Carbohydrates

Question 1

What are the molecular building blocks of life building blocks of life are

Answer 1

Is proteins lipids carbohydrates dna/RNA

These are organic compounds

Question 2

What is the biological importance of carbohydrates

Answer 2

They provide energy through oxidation
They supply carbon for synthesis of cell components
They serve as a form form of stored chemical energy
They form part of the structures of some cells and tissues

Question 3

What are carbohydrates and classes

Answer 3

Carbohydrates or saccharides are polyhydroxy aldehydes or ketones, or saccharides are polyhydroxy aldehydes or ketones, or substane that yield such compounds on hydrolysis.
Carbohydrates include not only sugar, but also the starches that we find in foods, such as bread, pasta, and rice.
- Monosaccharides
- Disaccharide
- Oligosaccharides
- Polysaccharide

Question 4

Describe and give an example for each of the classes of carbohydrates

Answer 4

1. Monosaccharide:
   Contain a single polyhydroxy aldehyde or ketone unit
   Example: Glucose, Fructose
2. Disaccharide:
   Consist of two monosaccharide units linked together by a covalent bond
   Example: Sucrose
3. Oligosaccharide:
   Contain from 3 to 10 monosaccharide unit
   Example: Raffinose
4. Polysaccharide:
   Contain very long chains of hundreds or thousands of monosaccharide units, which may be either in straight or branched chains
   Example: Cellulose, glycogen, starch

Question 5

What are Stereoisomers

Answer 5

Two isomeric forms that are mirror images of each other. For example Glyceraldehyde has two isomeric forms: L-glyceraldehyde and D-glyceraldehyde that are mirror images of each other. THey are also enantiomers of each other.
Glyceraldehyde is a chiral molecule, it cannot be superimposed on its mirror image.

Question 6

What are chiral carbons or center of chirality

Answer 6

Any carbon atom which is connected to four different groups will be chiral and will have two nonsuperimposable mirror images is called a chiral carbon or center of chirality. Chiral objects cannot be superimposed on their mirror images. Achiral is vice-versa.

Question 7

What are the two types of monossaccharide projections

Answer 7

Fischer projection:
Method of representing 3-dimensional structures of molecules on a page.

Haworth Projection:
Used for cyclic sugars
Clearly indicates sterochemical arrangement of groups on ring (up/down)
Not meant to accurately convey the ring conformation

Question 8

what is alpha and beta in the haworth projection

Answer 8

α (Alpha) – the name given to the configuration of a cyclic sugar where the oxygen on the anomeric carbon is on the opposite face of the ring relative to the substituent on the other carbon flanking the ring oxygen.
Contrasted with beta (β) which is where the two substituents are on the same faces of the ring.

Question 9

List some of the physical properties of monosaccharides

Answer 9

• Sweet taste
• Solids at room temperature
• High molecular weights
• Extremely soluble

Question 10

What makes monosaccharides extremely soluble in water.

Answer 10

Despite their high molecular weight, presence of large number of OH groups make monosaccharide much more water soluble that most molecules for similar molecular weight. Glucose can dissolve in minute amounts of water to make a syrup.

Question 11

What are glycosides

Answer 11

The hemiacetal and hemiketal forms of monosaccharides react with alcohol to form acetal and ketal structures called glycosides

Question 12

What is the new carbon oxygen bond of glycoside called?

Answer 12

Glycosidic linkage

Question 13

What are the important monosaccharides and their function.

Answer 13

Beta-D-ribose:
Forms the sugar backbone of RNA
Beta-D-deoxyribose:
Forms the sugar backbone of DNA
Beta-D-galactose:
Incoporated with glucose into lactose 
Beta-D-glucose:
Dextrose. Glucose is metabolized in the body for energy. Any other sugars absorbed must be converted to glucose by the liver.
Beta-D-fructose:
Levulose. Fructose is the sweetest. Used to sweeten foods.

Question 14

What are disaccharides and give some examples

Answer 14

Two monosaccharides linked together through glycosidic linkage.
Maltose
Lactose
Sucrose

Question 15

What is a Oligosaccharide and given an example

Answer 15

Molecules that contain 3 to 10 monosaccharide units.
For example Raffinose: An oligosaccharide that is found in peas and beans that has beta-D-alactose, alpha-D-glucose, beta-D-fructose in the chain.

Question 16

What are polysaccharides and give example

Answer 16

Contain hundreds or thousands of carbohydrate units.
They are not reducing sugars
For example: Starch, glycogen and cellulose

Question 17

Describe the structure of Starch

Answer 17

Polymer consisting of D-glucose units
Insoluble in water as they contain large numbers of OH and have a high molecular weight
High molecular weight
Two forms: amylose and amylopectin

Question 18

Difference between amylose and amylopectin

Answer 18

Amylose contain long, unbranched chains of glucose connected by alpha (1,4) glycosidic linkages. Amylopectin consists of long chains of glucose conencted by alpha(1,4) glycosidic linkages with alpha (1,6) branches every 24 to 30 glucose units.

10-20% of starch in plants is in amylose form.
80-90% of starch in plants is in amylopectin form

Amylose chain is flexible for molecules to twist into shape of helix because it packs more tightly. It is slower to digest than other starches.

Question 19

Describe the structure of Glycogen

Answer 19

• Known as Animal Starch
• Structurally similar to amylopectin
• Contain both alpha(1,4) glycosidic linkages and alpha(1,6) branch points.
• Highly branched, branches occuring every 8 to 12 glucose units.

Question 20

Function of Glycogen

Answer 20

Abundant in lover and muscles

On hydrolysis forms D-glucose which maintains normal blood sugar and provides energy

Question 21

What is the most important structural polysaccharide?

Answer 21

Cellulose

Question 22

Describe the structure of cellulose

Answer 22

It is a polymer consisting of long, unbranched chains of D-glucose connected by beta(1,4) glycosidic linkages.
COntain 300 to 3000 glucose units.

Question 23

How is the structure of cellulose different to amylose

Answer 23

Cellulose is a polymer consisting of long, unbranched chains of D-glucose connected by beta(1,4) glycosidic linkages. Amylose is a polymer consisting of long, unbranched chains of glucose connected by alpha (1,4) glycosidic linkages. The beta-linkages in cellulose gives it a different overall shape from amylose as it forms extended straight chains which hydrogen bond to each other resultin in a very rigid structure.

Question 24

Uses of cellulose

Answer 24

• Most animals lack enzymes needed to digest cellulose but it provides dietary fiber to stimulate contaction of intestines and help pass food through digestive system.
• Some animals can breakdown cellulose
• It is important inductrially for wood, paper, cotton, linen, nitrocellulose(guncotton)

Question 25

The difference betweeen soluble and insoluble fiber

Answer 25

Soluble fiber such as pectin, has a lower molecular weight, and is more water soluble. Insoluble fiber such as cellulose provides bulk to the stool helping the body to eliminate solid waste. Soluble fiber traps carbohydrates and slows their digestion and absorption, leveling out blood sugar levels during the day. Soluble fiber helps to lower chloesterol by binding to diestary chloesterol.

Question 26

Describe the strcuture of Chitin

Answer 26

A polymer of N-acetylglucosamine
Amide derivative of amino sugar glucosamine in which the OH groups is converted to an amine group. The polymer is extremely strong because of increases hydrogen bonding provided by amide groups.

Question 27

Where is Chitin found

Answer 27

Main component of cell walls of fungi
Exoskeletons of arthropods
Embedded in wither a protein matrix and calcium carbonate crystals.