Carbohydrates(CHO) e.g.Starch, Glucose,Sucrose
Lipids/Fats(CHO), e.g.Saturated,Unsaturated,Triglycerides
Proteins (CHON),e.g. Enzymes,Hormones,Antibodies
Biological Tests– chemical testingfor present ofthese molecules
Biological Molecules
What you need
to learn…
Importance ofWater &Inorganic Ions
The Importance of Water
Water is vital to all living organisms, it makes up 80% of cells, isused in transporting substances, is needed for metabolicreactions (like R/P) and helps with temperature control.
Properties of Water:
Polar – the negatively charged Oxygen atom and positivelycharged Hydrogen atoms
Cohesion – the negative & positive ends of water moleculescause them to attract to each other and form Hydrogen bonds(H bonds)
High Surface Tension – acts like it has a skin
High Specific Heat Capacity – it takes a lot of energy to heat itup (amount of energy needed to raise 1g by 1°C)
High Latent Heat – needs a lot of heat energy to evaporate it
Maximum Density at 4°C – means ice floats (less dense thanliquid form)
Water’s Polarity makes it a Good Solvent
Salt (Sodium Chloride)dissolving in water:
Oxygenatom
Hydrogenatoms
Click to see water in motion!
What molecules are foods made of?
There are three main types of food molecules.
Proteins are chains of differentamino acids.
Fats are made up of lipids. A lipidhas a structure of three fatty acidmolecules and a glycerol molecule.
Carbohydrates are chains ofrepeating molecules of glucoseand other sugars.
Food also contains vitamins and minerals, which are
needed in small amounts for a healthy body.
Carbohydrates
Monosaccharides(M/S)
•(or Simple sugars)
•All carbohydratesare made of sugarmolecules.
•A single sugarmolecule is called amonosaccharide
•E.g. Glucose,Fructose, Ribose
•Formed when two M/Sjoin together
•Occurs during aCONDENSATION REACTION– where a water moleculeis released
•The link between the twosugar molecules is calleda GLYCOSIDIC BOND.
•E.g. Sucrose, Maltose,Lactose
•Made up ofhundreds of M/Sjoined together
•Long chains of M/Sare joined byglycosidic bonds
•P/S can bebranched orunbranched.
•E.g. Starch,Cellulose, Glycogen
Disaccharides (D/S)
Polysaccharides (P/S)
Carbohydrates are compounds of Carbon, Hydrogen and Oxygen. Theyare the source of energy in all living things and can add strength andsupport to cell membranes & cell walls.
Monosaccharides (M/S)
-glucose
-glucose
Or more simply…
Disaccharides (D/S)
Examples of Disaccharides
Sucrose: glucose + fructose,Lactose: glucose + galactose,Maltose: glucose + glucose.
Sucrose is used in many plants for transporting foodreserves, often from the leaves to other parts of the plant.Lactose is the sugar found in the milk of mammals andmaltose is the first product of starch digestion and isfurther broken down to glucose before absorption in thehuman gut.
Polysaccharides
Poly-saccharide:
Function:
Structure:
Relationship ofstructure to function:
Starch
Main storagepolysaccharide inplants.
Made of 2 polymers - amylose andamylopectin.
Amylose: a long unbranched chain ofalpha-glucose. The angles of theglycosidic bonds give it a coiledstructure (also called a helix)
Amylopectin: a long branched chain ofalpha-glucose. Its side branches make itparticularly good for the storage ofglucose.
Insoluble therefore good forstorage.
Helix is compact and goodfor storage.
The branches mean that theenzymes can get to theglycosidic bonds easily tobreak them & release theglucose.
Glycogen
Main storagepolysaccharide inanimals andfungi
Similar to amylopectin but with manymore branches which are also shorter.
The number and length ofthe branches means that it isextremely compact and veryfast hydrolysis.
Cellulose
Main structuralcomponent ofplant cell walls
Adjacent chains of long, unbranchedpolymers of glucose joined by b-1,4-glycosidic bonds hydrogen bond witheach other to form microfibrils.
The microfibrils are strongand so are structurallyimportant in plant cell walls.
What they look like…
(Amylose)
(Amylopectin)
Cellulose
Starch
Glycogen
Lipids
Lipids are made up of the elements Carbon,Hydrogen and Oxygen but in differentproportions to carbohydrates (less O2). Themost common type of lipid is the triglyceride.
Lipids can exist as fats, oils and waxes. Fats andoils are very similar in structure (triglycerides).
•At room temperature, fats are solids and oils areliquids. Fats are of animal origin, while oils tendto be found in plants.
•Waxes have a different structure (esters of fattyacids with long chain alcohols) and can befound in both animals and plants.
Functions of Lipids
1.High-energy store - they have a high proportion of H atomsrelative to O atoms and so yield almost twice as much energythan the same mass of carbohydrate.
2.Thermal insulation - fat conducts heat very slowly so having alayer under the skin (adipose tissue) keeps metabolic heat in.
3.Shock absorption – acts as a cushion against blows (to organs)
4.Buoyancy - as lipids float on water, they can have a role inmaintaining buoyancy in organisms.
5.Storage - lipids are non-polar and so are insoluble in water, so can bestored/localised in animals.
6.Production of water - some water is produced as a final result ofrespiration.
7.Electrical insulation - the myelin sheath around axons prevents ionleakage.
8.Waterproofing - waxy cuticles are useful, for example, to prevent excessevaporation from the surface of a leaf.
9.Hormone production - steroid hormones. Oestrogen requires lipids forits formation, as do other substances such as plant growth hormones.
Triglycerides
A triglyceride molecule is made of a glycerolmolecule and three fatty acids.The molecules join together through the processof condensation losing a molecule of water eachtime a link is made.
Glycerolmolecule
3 FattyAcid Tails
How triglycerides are formed:
Fatty acids are chains of carbon atoms, the terminal one havingan OOH group attached making a carboxylic group (COOH).The length of the chain is usually between 14 and 22carbons long.
Three fatty acid chains become attached to a glycerol moleculewhich has 3 OH groups attached to its 3 carbons.
This is called a condensation reaction because 3 watermolecules are formed from 3 OH groups from the fatty acidschains and 3 H atoms from the glycerol.
The bond between the fatty acid chain and the glycerol is calledan ester linkage.
3 Water Moleculesare formed here
Ester links areformed betweenthese atoms
A Special Type of Lipid…Phospholipids
Phospholipids are important in the formationand functioning of cell membranes in cells.They have a slightly different structure totriglycerides:
• A phosphate group replaces one ofthe fatty acid chains/groups
• The phosphate group is hydrophilic(attracts water) and is polar
• The rest of the molecule (fatty acidtails) is hydrophobic (repels water) andnon-polar
Glycerol
Fatty Acid tails(hydrophobic)
Phosphate(hydrophilic)
Functions of proteins
1.Virtually all enzymes are proteins.
2.Structural: e.g. collagen and elastin in connective tissue,keratin in skin, hair and nails.
3.Contractile proteins: actin and myosin in muscles allowcontraction and therefore movement.
4.Hormones (Signal Proteins): many hormones have a proteinstructure (e.g. insulin, glucagon, growth hormone).
5.Transport: for example, haemoglobin facilitates the transport ofoxygen around the body, a type of albumin in the bloodtransports fatty acids.
6.Transport into and out of cells: carrier and channel proteins inthe cell membrane regulate movement across it.
7.Defensive: immunoglobulins (antibodies) protect the bodyagainst foreign invaders; fibrinogen in the blood is vital for theclotting process.
Proteins
Proteins are amino acid polymers. Twenty different aminoacids exist naturally. These link up in different orders to formall the many different proteins present in living organisms. Allamino acids contain four distinct chemical groups connectedto a central carbon atom:
• a single hydrogen atom
• an amino group (NH2)
• a carboxyl group (COOH)
• a side chain (this is represented by the letter R & differs indifferent amino acids)
Joining Amino acids Together
The amino acids in a protein are joined together byCONDENSATION reactions and broken apart byHYDROLYSIS reactions (just like in carbohydrates & lipids).The bonds formed between amino acids are calledPEPTIDE bonds.
Two amino acids joined together are called a dipeptide.
Structure of Proteins
Proteins are big complicated molecules. Their structure can beexplained in four ‘levels’. These levels are called the protein’sPRIMARY, SECONDARY, TERTIARY and QUATERNARYstructures.
The primary structureis the sequence of theamino acids in the longchain that makes up theprotein (the polypeptidechain)
Secondary Structure
Chains of amino acids (polypeptides) can formcoils (α-helix) or pleats (β-pleated sheets).This coiling or pleating is called the proteins’secondary structure. The secondary structure isheld together by Hydrogen bonds.
Tertiary Structure
Long polypeptide chains often fold and are joinedby additional, weak chemical (ionic) bonds thatgive the protein a complex 3-dimensonal shape.This is the tertiary structure.
Quaternary Structure
Finally, some proteins are made of several differentpolypeptide chains held together by variousbonds. The quaternary structure is the way thesedifferent parts are assembled together.
Types of bonds:
The shape of the protein is held together by Hydrogen bondsbetween some of the R groups (side chains) and Ionic bondsbetween positively and negatively charged side chains. These areweak interactions, but together they help give the protein a stableshape. The protein may be reinforced by strong covalent bondscalled Disulphide bridges which form between two amino acidswith sulphur groups on their side chains (cysteine).
Hydrophobic bonds form when water-repelling hydrophobic groupsare close together in the protein & tend to clump together
Each protein formed has a precise and specific shape.
Protein Shape Relates to Function
Fibrous proteins are made of long molecules arranged to formfibres (e.g. in keratin). Several helices may be wound around eachother to form very strong fibres. Collagen is another fibrousprotein, which has a greater tensile strength than steel because itconsists of three polypeptide chains coiled round each other in atriple helix. We are largely held together by collagen as it is foundin bones, cartilage, tendons and ligaments. Insoluble in H2O.
Globular proteins are made of chains folded into a compactstructure. One of the most important classes are the enzymes.Although these folds are less regular than in a helix, they arehighly specific and a particular protein will always be folded in thesame way to form a roughly spherical molecule. If the structure isdisrupted, the protein ceases to function properly and is said to bedenatured. An example is insulin, a hormone produced by thepancreas and involved in blood sugar regulation. Soluble in H2O.
A globular protein based mostly on an -helix is haemoglobin. Itsstructure is curled up, so hydrophilic (water attracting) side chains areon the outside of the molecule and hydrophobic (water repelling) sidechains face inwards. This makes it soluble and good for transport inblood,
Inorganic Ions in Living Things
Many inorganic ions that can dissolve in water are importantin the metabolism of organisms.
Remember: ions = charged particles
Inorganic ions = ions that don’t contain Carbon
ION
IMPORTANT USE
Calcium (Ca2+)
For forming Bones
Sodium (Na2+)
Involved in Nerve transmission
Potassium (K+)
Activates enzymes
Magnesium (Mg2+)
Contained in Chlorophyll
Chloride (Cl-)
Produces hydrochloric Acid (HCl) in Stomach
Nitrate (NO3-)
Makes Proteins in Plants
Phosphate (PO43-)
Needed for ATP production