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HUNT245 > Lecture 6: Carbohydrates > Flashcards

Lecture 6: Carbohydrates Flashcards

1
Q

What is anaerobic glycolysis?

A

the process of breaking down glucose (carbohydrate) to release energy to phosphorylate ADP and form ATP

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2
Q

When is anaerobic glycolysis used?

A

without oxygen, rapidly producing ATP for short-term, high-intensity activities

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3
Q

What is glucose broken down into during anaerobic glycolysis?

A

pyruvate and lactic acid

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4
Q

What is the final product of anaerobic glycolysis?

A

Lactate + H+

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5
Q

Where is glycogen stored?

A

in muscle or liver

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6
Q

What is glycogen?

A

the stored form of glucose

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7
Q

How many ATP is produced during anaerobic glycolysis from glucose?

A

2 ATP

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8
Q

How many ATP is produced during anaerobic glycolysis from glycogen?

A

3 ATP

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9
Q

What is aerobic metabolism?

A

the process by which cells produce energy (ATP) through the oxidative phosphorylation of glucose, fatty acids, or amino acids in the presence of oxygen

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10
Q

What is oxidative phosphorylation?

A

the process by which ATP is produced in the mitochondria through the transfer of electrons from NADH and FADH2 to oxygen

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11
Q

Does aerobic metabolism stop?

A

continuous supply of ATP as long as O2 is available

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12
Q

Where does aerobic metabolism occur?

A

Mitochondria

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13
Q

What are the 3 phases of aerobic metabolism?

A
  1. Preparation
  2. Krebs cycle/TCA cycle
  3. Electron transport chain (ETC)
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14
Q

What happens in the Krebs cycle/TCA cycle?

A

oxidises, removes, electrons

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15
Q

What happens during the ETC?

A

electrons undergo a number of reactions releasing energy to rephosphorylate ADP to ATP

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16
Q

How many ATP does aerobic metabolism produce?

A

30-32 ATP

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17
Q

What type of exercise is CHO one of our most important fuels for?

A

endurance exercise - anything over an hour, energy is generally coming from CHO sources

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18
Q

Where does carbohydrate digestion begin?

A

In the mouth

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19
Q

What happens to CHO in the mouth?

A

Salivary a-amylase hydrolyses dietary starch

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20
Q

Where does CHO go after the mouth?

A

The stomach

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21
Q

What happens to CHO in the stomach?

A

The acidity of the stomach temporarily inhibits a-amylase and stops carbohydrate digestion

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22
Q

Where does CHO go after the stomach?

A

The small intestine

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23
Q

Is the small intestine acidic?

A

No

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24
Q

How is the small intestine neutralized?

A

Bicarbonate secretion from the pancreas neutralises the stomach contents and pancreatic a-amylase continues to digest starch

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25
Q

How are CHO broken down into smaller molecules in the small intestine?

A

Several disaccharide enzymes breakdown disaccharides in the brush border of the small intestine producing monosaccharides

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26
Q

What are monosaccharides?

A

glucose, fructose, galactose

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27
Q

Where are CHO absorbed?

A

The small intestine

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28
Q

How is glucose absorbed in the small intestine?

A

via a sodium glucose transporter (SGLT-1)

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29
Q

How is fructose absorbed in the small intestine?

A

via the transporter GLUT5

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30
Q

How are glucose and fructose transported across the basolateral membrane?

A

via the transporter GLUT-2

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31
Q

After being transported out of the small intestine where do glucose and fructose go?

A

Transported to the liver where fructose is removed from the circulation

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32
Q

What is glycogenesis?

A

the process by which glucose molecules are converted into glycogen for storage in the liver and muscle cells

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33
Q

What is insulin?

A

a hormone produced by the pancreas that helps regulate blood glucose levels

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34
Q

How does insulin regulate blood glucose levels?

A

by facilitating the uptake of glucose into cells and promoting its storage as glycogen in the liver and muscles

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35
Q

What does CHO ingestion stimulate?

A

the release of insulin from the pancreas

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36
Q

What does insulin stimulate?

A

GLUT-4 translocation to muscle membrane

37
Q

What is glucose-6-phosphate?

A

an important intermediate in glycogenesis

38
Q

What does glucose-6-phosphate stimulate?

A

the production of glycogen

39
Q

What is the total carbohydrate store for an 80kg male?

A

approx. 450-500g

40
Q

What are carbohydrate stores affected by?

A

fasting, exercise and diet

41
Q

What is the biggest store of CHO?

A

Muscle

42
Q

What is the smallest store of CHO?

A

Blood

43
Q

What is the second biggest store of CHO?

A

Liver

44
Q

What is CHO a fuel for?

A

muscle and brain during exercise

45
Q

What do low levels of CHO cause?

A

fatigue and reduced performance

46
Q

What is the daily CHO recommendation for very light training?

A

3-5g/kg/d

47
Q

What is the daily CHO recommendation for moderate/low intensity training (1hr/d)?

A

5-7g/kg/d

48
Q

What is the daily CHO recommendation for moderate to heavy training (1-3hr/d)?

A

6-10g/kg/d

49
Q

What is the daily CHO recommendation for extreme exercise (>4-5hr/d)?

A

8-12g/kg/d

50
Q

Do athletes generally meet their CHO needs?

A

No, very few do

51
Q

What factors cause suboptimal intakes of CHO?

A
  1. Restricted energy intake
  2. Inadequate skills
  3. Culture
  4. Availability
  5. GI discomfort
  6. Fad Diets
  7. Chaotic lifestyle/travel
52
Q

What is the first step in changing future behaviour?

A

understanding current behaviour

53
Q

What is the stigma around CHO?

A

that if you eat a high carb diet you will get fat

54
Q

What happens when insufficient CHO is ingested?

A

Progressive decrease in muscle glycogen which don’t get replaced

55
Q

How do you replace glycogen stores?

A

With a high CHO diet

56
Q

How does a high CHO effect training?

A

Maintain performance better and have a higher mood state during intensified training

57
Q

Can CHO before exercise improve performance?

A

Yes, even if you have an overall high CHO diet, having right before/morning of CHO before exercise improves performance - this is because even when we are sleeping our glycogen stores are being used

58
Q

Why can we not endlessly consume CHO to improve performance?

A

GI stress

59
Q

When is GI stress common?

A

during long distance races

60
Q

Is GI stress consistent between different athletes?

A

No, highly individual, perhaps genetically determined

61
Q

What could GI stress be related to the intake of?

A
  • highly concentrated CHO solutions
  • hyperosmotic drinks
  • intake of fibre, fat and protein
62
Q

What is CHO/glycogen loading?

A

Maximizing the amount of glycogen stored in muscles and liver

63
Q

What is the downside of glycogen loading?

A

When we store glycogen in our muscles we also store water which can cause water retention in our muscles which makes the athletes feel very heavy

64
Q

What are the positive impacts of CHO loading?

A

improve performance approx. 2-3%

65
Q

How much CHO do you need to consume for loading?

A

can vary from around 10-12g/kg/d depending on the athlete and their activity

66
Q

What are pre-event meal considerations?

A
  • Time of day event is
  • Length of event
  • Nerves
  • Location
  • Past experience
  • GI stress
67
Q

What are the aims of pre-exercise fueling?

A
  • Prevent muscle and liver glycogen depletion
  • Prevent hypoglycaemia
  • Prevent GI stress
68
Q

What should dehydration be limited to during exercise?

A

limit to less than 2% BM loss

69
Q

The longer the exercise…

A

the more CHO needed per hour

70
Q

How much glucose can you utilize per hour?

A

about 60-90g, if you are consuming more then you need to increase the fructose

71
Q

Can the gut be trained?

A

By gradually increasing intakes the gut is able to increase uptake with exposure

72
Q

How do we restore muscle and liver glycogen levels to pre-exercise levels?

A

CHO intake of 1/5g/kg/d during first 30 mins and again every 2h for 4 to 6h

73
Q

What considerations need to be taken when restoring CHO stores?

A
  • Time to next session
  • Intensity of session
  • Demands of next session
  • GI tolerance
  • Logistics
74
Q

Why is it important to re-fuel directly after exercise?

A

first few hours are most important as the muscle is most receptive to storing glycogen

75
Q

What is oestrogen?

A

a group of steroid hormones responsible for regulate the development and function of the female reproductive system - present in smaller amounts in males

76
Q

What are the main types of oestrogen?

A

oestrone, oestradiol, oestriol

77
Q

What functions does oestrogen have?

A

important for muscle mass, inhibits bone resorption

78
Q

What is progesterone?

A

a steroid hormone that plays a crucial role in the menstrual cycle and pregnancy - present in smaller amounts in males

79
Q

What functions does progesterone have?

A

increases muscle protein synthesis rates, stimulates osteoblasts

80
Q

What is a eumenorrheic cycle?

A

a regular menstrual cycle characterized by predictable and consistent patterns

81
Q

What percentage of female athletes are eumenorrheic?

A

67-91%

82
Q

What does estrogen increase during exercise?

A

fatty acids availability and promote lipid oxidation

83
Q

What does progesterone limit during exercise?

A

fat oxidation

84
Q

Why is it important to individualise according to an athletes menstrual cycle?

A

there will be an increase and decrease in CHO and fat absorption over the month

85
Q

The menstrual cycle effects are seen to a greater extent in…

A

those with PMS, and recreational athletes

86
Q

How does hormonal contraception affect endurance exercise?

A

Elevated plasma estrogen concentrations increase the reliance on fat as an energy source during endurance exercise

87
Q

What is the best way to prescribe dietary CHO intake based on the menstrual cycle?

A

There is insufficient high quality evidence

88
Q

How much water retention is there per gram of glycogen?

A

Approx. 3g water per gram of glycogen

89
Q

In order for an athlete to actually oxidise 90g per hour they should likely ingest…

A

100-120g/h, owing to the fact that oxidation efficiency is not uniform

HUNT245 (14 decks)

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