3.1 Biological Molecules - Monomers and Polymers, Carbohydrates, Lipids, Proteins and Enzymes Flashcards
Monomers and Polymers, Carbohydrates, Lipids, Proteins and Enzymes
What are monomers?
The smaller units from which larger molecules are made from.
What are polymers?
Molecules made from a large number of monomers that join together.
Name three examples of monomers?
Monosaccarides, amino acids and nucleotides.
What is a condensation reaction?
Where two molecules join two molecules together with a formation of a chemical bond and an elimination of a water molecule.
What is a hydrolysis reaction?
Breaks a chemical bond between two molecules and involves the use of a water molecule.
What are monosaccarides?
They are monomers from which larger carbohydrates are made.
Name three examples of monosaccarides?
Glucose, fructose, and galactose.
What bond is formed between two monosaccarides during a condensation reaction?
A glycosidic bond.
What are disaccarides?
Formed by the condensation of two monosaccarides.
What is maltose?
A disaccaride formed by the condensation of two glucose molecules.
What is sucrose?
A disaccaride formed by the condensation of one glucose molecule and one fructose molecule.
What is lactose?
A disaccaride formed by the condensation of one glucose molecule and one galactose molecule.
What are isomers?
Molecules with the same chemical formula but have different structures.
What are the two glucose isomers?
α-glucose and β-glucose.
Where is the H in α-glucose?
At the top.
Where is the H in β-glucose?
At the bottom.
What are polysaccarides?
Polymers that are formed by the condensation of many glucose units.
Name three example of polysaccarides?
Cellulose, Starch, and Glycogen.
What is starch?
Where and how is it found?
What are the bonds?
A polysaccaride that is formed by the condensation of α-glucose.
Storage of glucose found only in plants as small grains.
1,4- and 1,6- glycosidic bonds.
How does the structure of starch differ?
Amylose is coiled/helical
Amylopectin is branched
What are the properties and functions of starch? (3)
- LARGE & INSOLUBLE = so water potential is not affected and does not diffuse out of cells.
- COILED/COMPACT = a lot of it can be stored in a small space.
- BRANCHED =ends can be acted on by enzymes to be hydrolysed quickly into glucose.
What is Glycogen?
Where and how is it found?
What are the bonds?
A polysaccaride formed by the condensation of α-glucose.
Storage of glucose in only animals as small granules in the liver and muscles.
1,4- and 1,6- glycosidic bonds.
What are the properties and function of glycogen?
- INSOLUBLE = does not affect water potential and cannot diffuse out of cells
- COMPACT = a lot of it can be stored in a small space
- HIGHLY BRANCHED = ends can be acted on at the same time by enzymes so can be hydrolysed quickly.
What is cellulose?
Where is it found?
A polysaccaride formed by the condensation of β-glucose.
Found only in plant cells to provide strength it
What are the properties and function of cellulose?
- Straight unbranched chains that run parallel to one another, allowing hydrogen bonds which forms cross-linkages between adjacent cells.
- Hydrogen bonds form micro-fibrils (fibres) to provide strength/rigidity to the cell wall.
- PERMEABLE = large gaps remain between different micro-fibrils to allow selective absorption at the cell membrane.
What characteristics do lipids have? –> What atoms do they contain and are they soluble in water?
They contain C, H, O atoms where the proportion of these atoms is smaller than carbohydrates.
They are insoluble in water but soluble in organic solvents such as alcohol.
What are the 4 roles of lipids?
- Source of energy = provide twice the energy of carbohydrates
- Waterproofing
- Insulation
- Protection (stored around the organs e.g. kidneys)
What are the two groups of lipids?
Triglycerides and phospholipids
What are triglycerides?
What bond will it form?
Formed by the condensation of one molecule of glycerol and three molecules of fatty acid.
This will form 3 ester bonds with 3 water molecules.
How does a triglyceride’s structure relate to its function? (4 points)
- HIGH RATIO of energy storing C-H bonds to C bonds so an excellent source of energy
- LOW MASS to energy ratio so good storage molecules with a lot of it stored in a small volume.
- LARGE AND NON POLAR so are insoluble and water potential is not affected.
- HIGH RATIO OF H-O ATOMS so can release water whenever they are oxidised to provide source of water.
What are phospholipids?
one of the fatty acids of a triglyceride is substituted by a phosphate-containing group.
How does a phospholipid’s structure relate to its function? (3)
- Polar molecules so in an aqueous environment meaning a bi-layer within the cell-surface.
- Hydrophilic heads helps to hold at the surface of the cell surface membrane.
- Form gylcolipids by combining with carbohydrates withing cell-surface membrane for cell recognition.
Which part is hydrophilic and which part of hydrophobic?
Phosphate head is hydrophilic and phosphate tail is hydrophobic creating.
Are micelles created by the phosphate head or tail?
What are they?
Enables lipid digestion products to be transported.
What are saturated fatty acids?
What do they form?
Fatty acids where there are no double bonds between the C atoms.
Form solids, most common in animals.
What are unsaturated fatty acids?
What do they form?
Fatty acids where there are one or more double bonds between the C atoms.
Form liquids, most common in plants.
What are amino acids?
Monomers from which proteins are made.
What 3 things does a general structure of an amino acid include?
- Amine group = NH2/H2N
- Carboxyl group = COOH
- R = side chain.
How many different types of amino acids are there?
20.
How do amino acids differ?
They have a different R group.
What are globular proteins?
soluble proteins where polypeptide has a 3D structure e.g. enzymes, hormones. (functional proteins)
What are fibrous proteins?
insoluble and strong proteins where polypeptide is linear and are usually structural proteins. e.g. keratin, collagen.
What bond does a condensation reaction between two amino acids form?
Peptide bond.
What are dipeptides?
Formed by the condensation of two amino acids.
What are polypeptides?
Formed by the condensation of many amino acids.
What is the role of hydrogen bonds in the structure of proteins?
Protein stability.
What is the role of ionic bonds in the structure of proteins?
bind basic proteins and potent electrostatic attractions.
What is the role of disulfide bridges in the structure of proteins?
Protein shape and stability.
Describe the primary structure of proteins:
= order and number of amino acids in the proteins.
- initial sequence of a protein that determines the function at the end.
- polypeptide chain held by peptide bonds.
Describe the secondary structure of proteins and the bonds:
- Polypeptide chains that form α-helix or β-pleated sheets.
- held together by weak hydrogen bonds (between carboxyl and amine group)
Describe the tertiary structure of proteins:
- secondary structure twists and folds again to create a 3D strucutre
Describe the tertiary structure of proteins:
- secondary structure twists and folds again to create a 3D structure
Describe the hydrogen bonds in tertiary structure:
there are numerous bonds that are weak.
Describe the ionic bonds in tertiary structure:
- forms between the carboxyl and amine group
- strong but can be easily broken by changes in pH, weaker than disulfide bonds.
Describe the disulfide bridges in tertiary structure:
- interactions between the sulfur in the R group of the amino acid cysteine which are strong and not easily broken.
Describe the quaternary structure of proteins:
- large and complex molecules with multiple binding sites
- formed by 2 or more polypeptide chains.
What are three examples of quaternary structure proteins and how many chains do they have?
- Collagen has 3
- Haemoglobin has 4
- antibodies have 3
What is the test for starch?
add few drops of iodine. Will turn from orange/brown to blue/black
What is the test for reducing sugars?
heat with Benedict’s solution. Will turn orange/brick red.
What is the test for non-reducing sugars?
Heat with Benedict’s solution.
Add HCL to hydrolyse gylcosidic bonds
Add sodium hydrogen carbonate to neutralise solution
Heat with benedicts which will turn brick red.
What is the test for lipids?
Add ethanol and shake vigorously.
Add water and shake gently.
Will turn cloudy/milky emulsion if lipid is present.
What is the test for proteins?
Add Biuret’s reagent to sample at room temp.
Colour change from blue to purple.
What are enzymes?
Biological catalysts/proteins that speeds up the reaction by lowering the activation energy without changing itself.
What makes enzymes specific?
they have specific active sites where only complementary substrates can bind, forming an enzyme-substrate complex.
What is the lock and key model?
Where the active site is rigid, and only complementary substrates can bind.
what is the induced-fit model?
The active site will change shape to enable the substrate to bind exactly to form an enzyme-substrate complex.
2 products will be formed and the enzyme will be unchanged.
How does enzyme concentration affect enzyme-controlled reactions?
- ↑ in enzyme concentration, ↑ rate of reaction as there will be more successful collisions and ES complex.
- Rate of reaction will no longer increase after a certain point because substrates are used up so becomes a limiting factor.
How does enzyme concentration affect enzyme-controlled reactions?
- ↑ in enzyme concentration, ↑ rate of reaction as there will be more successful collisions and ES complex.
- Rate of reaction will no longer increase after a certain point because substrates are used up so becomes a limiting factor.
How does substrate concentration affect enzyme-controlled reactions?
- ↑ in substrate concentration, ↑ rate of reaction as more successful collisions and ES complexes formed.
- Rate of reaction will no longer increase as enzyme concentration becomes a limiting factor.
How does pH affect enzyme-controlled reactions?
- Each enzyme have different optimum pH. If away from the optimum, bonds in tertiary structure break so it will lose its active site shape, not forming ES complex.
How does temperature effect enzyme-controlled reactions?
- as temp↑, rate of reaction↑.
- they have more kinetic energy which means molecules move faster, so more successful and frequent collisions. ↑ chance of forming ES complex.
- After optimum temp, H and ionic bonds will break and will lose its active site shape so enzyme will become denatured.
What is the effect on competitive inhibitors?
- ↑ competitive inhibitors, rate of reaction ↓.
- they have similar shapes to the substrates therefore will bind to the active site and block the substrates from binding, preventing ES complexes from forming.
How does the concentration of non-competitive inhibitors affect the rate of reaction?
- ↑ non-competitive inhibitors, rate of reaction ↓.
- These will bind to the allosteric site which will alter the active site
- less ES complex formed.
