stools, alleviates constipation and increases transit time

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21
Q

What are resistant starches and where are they found?

A

Starch that escapes digestion and can be fermented by bacteria to produce short chain fatty acids

  • physically enclose (trapped) starch, found on coarse
  • un-gelatinised (uncooked) starch (raw potatoes, green bananas)
  • retrograded amylose (starch polymers) form after starchy foods have been cooked and left to cool
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22
Q

What is physic acid?

A

Found accompanying dietry fibre

Close bonds make it impossible to determine whether dietary fibre, physic acid or both that binds with minerals, preventing their absorption

Binding - risk of mineral deficiency, lessened if fibre/mineral intake is reasonable

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23
Q

What is the goal of carb digestion?

A

Breaking down sugars and starches into small molecules (chiefly glucose) for body to absorb and use

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24
Q

What happens in the mouth in carb digestion?

A

Salivary enzyme (amylase) hydrolysis starch to shorter polysaccharides

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25
Q

What happens in the stomach in digestion?

A

Stalled bolus mixes with stomach acid and enzymes, inactive salivary amylase

Dietary fibre lingers in stomach, delays gastric emptying (satiety)

Stomach acid doesn’t contain enzymes to digest carbs

26
Q

What happens in the small intestine in carb digestion?

A

Major carb-digestive enzyme - pancreatic amylase - enters via pancreatic duct

Breaks down polysaccharides to shorter glucose chains and maltose

Goes to outer membranes of intestinal walls, where specific enzymes break down specific disaccharides

27
Q

What enzymes does maltese, sucrose and lactase break down?

A

Maltese - Breaks maltose into two glucose molecules

Sucrose - breaks sucrose into one glucose and one fructose molecule

Lactase - breaks lactose into one glucose and one galactose molecule

28
Q

What happens in the large intestine during carb digestion?

A

Dietary fibre remains in tract, attracting water, which softens stool for passge

Bacteria in GI tract also ferment some dietary fibre (forms water, gas, short-chain fatty acids)

Colon uses these fat molecules for energy

between 1-4 hours after meal, mostly digested

29
Q

How are glucose and galactose absorbed?

A

Glucose and galactose - traverses cell linking of small intestine by active transport

Requires energy in form of ATP - transport protein is loaded with sodium, then glucose/galactose

30
Q

How is fructose absorbed?

A

Absorbed by facilitated diffusion, which slows entry and produces smaller rise in blood glucose. It is ‘passive’ absorption

31
Q

How are carbs digested?

A

Unbranched chains of starch are digested slowly, place for enzymes to attack and release glucose fast

As blood from intestines circulated to lover, cells there take fructose and galactose and convert them (often to glucose)

32
Q

What is occurring in lactose intolerance?

A

Intestinal cells do not produce enough lactase (enzyme) to ensure disaccharides are digested and absorbed effectively

When more lactose is consumed than what lactase can handle, molecules remain undigested. Attracts water - causes abdominal discomfort and diarrhoea

Undigested lactose becomes food for intestinal bacteria, which multiplies and produces irritating acid and gas

33
Q

What is the role of glucose in the body?

A

glucose is the main source of energy for the central nervous system

Plays central role in carb metabolism

34
Q

How is glucose stored?

A

Stored as glycogen in liver, can release glucose into bloodstream when needed

Also stored in muscle cells - used mainly for exercise

Brain - emergency supply

35
Q

What happens when blood glucose rises?

A

Liver cells link excess glucose molecules into long branching chains of glycogen

Happens after a meal

36
Q

What happens when blood glucose falls?

A

Liver cells break glycogen by hydrolysis reactions into single molecules of glucose, releasing them into bloodstream

37
Q

Why can glycogen only be stored for short periods of time?

A

Because it holds water, is therefore bulky and cannot be stored in excess

Long-term energy uses abundant, water-free fat

38
Q

How is glucose broken down for energy?

A

Enzymes in cell breaks glucose down to carbon dioxide and water

39
Q

What is gluconeogenesis?

A

When glycogen stores become depleted, the body makes glucose from protein

40
Q

What is protein sparing?

A

The role of carbs - having an adequate amount of glucose in diet so protein can be stored

41
Q

How are ketone bodies made?

A

If less glucose than required for brain’s energy, fat fragments combine

Ketone bodies provide alternative fuel source during starvation

When production exceeds their use, accumulates in blood (called ketosis, disturbing acid-base balance)

42
Q

How does fat get made from glucose?

A

After meeting energy needs and filling glycogen stores, body stores the rest as fat

Liver forms glycerol (triglyceride)

Fat travels to fatty tissues for storage

43
Q

How does the body maintain glucose homeostasis?

A

Homeostasis: body must maintain blood glucose within limits that permit cells to nourish themselves

If glucose falls - dizzy and weak
If glucose rises - fatigued

Regulated by two hormones from pancreas: insulin and glucagon

44
Q

How does insulin work?

A

When blood glucose rises (after meal) pancreas respond by secreting insulin into blood

Insulin contacts receptors to move glucose from blood into cells, or conversion into fat

45
Q

How does glucagon work?

A

When blood glucose falls, pancreas secrete glucagon into blood.

Signals to liver to break down glycogen stores to release glucose into blood

46
Q

Why does adrenaline release glucose?

A

Adrenaline (fight or flight) signals liver to release glucose, to ensure body has energy to fuel emergencies

47
Q

Why do complex carbs delay insulin response?

A

Carbs that digest slowly prolong the presence of foods in the digestive tract, providing greater satiety

48
Q

What does epinephrine do?

A

Acts quickly to bring glucose out of storage during times of stress

49
Q

What is diabetes?

A

When blood glucose surges after meal, remains above normal levels as insulin is either inadequate or ineffective

50
Q

What is the difference between type 1 and type 2 diabetes?

A

type 1 - pancreas fail to produce insulin (genetic predisposition)

Type 2 - cells fail to respond to insulin (consequence of obesity)

51
Q

What is hypoglycaemia?

A

When blood glucose falls below normal

Consequence of poorly managed diet - too much insulin, strenuous physical activity, inadequate food intake of illness

Results in weakness, anxiety, hunger, trembling

52
Q

What is the glycemic response?

A

How quickly glucose is absorbed after a person eats, how high blood glucose rises and how quickly it returns to normal

53
Q

Is a low or high glycaemic response required?

A

Low: slow absorption, modest rise, smooth return to normal

54
Q

What is the glycemic index?

A

Classifying food according to their potential to raise blood glucose

Low GI foods also manage blood lipids to lower risk of heart disease

55
Q

What is a low, medium and high GI?

A

Low <55
Medium 56-69
High 70>

56
Q

What are some health effects caused by sugar?

A
  • Obesity/chronic disease
  • nutrient deficiencies (supplies energy without nutrients)
  • dental caries/tooth decay
57
Q

What are some alternative sweeteners?

A

Artificial sweeteners (no energy)
Herbal product (stevia)
Sugar alcohols (occurs naturally, bulk and sweetness)

58
Q

How many kj (out of 8000) of calories should a person have a day?

A

3600-5200kj a day

200-325g (dietary fibre 25-30g)

59
Q

What are the positive impacts of dietary fibre?

A

Fosters weight management
Lowers blood cholesterol
Enhances health of GI
Protects heart disease
Prevent colon cancer, diabetes, haemorrhoids, etc.

60
Q

What occurs with excessive intake of dietary fibre?

A

Displaces energy and nutrient-dense foods
Causes intestinal discomfort and distension
May interfere with mineral absorption

Human Nutrition (6 decks)

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