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Food Chemistry > Lecture 5 > Flashcards

Lecture 5 Flashcards

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1
Q

What are the fates of acetyl CoA?

A

Generation of ATP via TCA cycle and ETC. (This occurs when cell requires energy.)

Fat synthesis when body has enough ATP.

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2
Q

What are the net products of glycolysis?

A

2 ATP

4 NADH

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3
Q

Is the reaction converting Pyruvate to Acetyl CoA reversible?

A

No

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4
Q

Where do fatty acids enter the kreb’s cycle?

A

They can be broken down to form Acetyl CoA and can enter the kreb’s cycle from there.

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5
Q

What stage of respiration does glycerol join?

A

Glycerol can enter the glycolysis pathway and as a result can form pyruvate.

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6
Q

Which amino acids can be converted into pyruvate? Can they produce glucose?

A

Glucogenic amino acids These amino acids can also form glucose.

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7
Q

How do ketogenic amino acids enter the respiratory pathway?

A

They enter the kreb’s cycle by forming Acetyl-CoA.

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8
Q

What structures of the kreb’s cycle can pyruvate form directly?

A

Oxaloacetate (Reverse reaction can also occur.)

Acetyl -CoA (via PDH)

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9
Q

What is the purpose of the kreb’s cycle?

A

To generate NADH and FADH2 which can reduce the complexes of the electron transport chain. which can result in ATP production.

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10
Q

How many cycles of the TCA cycle are produced from each glucose molecule?

A

2

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11
Q

What is the function of oxygen in respiration?

A

Oxygen is the final electron acceptor of the electron transport chain..

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12
Q

What is the difference in contribution to the ETC between FADH2 and NADH?

A

FADH2 supplies electrons later into the electron transport chain than NADH

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13
Q

What are the calories found in each macronutrient?

A

Fat = 9kcal/g

Carbohydrate = 4

protein = 4

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14
Q

What happens to excess glucose?

A

Excess glucose is stored as glycogen in liver (8% of wet weight) and muscle (0-1% of wet weight)

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15
Q

What happens during fasting or no carb diets?

A

In fasting (low carb diet) fats are broken down first followed by proteins to provide energy.

Glucogenic amino acids from protein are converted to pyruvate which can form glucose by gluconeogenesis.

During ketosis high intake of protein does not substitute carbohydrate ingestion.

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16
Q

What is the benefit of carbohydrate ingestion over ketosis?

A

carbohydrate has protein sparing action.

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17
Q

What are ketones?

A

Ketone bodies are an alternative fuel source during starvation.

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18
Q

What is ketosis?

A

Ketosis is the accumulation of ketone bodies in the blood due to excess production.

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19
Q

What is the problem with ketosis?

A

Ketosis can upset the acid-base balance in the body and can cause death as a result.

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20
Q

Where are ketone bodies produced?

A

in the liver

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21
Q

What are ketone bodies produced from?

A

from ketogenic amino acids and fatty acid metabolic products during periods of fasting or starvation.

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22
Q

What are the steps in ketone production?

A

1) Acetyl CoA + Acetyl CoA - CoA -> compound that is converted to the first ketone body.
2) CO2 lost to form another ketone
3) the other ketone may add 2 hydrogens to form another ketone body. (acetone can be another product)

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23
Q

Can fats be used to make glucose?

A

Fats cannot be used to make glucose but glycerol can.

24
Q

Can glucose be used to make fat?

A

In the liver Acetyl CoA can be converted into fat creating a pathway from glucose to fat.

25
Q

What happens during fasting?

A

Brain uses glucose exclusively for energy.

During fasting, protein can meet this glucose need.

Body metabolism shifts to ketosis.

Ketone bodies cause apetite suppression.

Metabolic acidosis can result from ketosis.

26
Q

What are the 2 main types of ketosis?

A

Normal ketosis: Ketones produced when glucose not available.

Pathological ketosis: Ketones produced due to organ failure, diabetes, and alcohol abuse.

27
Q

What is another cause of acidosis of the blood?

A

Excess vitamin C can result in acidosis

28
Q

What are dietary fibres?

A

Dietary fibres are a fraction of edible parts of plants or carbohydrates that are resistant to digestion and absorption in large intestines.

29
Q

What are total dietary fibers according to the AOAC?

A

Total dietary fibers (definition by AOAC); food residues remaining after removal of lipid proteins and starch. 2 types:

Cellulose

Noncellulose polysaccharides.

30
Q

What are functional fibers?

A

Functional fibers are fibers that are added to food and are derived from plant and non-plant fibers.

31
Q

How do different fibers differ?

A

Fibers from cereals, fruits, and vegetables differ in chemical compositionas well as physiological effects in humans.

32
Q

What fibers can be found in leaves?

A

Leaves have high water content and low cell wall components and no lignins.

33
Q

What kind of fibers do fruits have?

A

fruits have pectic substances.

34
Q

What kind of fibers do legumes have?

A

legumes have high level of cell wall polysaccharides. (water soluble)

35
Q

What kind of fibers do whole grain cereals have?

A

High cell wall polysaccharides and are less water soluble.

36
Q

What is the most abundant form of biomass on earth?

A

cellulose is the most abundant biomass on earth (followed by lignins).

37
Q

What is interesting about dietary fibers?

A

Different dietary fibers have different functions. Only specific dietary fibers can lower blood sugar level and these fibers are associated with beta glucans.

38
Q

What are some features that fibers are classified by?

A

Solubility

digestablilty by bacteria in the gut.

39
Q

What are some features of solubility that define different fibers?

A

Soluble fibers are viscous and can be digested by intestinal bacteria. Whereas the opposite is true for insoluble fibers.

Most fibers exists in between. Solubility is a spectrum.

40
Q

Which fibers does bacterial digestion require?

A

Bacterial digestion requires soluble fibers. Bacterial degradation of fibers

41
Q

What are the classes of fibres?

A

Plant cell wall structural polysaccharides:

Cellulose (present in all plant materials and is insoluble in water, linkage is beta(1,4))

Hemicellulose (made up of arabinoxylans and is insoluble and found in wheat bran, husks and endosperms)

Pectic substances (found in fruits and veggies and is made up of galactouronic acids It is highly soluble)

42
Q

Are all pectins the same?

A

No, pectin in different fruits are different and have a different effect in the GI tract.

43
Q

Are all beta glycans capable of lowering cholesterol levels?

A

beta glucans from oats are different to those from barley. From oats the beta glucans have a cholesterol lowering effect.

44
Q

What are the properties of gums?

A

gums are highly soluble and are made up of mannose (galactomannans)

45
Q

What foods contain galacto-oligosaccharides? What are their properties and food sources?

A

galacto-oligosaccharides are highly soluble and found in legumes and other plants. 1-8% in legumes. Bacteria generate large amounts of gas from these oligosaccharides.

46
Q

Are fructo-oligosaccharides soluble?

A

fructo-oligosaccharides are partially soluble.

47
Q

What are seawood polysaccharides used for?

A

seaweed polysaccharides are highly charged and highly soluble and used to increase viscosity of food.

48
Q

What are the 2 types of seaweed oligosaccharides?

A

2 types of seaweed polymers:

Alginates and carrageenans(highly sulphated polymer of galactors)
both are highly soluble

49
Q

What are the health benefits of fibre intake?

A

Reduce calorie intake by providing fullness from meal and promoting satiety.

Prevents constipation

promotes elimination of toxins from digestive tract.

50
Q

How do fibres prevent constipation?

A

retains water in stool based on soluble properties.

51
Q

How does the state of the fiber affect the satiety of the food?

A

Solid promotes satiety better than liquid.

52
Q

How do fibres promote elimination of toxins from the digestive tract?

A

provides bulk for toxin elimination

53
Q

How can fibers modulate postprandial hyperglycaemia and insulin response?

A

.Controls rate of starch digestion

suppress starch digestion

54
Q

How do fibers lower risk of atherosclerosis?

A

Reduces blood cholesterol levels.

Binds bile aiding elimination resulting in increase bile synthesis in liver using body cholesterol.

Binds cholesterol aiding elimination.

55
Q

How do fibers reduce cardiovascular risk?

A

Reduces absorption of fats.

Binds fats aiding elimination.

Fat insoluble fibers typically have this effect.

56
Q

How can fibers aid prebiotic growth?

A

promotes beneficial bacterial growth in gut. (fermentable fibers promote growth of these gut bacteria)

Food Chemistry (12 decks)

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