B1.1 CARBOHYDRATES AND LIPIDS

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explain the chemical properties of a carbon atom which allows for the formation of diverse compounds upon which life is based

• is an organic compound (compound containing C and found in living things) (except for carbonates, CO2, cyanide)

• carbon can form up to four covalent bonds (single or double) with other carbons or non-metallic elements (O,H,S,N,P)

  • structures can vary from unbranched, branched, ring, cyclic

  • bonds between carbon is extremely stable

    • more than most atoms in the periodic table, results in formation of diverse compounds of which life is based on

      • EXAMPLE: amino acids, nucleotides, carbs

outline the production of macromolecules by condensation reaction that link monomers to form a polymer

• monomers are recurring subunits covalently joined to form polymers

• polymers form monomers by condensation reactions

  • water molecule removed as a byproduct

outline the the digestion of polymers into monomers by hydrolysis reactions

• polymers broken down into monomers by hydrolysis

  • water molecule added as a reactant to facilitate the breakage of covalent bonds between the monomers

carbohydrates, proteins and nucleic acids

examples: (subcatagory) monomers → (catagory) polymers (bond between monomers)

examples: monomers → polymers (bond between monomers)

• monosaccharide, disaccharide, polysaccharide → carbohydrate (glycosidic bond)

• amino acid, polypeptide → protein (peptide bond)

• nucleotide, polynucleotide → nucleic acids (phosphodiester bond)

outline the form and function of monosaccharides

• carbohydrates composed of reaccuring monomers called monosaccharides

  • they are single sugar units

• serve as source of energy for cells, oxidised to produce large quantities of ATP

  • solubility: polar molecules so they dissolve in H2O

  • stability: cyclic/ring structure

  • transport: soluble and stable, good transport in aqueous solutions

  • potential energy: have high energy due to presence of multiple C–H bonds

• classified by the number of carbon atoms

  • pentose(5C) - deoxyribose, ribose

  • hexose(6C) - primarily used as energy source for cellular respiration

state the 2 isomers of glucose and draw them

• 2 isomers: α-glucose and β-glucose

  • α-glucose - OH group point down on 1’ C

  • β-glucose - OH group point up on 1’ C

use glucose as an example of a monosaccharide to outline the structure, properties, and function

• isomers play an important role in the formation of different structures of polysaccharides

• soluble molecule

  • presence of many -OH groups cause it to be polar

  • O in the ring is slightly negative

  • formation of hydrogen bonds between hydroxyl group and water causes it to dissolve easily and can be transported in blood and in fluids between cells

• stable molecule

  • cyclic structure

  • polysaccharides it forms are also stable

  • glycosidic bonds within glucose are stable covalent bonds

• yields a lot of chemical energy when the covalent bonds are hydrolysed

outline the formation of the disaccharide, maltose

• condensation reaction between 2 α-glucose creates maltose + H2O

• 1,4 glycosidic bond is formed between the groups attached to carbon-1 of the first glucose molecule and carbon-4 or the second

explain how polysaccharides can act as energy storage compounds

• energy storage compounds

  • easy to add/remove α-glucose monomers to build/imobilise energy stores

  • insoluble due to large molecular size

  • examples: starch in plants, glycogen in animals (both are polymers made up of α-glucose)

• structural compounds

  • branching to adopt more compact structures (however large sizes are insoluble in water, therefore they cannot be transported within aqueous solutions such as blood)

  • examples: cellulose (made up of β-glucose)

examples of polysaccharides: outline the structure of cellulose and how it supports the function

• composed of β-glucose subunits with β-1,4 glycosidic bonds

  • alternating orientation of β-glucose monomers to create a straight chain

  • straight chain is then grouped in bundles and cross-linked with hydrogen bonds

    • increases structural identity

    • prevents access to water, making cellulose resistant to hydrolysis (acts as an excellent structural compound)

• structure:

  • composed of β-glucose subunits with β-1,4 glycosidic bonds

    • alternating orientation of β-glucose monomers to create a straight chain

    • straight chain is then grouped in bundles and cross-linked with hydrogen bonds

• function:

examples of polysaccharides: outline the structure of starch and how it supports the function

• structure:

  • composed of 2 α-glucose subunits, amylose and amylopectin

    • amylose: 1,4 glycosidic linkages formed into helical arrangement

    • amylopectin: 1,4 glycosidic and 1,6 glycosidic linkages

  • Insoluble due to large molecular size

• function:

  • storage molecule in plants

    • insoluble in H2O

      • will not affect the osmotic potential

    • compact structure

      • able to store alot of glucose in a very small space

examples of polysaccharides: outline the structure of glycogen and how it supports the function

• structure:

  • composed of α-glucose (similar to amylopectin but more cross-links, highly branched and shorter α 1,4 chains)

• function:

  • storage molecule in animals

    • insoluble in H2O

      • will not affect the osmotic potential

    • compact structure

      • able to store alot of glucose in a very small space

explain the role of glycoproteins in cell–cell recognition

• glycoproteins are proteins that are attached to carbohydrates to perform cell-cell recognition, acting as markers on the cell surface

  • example: human RBC (ABO blood types)

    • categorised into blood types by surface glycoproteins which function as identification tags for the immune system

outline the properties of lipids and give examples of the different types

• lipids are hydrophobic

• non-polar organic molecules

  • composed of hydrocarbon chains/rings (non-polar covalent bonds)

• they are fatty acids

• soluble in non-polar solvents and slightly soluble in polar solvents

• examples of lipids include waxes, steroids, phospholipids, triglycerides

outline what waxes are, its structure and its function

• composed of C, H , O atoms

• hydrophobic

• contists of an ester

  • a fatty acid and alchohol undergoes a condensation reaction to make wax, h2o is released and the fatty acid and alcohol are linked by an ester bond

outline what steroids are, its structure and its function

• composed of C, H, O atoms

• made of 4 hydrocarbon rings fused together

• hydrophobic

• used as building blocks for steroid hormone (testosterone, progesterone)

outline what triglycerides are, its structure and its function

• composed of C, H, O atoms

  • don’t release that much energy when oxidised

• hydrophobic

  • helps with long term energy storage as it will not affect the osmotic pressure

• made up of glycerol and 3 fatty acid molecules (cis, trans, saturated

outline what phospholipids are, its structure and its function

• composed of C, H, O, P molecules

• consists of a polar head which is hydrophilic and 2 non polar tails which are hydrophobic (it is amphipathic)

• phospholipids spontaneously arrange into bilayer which is held by hydrophobic interactions between non polar tails

outline the formation of triglycerides and phospholipids by condensation reactions

outline the structure and properties of glycerol

• highly soluble

outline the different types of fatty acids, the structure, and its properties

mono-unsaturated: one double bond

poly-unsaturated: more than one double bond

explain the use of saturated and unsaturated fatty acids in oils and fats used for energy storage in plants and endotherms respectively

explain why triglycerides in adipose tissues are ideal for energy storage and thermal insulation

explain the ability of non-polar steroids to pass through the phospholipid bilayer

• steroids are composed of four fused C rings

  • they are non polar meaning they are hydrophobic

  • they are small in size, allowing them to fit in between the bilayer

• since the phospholipid bilayer consists of hydrophobic tails, the steroids are able to pass through as they are the same medium steroid hormone freely pass through the phospholipid bilayer and bind to receptors within cell, but cannot be transported by blood

• steroid hormone freely pass through the phospholipid bilayer and bind to receptors within cell, but cannot be transported by blood