Biological Molecules

Carbohydrates (CHO) e.g. Starch, Glucose, Sucrose Lipids/Fats (CHO), e.g. Saturated, Unsaturated, Triglycerides Biological Molecules Importance of Water & Inorganic Ions What you need to learn… Proteins (CHON), e.g. Enzymes, Hormones, Antibodies Biological Tests – chemical testing for present of these molecules

The Importance of Water Water is vital to all living organisms, it makes up 80% of cells, is used in transporting substances, is needed for metabolic reactions (like R/P) and helps with temperature control. Properties of Water: Polar – the negatively charged Oxygen atom and positively charged Hydrogen atoms Cohesion – the negative & positive ends of water molecules cause 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 it up (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 than liquid form)

Oxygen atom Hydrogen atoms Water’s Polarity makes it a Good Solvent Click to see water in motion! http://www.northland.cc.mn.us/biology/Biology1111/animations/hydrogenbonds.html Salt (Sodium Chloride) dissolving in water:

Food also contains vitamins and minerals, which are needed in small amounts for a healthy body. What molecules are foods made of? There are three main types of food molecules. • Carbohydrates are chains of repeating molecules of glucose and other sugars. • Proteins are chains of different amino acids. • Fats are made up of lipids. A lipid has a structure of three fatty acid molecules and a glycerol molecule.

http://www.bbc.co.uk/education/asguru/biology/02biologicalmolecules/02carbohydrates/index.shtmlhttp://www.bbc.co.uk/education/asguru/biology/02biologicalmolecules/02carbohydrates/index.shtml Carbohydrates Carbohydrates are compounds of Carbon, Hydrogen and Oxygen. They are the source of energy in all living things and can add strength and support to cell membranes & cell walls. • Monosaccharides (M/S) • (or Simple sugars) • All carbohydrates are made of sugar molecules. • A single sugar molecule is called a monosaccharide • E.g. Glucose, Fructose, Ribose • Formed when two M/S join together • Occurs during a CONDENSATION REACTION– where a water molecule is released • The link between the two sugar molecules is called a GLYCOSIDIC BOND. • E.g. Sucrose, Maltose, Lactose • Made up of hundreds of M/S joined together • Long chains of M/S are joined by glycosidic bonds • P/S can be branched or unbranched. • E.g. Starch, Cellulose, Glycogen Disaccharides (D/S) Polysaccharides (P/S)

Monosaccharides (M/S) http://www.bbc.co.uk/education/asguru/biology/02biologicalmolecules/02carbohydrates/15monosaccharides/index.shtml -glucose -glucose Or more simply…

http://www.bbc.co.uk/education/asguru/biology/02biologicalmolecules/02carbohydrates/16disaccharides/index.shtmlhttp://www.bbc.co.uk/education/asguru/biology/02biologicalmolecules/02carbohydrates/16disaccharides/index.shtml Disaccharides (D/S) Examples of Disaccharides Sucrose: glucose + fructose,Lactose: glucose + galactose,Maltose: glucose + glucose. Sucrose is used in many plants for transporting food reserves, often from the leaves to other parts of the plant. Lactose is the sugar found in the milk of mammals and maltose is the first product of starch digestion and is further broken down to glucose before absorption in the human gut.

Poly-saccharide: Function: Structure: Relationship of structure to function: Starch Main storage polysaccharide in plants. Made of 2 polymers - amylose and amylopectin. Amylose: a long unbranched chain of alpha-glucose. The angles of the glycosidic bonds give it a coiled structure (also called a helix) Amylopectin: a long branched chain of alpha-glucose. Its side branches make it particularly good for the storage of glucose. Insoluble therefore good for storage. Helix is compact and good for storage. The branches mean that the enzymes can getto the glycosidic bonds easily to break them & release the glucose. Glycogen Main storage polysaccharide in animals and fungi Similar to amylopectin but with manymore branches which are also shorter. The number and length of the branches means that it is extremely compact and very fast hydrolysis. Cellulose Main structural component of plant cell walls Adjacent chains of long, unbranched polymers of glucose joined by b-1,4-glycosidic bonds hydrogen bond with each other to form microfibrils. The microfibrils are strong and so are structurally important in plant cell walls. Polysaccharides

What they look like… Starch (Amylose) (Amylopectin) Cellulose Glycogen

http://www.bbc.co.uk/education/asguru/biology/02biologicalmolecules/03lipids/index.shtmlhttp://www.bbc.co.uk/education/asguru/biology/02biologicalmolecules/03lipids/index.shtml Lipids Lipids are made up of the elements Carbon, Hydrogen and Oxygen but in different proportions to carbohydrates (less O2). The most common type of lipid is the triglyceride. Lipids can exist as fats, oils and waxes. Fats and oils are very similar in structure (triglycerides). • At room temperature, fats are solids and oils are liquids. Fats are of animal origin, while oils tend to be found in plants. • Waxes have a different structure (esters of fatty acids with long chain alcohols) and can be found in both animals and plants.

Functions of Lipids • High-energy store - they have a high proportion of H atoms relative to O atoms and so yield almost twice as much energy than the same mass of carbohydrate. • Thermal insulation - fat conducts heat very slowly so having a layer under the skin (adipose tissue) keeps metabolic heat in. • Shock absorption – acts as a cushion against blows (to organs) • Buoyancy - as lipids float on water, they can have a role in maintaining buoyancy in organisms. • Storage - lipids are non-polar and so are insoluble in water, so can be stored/localised in animals. • Production of water - some water is produced as a final result of respiration. • Electrical insulation - the myelin sheath around axons prevents ion leakage. • Waterproofing - waxy cuticles are useful, for example, to prevent excess evaporation from the surface of a leaf. • Hormone production- steroid hormones. Oestrogen requires lipids for its formation, as do other substances such as plant growth hormones.

Glycerol molecule 3 Fatty Acid Tails Triglycerides A triglyceride molecule is made of a glycerol molecule and three fatty acids.The molecules join together through the process of condensation losing a molecule of water each time a link is made.

How triglycerides are formed: Fatty acids are chains of carbon atoms, the terminal one having an OOH group attached making a carboxylic group (COOH). The length of the chain is usually between 14 and 22 carbons long. Three fatty acid chains become attached to a glycerol molecule which has 3 OH groups attached to its 3 carbons. This is called a condensation reaction because 3 water molecules are formed from 3 OH groups from the fatty acids chains and 3 H atoms from the glycerol. The bond between the fatty acid chain and the glycerol is called an ester linkage. 3 Water Molecules are formed here Ester links are formed between these atoms

Phosphate (hydrophilic) Glycerol Fatty Acid tails (hydrophobic) A Special Type of Lipid…Phospholipids Phospholipids are important in the formation and functioning of cell membranes in cells. They have a slightly different structure to triglycerides: • A phosphate group replaces one of the fatty acid chains/groups • The phosphate group is hydrophilic (attracts water) and is polar • The rest of the molecule (fatty acid tails) is hydrophobic (repels water) and non-polar

Functions of proteins • Virtuallyall enzymes are proteins. • Structural: e.g. collagen and elastin in connective tissue, keratin in skin, hair and nails. • Contractileproteins: actin and myosin in muscles allow contraction and therefore movement. • Hormones (Signal Proteins): many hormones have a protein structure (e.g. insulin, glucagon, growth hormone). • Transport: for example, haemoglobin facilitates the transport of oxygen around the body, a type of albumin in the blood transports fatty acids. • Transport into and out of cells: carrier and channel proteins in the cell membrane regulate movement across it. • Defensive: immunoglobulins (antibodies) protect the body against foreign invaders; fibrinogen in the blood is vital for the clotting process.

http://www.bbc.co.uk/education/asguru/biology/02biologicalmolecules/01proteins/index.shtmlhttp://www.bbc.co.uk/education/asguru/biology/02biologicalmolecules/01proteins/index.shtml Proteins • Proteins are amino acid polymers. Twenty different amino acids exist naturally. These link up in different orders to form all the many different proteins present in living organisms. All amino acids contain four distinct chemical groups connected to 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 in different amino acids)

http://www.bbc.co.uk/education/asguru/biology/02biologicalmolecules/01proteins/12polymers/index.shtmlhttp://www.bbc.co.uk/education/asguru/biology/02biologicalmolecules/01proteins/12polymers/index.shtml http://student.ccbcmd.edu/~gkaiser/biotutorials/proteins/peptide.html Joining Amino acids Together The amino acids in a protein are joined together by CONDENSATION reactions and broken apart by HYDROLYSIS reactions (just like in carbohydrates & lipids). The bonds formed between amino acids are called PEPTIDE bonds. Two amino acids joined together are called a dipeptide.

http://www.bbc.co.uk/education/asguru/biology/02biologicalmolecules/01proteins/13structures/index.shtmlhttp://www.bbc.co.uk/education/asguru/biology/02biologicalmolecules/01proteins/13structures/index.shtml Structure of Proteins Proteins are big complicated molecules. Their structure can be explained in four ‘levels’. These levels are called the protein’s PRIMARY, SECONDARY, TERTIARY and QUATERNARY structures. The primary structure is the sequence of the amino acids in the long chain that makes up the protein (the polypeptide chain)

Secondary Structure Chains of amino acids (polypeptides) can form coils (α-helix) or pleats (β-pleated sheets). This coiling or pleating is called the proteins’ secondary structure. The secondary structure is held together by Hydrogen bonds. Tertiary Structure Long polypeptide chains often fold and are joined by additional, weak chemical (ionic) bonds that give the protein a complex 3-dimensonal shape. This is the tertiary structure.

Quaternary Structure Finally, some proteins are made of several different polypeptide chains held together by various bonds. The quaternary structure is the way these different parts are assembled together. Types of bonds: The shape of the protein is held together by Hydrogen bonds between some of the R groups (side chains) and Ionic bonds between positively and negatively charged side chains. These are weak interactions, but together they help give the protein a stable shape. The protein may be reinforced by strong covalent bonds called Disulphidebridges which form between two amino acids with sulphur groups on their side chains (cysteine). Hydrophobic bonds form when water-repelling hydrophobic groups are 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 form fibres (e.g. in keratin). Several helices may be wound around each other to form very strong fibres. Collagen is another fibrous protein, which has a greater tensile strength than steel because itconsists of three polypeptide chains coiled round each other in a triple helix. We are largely held together by collagen as it is found in bones, cartilage, tendons and ligaments. Insoluble in H2O. Globular proteinsare made of chains folded into a compact structure. One of the most important classes are the enzymes.Although these folds are less regular than in a helix, they are highly specific and a particular protein will always be folded in the same way to form a roughly spherical molecule.If the structure is disrupted, the protein ceases to function properly and is said to be denatured. An example is insulin, a hormone produced by the pancreas and involved in blood sugar regulation. Soluble in H2O. A globular protein based mostly on an a-helix is haemoglobin. Its structure is curled up, so hydrophilic (water attracting) side chains are on the outside of the molecule and hydrophobic (water repelling) side chains face inwards. This makes it soluble and good for transport in blood,

Inorganic Ions in Living Things Many inorganic ions that can dissolve in water are important in the metabolism of organisms. Remember:ions = charged particles Inorganic ions = ions that don’t contain Carbon

Biological Molecules