Topic 1A-Biological Molecules Flashcards
What are monomers?
Small basic molecular units
Give three examples of monomers
Monosaccharides, amino acids and nucleotides
What elements are carbohydrates made of?
Carbon, hydrogen and oxygen
What are the three carbohydrate monomers/monosaccharides?
Glucose, fructose and galactose
How many carbons does glucose have? What type of sugar is it?
6- hexose sugar
What are the two types of glucose?
Alpha and beta
What is the difference between alpha glucose and beta glucose?
In an alpha glucose molecule, H is arranged above OH but in a beta glucose molecule, OH is arranged above H on the right hand side
What type of reaction joins monosaccharides together?
Condensation reaction
What is released in a condensation reaction?
A water molecule
What type of bond forms between the two monosaccharides in a condensation reaction?
Glycosidic
What is the name given to a molecule consisting of two monosaccharides that have joined together?
Disaccharide
Glucose + glucose ->
Maltose
Glucose + fructose ->
Sucrose
Glucose + galactose ->
Lactose
Name three disaccharides
Maltose, galactose and sucrose
What reaction breaks polymers apart?
Hydrolysis
A hydrolysis reaction is the opposite of what reaction?
Condensation reaction
What is a hydrolysis reaction?
Adding water to break down a chemical bond between monomers
In a hydrolysis reaction, carbohydrates are broken down into what?
Their constituent monosaccharides
What test is used to test for sugars?
The Benedict’s Test
Describe the Benedict’s test for reducing sugars
1) Add Benedict’s reagent (which is blue) to a sample and heat it in a water bath until it begins to boil
2) If the test is positive it will form a coloured precipitate
3) The higher the concentration of the reducing sugars, the further the colour changes
4) Filter the solution and weigh the precipitate for quantitative results
What do all reducing sugars contain?
Monosaccharides and some disaccharides
What colour is Benedict’s reagent?
Blue
What colour changes occur in the Benedict’s test? (List the whole spectrum)
Blue to green to yellow to orange to brick red
What colour does the solution turn in a positive Benedict’s Test for a reducing sugar?
Brick red
How are results determined qualitatively in the Benedict’s Test for reducing sugars?
Compare the colours of the precipitate and solution
How are results determined quantitively from the Benedict’s Test for reducing sugars?
The solution is filtered and the precipitate is weighed
What are polymers?
Large complex molecules composed of long chains of monomers joined together
Describe the Benedict’s Test for non-reducing sugars
1) Perform the test for reducing sugars and obtain a negative results
2) Get a new sample of the test solution and add dilute hydrochloric acid then heat in a water bath
4) Neutralise with sodium hydrogencarbonate
5) Carry out the test as normal (leave to boil and then observe a colour change)
6) If the test is positive it will form a coloured precipitate and if it’s negative the solution will stay blue
If the Benedict’s test for reducing sugars is negative, what does this show?
The absence of a reducing sugar
If the Benedict’s test for non-reducing sugars is positive, what colour will the solution be?
Brick red
If the Benedict’s Test for non-reducing sugars is negative, what colour will the solution be?
Blue
What are polysaccharides?
More than two monosaccharides joined together
What reaction forms polysaccharides?
Condensation reaction
Name three polysaccharides
Starch, glycogen and cellulose
What is the main energy store in plants?
Starch
Where do cells get their energy from?
Glucose
How do plants store glucose?
As starch
When a plant needs more glucose for energy, what does it do?
It breaks down starch to release glucose
What two polysaccharides of alpha-glucose does starch consist of?
Amylose and amylopectin
What is amylose?
A long unbranched chain of alpha-glucose
What is the structure of amylose like?
Coiled, cylindrical structure
Why us amylose good for storage?
It’s compact so can fit more in a small space
What is amylopectin?
A long branched chain of alpha glucose
Why is amylopectin branched?
So that enzymes can break down the molecule and get to the glycosidic bonds quickly and release glucose for energy
Is starch soluble in water?
No, it’s insoluble
What are the benefits of starch being insoluble?
It doesn’t affect the water potential of cells so doesn’t cause water to enter by osmosis. This also makes it good for storage.
What test is used for starch?
Iodine test
Describe the iodine test
Add iodine dissolved in potassium iodide solution to a test sample.
If starch is present the sample changes from browny-orange to blue-black
What colour does a negative test for starch show?
Browny-orange
What colour does a positive test for starch show?
Blue-black
What is the main energy storage material in animals?
Glycogen
Where do animal cells get their energy from?
Glucose
How do animals store excess glucose?
Glycogen
What is glycogen?
A polysaccharide of alpha-glucose
Describe the structure of glycogen
It’s similar to amylopectin
It had many more side branches coming off it
Why is glycogen branched?
So that glucose can be released quickly which is important for animals because they need energy for movement and maintaining body temperature
How is glycogen good for storage?
It’s a very compact molecule
What is the major component of cell walls in plants?
Cellulose
What is cellulose made of?
Long, unbranched chains of beta-glucose
When beta-glucose molecules bond, what do they form?
Straight cellulose chains
What are cellulose chains linked by?
Hydrogen bonds
What do the strong hydrogen bonds in cellulose chains form?
Microfibrils
What is the purpose of microfibrils in cellulose?
They provide structural support for cells
What are triglycerides a type of?
A type of lipid
What are triglycerides made of?
One molecule of glycerol and three fatty acids
What are fatty acid molecules in triglycerides made of?
Hydrocarbons
Describe the tail of a fatty acid
Hydrophobic tail (repel water)
Why are lipids insoluble in water?
They have hydrophobic tails
What is the basic structure of a fatty acid?
C in the centre single bonded to HO and also double bonded to O. The C is also bonded to the ‘R’ group; the variable hydrocarbon tail
How are triglycerides formed?
Condensation reaction
What bond is formed when a fatty acid joins to a glycerol molecule?
Ester bond
Describe the difference between saturated and unsaturated fatty acids
Saturated fatty acids don’t have double bonds
Unsaturated fatty acids do have double bonds
What lipids are found in cell membranes?
Phospholipids
What is the difference between a triglyceride and a phospholipid?
A phospholipid replaces one of the fatty acids with a phosphate group
Describe the structure of a phospholipid
Glycerol molecule bonded to two fatty acids and a phosphate group
How does water behave with a phospholipid?
The phosphate group is hydrophilic and attracts water whereas the fatty acid tails are hydrophobic and repel water
What are triglycerides used for?
Energy storage
Where is the chemical energy stored in a triglyceride?
The hydrocarbon tail
Why don’t triglycerides affect the water potential of a cell?
They’re insoluble. This is because the hydrophobic tails face inwards shielding themselves from water with the glycerol heads
What makes up the bilayer of cell membranes?
Phospholipids
What do cell membranes do?
Control what enters and leaves a cell
In a phospholipid bilayer cell membrane, how do the phospholipids arrange themselves?
The hydrophilic heads face outwards on either side and the hydrophobic tails meet at the centre so water soluble substances can’t easily pass through
What test is used to find lipids(fats)?
The emulsion test
Describe the emulsion test
1) Shake the test substance with ethanol for a minute so that it dissolves then pour the solution into water
2) Any lipid will show up as a milky emulsion
3) The more lipid there is the more noticeable the milky colour will be
What will the emulsion test for lipids show if it’s a positive result?
A milky emulsion
What are proteins made from?
Long chains of amino acids
What are the monomers of proteins?
Amino acids
What is formed when two amino acids join together?
Dipeptide
What is a polypeptide?
More than two amino acids joined together
What are made up of one or more polypeptides?
Proteins
What do all amino acids contain?
A carboxyl group (-COOH)
An anime or amino group (-NH2)
A carbon containing R group (variable group)
How many amino acids are there?
20
What is the only amino acid that doesn’t contain carbon in its R group? (Its R group consists of just 1 H atom)
The first amino acid: glycine
How are amino acids linked together to form polypeptides?
Condensation reactions
What is released in a condensation reaction?
A water molecule
What is the bond between amino acids called?
Peptide bonds
When does the reverse of a condensation reaction to form polypeptides happen?
During digestion
What is the primary structure of a protein?
The sequence of amino acids in the polypeptide chain
What is the secondary structure in a protein?
The coiled alpha-helix or beta-pleated sheet
What is the tertiary structure of a protein?
The final 3D structure: globular or fibrous
What is the quaternary structure of a protein?
This is for proteins made from more than one polypeptide chain
The way some polypeptide chains are assembled together
What bonds form in the proteins that affect the secondary structure?
Hydrogen bonds
What are the types of bonds in a protein that affect its tertiary structure?
Hydrogen bonds, ionic bonds, disulphide bonds
Give three examples of proteins with a quaternary structure
Haemoglobin, insulin and collagen
What are enzymes?
A type of protein that acts as a biological catalyst and speeds up the rate of reaction without being altered structurally or used up
What shape do most enzymes take? Why?
Spherical due to tight folding in the polypeptide chain
Are enzymes soluble?
Yes
What do enzymes have a key role in?
Digestion
What are antibodies a type of?
Protein
What are antibodies involved in?
Immune responses
What are antibodies made up of?
Two light (short) polypeptide chains and two heavy (long) polypeptide chains bonded together
Where are transport proteins present?
Cell membranes
What do channel proteins do?
Transport molecules and ions across membranes
What makes channel proteins fold up and form a channel?
They contain hydrophobic and hydrophilic amino acids
What do structural proteins consist of?
Long polypeptide chains running parallel to each other with cross links between them
Give two examples of structural proteins
Keratin and Collagen
Give two examples of globular proteins
Haemoglobin and insulin
Give three examples of fibrous proteins
Collagen, keratin and elastin
Which protein, globular or fibrous, is soluble?
Globular-soluble
Fibrous-insoluble
What is a globular protein?
A polypeptide chain folded into a globular shape
What is a fibrous protein?
A structural protein which consists of long, parallel polypeptide chains
What test is used for proteins?
Biuret test
Describe the biuret test for proteins
1) Add a few drops of sodium hydroxide solution to ensure that the test solution is alkaline
2) Add copper (II) sulphate solution
3) If a protein is present it turns purple, if no protein is present it stays blue
What is the positive result of the biuret test for proteins?
Purple colour
What is the negative result for the biuret test for proteins?
Blue colour
What do enzymes catalyse?
Metabolic reactions (at a cellular levels and for the organism as a whole)
Enzymes can be intracellular or extracellular, what does this mean?
Intracellular-inside cells
Extra cellular- outside cells
What is an enzymes active site?
It is the part of the enzyme where substrate molecules bind to and it has a specific shape
How do enzymes affect the activation energy of a reaction?
They lower it
What is activation energy?
The minimum amount of energy required for a reaction to take place
What does enzyme-substrate complex mean?
When a substrate fits into the enzymes active site
Give a reason why the enzyme-substrate complex lowers the activation energy of a reaction where two substrate molecules need to be joined together
if two substrate molecules need to be joined, being attached to the enzyme holds them closer together and reduces repulsion between the molecules so they can bond more easily
Give a reason why the enzyme-substrate complex lowers the activation energy of a reaction where two substrate molecules need to be broken down
Fitting into the active site puts a strain on bonds in the substrate so it breaks more easily
What is the lock and key hypothesis?
The substrate fits into the enzyme the same way a key fits into a lock
What is the induced fit theory?
It states that the substrate doesn’t have to be the right shape to fit the active site but it has to make the active site change shape in the right way. It suggests that the substrate can change its shape to fit the active site of an enzyme
Why are enzymes so very specific? (Why do they only catalyse one reaction?)
Only one complementary substrate will fit into the active site
What is an enzymes active site determined by?
The enzymes tertiary structure which is determined by the proteins primary structure
What happens if an enzyme and substrate don’t complement each other?
The enzyme will not catalyse the reaction
What happens if the structure of an enzyme is altered?
The shape of the active site changes and the enzyme won’t catalyse the reaction
What determines the primary structure (amino acid sequence) of a protein?
A gene
If a mutation occurs in the gene that controls the primary structure of a protein, what happens to the enzyme produced?
The tertiary structure or active site would be changed
What five factors affect enzyme activity?
Temperature, pH, enzyme concentration, substrate concentration and enzyme inhibitors
When the temperature is increased what happens to the rate of an enzyme controlled reaction?
Increases to a certain point then decreases rapidly
Why does the rise in temperature initially speed up an enzyme controlled reaction?
More heat means more kinetic energy so the molecules vibrate more and are more likely to have successful collisions and cause a reaction.
In an enzyme controlled reaction, if the temperature goes above a specific point what happens and why?
The rate of reaction decreases suddenly because the vibrations brea the bonds that hold the enzyme in shape and alter the shape of the active site which is called the denaturation of the enzyme
What happens when you increase the pH in an enzyme controlled reaction?
The rate of reaction increases to an optimum point then falls again
Why do pH values above and below optimum affect the rate of reaction in an enzyme controlled reaction?
H+ and OH- ions found in acids and alkalis can mess up the ionic bonds and hydrogen bonds that hold an enzymes tertiary structure in place. This changes the shape of the active site so the enzyme is denatured.
Explain how enzyme concentration affect the rate of reaction?
The more enzyme molecules in a solution the more likely a substrate molecule is to collide with another molecule. This increases the rate of reaction.
If the amount of substrate is limited but the enzyme concentration is high, what will happen to the rate of reaction?
It has no further affect because all the available substrate reacts
How does substrate concentration affect the rate of reaction?
The higher the substrate concentration the faster the reaction(because a collision is more likely) but only up to saturation point.
What happens at saturation point in a reaction where substrate concentration is increased?
There is no further effect on the rate of reaction
What are the two types of enzyme inhibitors?
Competitive and non-competitive
Describe the shape of competitive inhibitors
Similar to the substrate molecule
How do competitive inhibitors inhibit a reaction?
They compete with the substrate molecules and bind to the active site so they block active sites and no further reactions (with substrate molecules) can take place
What factor affects how much the enzyme is inhibited
The relative concentrations of the inhibitor and the substrate
A high concentration of competitive inhibitors to active sites has what effect?
Slows down the rate of reaction
How do non competitive inhibitors affect the rate of reaction?
They bond to the enzyme away from its active site and cause the active site to change shape
What effect would increasing the concentration of substrate have on the rate of reaction with non-competitive inhibitors?
No effect
What are the two ways of measuring the rate of an enzyme controlled reaction?
Measure how fast the product is made or measure how fast the substrate is broken down
How do you carry out the experiment for how fast the product is made in an enzyme controlled reaction?
1) Add equal volumes and concentrations of hydrogen peroxide to multiple test tubes and add the same volume of buffet solution
2) Set up the apparatus
3) Put 2 boiling tubes in a each water bath set to different temperatures
4) Add catalase to one of each boiling tube and add a bung to the delivery tube
5) record how much oxygen is produced
6) repeat for each temperature
7) calculate the average
How can we measure how fast the substrate is broken down in an enzyme controlled reaction?
1) Add iodine potassium iodide to each well on a spotting tile
2) Mix a known concentration of amylase and starch on a test tube
3) Add a drop of this mixture into one of the wells at regular intervals an watch the colour change
4) it goes blue black when starch is present so time how long it takes for this colour change to occur
What catalyses the breakdown of hydrogen peroxide into water and oxygen?
Catalase
What is a buffer solution?
It resists changes in pH when small amounts of acid or alkali are added
What enzyme catalyses the breakdown of starch to maltose?
Amylase
What colour does iodine solution turn when starch is present?
Blue-black
