2.3 Carbohydrates and lipids Flashcards
Define polymer
A material or substance that is made of large molecules composed of multiple, repeating sub-units
3 examples of hexose mono-saccharides
Galactose, glucose, fructose
Monosaccharides–> Disaccharides: What type of reaction and which bond is formed?
Condensation reaction and a glycosidic bond is formed.
What is needed to make the condensation reactions occur?
A catalyst
Maltose, sucrose, lactose: Animals or plants?
Maltose: Animal
Lactose: Animal
Sucrose: Plant
What is maltose made of and where is it found?
Made of glucose + glucose and commonly found in starchy grains
What is lactose made of and where is it found?
Glucose + Galactose. Commonly found in milk
What is sucrose made of and where is it found?
Glucose + Fructose. Commonly found in sugar canes and sugar beets
What are the 4 common polysaccharides?
Cellulose, starch (amylose), starch (amylopectin), glycogen
Orientation and bonding of cellulose
1-4 bonds between alternately oriented Beta-D glucose molecules
Orientation and bonding of amylose
1-4 glycosidic bonds between Alpha-D glucose
Orientation and bonding of amylopectin
1-6 links in the branches but mostly 1-4 links
Orientation and bonding of glycogen
Consists of 1-4 and 1-6 bonds between Alpha-D glucose
What does a 1-4 bond mean?
A bond between first and fourth carbon
Is the chain straight or bent for 4 polysaccharides?
Cellulose- Straight
Amylose- Bent and helical
Amylopectin- Bent and globular
Glycogen- Bent
Is the chain branched or unbranched for the 4 polysaccharides?
Unbranched: Cellulose and amylose
Branched: Amylopectin and glycogen
Properties of cellulose
Insoluble, high tensile strength, low conductivity
Properties of starch
Insoluble, doesn’t affect osmotic balance, molecules vary in size, easy to remove and add glucose units
Properties of glycogen
More extensively branched and compact than amlyopectin
Function of cellulose
Structural component of plant cell walls
Function of starch
Useful for glucose and energy storage. It is a temporary store in plant cells when glucose is being made faster than it’s being exported
Function of glycogen
Form of medium term energy storage in animals
How is amylopectin useful?
It gives starch its characteristic stickiness. Useful in food, paper, chemical industries as glue and lubricant.
Difference between glucose and fructose
Glucose and fructose both have 6 carbons however glucose has a hexagonal ring with 5 carbons and the 6th connected to the 5th. Fructose has a pentagonal ring with 4 carbons and the one connected to the first and fourth carbon each.
What is the structure of sucrose?
It is made of fructose and glucose so they are connected by an oxygen atom at the first carbon of glucose and the fourth carbon of fructose
Similarities and differences between glycogen, amylose and amylopectin
All 3 are curved and consist of alpha-glucose. Amylose is unbranched. Amylopectin is branched but after around every 20 subunits while glycogen is branched but after around every 10 subunits
Generalized structure of a fatty acid
CH3(CH2)xCOOH
What is a saturated fatty acid?
It is a fatty acid that has no double bonds between any of the carbon atoms
Monounsaturated
Only one double bond in the carbons
What do you call a fatty acid with multiple double bonds in the carbons?
Polyunsaturated
What are the types of unsaturated fatty acids?
Cis-isomers and trans-isomers
Cis/trans-isomers: Natural or synthesized?
Cis: Very common in nature
Trans: Rare in nature, usually artificially produced
How are trans-isomers artificially produced to produce solid fats like margarine from veg. oils?
They are hydrogenated: Hydrogen is added under pressure to increase spreadability and increase shelf life
Cis/trans-isomers: Positioning of hydrogen atoms
Cis: All on the same side of the carbon atoms
Trans: Position will alternate on every carbon
Cis/trans-isomers: Shape of fatty acid chain
Cis: Double bond causes a bend in the chain
Trans: There will be no bend
Cis/trans-isomers: Packing of fatty acids
Cis: Loosely packed due to bend
Trans: Can be closely packed
Cis/trans-isomers: Liquid or solid at RTP
Cis have low MP so liquid at RTP while trans have high MP so solid at RTP
Causes of CHD
- Caused by buildup of fatty deposits around artery walls so blood flow is restricted
- High levels of LDL means more deposits
- Factors can include smoking, high cholesterol/BP, sedentary lifestyle
Possible effects of CHD
- Reduction of blood flow = chest pain, shortness of breath, blood clots or a heart attack
Why is cellulose indigestible for most animals?
It is made of beta-glucose and most animals lack the enzyme to break it down
Why is amylose preferred storage in plants?
They take up less space
What do triglycerides consist of?
One glycerol molecule and 3 fatty acids
What does a glycerol molecule look like?
It has 3 carbons. Each carbon has a hydrogen and OH group while the carbon ends also have an extra hydrogen
What are the bonds between the fatty acid and the glycerol molecule?
Ester bonds
How are ester bonds formed?
Through condensation between the OH groups of glycerol and fatty acids to produce water and an ester bond.
How are phospholipids different from triglycerides?
They also have a glycerol molecule but they only have 2 fatty acids and a chain with a phosphate group instead.
Why are steroids considered lipids?
Because they are hydrophobic and insoluble even though they have a four-ring structure
Word equation for formation of triglycerides
Glycerol + 3 fatty acids –> Triglyceride + 3H2O
Lipids and carbs: Short or long term energy storage
Lipids: Long term
Carbs: Short term
The chemical energy in glucose is for immediate use in which process?
Respiration
Where is glycogen stored?
In the liver and muscles
Why is glycogen used in preference to lipids?
Short term as it can be broken down easily. It can be used in aerobic and anaerobic conditions unlike fats which require aerobic only
Where and how are lipids stored in animals?
Stored in specialized groups of cells called “Adipose tissues”. They are usually located beneath the skin or around organs like kidneys
How are lipids better than carbs in terms of storage?
- The amount of energy released per gram is double in lipids so it’s more efficient.
- They are also much lighter
- Fats are stored as droplets while 1g of carbs is associated with 2g of water
Advantages of lipids
- Non polar so they will dissolve other non-polars without affecting movement of water
- Water-insoluble so they provide waterproof layers
- They provide excellent insulation
- Fat is liquid at body temp. so it can act as a shock absorber hence its position around organs.
What does BMI stand for?
Body Mass Index
How is BMI calculated?
Mass(kg)/ Height(m)^2
How would relationship of height and BMI change with fixed body mass?
If height increases, BMI will decrease and vice-versa. Negative correlation
How can one reduce body mass?
- Exercise more
- Reduce amount of fats in their diet (lipid intake)
- Drink more water and cut down on sugar
How does one use a nomogram?
Draw a line from person’s height to body mass and where it crosses scale in between is respective BMI
How is the lightness of lipids an advantage for birds?
It is important for animals that fly like birds and bats as it helps when they migrate or fly long distances and hence require long-term energy storage that’s also light.
How do the different fats influence HDL and LDL levels in the blood?
- Saturated increase LDL levels (bad)
- Trans fats increase LDL AND decrease HDL (bad)
- Cis fats increase HDL levels (good)
What are HDLs and LDLs
High density and low density lipoproteins
What do LDLs do?
They carry cholesterol from liver to the rest of the body
What do HDLs do?
They gather excess cholesterol and carry it back to the liver for disposal
Do LDLs raise or lower cholesterol levels?
LDLs increase while HDLs decrease
2 main lipid health claims
- Diets rich in saturated fats and trans fats increase the risk of CHD
- Diets rich in monounsaturated and polyunsaturated (cis) fats decrease the risk of CHD
How has evidence for lipid health claims been collected?
- Epidemiological studies comparing different population groups
- Intervention studies that monitor cohorts following dietary modifications
- Experimental designs utilising animal models or data based on autopsies
What is the counter argument for correlation between saturated fats and CHD?
Certain populations do not fit this trend (e.g. the Maasai tribe in Africa have a fat-rich diet but very low rates of CHD)
Counter argument for: people who have died from CHD have been found to have high conc. of trans-fats in the fatty deposits
Genetic factors may play a role (e.g. blood cholesterol levels only show a weak association to dietary levels)
