Unit 2.3 Carbohydrates And Lipids

Question 1

Essential idea carbs and lipids

Answer 1

Compounds of carbon, hydrogen and oxygen are used to supply and store energy

Question 2

3 categories of carbohydrates

Answer 2

• monosaccharides
• disaccharides
• polysaccharides

Question 3

Monosaccharides

Answer 3

• simplest form of carbohydrate
• 2 to 7 atoms
• carbons joined to a hydroxyl group (-OH)
• e.g ribose, glucose, fructose, galactose
• act as a monomer
• linked by condensation reaction to form a glycosidic bond to produce a disaccharide

Question 4

Glucose

Answer 4

-monosaccharide that exists in two forms D-glucose and L-glucose
With the same chemical formula but a different arrangement
- 2 forms of D-glucose alpha-d-glucose and beta-d-glucose

Question 5

Difference between alpha-D glucose and beta-D glucose

Answer 5

Differ in placement go -OH group on carbon 1
Alpha d glucose = -OH below -H
Beta D glucose = -OH above -H

Question 6

Polysaccharides

Answer 6

Large molecules made of multiple monosaccharides e.g cellulose, starch and glycogen

Question 7

Function of polysaccharides

Answer 7

• polysaccharides play an important role in energy storage
• starch used to store energy in plants
• glycogen used to store energy in animals
• ## can also be a structural component, cellulose in plants creates cell wall and prevents bursting

Question 8

Disaccharides

Answer 8

• polar and water soluble

- maltose, lactose, sucrose

Question 9

Starch in industry

Answer 9

• amylopectin found in starch gives it stickiness and is useful in food industry or to create adhesives or lubricants

Question 10

Lipids

Answer 10

Diverse group of organic compounds, all which have little to no affinity for water

Question 11

Triglycerides

Answer 11

Formed by condensation reactions between one glycerol and three fatty acids, creating fats (solid at room temp) and oils (liquor at room temp)

Question 12

Fatty acids

Answer 12

Fatty acids are carboxylic acids (possess a carboxyl group) attached to the head of a long hydrocarbon chain. Can be saturated and unsaturated

Question 13

Saturated fatty acid

Answer 13

No double bonds between any of the carbon atoms in the hydrocarbon chain of

Question 14

Unsaturated fatty acid

Answer 14

Can be monounsaturated with one double bond or polyunsaturated with many double bonds. Can be trans or cis depending on position of the two hydrogen atoms (trans = bent, cis = straight)

Question 15

Cis-isomers

Answer 15

• commonly occur in nature
• two hydrogen atoms attached to same side of two carbon atoms
• lower melting points and are generally liquid at room temperature
• healthier, promote good cholesterol

Question 16

Trans-isomers

Answer 16

• artificially produced when lipids formed by polyunsaturated fatty acids from plants are partially hydrogenated chemically
• makes fatty acids behave like solids with higher melting points
• dangerous for cardiovascular system

Question 17

Phospholipids

Answer 17

• One fatty acid in a triglyceride is replaced by a phosphate group (-PO4)
• major component in membrane

Question 18

Lipids and energy stored

Answer 18

• lipids have a higher energy content than carbohydrates
• lipids also act as thermal insulators
• 1 gram of lipid has twice the energy as 1 gram of glycogen
• each gram of glycogen is associated with 2 grams of water, bulking up organisms which is bad for mobility

Question 19

Lipids and health

Answer 19

• high energy content may contribute to obesity when consumed in excess
• hypothesis = trans fats and saturated fats contribute to the formation of atherosclerotic plaques in the arteries which lead to heart attacks
• positive correlation examined, but no direct causal link found
• exceptions = Mediterranean diet and Maasai of Kenya