B1.1: Carbohydrates and LIpids IBDP Biology

Chemical properties of carbon atom

-Carbon has 4 valencies, can form 4 single bonds or 2 double bonds or both single and double

- covalent bonds with other compounds

-Covalent bonds formed by carbon atom can spread apart to form a tetrahedral shape

-there can be branced or unbranced chains formed

- formation of single or multiple rings

what are macromolecules

large molecules formed from a lagre number of atoms

what are monomers

Subunits of polymers, which may be identical or of different types

what are polymers

long chain of monomers used to form macromolecules

examples/ classes of macromolecules

polysaccharides (ex: cellulose) , poplypeptides(proteins) and nucleic acids(DNA)

polymers can turn to monomers by which reaction

hydrolysis

what is hydrolysis

the chemical breakdown of a compound due to reaction with water.

-Water molecules are split to provide the -H and -OH groups that are incorporated to produce monomers,

hence the name of this type of reaction.

which elements do carbohydrates contain

carbon, hydrogen and oxygen

What are monosaccharides?

simple sugars

have 3-7 carbon atoms

Examples of monosaccharides

glucose (hexose sugar), ribose (pentose sugar), fructose

how are monosaccharides linked

by condensation reactions to form disaccharides and polysaccharides

properties of monosacchride (ex:glucose)

-soluble and small

-easily transported

-circulates in blodd, dissolved in plasma

- chemically stable

-if stored in large quantities can cause osmotic problems

-yields energy when oxidised

Oligosaccharides

2-8 units of carbohydrates

Polysaccharides

9 or more units of carbohydrates

examples of polysacchardies

starch, glycogen, cellulose

why are polysaccharides used as enegry stores

compact nature of starch in plants and glycogen in animals due to coiling and branching during polymerization

-the relative insolubility of these compounds due to large molecular size and the relative ease of adding or removing alpha-glucose monomers by condensation and hydrolysis to build or mobilize energy stores.

what are the bonds formed in polysaccharides

1-4 glycodisc bonds and 1-6 glycosidic bonds

alpha and beta glucose

Alpha: hydroxyl group of carbon-1 is below the plane of ring

Beta: hydroxyl group of carbon-1 is above the ring

Structure of cellulose

-alternating orientation of beta-glucose monomers

-giving straight chains that can be grouped in bundles and cross-linked with hydrogen bonds.

- all are 1-4 glycosidic bonds, unbranched chain

-strong tensile strength (prevents plant cells from bursting)

what are 2 forms of starch

amylose and amylopectin

What is amylose and amylopectin?

-amylose is a linear polysaccharide, with a 1 → 4 α(alpha)-linkage

- amylopectin is a branched polysaccharide, has both 1 → 4 and 1 → 6 α -linkages.

Glycoproteins

poplypeptides with carbohydrate attached (mostly an oligosaccharide)

Role of glycoproteins

By displaying distictive glycoproteins, cells allow other cells to recognise them

-cell-to-cell recognisition (helps with organisation of tissues, allow foreign substances to be identified)

Examples of glycoproteins

ABO antigens in RBC

why glycoprotein O does not cause rejection for blood donation

it has same strcture as A and B but with one less monosaccharide

Lipids

substances that dissolve in non-polar solvents (lipids are hydrophobic)

examples of lipids

fats,oils, waxes, steroids

Importance of lipids

Storage, insulation, protection

Formation of triglycerides

by condensation reactions, One glycerol molecule can link three fatty acid molecules , 3 water molecules produced

Different types of fatty acids

-saturated(Carbon Carbon single bonds)

- unsaturated- monounsaturated(1 Carbon Carbon double bond)

-and polyunsaturated(more than 1 Carbon Carbon double bond)

Fetaures of phospholipids

-stable structures

-basis of cell membrane

-Amphipathic (hydrophilic and hydrophobic)

Formation of phospholipids

two fatty acid molecules and one phosphate group. Phosphate grop is hydrophilic so phospholipids are both hydrophobic and hydrophilic

Where are lipids stored

In adipose tissue, ommediately beneath the skin and also around some organs

general formula for fatty acid

CH3(CH2)nCOOH

what are cis fatty acids

has both hydrogen atoms located on the same side

what are trans fatty acids

trans fatty acid has the two hydrogen atoms on opposite sides.

double carbon (C=C) bonds and how this affects melting point

The intermolecular interactions are much weaker than saturated molecules. As a result, the melting points are much lower for unsaturated fatty acids.

Triglycerides in adipose tissues

-energy storage cause they are chemically stable so enegry is not lost over time

-thermal insulation

-immisible with water so forms droplets in cytoplsm to avoid osmotic effects

-more energy than carbohydrates

-poor conductors of heat

-liquid at body temp, shock absorber

Steroids

4 fused ring of carbon atoms, hydrophobic so can pass through phospholipid bilayerand can enter or leave cells easily

strcture of steroids

3 cyclohexane rings, 1 cyclopentane ring

examples of steroids

oestradiol and testosterone