Edexcel B A Level Biology Topic 1

monosaccharides

single simple sugar molecule

disaccharides

sugar made up off two monosaccharide units joined by a glycosidic bond formed in a condensation reaction

polysaccharides

polymer made up of long chains of monosaccharide units joined by glycosidic bonds

condensation reaction

reaction in which a molecule of water is removed from the reacting molecules as a bond is formed between them

glycosidic bond

covalent bond formed in a condensation reaction

anion

negative ion formed when an atom gains an electron

cation

positive ion formed when an atom loses an electron

ionic bonds

attractive forces between oppositely charged ions

covalent bonds

formed when atoms share electrons

dipole

separation of charge in a molecule when the electrons in a covalent bond are not evenly shared

polar molecule

molecule containing a dipole

hydrogen bonds

weak electrostatic intermolecular bonds formed between polar molecules containing at least one hydrogen atom

monomer

small molecule that is a single unit of a larger molecule called a polymer

polymer

long chain molecule made up of many smaller repeating monomer units joined together by chemical bonds

macromolecule

very large molecule formed by polymerisation

starch

energy store in plants made of amylose and amylopectin. Insoluble and compact and can be broken down rapidly to release glucose

sucrose

sweet tasting disaccharide formed by the joining of a glucose and fructose by a glycosidic bond

glucose

hexose sugar

triose sugar

sugar with 3 carbon atoms and important in mitochondria

pentose sugar

sugar with 5 carbon atoms and important in nucleic acid

ribose

pentose sugar that makes up part of the structure of RNA

deoxyribose

pentose sugar that makes up part of the structure of DNA

deoxyribonucleic acid

nucleic acid that acts as the genetic material in many organisms

ribonucleic acid

nucleic acid which can act as the genetic material in some organisms and is involved in protein synthesis

hexose sugar

sugar with 6 carbon atoms and taste sweet

isomers

molecules that have the same chemical formula, but different molecular structures

nitrate ions (NO3)-

needed in plants for formation of amino acids and DNA

phosphate ions (PO4)3-

forms ATP, ADP, DNA and RNA

calcium ions (Ca)2+

forms calcium pectate for middle lamella between cell walls

magnesium ions (Mg)2+

produces chlorophyll in plants

water- polar solvent

ionic substances dissolve in it and can carry other substances

water- transport

substances dissolve in it and can be transported

water- density

ice is less dense than water, and maximum density at 4C

water- high SHC

slow to absorb and release heat and a large amount of energy is needed to change temp of large bodies

water- hydraulics

liquid can't be compressed

water- cohesive

sticks together and helps movement of water from root to leaves

water- adhesive

stick to other molecules and helps plant transport systems and surface tensions

water- high surface tension

attraction between molecules is greater than attraction to air, so helps life at surface of ponds

water- incompressibility

molecules are close together so can't be compressed

𝛼 glucose

isomer

β glucose

isomer

hydrogenation of sugars

reduces energy they provide but taste sweet so used for weight loss

1,4 glycosidic bond

bond between carbon 1 and carbon 4

1,6 glycosidic bond

bond between carbon 1 and carbon 6

lactose (1,4)

glucose and galactose- present in mammalian milk

maltose (1,4)

glucose and glucose- formed by amylase in starch

sucrose (1,2)

glucose and fructose- found in sugar cane

benedicts test- reducing sugars

colour change from blue copper ii ions to orange copper i ions, forming a precipitate- all monosaccharides and disaccharides

benedicts test- non reducing sugars

heat with HCl and neutralise with sodium hydrogen carbonate to hydrolyse the glycosidic bonds, producing monosaccharides

polysaccharides' properties

good storage and can form compact molecules, also inactive and not very soluble so doesn't interfere with osmosis

hydrolysis

breaking of a glycosidic bond with the addition of a water molecule

amylose

long chains of 𝛼 glucose- unbranched and spirals so very compact

only 1,4 glycosidic bonds so release glucose slowly over long time

amylopectin

long chains of 𝛼 glucose- branched so terminals break off easily when energy is needed

mainly 1,4 glycosidic bonds but a few 1,6

glycogen

aka animal starch- storage carb in fungi and very similar to amylopectin- even more 1,6 glycosidic bonds so many side branches s

can be broken down even more rapidly

source of glucose for active tissue (muscle)

cellulose

insoluble and keeps cell wall strong

made of β glucose and help together by 1,6 glycosidic bonds

every other glucose is inverted for bonding and H bonds form between hydroxyl group and oxygen toms

known as cross linking and holds neighbouring chains together

doesn't coil or spiral and cannot be digested by animals so acts as roughage in human diet

lipids

part of cell membranes

used as an energy store

ester bond

formed between glycerol and fatty acids

lipids' energy

3 times more energy than carbohydrates released during condensation reaction, so 3 water molecules released

properties of lipids

insulators

low density so float

dissolve in solvents but insoluble in water so don't interfere with reactions in the cytoplasm

phospholipids

created when hydroxyl groups of glycerol react with a phosphate instead of fatty acid in the cytoplasm

micelle

hydrophilic head

hydrophobic tail

monolayer

bilayer

proteins

made up of amino acids

amino acids

20 different naturally occurring types that combine in different ways to produce different proteins

peptide bond

formed between the carboxyl group and amino group of amino acids

protein bonds- hydrogen

formed between + change of H and - charge of O of the carboxyl group

very weak

easily break of pH or temp changes

protein bonds- disulphide

oxidation reaction between 2 sulphur containing R groups

very strong but not many

protein bonds- ionic

form between very strong + and - chains

aka salt bridges

very strong but not common

primary structure of proteins

linear sequence of amino acids in a polypeptide chain

secondary structure of proteins

alpha helix caused by peptide bonds with the R group sticking out

beta sheets held together by hydrogen bonds

fibrous

tertiary structure of proteins

alpha helices and beta sheets folded further with bonds holding 3d shapes in place

quaternary structure of proteins

3d arrangement of tertiary polypeptide chains

fibrous proteins

long parallel polypeptide chains with cross linkages that form fibres

insoluble in water

collagen

35% of protein in our bodies is collagen and it is very strong

globular proteins

tertiary and quaternary structure folded into spherical shapes

keep the structure in the cytoplasm

instead of dissolving in water they form a colloid as so big

conjugated protein

prosthetic group-what some protein molecules are joined with

glycoproteins- have a carb prosthetic group so can hold a lot of water and harder for proteases to break them down