1A - Biological Molecules Flashcards
Define monomer
Small, basic molecular unit.
Give three examples of polymers
Carbohydrate,
Protein,
Nucleic acid.
Give three examples of monomers
Monosaccharides,
Amino acids,
Nucleotides.
Give a basic definition of a condensation reaction
Molecules join together with the formation of a new chemical bond. A water molecule is released.
Give a basic definition of a hydrolysis reaction
Polymers can be broken down into monomers by hydrolysis reactions. A hydrolysis reaction breaks the chemical bond between monomers using a water molecule.
What are the monomers that make up carbohydrates?
Monosaccharides
What elements do all carbohydrates contain?
C, H and O
Give three examples of monosaccharides.
Glucose, fructose, galactose.
Give three examples of disaccharides.
Maltose
Sucrose
Lactose
Why can glucose be called a “Hexose Sugar”?
Glucose is a MONOSACCHARIDE with SIX carbon atoms in each molecule.
What are the two types of glucose?
Alpha and Beta
Alpha Glucose and Beta Glucose are isomers.
Explain what this means.
Both alpha glucose and beta glucose have the same molecular formula but different structural formula.
Describe a condensation reaction in carbohydrates in which a disaccharide is formed.
- Monosaccharides are joined together by condensation reactions.
- a glycosidic bond forms between the two monosaccharides as a molecule of water is released.
- When two monosaccharides join together, a disaccharide is formed.
Define polymer
Large, complex molecules composed of long chains of carbon atoms joined together.
List three disaccharides and their constituent monosaccharides
Maltose= glucose + glucose Sucrose= glucose + fructose Lactose= glucose + galactose
Describe hydrolysis in carbohydrates.
Carbohydrates can be broken down into their constituent monosaccharides by hydrolysis reactions, with the addition of an enzyme and a water molecule.
What is a polysaccharide?
When more than two monosaccharides join together by condensation reactions.
Name the test for carbohydrates
Benedict’s Test
Define the term “sugar”
A general term for monosaccharides and disaccharides.
What can all sugars be classified as?
Reducing or non reducing.
Give examples of reducing sugars
ALL monosaccharides (e.g Glucose, Fructose, Galactose) and SOME disaccharides (e.g Maltose, Lactose).
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 that has been brought to the boil.
2 Positive Result: A coloured precipitate will be formed, the higher the concentration of the reducing sugar the further the colour change goes. This can be used to compare the amount of reducing sugar in different solutions.
Describe a more accurate way to measure the amount of reducing sugar in a solution, rather than observing the colour change.
Filter the solution and weigh the precipitate.
What is the colour change in Benedict’s Test?
Blue > Green > Yellow > Orange > Brick Red
When would the non-reducing sugars test be carried out?
When the result of the reducing sugars test is negative.
Give an example of a non reducing sugar
Sucrose
Describe the test for non reducing sugars
(You first have to break the sample down into its monosaccharides)
• Get a new sample of the test solution and add dilute Hydrochloric Acid, heat carefully in a water bath that has been brought to the boil. Then neutralise with sodium hydrogencarbonate.
• Carry out Benedict’s test as usual.
• Positive result = coloured precipitate
• Negative result = no sugars present, solution stays blue.
Give three examples of carbohydrates
Starch, Glycogen and Cellulose
How is starch a good energy source for plants? (Describe how plants get energy from starch)
Cells get energy from glucose.
Plants store excess glucose as starch. When a plant needs more glucose for energy, it breaks down the starch to release glucose.
What is starch made up of?
It is a mixture of two polysaccharides of alpha-glucose.
Amylose is one polysaccharide of alpha glucose that makes up starch.
Describe its structure and function.
It is a long, un branched chain of Alpha Glucose. The angles of the glycosidic bonds give it a coiled structure, almost like a cylinder. This makes it compact, so it’s really good for storage. (Because you can fit more in a small space).
Why is amylose good for storage ?
The angles of the glycosidic bonds give it a coiled structure, making it compact, like a cylinder. (You can fit more in a small space).
Amylopectin is a polysaccharide of Alpha Glucose that makes up Starch.
Describe its structure and function.
It is a long, branched chain of Alpha Glucose. Its side branches allow the enzymes that break down the molecule to get at the glycosidic bonds easily. This means the glucose can be released quickly.
How does amylopectin allow glucose to be released quickly?
I has many side branches which allow the enzymes that break down the molecule to get at the glycosidic bonds more easily.
Describe the test for starch.
Add iodine dissolved In potassium iodide solution to the test sample. If there is starch present, the sample changes from browny orange to a dark blue black colour.
Describe the colour change in the test for starch.
A positive result (starch present) goes from browny-orange to blue-black.
Starch is insoluble in water. Comment on how this is beneficial for its function.
Starch is good for storage. It is insoluble in water and therefore doesn’t affect water potential. So it doesn’t cause water to enter cells by osmosis, which would make them swell. Making it good for storage.
Starch is the main energy storage material in ____ ?
Complete the sentence
Starch is the main energy storage material in PLANTS!!
Starch is in Potatoes- Plants
Glycogen is the main energy storage material in _____ ?
Complete the sentence
Animals
What is glycogen made up of?
it is a polysaccharide of alpha glucose.
Describe how glycogen results in energy release.
Animals get energy from glucose. Plants store excess glucose as glycogen. When animals need more glucose for energy, they break down the glycogen to release glucose.
Describe the structure of glycogen and how this relates to its function.
It is a long, branched chain of Alpha-Glucose. (with lots more side branches than amylopectin). This means that stored glucose can be released quickly. Which is important for energy release in animals. It’s also a very compact molecule so it is good for storage.
Describe the structure of cellulose
It is a long, unbranched chain of beta-glucose.
What happens when beta-glucose molecules bond?
They form straight cellulose chains.
Describe the bond structure between cellulose chains and how helps cellulose provide structural support.
They are linked together by hydrogen bonds to form strong fibres called microfibrils. The strong fibres mean cellulose provides structural support for cells (eg in plant cell walls)
What is a triglyceride made of?
One molecule of glycerol with three fatty acids attached.
Describe the structure of the fatty acid tails in triglycerides.
Fatty acid molecules have long “tails” of hydrocarbons. The tails are “hydrophobic” (this means they repel water molecules). These tails make lipids insoluble in water.
Define hydrophobic
Repel water molecules.
Why are lipids insoluble in water?
They have fatty acid hydrocarbon tails which are hydrophobic.
All fatty acids have the same basic structure.
Briefly describe this and explain what the variable group is.
Central carbon atom with
1) a double bonded oxygen attached.
2) an OH attached.
And 3) a variable “R” group hydrocarbon tail.
How are triglycerides formed? (Brief)
Condensation reactions
Describe a condensation reaction to form triglyceride.
The OH of a 3 fatty acids combines with the 3 separate OH’s of a glycerol molecule. 3 water molecules released and 3 ester bonds are formed.
What are the two different types of fatty acid?
Saturated and unsaturated.
What is the difference between an unsaturated and saturated fatty acid?
The hydrocarbon tail! (R group)
Describe the structure of a saturated fatty acid tail
Don’t have any double bonds between their carbon atoms.
The fatty acid is “saturated” with hydrogen.
Describe the structure of an unsaturated hydrocarbon tail
They have at least one double bond between carbon atoms, which causes the chain to link.
Where are phospholipids found?
Cell membranes.
Describe the structure of a phospholipid.
Similar to a triglyceride.
One glycerol molecule with TWO fatty acids attached. A phosphate group replaces the third fatty acid.
Which parts of a phospholipid are hydrophilic and hydrophobic?
Phosphate group is hydrophilic
Fatty acid tails are hydrophobic.
What are triglycerides mainly used as?
Energy storage molecules.
How do the long hydrocarbon tails in triglycerides make them effective energy storage molecules?
The long hydrocarbon tails of fatty acids contain lots of chemical energy. (Basically, a lot of energy is released when they’re broken down). Because of these tails, lipids contain about twice as much energy per gram as carbohydrates.
Triglycerides are insoluble.
Explain how this relates to their structure.
They’re insoluble, so they don’t affect the water potential of cells ( which would cause water to enter by osmosis). The triglycerides clump together as insoluble droplets in cells because the fatty acid tails are hydrophobic. The tails face inwards, shielding themselves from water with their glycerol heads.
What is the function of phospholipids.
They make up the bilayer of cell membranes. (Cell membranes control what enters and leaves a cell).
Explain how the structure of phospholipids results in a bilayer.
- Their heads 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 water soluble substances can’t easily pass through it, the membrane acts as a barrier to those substances.
What is the name for the test for lipids?
Emulsion Test
Why would you use the emulsion test for lipids?
To find out if there was any fat in a particular food.
Describe how to carry out the emulsion test for lipids.
1) Shake the test substance with ETHANOL for about a minute so that it dissolves.
2) Then pour the solution into water.
3) Any lipid will show up as a milky emulsion.
Describe what a positive result would look like in the emulsion test.
A milky emulsion. The more lipid there is, the more noticeable the milky colour will be.
What is the name of the bond between triglycerides?
Ester bond.
What are the monomers of proteins?
Amino acids
When is a dipeptide formed?
When two amino acids join together.
When is a polypeptide formed?
When more than two amino acids join together.
What are proteins made up of? (Brief)
One or more polypeptides.
Amino acids have the same general structure.
Describe this and explain what the variable group is.
They all have the same:
• carboxyl group (COOH)
• an amine / amino acid group (NH2)
Variable:
• carbon-containing R group (also known as a variable side group)
Name the amino acid that has one carbon in its side group.
Alanine
Name the amino acid that has no carbons in its side group/R group.
(It has only an H)
Glycine.
Complete the sentence:
“All living things share a bank of only _____ amino acids.”
And, what is the only difference between amino acids?
1• all living things share a bank of only 20 amino acid.
2• the only difference between then is what makes up their carbon-containing R group.
How are polypeptides formed?
(1 mark)
By condensation reactions
Describe how polypeptides are formed in condensation reactions.
Amino acids are linked together by condensation reactions to form polypeptides. A molecule of water is released during the reaction. The bonds formed between amino acids are called PEPTIDE BONDS.
• An H from the amine group of one amino acid joins with the carboxyl group of another amino acid. A molecule of water is released from wee forming the peptide bond.
Polypeptides are formed by condensation reactions. When does the reverse reaction happen?
During digestion.
What are the four structural levels f proteins called?
- primary structure.
- secondary structure.
- tertiary structure.
- quaternary structure.
Describe the primary structure of proteins.
This is the sequence of amino acid in the polypeptide chain.
Describe the secondary structure of proteins.
The polypeptide chain doesn’t remain flat and straight. Hydrogen bond form between the amino acids in the chain. This makes it either:
• coil into an Alpha Helix
• fold into a Beta pleated sheet.
Describe the tertiary of proteins.
The coiled or folded chain of amino acids is often coiled or folded further. More bonds form between different parts of the polypeptide chain, including hydrogen bonds and ionic bonds. Disulfide bridges also form whenever two molecules if 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 one single polypeptide chain, the tertiary structure forms their final 3D structure.
Describe the quaternary structure of proteins.
For the proteins that are made of several different polypeptide chains, these chains are held together by bonds. The quaternary structure is the way these polypeptide chained are assembled together. For proteins made from more than one polypeptide chain the quaternary structure is the proteins final 3D structure.
Give 3 examples of proteins made from more than one polypeptide chain.
• (Meaning the quaternary structure is their final 3D structure.
Haemoglobin
Insulin
Collagen
How are proteins able to carry out particular jobs?
They’ve all got different structures and shapes which makes them specialised to carry out particular jobs.
Name the test for proteins.
Biuret Test
Name the bond formed between dipeptides
Peptide bond
Why would you carry out the biuret test for proteins?
To find out if a substance (eg food sample) contained a protein.
Describe how to carry out the biuret test.
- the test solution needs to be alkaline, so first add a few drops of sodium hydroxide solution.
- then add some copper(II) sulfate solution.
In the biuret test describe the colour change.
•If protein is present, the solution turns purple.
•If there’s no protein, the solution will stay blue.
- The colours are very pale so look carefully!
Enzymes are proteins.
Describe the structure of enzymes and a particular function that requires them to be specialised.
(Think about the 4 structural levels of proteins!)
Enzymes are usually roughly spherical in shape due tithe tight folding of the polypeptide chains. They’re soluble and often have roles in metabolism- some enzymes real down large food molecules. Other enzymes help to make (synthesise) large molecules.
Antibodies are proteins. Describe their structure.
They’re made up of two light (short) and two heavy (long) polypeptide chains bided together. Antibodies have variable regions, the amino acid sequences in these regions varies greatly.
Describe the structure of transport PROTEINS.
Channel proteins contain hydrophobic (water hating) and hydrophilic (water loving) amino acids, which cause the protein to fold up and form a channel.
Describe the structure if structural PROTEINS.
Structural proteins are physically strong. They consist of long polypeptide chains lying parallel to each other with cross-links between them.
Give 2 examples of structural proteins and where they are found.
- keratin (found in hair and nails)
* collagen (found in connective tissue)
What is the function of transport proteins?
They transport molecules and ions across membranes.
Enzymes can act as “biological catalysts” what does this mean?
They speed up chemical reactions.
What is a catalyst?
A substance that speeds up a chemical reaction without being used up in the reaction itself.
Enzymes catalyse metabolic reactions. Give 2 examples.
- respiration (this is at a cellular level)
* digestion in mammals (this is for the organism as a whole).
Enzymes can affect structures in an organism as well as functions. Give 2 examples.
- Structures: enzymes are involved in the production of collagen, (an important protein in the connective tissues of animals.)
- functions: respiration.
Enzyme action can be intracellular and extracellular. Define both terms.
INtracellular: withIN cells
EXtracellular: outside cells (EXternal)
Enzymes have an active site. What is this?
The active site is a specific shape. It is part of the enzyme where the substrate molecules bind to.
What are “substrate molecules”?
The substance that an enzyme interacts with.
How are enzymes highly specific? (Brief, 1 mark).
Due to their tertiary structure.
Overall, what do enzymes do to a reaction?
Lower the activation energy, therefore speeding it up.
define Activation Energy
In a chemical reaction, a certain amount of energy needs to be supplied to the chemicals before the reaction will start. This is called the Activation Energy and is often provided as heat.
Explain what do enzymes do to a reaction?
They lower the amount of activation energy that’s needed, often making reactions happen at a lower temperature than they would without an enzyme. This speeds up the rate of reaction.
What is an “enzyme-substrate” complex?
This occurs when a substrate fits into the enzyme’s active site.
How does an Enzyme-Substrate complex lower activation energy?
1) if two substrate molecules need to be joined, being attached to the enzyme holds them close together, reducing any repulsion between the molecules so they can bond more easily.
2) if the enzyme is catalysing a breakdown reaction, fitting into the active site puts a strain on bonds in the substrate, so the substrate molecules break up more easily.
Describe the “Lock and Key” model
This is where the substrate fits into the enzyme in the same way that a key fits into a lock.
Describe the “Induced Fit” model
The enzyme-substrate complex changes shape slightly to complete the fit. This locks the substrate even more tightly to the enzyme.
Discuss how the “induced fit” model explains why enzymes are so specific (and only bond to one particular substrate).
The substrate doesn’t only have to be the right shape to fit the active site, it has to make the active site change shape in the right way as well.
Give an example of a widely accepted theory that has now changed as new evidence has come along.
The “lock and key” model has changed and become the induced “fit” model.
Complete the sentence.
“Enzyme properties relate to their ______ structure.”
Tertiary
What determines the shape of an enzyme’s active site?
It is determined by the enzyme’s tertiary structure which is determined by the enzymes primary structure.
What happens if the substrate shape doesn’t match the active site?
An enzyme-substrate complex won’t s formed and the reaction won’t be catalysed.
What happens if the tertiary structure of an enzyme is altered in any way?
The shape of the active site will change. This means the substrate won’t fit into the active site. Therefore an enzyme substrate complex won’t be formed and the enzyme will no longer be able to carry out its function.
How could the tertiary structure of an enzyme be altered?
By changes in pH or temperature.
How is the primary structure of an enzyme (protein) determined?
What would happen if a mutation occurred here?
The primary structure is the amino acid sequence. This is determined by a gene. If a mutation occurs in this gene, it could change the tertiary structure of the enzyme produced.
What is an enzyme? (1)
A biological catalyst
Describe what happens in an enzyme controlled reaction when the temperature is increased.
(Why is each collision more likely to result in a reaction?)
(not past the optimum)
The rate of the enzyme-controlled reaction increases when the temperature is increased. More heat means more kinetic energy, so molecules move faster. This makes the enzyme more likely to collide with the substrate molecules. The energy of these collisions also increases, which means each collision is more likely to result in a reaction.
Describe what happens to the enzymes (in an enzyme-controlled reaction) when the temperature goes above the optimum.
- The rise in temperature makes the enzyme’s molecules vibrate more.
- If the temperature goes above a certain level, this vibration breaks some of the bonds that hold the enzyme in shape.
- The active site changes shape and the enzyme and substrate no longer fit together.
- At this point, the enzyme is DENATURED, (it no longer functions as a catalyst).
Give an example of two enzymes where their optimum temperature relates to their function.
37 degrees Celsius for most human enzymes
60 degrees Celsius for enzymes used in biological washing powders.
Give an example of two enzymes where the optimum temperature is related to the function
Most human enzymes work best at pH 7.
Pepsin (found in the stomach) works best at pH 2.
Describe what happens to an enzyme if the environment is above or below its optimum pH.
(Basically- How does it become denatured?)
Above and below the optimum pH, the H+ and OH- ions found in acids and alkalis can interfere with the ionic and hydrogen bonds that hold the enzyme’s TERTIARY structure in place. This makes the active site change shape so the enzyme is DENATURED.
Explain how increasing the enzyme concentration in an enzyme controlled reaction, increases the rate of reaction.
The more enzyme molecules there are in a solution, the more likely a substrate molecule is to collide with one and form an enzyme-substrate complex. So increasing the concentration of the enzyme increases the rate of reaction.
If you increase enzyme concentration in an enzyme-controlled reaction, explain what happens if the substrate is limited.
The increase in enzyme concentration will increase the rate of reaction up to a point, (as more active sites will become available.) But there comes a point when there’s more than enough enzyme molecules to deal with all the available substrate, so adding more has no further effect.
Explain how increasing substrate concentration can increase the rate of reaction.
The higher the substrate concentration, the higher the rate of reaction as there are more substrate molecules which means a collision between substrate and enzyme is more likely, and so more active sites will be used.
You are increasing substrate concentration in an enzyme-controlled reaction.
What happens when a ‘saturation’ point of substrate is reached?
There are only so many substrate molecules that the enzymes can cope with, (all the active sites are full), and adding more makes no difference.
Explain why the initial rate of reaction is the highest.
Because substrate concentration decreases over time during a reaction, (unless more substrate is added to the reaction mixture), so if no other variables are changed, the rate of reaction will decrease over time too. This makes the initial rate of reaction the highest.
What are “enzyme inhibitors”? What do they do?
Brief
Enzyme inhibitors prevent enzyme activity.
Enzyme inhibitors are molecules that bind to the enzyme they inhibit .
What are the two types of enzyme inhibition?
Competitive or non-competitive.
Explain what competitive inhibitor molecules do during a reaction.
Competitive inhibitor molecules have a similar shape to that of the substrate molecules.
They compete with the substrate molecules to bind to the active site, but no reaction takes place.
Instead they block the active site, so no substrate molecules can fit in.
How much an enzyme is inhibited depends on the relative concentrations of the inhibitor and substrate.
Explain what happens in a reaction if there is a higher concentration of inhibitor.
The inhibitor will take up nearly all the active sites and hardly any of the substrate will get to the enzyme.
How much an enzyme is inhibited depends on the relative concentrations of the inhibitor and substrate.
Explain what happens in a reaction if there is a higher concentration of substrate.
The substrates chances of getting to an active site before the inhibitor increase. So increasing the concentration of substrate will increase the rate of reaction, (up to a point).
Where do non-competitive inhibition molecules bind?
To an enzyme away from its active site.
A non-competitive inhibition molecule binds to an enzyme. What happens to the enzyme?
The active site changes shape, so the substrate molecules can no longer bind to it.
Explain how enzyme activity can become inhibited by using a non-competitive inhibitor molecule in a reaction.
Non competitive inhibitor molecules bind to an enzyme away from its active site. This causes the active site to change shape so the substrate molecules can no longer bind to the enzyme. The inhibitor molecules don’t “compete” with the substrate molecules to bind to an active site because they are a different shape. Increasing the concentration of the substrate won’t make any difference to reaction rate, enzyme activity has become inhibited.
