B1.1 Carbohydrates and lipids

B1.1.1 B1.1.2 B1.1.3 B1.1.4 B1.1.5 B1.1.6 B1.1.7 B1.1.8 B1.1.9 B1.1.10 B1.1.11 B1.1.12 B1.1.13

Describe the chemical properties of a carbon atom that allows for the formation of diverse compounds

1. Carbon has 4 electrons in it’s second shell and can form strong, stable covalent bonds.

2. Covalent bonds provide great stability and are able to form covalent bonds with atoms of O N and S with each molecule having distinctive properties.

3. Covalent bonds are only broken during specific chemical reactions.

4. Covalent bonds: give stable chain, branched chains and cyclic structures.

5. The 4 covalent bonds point to the corners of a regular Tetrahedron [electrons repel each other] , C atoms with 4 different atoms attached are asymmetric and some are mirror.

6. The ability to form more than 1 bond

7. Functional groups attached which make the molecule reactive in order to form lager molecules each functional group: unique physical and chemical properties.

Which functional groups do each of these biomolecules have?
a. Carbohydrates

b. Lipids

c. Fatty acids

a. Hydroxyl group (OH)

b. Ester group (COO)

c. Carboxyl group (COOH)

Isomers

Carbon atoms with 4 different atoms/groups (asymmetric)

Functional groups

The chemically active part of a series of organic molecules

List the Subcategories of Carbs with 2 examples of each

Monosaccharides
[Glucose, fructose, ribose, galactose]

Disaccharides
[maltose, lactose, sucrose]

Polysaccharides
[starch, cellulose, glycogen, chitin]

List the Subcategories of Lipids with 2 examples of each

Triglycerides
[Fat stored in adipose cells]

Phospholipids
[Lipids forming a bilayer in cell membranes]

Steroids
[Some hormones]

List the Subcategories of Nucleic acids with 2 examples of each

Nucleotides
[DNA RNA ATP]

General formula of Carbohydrates

• C_n (H₂O)_n  .

• n = 3, 4, 5 and 6.

Examples of cyclic molecules of Carbohydrates

D-fructose

D-ribose

D-maltose

Monosaccharides

small molecules; taste sweet; soluble in water
eg. Glucose

Why is glucose important?

1. All green leaves synthesize glucose in chloroplasts using light energy

2. Our bodies transport glucose in blood

3. All cells use glucose in respiration

4. the building block of many larger molecules, such as cellulose and starch in plants and glycogen in animals

Outline the properties of glucose

1. Molecular stability – The bonds within the glucose molecule are stable covalent bonds that do not break easily.

2. High solubility in water – Glucose is polar and readily dissolves in a polar solvent like water.

3. Easily transportable – Because glucose is soluble in water, it can easily circulate in blood and in fluids between cells.

4. Yields a great deal of chemical energy – when covalent bonds are broken, it yields high energy. 

   • Reactions are called oxidation reactions.

   • High energy yield means glucose is a good store of energy.

Isomers

Compounds that have the same component atoms in their molecules but differ in the arrangement of the atoms

What is a plane-polarized light?

Polarized light has electric fields oscillating in one direction.

Optical isomers

2 types of isomers that can rotate the plane of polarized light in opposite directions.
(one to the right [D], and the other to the left [L])

Condensation reaction

reaction what combines 2 molecules while removing 1 small molecule (H2O)

What is the covalent bond between monosaccharide residues in disaccharides and polysaccharides?

Glycosidic linkage

Hydrolysis reaction

reaction where hydrogen and hydroxide ions from water are added to a large molecule causing it to split into smaller molecules.

Formation of Polysaccharides

Built from many monosaccharide molecules condensed together linked by glycosidic bonds.

Digestion of polysaccharides

Hydrolysis
-Glycosidic bonds in polysaccharides are broken down with the addition of water.
-The rate of the reaction is increased by the enzyme. [eg. amylase]

Formation of Polypeptides

Formed by condensation reactions between many amino acids. [ribosomes, rER]

Digestion of polypeptides

Proteins are digested into shorter chain peptides and ultimately into amino acids.

Catalyzed by Protease enzymes in animals

Formation of Nucleic acids

Condensation reaction between a phosphate group on one nucleotide and a hydroxyl group on a second nucleotide. During this process, a phosphodiester bond is formed, which is the backbone of the nucleic acid structure.

Digestion of nucleic acids

The phosphodiester bond between 3’ carbon of one sugar molecule and 5’ carbon of another sugar molecule.

The hydroxyl group is at the 3’ C atom and the phosphate group is at the 5’ carbon atom.

Hydrolyzed to produce: 3-OH-deoxyribose-5-Phosphate

What are the 2 polysaccharides starch is made up of?

Amylose
[unbranched chain,1,4 linked alpha-glucose units]

Amylopectin
[shorter chains of 1,4 alpha-glucose+ branches of alpha-1,6 glycosidic links]

Describe the structure of starch

• The bonds between glucose residues bring the molecules together as a helix.

• It’s stabilized by many hydrogen bonds the glucose molecules

Why is starch used as a storage in plants rather than glucose?

Starch is insoluble in water, therefore isn’t involved in osmotic movement.

Where is the starch stored in plants?

Plastids

Plastids

• double-membrane organelles which are found in the cells of plants and algae.

• responsible for manufacturing and storing of food.

• often contain pigments that are used in photosynthesis and different types of pigments that can change the color of the cell.

Test for starch

Solution of iodine in potassium iodide

Explain how the compact nature of starch is achieved in plants

Due to the coiling and branching during polymerization.

Glycogen

polymer of alpha-glucose
formed by condensation reactions between monomers of alpha-glucose

Why is glycogen important (or useful)?

• No osmotic effect

• branching; compact structure; stored in small volume

• many non-reducing ends due to the branches: rapid-enzyme controlled hydrolysis during times of high demand

Difference between cellulose molecules, fibrils and fibres

molecules of beta-glucose join together to form cellulose molecules

cellulose molecules join together via hydrogen bonds to form cellulose fibrils

cellulose fibrils join together to form cellulose fibres

Distinguish between the 2 isomers of glucose

alpha-glucose
synthesis of starch and glycogen

beta-glucose
synthesis of cellulose

How and why does the function cellulose differ from the functions of starch and glycogen

Starch and glycogen: used for energy storage

cellulose: primarily for structural support and mechanical strength in plant cell walls.
[the orientation of beta-glucose molecules in cellulose allows hydrogen bonds o form between parallel strands, and between adjacent glucose units in the same strand which strengthens the cellulose polymer]

What are the carbohydrate molecules of the cell membrane? What are they called?

Glycoproteins; Glycolipids
Glycocalyx

What is the role of glycoproteins?

• Cell-cell recognition

• act as receptor sites for chemical signals

• cell adhesion

Antigens

a substance (usually glycoprotein) capable of binding specifically to an antibody.

recognized by the body as foreign and stimulates an immune response

Antibody

a protein produced by blood plasma cells derived from B lymphocytes when in a presence of a specific antigen, which then binds with the antigen, aiding it’s destruction

Agglutination

process in which red blood cells are clumped together by an antibody
which results in blocking of smaller blood vessels and capillaries

describe how agglutination occurs

When there is a blood transfusion between different blood groups [except O]
- If blood group A receives a transfusion of blood group B, then the anti-B antibodies agglutinate foreign B cells.

Blood group A

RBC surface: A antigens

Plasma: anit-B antibodies

Transfusion: A or O

Blood group B

RBC surface: B antigens

Plasma: anti-A antibodies

Transfusion: B or O

Blood group AB

RBC surface: A+B antigens

Plasma: no antibodies

Transfusion: A, B, AB or O

Blood group O

RBC surface: no antigens

Plasma: anti-A antibodies, anti-B antibodies

Transfusion: O only

Formation of Triglycerides

reaction between glycerol and fatty acids

Triglycerides

An ester made from glycerol and 3 fatty acid groups

Fatty acids

long carboxylic acids with long hydrocarbon tails

why are fatty acid molecules named ‘acids’?

their functional group (-COOH) tends to ionize to produce hydrogen ions (property of acids) in aqueous solutions

Ester bonds (in triglycerides)

form between alcohols (1 glycerol) and carboxylic acids (3 fatty acids)

Saturated fats
Unsaturated fats
Monounsaturated fats
Polyunsaturated fatty acids

Built from only saturated fatty acids

Built from 1 or more unsaturated fatty acids

Built from only 1 double bond in the carbon chain of a fatty acid

Built from large amounts of double bonds in the carbon chain of a fatty acid

Excess of lipids and fatty acids in diets

Lack of lipids and fatty acids in diets

• excess fat in the fat cells that make up the adipose tissue

• type 2 diabetes

• obesity, overweight

• high blood pressure

- amino acids derived from protein digestion
- muscle proteins broken down

Adipose tissue

a tissue found beneath the skin layer, containing fat cells (subcutaneous fat)

Fat as buoyancy aid and thermal insulator

Blubber present in aquatic mammals gives buoyancy to the body as fat isn’t as dense as muscle or bone.

When there is restricted blood supply and heat is not distributed to the fat under the skin, then the subcutaneous fat functions as a heat insulation layer.

Fats as energy source and metabolic water source

• Fats and oils release twice the energy as carbohydrates during respiration.

• Fats are more reduced than carbs (have more hydrogen atoms)

• Oxygen for respiration of fats comes from the atmosphere while for carbs it comes from the molecule itself making fats a more concentrated insoluble energy source.

• Complete oxidation of fats and oils produces a large amount of water compared to the respiration of carbs.

• This metabolic water is used by animals like camels and desert rats for survival.

How do phospholipid bilayers form

Due to its amphipathic nature:

Hydrophobic tail repels water

Hydrophilic head attracted to water

Presence of water results in the bilateral arrangement.

What are the consequences of the amphipathic nature of phospholipid?

• Remains as a discrete bubble when in contact with a solid surface but spreads out when in contact with water

• Bilayer is formed precentung the hydrophobic tails from contact with water.

• Attraction between tails and heads forms a strong, stable barrier.

• Components of triglycerides

• 3 fatty acid molecules

• 1 glycerol molecule

• Components of phospholipid

• 2 fatty acid molecules

• 1 glycerol molecule

• 2 phosphate group

Components of cholesterol

• Carbon skeleton with 4 fused carbon rings

• Hydrocarbon tail

• Hydroxyl group

Bond between the components of triglycerides

Ester bonds

Bonds between the components of phospholipids

2 ester binds

1 phosphoester bond

Binds between the components of cholesterol

Carbon-Carbon single bonds

Carbon-Hydrogen single bonds

Properties of triglycerides

• Non polar

• Insoluble in water

• Soluble in organic solvents

• More compact than carbohydrates

Properties of phospholipids

• Amphipathic

• Soluble in water and oil

• More compact than carbohydrates

Properties of cholesterol

• Non polar

• almost insoluble in water

• Soluble in organic solvents

• More compact than carbohydrates

Function of triglycerides

• Energy store

• Thermal insulation

• Protection

• Buoyancy

Function of phospholipid

• Basic structure of plasma membrane

• Association with oligosaccharides to form glycolipids which help in cell recognition and adhesion

Function of cholesterol

• Complement of cell membrane

• Regulates membrane fluidity

• Maintains mechanical stability

• Prevents leakage of small polar molecules

• Involved in synthesis of steroid hormones

What is the lipid bilayer permeable to

Non polar substances including steroids

Steroid hormones

Oestrodiol

Testosterone

Oestrodiol

Involved in the coordination of menstrual cycle

Development of secondary sexual characteristics

Testosterone

Development of secondary sexual characteristics

Why are Oestrodiol and testosterone anabolic steroids

Because their increased secretion stimulates muscle protein formation and bone growth