UNIT 5: CARBS

Question 1

Carbohydrates are a major _______, but do not ______.

Answer 1

major source of energy/fuel (~50%)

do not contain essential nutrients

Question 2

Carbohydrates are not an essential _____ but are an essential ____.

Answer 2

nutrient
metabolite
- i.e. blood glucose is an essential metabolite but can be obtained from dietary protein

Question 3

Sugars must possess:

Answer 3

• aldehyde or ketone functional group

- hydroxyl groups

Question 4

Sugars are joined together by ______

Answer 4

glycosidic bonds

Question 5

Anomeric carbon is the carbon with…

Answer 5

the carbonyl group

- carbon closest to

Question 6

Fischer projection L vs D is defined by?

Answer 6

• highest chiral carbon
• direction of carbonyl group
• OH to left = L
• OH to right = D

Question 7

Glucose in aqueous solution equilibrium is…

Answer 7

1/3 alpa-D-glucose, 2/3 beta-D-glucose

Question 8

Alpha is when ____ points ___ and Beta is when it points ____.

Answer 8

alpha: -OH points down
beta: -OH points up

Question 9

Which carbon becomes the anomeric carbon when cyclized?

Answer 9

The carbonyl carbon.

it is attacked by the -OH of highest chiral carbon.

Question 10

Glucose is a ____ while Fructose is a ____

Answer 10

• glucose is aldose
• fructose is ketone

Fructose is a ketone or hemi-ketal ring

Question 11

Plant cells use ____,
Grain cells use _____,
Muscle cells use _____.

Answer 11

Plant: beta-D-glucose
Grain: alpha-D-glucose
Muscle-alpha-D-glucose

Question 12

The disacchardes: 
Sucrose
Lactose
Maltose 
are made of...

Answer 12

Sucrose = alpha glucose + beta fructose
Lactose = alpha or beta glucose + beta galactose
Maltose = alpha glucose + alpha or beta glucose

Question 13

Of the 3 disacchardies, which are the reducing sugars and which are the non-reducing sugars?

Answer 13

Reducing: lactose and maltose
- they have hemiacetal that can reduce reduce aldehyde to continue link
Non-reducing: sucrose, both anomeric carbons used to form glycosidic bond so cannot reduce

Question 14

Non reducing sugars are ______ chemically reactive than reducing sugars.

Answer 14

Non-reducing sugars are less reactive, and need to be digested to monosacharides before absorbed

Question 15

Homopolysaccharides are ____ abundant than Heteropolysaccharides

Answer 15

more abundant

Question 16

Plants produce 2 types of starches:

Answer 16

• amylose -> a-1-4 glucose (linear)

- amylopectin -> a-1-6 glucose (for branching)

Question 17

Starch in plants is like _____ in humans.

Answer 17

Glycogen

Question 18

Which is more dense? Starch or glycogen?

Answer 18

Glycogen

• dense branching
• this forms granules
• prevents glycogen accumulation from disrupting muscle and liver cells

Question 19

Compare soluble and insoluble fibres.

Answer 19

Insoluble fibres: 
cellulose, hemicellulose, lignin
- remains intact through GI tract (only some fermentation)
- does not dissolve in water
Soluble fibres:
pectins, gums, mucilages
- forms a gel
- ferments in colon -> VFA
- does dissolve in water

Question 20

A fibre is digestible if….

Answer 20

1. the fibre is soluble enough that enzymes can attack it

2. enzymes are present

Question 21

What is so interesting about resistant starch?

Answer 21

• we have enzymes to digest starch
• tight granule structure
• goes to colon for fermentation

Question 22

What happens to insoluble fibres with wetted surface?

Answer 22

fermentation

Question 23

Soluble fibres have a _____ glycemic index.

Answer 23

lower glycemic index

- slow appearance of glucose in blood stream

Question 24

In terms of transit time, compare insoluble vs soluble fibres.

Answer 24

Insoluble fibres have a low transit time so promotes bowel movements.
Soluble fibres have increased transit time and slow stomach emptying, slowing nutrient absorption.

Question 25

Cellulose is linked by

Answer 25

beta bonds, beta-1-4 glucose