biological molecules

What are the four types of biological molecules

• carbohydrates

• Lipids

• Proteins

• Nucleus acids

  These molecules are all organic, so contain carbon alongside hydrogen and oxygen.

  • Carbon = C, H, O

  • Lipids = C, H, O

  • Proteins = C, H, O, N

  • Nucleic acids = C, H, O, N, P

Carbon

• forms 4 covalent bonds

• Single or double bonds

• Has flexibility to form variety of structures

• Strong bonds due to shared electrons between atoms

What is a monomer

• small basic units that can join together to form larger structures

  • In carbohydrates they are called monosaccharides (single sugars)

  • In proteins they are called amino acids

  • In nucleic acids they are called nucleotides

What is a polymer

• large molecules made of repeating units of monomers to form chains that are all linked together

  • in carbohydrates they are called polysaccharides (e.g glycogen which is made up of glucose monomers)

  • In proteins they are called polypeptides

  • In nucleotides they are called polynucleotides (e.g each DNA strand in made up of a long chain of nucleotides)

What is polymerisation

• The process when monomers join to form polymers

• Each monomer is joined together between a hydroxide (HO + H) on each monomer during a condensation reaction

• Polymers are broken back down into monomers by a hydrolysis reaction

Lipids

• made up of subunits (glycerol and fatty acids)

• Not made up of repeating units

• Not exactly a polymer

What are condensation reactions

• how most polymers are synthesised (made)

• Water is removed to form chemical bonds between molecules. This means a hydroxyl group(OH) from one molecule and a Hydrogen (H) from another molecule is removed which forms water

• Water molecule is released

• Requires energy (supplied by ATP)

What’s a hydrolysis reaction

• polymers, or other large molecules are broken down into sub units

• Water is used to break chemical bonds

• The splitting of water provides the OH and H groups needed to separate the molecule back into its sub units Water

• Releases energy

• Enzymes must be at a low temperature to maintain its complimentary shape and not denature

What’s an iron

A charged particle

What’s covalent bonding

• between 2 non metals

• Electrons shared

• Atoms become stable with complete outer shell

What’s ionic bonding

• between non metals Electrons shared and a metal

• Electrons transferred

• Metal becomes + ion

• Non metal becomes - ion

What is the bonding between hydrogen

• hydrogen bonding is a form of weak electrostatic forces of attraction between polarised molecules

• Electrons not always evenly distributed within a molecule

• Bottemly concentrated

• Polar substance ad its delta + at top and delta - at bottom

What are carbohydrates

• contain carbon, hydrogen and oxygen (twice as many hydrogen atoms compared to oxygen)

• Monosaccharides are single sugars

• Disaccharides are two sugar molecules

• Polysaccharides are many sugar molecule

• Simple carbohydrates supply energy directly to cells eg during respiration

• Complex carbohydrates stores energy (starch in plants and glycogen in animals)

• Can form structural complements eg cellulose (in plant cell walls)

• Involved in cellular recognition using glycoproteins (proteins with carbohydrate parts attached and help cells identify and communicate with each other)

What are monosaccharides

• sweet tasting

• Soluble → can form hydrogen ones with the hydroxyl groups so can be transported around body via plasma

• Generic formula Cn(H2O)n

  → n can be between 3 and 7 and are categorised based on the number of carbon atoms they contain

• Examples are glucose, fructose and galactose (hexose sugars - has 6 C atoms)

• All hexose sugars

• Have different molecular arrangements called isomers (e.g alpha and beta glucose)

What are disaccharides

• two sugar molecules joined together

• Glucose + glucose → maltose

• Glucose + fructose → sucrose

• Glucose + galactose → lactose

• 1-4 Glycosidic bonds join the monosaccharides together (condensation reaction)

• Hydrolysis breaks them back down as breaks glycosidic bonds and releases monosaccharides

When glucose combines with fructose to form the disaccharides sucrose, what is the formula

C6H12O6 + C6H12O6 → C12H22O11

What are examples of polysaccharides

• starch (plants)

• Glycogen (animals)

• Cellulose (cell walls of plants)

What are the functions of polysaccharides

For living organisms they:

• act as energy storage molecules

• Provide structural support

What’s the structure and function of starch

• Storage molecule

• 2 forms of starch → amylose and amylopectin. Both are made from alpha glucose monomers joined together by glycosidic bonds Compact

• Amylose: unbranched because of the 1-4 glycosidic bonds. Molecule coils into helical shape

• Amylopectin: branched because of its 1-6 glycosidic bonds (bonds formed between both carbon 1 and 4 and carbon 1 and 6)

• Main function is to store glucose in plants to do this its:

  • insoluble (doesn’t effect osmosis),

  • its large (doesn’t easily diffuse out of cells),

  • amylose is coiled (makes it compact)

  • amylopectin has lots of side branched (easier for enzymes to hydrolyse glycosidic bonds and break off glucose for respiration)

How do u test for starch

To test for starch add iodine and it will turn blue black

Method:

1. Place 2 cm³ of your food sample into a test tube

2. Add a couple of drops of iodine solution and shake

3. If starch is present, the solution will turn from orange to blue black

What’s the structure and function of glycogen

• made of alpha glucose monomers

• Branched as its made up of 1-4 glycosidic bonds and 1-6 glycosidic bonds

• Function: store glucose in animals and bacteria. To do this its

  • insoluble

  • Large and compact

  • Less dense and more soluble than starch

  • Even more branched than starch as animals are more active than plants so need a quicker access to energy stores. more branches means it can store more energy and there are more ends to the glucose molecule so its easier to break off glucose molecules for respiration → allows for rapid and efficient access to glucose as the linear chains of glucose can rapidly be broken down by glycogen phosphorylase, which removes the glucose molecules off the ends of the chains and many glucose monomers can be released at once

What’s the structure and function of cellulose

• beta glucose

• Form long, unbranched chains

• Very other beta glucose molecule is rotated 180 degrees so the hydroxide (OH) groups are close enough to react and form glycosidic bonds)

• 1-4 beta glycosidic bonds

• Chains are cross linked by hydrogen bonds. Hydrogen bonds hold chains together to form strong bundle called microfibrils. Microfibril join together to form a

• Cell wall completely external from cell membrane

• Insoluble

• Formed by condensation reaction between beta glucose molecules

• Arrangement of cellulose microfibres within a matrix of hemi

What are lipids and their roles

• Roles of lipids:

  • energy supply

  • Structural components (phospholipids used in cell membranes)

  • Waterproofing (insoluble lipids are used to form water resistant barriers

  • Insulation (lipids can help retain hear or act as electrical insulators)

  • Protection (organs surrounded by a layer of fat)

What’s the structure of lipids

• contains hydrogen, oxygen, carbon → lower proportion of oxygen compared to carbohydrates

• Made up of fatty acids combined with alcohol

• Triglycerides is a lipid that contains 3x fatty acids and one glycerol

• Fats = solids at room temperature

• Oils = liquids at room temperature

• Don’t form polymers as not made up of long chains of monomers

What’s the difference between saturated and unsaturated fatty acids

Typical fatty acids are made up of a hydroxyl group and a r group. The r group is a hydrocarbon chain

• saturated fatty acids

  • fully saturated with hydrogen (carbons bonded to maximum number of hydrogens).

  • No carbon-carbon DOUBLE bonds

  • Lipids that contain saturated fatty acids have higher melting points so are solid at room temperature

What are unsaturated fatty acids

• have hydrocarbon chains that do not contain the maximum number of hydrogen atoms bonded to the carbon-carbon double bond, which causes the chain to kink

• Lipids that contain unsaturated fatty acids have lower melting points and so are usually liquid at room temperature (oils)

• Can be either monounsaturated (one double bond) or polyunsaturated (two or more double bonds)

How do you test for lipids

• must carry out emulsion test

• Method:

  1. Place your food sample in a test tub

  2. Add 2cm³ of ethanol

  3. Shake

  4. Add 2cm³ of distilled water

  5. If lipids are present a milky white emulsion will appear

What are triglycerides

• type of lipid

• used as a store of energy in animals, plants and some bacteria

• Consists of a glycerol backbone attached to 3 fatty acid tails. Each fatty acid tail contains a hydrocarbon chain (R) which can vary in length and may be saturated or unsaturated

What features allow triglycerides to store energy efficiently

1. Long hydrocarbon tails → their many carbon-hydrogen bonds can be broken to release energy

2. Low mass to energy ration → lots of energy can be stored in a small volume

3. Insoluble → they do not affect the water potential of calls as they are large and non-polar

4. High ratio of hydrogen to oxygen atoms → triglycerides will release water when oxidised

How do triglycerides form and break down

• condensation reactions

  • hydroxyl groups (OH) on the glycerol and on the three fatty acids react together to release three water molecules (H2O)

  • This results in 3 ester bonds between the glycerol and the fatty acids

• Hydrolysis

  • addition of 3 water molecules (H2O) breaks the ester bonds

  • This separates the glycerol and the fatty acids

What’s a phospholipid

• phospholipid is a type of lipid

• used as a structural component of the cell membrane

• Instead of 3 fatty acids like in triglycerides, a phosphate group replaces one

Why are phospholipids polar

• made up of 2 parts 1. A hydronic ‘head’ → this contains glycerol and phosphate 2. A hydrophobic ‘tail’ → contains fatty acids

• The phosphate group is polar and so attracts water (hydrophilic) whereas the fatty acids Hydrolysis tails repel water (hydrophobic)

What’s a phospholipid bilayer

• when phospholipids are placed in water, they arrange themselves into a double layer (bilayer) so that the hydrophilic heads are facing out (towards the water) and the hydrophobic tails are facing in (away from the water)

• This arrangement creates a hydrophobic centre in the bilayer so that water-soluble substances cannot pass through

How do you test for proteins

• biuret test confirms precedes of peptide bonds

1. Add equal volume of sodium hydroxide to sample at room temperature

2. Add drops of dilute copper (II) sulfate solution. Swirl to mix

3. Positive result = colour changes from blue to purple

Negative result = solution remains blue

What’s the structure of proteins

• proteins are different between all species

• Structure of proteins is determined by a gene and their functions to all living things

• Monomers of proteins are amino acids

What bonds do proteins form

Peptide bonds

• Proteins join together in a condensation reaction.

• Peptide bonds form between the N on the amino group and the C on the carboxylate group

• Peptide bonds can be broken by hydrolysis (addition of water)

• Multiple condensation reactions in a sequence is called polymerisation reaction. This forms a polypeptide chain (primary protein structure)

What’s a proteins secondary structure

• can be a beta pleat sheet or an alpha helix

• Held together by hydrogen bonds between -NH group + negative C=O group

• In a large chain it can be a mix of the two

What’s a proteins teritiary structure

• secondary structures can be twisted into more complex 3D structures

• Different bonds hold these structures together

- disulphide bridges (strong bonds)

- Ionic bonds (formed between any carboxyl group and

Amino acid) → weaker than disulphide but strong

- hydrogen bonds

What’s a proteins quaternary structure

• multiple poly peptide chains joined together to make more complex structure

What are roles of proteins

1. Enzymes → these proteins are used to break down and synthesise molecules

2. Antibodies →proteins involved in immune response

3. Transport → some proteins can move molecules or ions across membranes

4. Structural components → proteins like keratin and collagen are used to create strong fibres

5. Hormones → proteins act as chemical messengers in body

6. Muscle contraction → muscles made up of proteins

What are enzymes

• biological catalysts as they increase the rate of a chemical reaction without being used up itself.

→ it does this by lowering the activational energy and providing an alternate reaction pathway

• Proteins

What are intra cellular enzymes

These enzymes act within the cells that produce them

What are extracellular enzymes

These enzymes act outside the cells that produce them and are secreted

How do enzymes bind with substrates

• enzymes have unique tertiary structures with determine the shape of their active site. This shape is complimentary to the substrate

• The substrate bind a to the active site to form an enzyme-substrate complex

• Temporary bonds form between these R groups within the active site and the substrate into products

• These products are released from the active site, leaving the enzyme free to be used again

What are the two models of enzymes action

• lock and key model

• Induced fit model

What’s the lock and key model

• If the substrate does not fit perfectly into the enzyme’s active site so reaction wont be catalysed. The substrate must be complimentary to the enzymes active site.

What’s the induced fit model

• the substrate does not fit perfectly into the enzymes active site. As the substrate enters the enzyme, the active sister changes shape slightly. This puts a strain on substrate bonds which lowers activation energy

What factors effect enzyme action

• pH

• Temperature

• Substrate concentration

• Enzyme concentration

How does temperature effect enzyme action → explanation

1. The molecules have more kinetic energy causing more collisions and enzyme-substrate complexes

2. The optimum temperature is the temperature this enzyme works fastest at

3. Too much kinetic energy causes the site to change shape and the enzyme denatures

How does temperature effect enzyme action → description

1. As temperature increases, rate of reaction increases

2. The maximum rate of reaction is reached at optimum temperature

3. As temperature increases past optimum temperature, the rate of reaction decreases until the reaction stops

How does pH effect enzyme action → explanation

1. In acidic conditions, H+ ions break ionic/ hydrogen bonds and denature enzymes

2. The optimum pH is the pH enzymes work fastest at

3. In alkaline conditions the OH- ions break ionic bonds or hydrogen bonds and denature enzymes

How does pH effect enzyme action → description

1. Below optimum pH, the rate of reaction is low or at 0

2. The maximum rate of reaction is reached at optimum pH

3. Abound optimum pH, the rate of reaction is low or 0

How does substrate concentration effect enzyme action → explanation

1. There are more substrate molecules to form more enzyme- substrate complexes

2. This is the saturation point, which is when all active sites are occupied by a substrate and enzyze concentration becomes a limiting factor

How does substrate concentration effect enzyme action → description

1. As the rate of substrate concentration increases, the rate of reaction increases

2. As the concentration increases further, the rate of reaction plateaus

How does enzyme concentration effect enzyme action → explanation

1. Their are more enzyme molecules to form enzyme- substrate complexes

2. All substrate molecules available are being acted upon and substrate concentration becomes the limiting factor

How does enzyme concentration effect enzyme action → description

1. As the enzyme concentration increases, the rate of reaction increases

2. As the enzyme concentration increases further, the rate of reaction plateaus

Why ate the two types of inhibitors

• competitive

• Non competitive

These can both be reversible (form weak bonds with they enzyme (e.g hydrogen or ionic) so can be easily broken) or irreversible ( these form strong bonds with the enzyme (e.g covalent) so require large amounts of energy to break)

What are competitive inhibitors

• they bind to the active site of an enzyme to prevent enzyme-substrate complexes being formed

• Have similar shape to enzymes normal substrate (only differ by a few molecules). This prevents the substrate from binding and reduces the formation of enzyme-substrate complexes. This results in a decrease in the rate of enzyme catalysed in the reaction

• Most are reversible as only temporarily bind to enzyme

How does increasing substrate concentration effect competitive inhibitors

• competitive inhibitors can be overcome by increasing substrate concentration

• The higher the substrate concentration, the more likely it is that substrates will bind to active site rather than inhibitor molecules. This will reduce the effect of the competitive inhibitor

What are non competitive inhibitors

• bind to enzymes allosteric sites (somewhere away from active site) to prevent enzyme-substrate complexes

• The binding changes the tertiary structure of the enzyme, causing the active site to change shape

• This results in the active site no longer being complimentary to the substrate so enzyme and substrate cannot bind. Less enzyme- substrate complexes are formed and rate or the enzyme catalysed reaction decreases

How does substrate concentration effect non competitive inhibitors

• increasing substrate concentration has no impact rate of reaction and the non competitive inhibitors cannot be overcome.

• Non competitive inhibitors do not compete with the substrate to bind with active site