Topic 1A - Biological molecules Flashcards
Even though there are a variety of living organisms on earth, their biochemistry is…….. (different?/similar?)
Similar
What are monomers?
Monomers are small, basic, molecular units
What are polymers?
Polymers are molecules made from a number of monomers joined together
Give 3 examples of monomers?
- Monosaccharides
- Nucleotides
- Amino Acids
What happens in a condensation reaction?
Two molecules join together with the formation of a new chemical bond, and a molecule of water is released
What is a hydrolysis reaction?
A reaction that breaks the chemical bond between monomers using a water molecule
Give three examples of monosaccharides?
- Glucose
- Fructose
- Galactose
What bond is formed in a condensation reaction between two monosaccharides, as water is released?
A glycosidic bond
How are disaccharides formed? (note to self: practise drawing condensation reactions)
Disaccharides are formed by the condensation of two monosaccharides
What is maltose and how is it formed?
Maltose is a disaccharide and it is formed by the condensation of two glucose molecules (joined together by a glycosidic bond)
What is Sucrose and how is it formed?
Sucrose is a disaccharide and it is formed by the condensation of a glucose molecule and a fructose molecule (joined together by a glycosidic bond)
What is Lactose and how is it formed?
Lactose is a disaccharide and is it formed by the condensation of a glucose molecule and a galactose molecule (joined together by a glycosidic bond)
What is an isomer?
Molecules with the same molecular formula but the atoms connected in a different way
Draw out the alpha glucose and the beta glucose structure in your book
- a-glucose: H at top, OH at bottom
- b-glucose: OH at top, H at bottom
How are polysaccharides formed?
They are formed when more than two monosaccharides are joined together by condensation reactions
What are the two polysaccharides of starch called?
- Amylose
2. Amylopectin
Describe the structure of amylose and why its useful for its function? (in starch)
Structure
- long, unbranched chains of a-glucose, joined together by 1-4 glycosidic bonds
- (Angles of glycosidic bond gives it a coiled structure (cylinder)
Function
- coiled shape makes amylose compact so it’s good for storage.
Describe the structure of amylopectin and why its useful for its function? (in starch)
Structure
- long branched chain of a-glucose, joined together by both 1-4 and 1-6 glycosidic bonds
Function
- Side branches allow enzymes (that break down molecule) to get at the glycosidic bonds. This means the glucose can be released quicky.
- compact so good for storage
Why is it a good thing that starch is insoluble in water?
It doesnt cause water to move into cells by osmosis, which would make them swell. This makes it good for storage
Where do plant cells get their energy?
Plant cells get their energy from glucose. Excess glucose is stored as starch and when the plant needs the glucose for energy, it breaks down the starch.
Describe the structure of glycogen (for animals) and why its useful for its function?
Structure
- same as amylopectin except more 1-6 glycosidic bonds
Function
- same as amylopectin, except it’s hydrolysed to aid energy release IN ANIMALS, not plants.
Describe the structure of cellulose and why its useful for its function? (in plants)
Structure
- long unbranched chains of beta-glucose, joined together by 1-4 glycosidic bonds.
- cellulose chains linked together by hydrogen bonds to form strong fibres called microfibrils
Function
- Strong fibres mean cellulose provides structural support for cells (in cell walls)
What do reducing sugars include?
All monosaccharides (glucose) and some disaccharides (maltose and lactose)
Describe how to test for reducing sugars.
- Add EXCESS Benedicts reagent in solution and heat in water bath (brought to boil)
- If test is positive, coloured precipitate forms
- Blue Giants Yell On Buses
- Higher concentration of sugars, the further the colour change goes
*use excess benedicts reagent so that all of the solution reacts
Describe how to test for non-reducing sugars.
- Break down solution into monosaccharides by adding dilute HCL to it and heat it in a water bath brought to a boil
- Neutralise it with sodium hydrogencarbonate and then carry out reducing sugar experiment
- If test is positive = colour change, If solution stays blue = no sugars present
Describe how to test for starch
- Add iodine dissolved in Potassium Iodide solution to test sample
- If starch is present, solution turns changes from browny-orange to blue-black
- If not, solution stays browny-orange
Name the two groups of lipids
Triglycerides and Phospholipids
How are triglycerides formed?
They are formed by the condensation of one molecule of glycerol and a fatty acid molecule (happens twice more to form triglyceride)
Describe the properties and function of the ‘tail’ in a fatty acid molecule
properties:
- hydrocarbon tail that varies in each fatty acid
- Tails are ‘hydrophobic’ (repel water molecules), making lipids insoluble in water
Draw out the basic structure of a fatty acid
O double C H O R
- r relates to variable hydrocarbon tail
- carbon atom links fatty acids to glycerol
What happens when a fatty acid joins to a glycerol molecule in a condensation reaction?
An ester bond is formed and water is released (process happens twice more to form a triglyceride)
Draw out a glycerol joining onto a fatty acid AND draw out the structure of a triglyceride (with the ester bonds)
draw in book
Define ‘saturated’ and ‘unsaturated’ fatty acids? (DRAW)
Saturated - no double bonds between their carbon atoms
Unsaturated - at least one double bond between carbon atoms, causing a kink in the chain
Which part of a fatty acid determines whether it is saturated or not?
The R group of the fatty acid
What do you call the lipids found in the bilayer of cell membranes?
Phospholipids
What is the main difference between phospholipids and triglycerides?
Unlike tiglycerides, one of the fatty acids molecules in phospholipids is replaced by a phosphate containing group
Describe the emulsion test
Emulsion test
- Shake the test substance with ethanol for a min till it dissolves, pour solution in water
- If lipids are present, they will precipitate out of the liquid and show as a milky emulsion
- the more lipid there is, the more noticeable the milky colour will be
How are triglycerides adapted for their function (DG)
- the long hydrocarbon tails contains lots of chemical energy (a load of energy’s released when they’re broken down). Lipids contain twice as much energy per gram as carbs
- As tails are hydrophobic, they’re insoluble and don’t affect water potential/osmosis.
- They clump together as insoluble droplets in cells - the tails-face inwards shielding themselves from water with their glycerol heads
Describe the structure of phospholipids (DG)
- Their heads (phosphate group) are hydrophilic and their tails are hydrophobic, so they form a double layer with their heads facing out towards the water on either side
- The centre of the bilayer is hydrophobic so the membrane acts as a barrier so that water-soluble substances cant pass through
What are amino acids?
Amino acids are the monomers from which proteins are made
Describe the general structure of an amino acid. (AND DRAW)
- carboxyl group (COOH)
- amine/amino group (NH2)
- carbon containing R Group/side group
- all living things share a bank of ….. amino acids.
2. If so, what is the difference between them?
- 20
2. The only difference between them is wha tmakes up their side group
How are dipeptides and polypeptides formed? (BRIEF)
- Dipeptides are formed by a condensation reaction between the carboxyl group of 1 amino acid and the amine group of the other.
- Polypeptides are formed by the condensation of many amino acids. (water is released)
What do you call the bonds formed between amino acids (in condensation reactions)?
- (DRAW)
Peptide bonds
What are enzymes?
- (properties/stucture)?
- (functions)?
PROPERTIES/STRUCTURE
- They’re spherical in shape due to the tight folding of the polypeptide chains.
- They’re soluble
FUNCTIONS
- often have role in metabolism e.g. breaking down food molecules
- helps to synthesis large molecules
What are antibodies?
- (properties/stucture)?
- (functions)?
PROPERTIES/STRUCTURE
- made up of two light polypeptide chains and two heavy polypeptide chains bonded together
- have ‘variable regions’ - the amino acids in these regions vary greatly
FUNCTIONS
- involved in the immune response
What are transport proteins?
- (properties/stucture)?
- (functions)?
PROPERTIES/STRUCTURE
- A type of transport protein e.g. Channel proteins contain hydrophobic and hydrophilic amino acids
- hydrophilic and hydrophobic amino acids means proteins can fold up and form a channel
FUNCTIONS
- channel proteins can transport molecules and ions across membranes
What are structural proteins?
- (properties/stucture)?
- (examples of structural proteins)?
PROPERTIES/STRUCTURE
- physically strong
- consist of long polypeptide chains lying parallel to each other with cross-links between them
EXAMPLES
- keratin (hair and nails)
- Collagen (found in connective tissue)
Name the four structural levels for proteins?
- Primary
- Secondary
- Tertiary
- Quaternary
Describe the primary structure of proteins? (refer to diagram in book)
The sequence of amino acids in the polypeptide chain (flat)
Describe the secondary structure of proteins? (refer to diagram in book)
Hydrogen bonds form between amino acids in chain.
- This makes it automatically coil into an alpha helix or fold into beta pleated sheet
Decribe the tertiary structure of proteins? (refer to diagram in book)
- more coiled and folded further
- more bonds form between different parts of the polypeptide chain e.g. hydrogen and ionic bonds
- Disulfide bridges form whenever two molecules of the amino acid cysteine come close together - the sulfur atom in one cysteine bonds to the sulfur atom in the other
- For proteins made from single polypeptide chain, tertiary structure forms their final 3D structure
Describe the quarternary structure? (refer to diagram in book)
- When several different polypeptide chains are held together by bonds, can form quartenary structure
- Can be a proteins final 3D structure if it is made from more than one polypeptide chain (e.g. insulin, heamoglobin, collagen)
Describe the biuret test?
- To make solution alkaline, add few drops of sodium hydroxide
- The add copper sulfate
- if it turns purple, proteins are present
- if it remains blue, no proteins are present
Define activation energy and what form of energy is it usually provided as?
- Activation energy is the amount of energy needed to be supplied to the chemicals before the reaction can start
- It is often provided as heat
What do enzymes do to activation energy? (DIAGRAM)
They lower the activation energy needed for a reaction to catalyse, speeding up the rate of the reaction (whilst making reactions take place at lower temps than usual)
How does the induced model explain why enzymes are so specific?
The induced model states that, as a substrate comes closer to an enzyme, bonds will form at different places to allow the active site to change shape and become complementary to the substrate
How do Enzyme properties relate to their tertiary structures?
- The active sites shape is determined by an enzymes tertiary structure (each enzyme has a different tertiary structure and so a different shaped active site)
- If tertiary structure is altered, the shape of the active site will change so the substrate may not fit
- Tertiary structure may be altered by changes in pH or temperature
How does primary structure relate to Tertiary structure in enzymes?
- Tertiary structure is determined by an enzymes primary structure
- The primary structure is determined by a gene. If there is a mutation in a gene, it couLd change tertiary structure ( active site shape)
WHERE can enzyme action take place?
Within cells (intracellular) and outside cells (extracellular)
How can enzymes lower activation energy when two enzymes need to be joined?
The enzyme can hold the substrate molecules together, reducing any repulsion between the molecules so they bond more easily
How can enzymes lower activation energy when it needs to catalyse a breakdown reaction?
Fitting into the active site puts a strain on bonds in the substrate, so the substrate breaks up more easily
How does temperature affect enzyme activity? (GRAPH)
- Rise in temp causes enzymes molecules to vibrate more
- If temp is too high, vibration breaks some bonds holding enzyme in shape
- This changes shape of active site and enzyme and substrate cant fit together
- Enzyme is denatured
How does pH affect enzyme activity? (GRAPH)
1- Above or below optimum pH, the H+ and OH- ions in acids and alkalis, can mess up ionic and hydrogen bonds that hold the enzymes tertiary stucture in place.
2- This changes shape of active site and denatures enzyme
How does enzyme concentration affect the rate of a reaction? (GRAPH)
- The more enzyme molecules present, the more likely they will collide with a substrate to form an enzyme-substrate complex. So increasing enzyme conc, increases rate of reaction
- If all amount of substrate is limited and they are all catalysed by enzymes, enzyme conc wont make a difference
How does substrate concentration affect the rate of a reaction? (GRAPH)
- More substrates means it will be more likely that a substrate and enzyme will collide so more active sites will be used.
- When all active sites are full, substrate conc wont make a difference
- Substrate concentration decreases overtime so rate of a reaction will also decrease over time (if no over variables are changed)
When is the rate of a reaction the fastest? (what point during a reaction)
During the beginning of the reaction
What is a competitive inhibitor?
A molecule that has a similar shape to that of a substrate and competes with a substrate to bind to the active site (but no reaction takes place)
How does competitive inhibition affect reaction rate? (GRAPH)
- If there is a high conc of inhibitors, it’ll take up nearly all of the active sites and hardly any of the substrate molecules will get to the active site (low reaction rate)
- If there is a high conc of substrates, it is more likely to get to the active sites before the inhibitors (high reaction rate)
What is a non competitive inhibitor?
- A molecule that binds to an allosteric in an enzyme (a site other than the active site).
- This interferes with enzymes bonds so active site changes shape and substrate molecules can no longer bind to it
How do non-competitive inhibitors affect reaction rate? (GRAPH)
Causes reaction rate to decrease (Increasing conc of substrate won’t make a difference to the reaction rate)
What is the main difference between globular proteins and fibrous proteins?
Globular proteins form a complex 3D tertiary structure whilst fibrous proteins form the primary structure
