Lecture 5 - Carbohydrates

Question 1

What is the most common monosaccharide

Answer 1

glucose

Question 2

What is the most common disaccharide

Answer 2

sucrose

Question 3

How are polysaccharides stored in animals vs plants

Answer 3

animals = glycogen
plants = cellulose & starch

Question 4

What carbon count monosaccharides are the most important for nutrition

Answer 4

hexoses

Question 5

What are enantiomers

Answer 5

mirror images

Question 6

What are diastereoisomers

Answer 6

not a mirror image

Question 7

What is a chiral carbon

Answer 7

carbon surrounded by 4 molecules

Question 8

What determines D vs L configuration

Answer 8

determined by the -OH group on the highest chiral carbon (furthest from carbon 1)
- if -OH is on left, its L, if -OH is on right, its D

Question 9

What is the equation for the # of stereoisomers

Answer 9

2^n where n is the number of chiral carbons

Question 10

What is Fischer projection

Answer 10

the linear configuration of a sugar

Question 11

What is a Haworth model

Answer 11

the ring configuration of a sugar

Question 12

What is the different between a hemiacetal and a hemiketal

Answer 12

hemiacetal = made from aldose
hemiketal = made from ketose

Question 13

How to determine whether a sugar is alpha or beta

Answer 13

in Fischer, if the -OH is on the left, it will point up in Haworth, if the -OH is on the right, it will point down in Haworth
- up = beta, down = alpha

Question 14

What type of bond connects monosaccharides to make a disaccharide

Answer 14

a glycosidic bond between 2 OH groups

Question 15

What is sucrose

Answer 15

found in sugar cane and fruits
glucose + fructose
non-reducing - both anomeric carbons are occupied

Question 16

What is lactose

Answer 16

found in milk
galactose + glucose
reducing

Question 17

What is maltose

Answer 17

found in beer and liquor
glucose + glucose
reducing

Question 18

What is the benefit of insoluble fibre

Answer 18

increases intestinal movement (remains intact and reduces transit time)

Question 19

What is the benefit of soluble fibres

Answer 19

gives good health benefits by increasing transit time and slowing down the rate of nutrient absorption

Question 20

What is the make up of cellulose

Answer 20

homopolysaccharide of B-1,4 glucose units

Question 21

Why can’t humans digest cellulose

Answer 21

lack the cellulose-fermenting microbes in their gut microbiome

Question 22

Want is the make up of hemicellulose

Answer 22

a mixture of alpha and beta glycosidic linkages
can contain both pentoses and hexoses

Question 23

What is pectin and where is it found

Answer 23

backbone of unbranched a-1,4-linked-D galacturonic acid
- part of cell wall in plants

Question 24

What is resistant starch and where is it found

Answer 24

found in plant cell walls
resistant to amylase activity

Question 25

What fibre is good for decreasing constipation

Answer 25

insoluble

Question 26

What fibre is good for increasing satiety

Answer 26

soluble fibre

Question 27

Why do insoluble fibres decrease constipation

Answer 27

because they don't dissolve, so they stimulate muscle movement, decreasing constipation

Question 28

How can soluble fibre increase health and decrease disease risk

Answer 28

decrease cardiovascular disease risk by lowering blood cholesterol

Question 29

What is the function of a-amylase in the mouth

Answer 29

breaks down a-1,4 glycosidic bonds

Question 30

What sugars are resistant to a-amylase

Answer 30

cellulose and lactose

Question 31

What inactivates a-amylase digestion

Answer 31

in the stomach, pH drops and a-amylase is inactivated

Question 32

How does a-amylase continue digestion in the small intestine

Answer 32

secreted from the pancreas and activated again in small intestine due to neutral pH

Question 33

What is the other name for isomaltase and what is its function

Answer 33

alpha-dextrinase - breaks a-1,6 linkages

Question 34

What is the other name for invertase and what is its function

Answer 34

sucrase - breaks sucrose down

Question 35

What is maltase and what is its function

Answer 35

enzyme - breaks down maltose

Question 36

What is lactase and what is its function

Answer 36

enzyme - breaks down lactose

Question 37

What causes lactose intolerance

Answer 37

under normal circumstances lactase breaks down lactose into galactose and glucose under the circumstance where lactase is not present, lactose is broken down by gut bacteria which causes build up of gases and irritation, leading to the side effects of lactose intolerance

Question 38

What takes up monosaccharides in the body for absorption

Answer 38

enterocytes

Question 39

What happens to glucose

Answer 39

small amounts leak back out into lumen from the enterocyte small amounts diffuse into blood through basolateral membrane most is transported to blood by GLUT-2

Question 40

Transport of glucose and galactose from lumen to blood is dependant on...

Answer 40

Na-K ATPase activity

Question 41

Transport of fructose is facilitated by...

Answer 41

facilitated transport (GLUT 5)

Question 42

glucose, galactose, and fructose are all sent to bloodstream via...

Answer 42

GLUT 2

Question 43

What are the main functions of carbs in the body

Answer 43

glucose is the main energy source carbs spare protein (prevent the breakdown of protein for energy) carbs prevent ketosis (breakdown of fats for energy)