Biological Molecules Flashcards
BIOCHEM IS FUN WHEYYYYY
What are the 4 organic molecules?
Carbohydrates, Lipids, Proteins, Nucleic acids.
What nucleic acids do all organisms use?
The same ones as each other.
How many amino acids are there?
20.
What molecules do all organisms use for energy?
Carbohydrates.
What do all organisms use for cell membranes?
Lipids.
What thory does the biological similarities between organisms support?
Theory that all animals and plants share a commono ancestor.
What are monomers?
The smaller units that can join together to make larger molecules.
What are polymers?
Molecules made from lots of repeating unts joined together.
Give 3 examples of monomers.
Monosaccharides, amino acids and nucleotides.
What happens in condensation?
Two monomers join together and form a covalent bond with the elimination of water.
What happens in hydrolysis?
Addition of a water molecule is used to break apart the covalent bond between monomers.
What is a monosaccharide?
Monomer of a carbohydrate.
What are 3 examples of monosaccharides?
Glucose, fructose, galactose.
What are the differences between hexose and pentose sugars?
Hexose sugars have 6 carbons and pentose sugars have 5 carbons.
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Is glucose a hexose or pentose sugar?
Hexose.
What is an isomer?
Molecules with the same forumla but have different structures.
What are the 2 isomers of glucose?
alpha and beta.
How are glucose’s isomers different.
The hydrogen and hydroxide on carbon 1 are the other way around.
How are carbons numbered in diagrams of glucose?
Clockwise, with carbon 1 being first after the oxygen.
How do monosaccharides bond together?
Condensation reactions.
What type of bond forms from condensation of monosaccharides?
A glycosidic bond.
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What are disaccharides?
Two monosaccharides bonded together.
Give 3 examples of disaccharides.
Maltose, Sucrose, Lactose.
What monosaccharides make maltose?
Glucose-glucose
What monosaccharides make sucrose?
Glucose-fructose
What monosaccharides make lactose?
Glucose-galactose.
What can reducing sugars do?
Donate electrons to other compounds.
Give 5 examples of reducing sugars.
Glucose, fructose, galactose, maltose, lactose.
Give an example of a non-reducing sugar.
Sucrose.
What are polysaccharides?
Polymer carbohydrates.
What are polysaccharides made of?
Lots of monosaccharides bonded together.
Give 3 examples of polysaccharides.
Glycogen, cellulose, starch.
What is starch made of?
Alpha glucose.
What is the diference between 1-4 and 1-6 glycosidic bonds?
The carbons that are joining together.
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What 2 polysaccharides is starch made up of?
Amylose and amylopectin.
Describe the shape of amylose.
A long unbranched chain that forms a coiled helical shape.
What type of bonds does amylose contain?
Alpha 1-4 glycosidic bonds.
What is amylose used for?
Storing excess glucose to convert back for energy.
How does the structure of amylose help with its function?
Helical shape allow it to be compact so lots can be stored in a small space.
Describe the structure of amylopectin.
A long branched chain of alpha glucose.
What is amylopectin used for?
Storing excess glucose that can be used later.
How does the structure of amylopectin aid its function?
Branches increase the surface area so it can be hydrolised for glucose easily.
How do the properites of starch aid their function? (2)
It is too large to leave cells so will always be readily available.
It is insoluble so cannot affect water potential and osmosis.
What type of bonds does amylopectin contain?
Alpha 1-4 and alpha 1-6 glycosidic bonds.
What is glycogen made out of?
Alpha-glucose.
Describe the structure of glycogen.
Long branched polysaccharide.
How does the structure of glucose compare to amylopectin?
Glucose has many more branches.
What type of bonds does glycogen contain?
Alpha 1-4 and alpha 1-6 glycosidic bonds.
Where is glycogen found?
In animal cells.
What is glycogen used for?
Storing excess glucose.
Where in the body is glycogen usually found in cells?
Muscles and the liver.
How does the structure of glycogen aid its function? (2)
The branches increase the surface area so it can be hydrolysed more easily.
It is a compact molecule so is good for storage.
Where is cellulose found?
In plant cell walls.
What is cellulose made of?
Beta-glucose
What bonds make up glucose?
Beta 1-4 glycosidic bonds.
How are the glucose molecules oriented in cellulose? (why?)
Alternating molecules are inverted so the -OH groups are lined up to form bonds.
Describe the general structire of cellulose.
Long unbranched chains held together by hydrogoen bonds.
What do the cellulose chain form when joined by hydrogen bonds?
Fibres called microfibrils.
What is cellulose used for?
Providing structure in cell walls, allowing the wall to stay rigid.
How do the properties of cellulose help with its function?
Hydrogen bonds make microfibrils very strong but also flexible.
Where are 1-6 glycosidic bonds found?
At points where polysaccharide chains are branched.
How are lipids different from carbohydrates and proteins?
Lipids are NOT polymers.
What are the main functions of lipids? (4)
Waterproofing, insulation, protection/membranes, and emergency energy supplies.
What is a triglyceride made up of?
A glycerol molecule and three fatty acid chains.
What can triglycerides be used for?
An energy store, as lots of energy can be released as chains are broken down.
What bonds do lipids form during condensation?
Ester bonds.
What do ester bonds form between?
Between -OH groups on fatty acid chains and on the glycerol molecule.
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What property can the fatty acid HYDROCARBON chain have in triglycerides?
They can be saturated or unsaturated.
Define saturated.
Only single bonds between the carbons in the chain, so the maximum number of hydrogens can bond to each carbon atom.
Define monounsaturated.
There is only one c=c double bond between carbons in the chain.
Define polyunsaturated.
More than one c=c double bonds between carbons within the chain.
Why are lipids insoluble in water?
They are not polar (do not have a charge)
How do phospholipids react in water?
They bundle together as insoluble droplets with the glycerol heads shield the tails from the water.
What are phospholipids made up of?
A glycerol molecule, a phosphate group, and two fatty acid chains.
How does the structure of a phospholipid differ from a triglyceride?
In phospholipids, one of the fatty acid chains is replaced by a phosphate group.
What can phospholipids be used for?
Membranes and hormones.
How do the different parts of a phospholipid behave near water?
The head is hydrophilic and the 2 tails are hydrophobic.
What is different about the specific structures of the fatty acid chains in phospholipids?
There is always one saturated and one unsaturated chain.
What feature do unsaturated fatty acid chains have? (why?)
The c=c double bond causes the chain to bend and create a kink, as the lack of hydrogens in the way allows the carbons to move closer together.
How do the properties of phospholipids aid its function?
Thy hydrophobic tails and hydrophilic head allow phospholipids to form bilayers for membranes.
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Why can water soluble substances not easily pass through a phospholipid bilayer?
The centre of the bilayer is hydrophobic.
What is the monomer for proteins?
Amino acids.
How many amino acids are there?
20.
What do all amino acids share?
A basic structure.
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What is the variable part of a molecule called?
R-group
What is the R-group of molecules?
The part of the molecule that may vary between different molecules.
What is the R-group of glycine?
Just a hydrogen.
What can the R-group contain other than C,O,H?
Other elements (cytesine has sulfur).
How do amino acids join?
Condensation reactions.
What bond forms between amino acids?
Peptide bonds.
Where does the peptide bond form between amino acids?
Between the amine group of one and the carboxyl group of another amino acid.
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What is made when 2 amino acids are joined?
Dipeptide.
What is the amine group?
-H2N
What is the carboxyl groups?
-COOH
How are dipeptides and polypeptides broken down?
Hydrolysis.
What is a hydroxyl group?
-OH
How many levels of protein structure are there?
4.
How do proteins form? (get to each stricture)
The polypeptides fold.
What is the primary structure of proteins?
Simple polypeptide chains.
Can a primary structure protein function?
NOPE AND THATS A BIT OF AN L.
What is important about the structure of primary proteins?
The number and sequence of the amino acids determines the tertiary structure.
What about enzymes can the the order and number of amino acids in a polypeptide affect?
The shape of the active site.
What is the secondary structure of proteins?
Alpha-helix or beta-pleated sheet.
Why do polypeptides start to fold into the secondary structure?
Hydrogen bonds forming between the amino acids.
What does hydrogen bonds forming between amino acids cause?
Folding into an alpha-helix or a beta-pleated sheet.
Why is the secondary structure of proteins stable?
The hydrogen bonds keep the structure stable.
What is a use of alpha-helices?
Channel proteins in membranes.
What is the structure of teriary proteins?
The fully formed shape of the 3D polypeptide chain.
What is a tertiary protein? (description)
A complex folded 3D shape made of a polypeptide chain.
Why do tertiary proteins have a very specific shape?
Thw sequence of amino acids determines which R-groups begin to form bonds.
What types of bond can form between the R-groups of tertiary proteins? (3)
Hydrogen bonds, ionic bonds, disulphide bridges (covalent).
Give 3 examples of tertiary proteins.
ALL enzymes, ALL anitibodies, SOME hormones.
WHO’S THE MOST SIGMA
GRACE OFC
What are quaternary proteins made of?
Multiple polypeptide chains.
Give an example of a quaternary protein
Haemoglobin.
What is a prosthetic group?
A non-protein group that is part of a quaternary protein.
What is the prosthetic group in haemoglobin, and what does it contain?
The haem group that contains iron.
What is a glycoprotein?
A protein that also contains a carbohydrate group.
What is a lipoprotein?
A protein that also contains a lipid group.
What is the function of enzymes?
Speed up rates of reaction.
What are enzymes?
Biological catalysts.
How do enzymes achieve their function?
By lowering activation energy.
What is a catalyst?
A substance that can speed up a chemical reaction without getting used up in the process.
What reactions can a single enzyme catalyse? (how broad)
Enzymes catalyse a specific ?, typically only one.
What is a catabolic reaction?
A reaction that breakes a substrate down.
What is an anabolic reaction?
A reaction that joins substrates together.
What type of structure do enzymes have?
3D tertiary protein structure.
What sort of shape is an enzyme’s active site?
Specific.
What type of substrates can a certain enzyme bind to?
Certian substrates only.
What is formed when an enzyme and a substrate bind?
An enzyme-substrate complex (E-S complex).
What is an enzyme-substrate complex?
A substance formed of an enzyme that has bound to a substrate.
How can you describe an enzyme’s active site when compared to the substrate?
The shapes are complimentary.
Define complimentary.
The way that 2 shapes fit together (enzymes)
What does a lower activation energy allow in reactions?
The reaction can take place at a lower temperature.
How do enzymes lower activation energy? (2)
Holding substrates together so there is less repultion and they can bond more easily.
Putting more strain on the bonds of a substrate so it can break apart.
What is the lock and key model?
The enzyme active site is exactly complimentary to the shape of the substrate so they fit together perfectly (hence enzymes are specific).
What is the induced fit model?
The active site can change slightly to fit the substrate when they collide and form an e-s complex.
What made the induced fit model more plausible?
Enzymes being able to catalyse multiple substrates.
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What factors are able to affect enzyme action? (4)
Enzyme concentration, substrate concentration, temperature, pH
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How does enzyme concentration affect rate of reaction?
There are more enzymes that are available to form E-S complexes so the rate will increase.
Why does a graph of enzyme concentration plateau?
The substrate becomes the limiting factor so increasing number of enzymes will not affect the rate.
How does substrate concentration affect rate?
It will initially increase as there are more collisions occuring, but then it will slow as enzymes become a limiting factor. As all active sites are occupied (saturation point) increasing the substrate will have less effect.
What is the saturation point (enzymes)?
Where all the enzyme active sites are occupied.
How does temperature affect enzyme concentration?
There is more kinetic energy so molecules move faster and there are more successful collisions. Rate will increase up to the point where it is too hot and bonds eithing the enzymes break, causing the tertiary structure to change so no more substrates can react (active site is different). The enzyme is permanently denatured.
What does denatured mean?
When the enzyme permanently changes shape as the bonds in the tertiary structure have broken.
How does pH affect enzyme function?
Above and below the optimum pH the concentrations of H+ and OH- ions disrupt ionic and hydrogen bonds, causing the enzyme to denature.
How do inhibitors prevent enzyme function?
They stop substrates from binding.
What is an inhibitor?
A substance that prevents enzyme function by stopping substrates from binding.
What are the 2 types of inhibitor?
Competitive and non-competitive.
How are competitive inhibitors similar to substrate molecules?
They both have a similar shape.
How do competitive inhibitors prevent enzyme function?
They compete with substrates to block the active site, so substrates cannot bind anymore.
How can competitive inhibitors be challenged?
Increasing the substrate concentration will increase the rate of reaction still as the substrates out-compete the inhibitor for enzyme active sites.
Where do non-competitive inhobitors bind?
The allosteric site of the enzyme.
How do non-comopetitive inhibitors affect enzyme function?
By binding to the allosteric site they change the shape of the active site so it is no longer complimentary to the substrate.
Can you out-compete a non-competitive inhibitor?
No. as the substrates can no longer bind anyway.
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What is the reducing sugars test used to find? (examples)
All monosaccharides, some disaccharides like maltose and lactose.
What is the reagent for the reducing sugars test?
Benedict’s reagent.
What colour is benedict’s reagent at the start of the test?
Pale blue.
What are hazards for the reducing sugars test? (2)
Benedict’s reagent is an irritant.
Hot water can cause burns.
What are precautions taken for the reducing sugars test? (2)
Wear goggles, wash hands on contact (benedict’s).
Use caution when pouring or carrying (hot water).
What is the method for the reducing sugars test?
Add excess benedict’s to the sample, heat in boiling water bath (>80 degrees)
What is a positive result for the reducing sugars test?
A precipitate (colour from yellow to brick red based on amount of sugar) will form.
What is a negative result for the reducing sugars test?
The solution will remain blue.
What is the non-reducing sugars test to find? (examples)
Disaccharides or polysaccharides like sucrose.
When is the non-reducing sugars test used?
If a negative result is taken from the reducing sugars test.
How does the non reducing sugars test vary from the reducing sugars test?
Add dilute HCl and heat to break bonds FIRST.
Then add an alkali (NaOH) to neutralise
Continue as for reducing sugars.
How can results from sugar tests be made quantitative? (2)
Filter and weigh the precipitate.
Remove precipitate and use a colourimeter.
How do you test for starch?
Add iodine.
What hazards and precautions are taken when testing for starch?
Iodine is an irritant so wear goggles and wash hands if comes into contact.
What are the possible results for a starch test?
Positive: goes blue/black
Negative: stays brown/yellow.
What type of data is a result from a starch test?
Qualitative only (it is yes/no)
What is the protein test for? (examples)
Presence of amino acids.
What is the reagent in the protein test?
Biuret reagent.
What colour is biuret reagent?
Pale blue (dilute CuSO4 and NaOH)
What hazards and precautions are found for the protein test?
Biuret is an irritant: goggles are worn, hands washed when in contact.
What is the method for the protein test?
Add excess biruet and shake.
What are the results for the protein test?
Positive: goes purple
Negative: stays blue.
How could you make a protein test quantitative?
Chromatography can be used to identify certian amino acids in a mixture by separating them by mass.
Why is the protein test qualitative?
A stronger purple means more amino acids are present.
What is the lipids test for?
Lipids you fool what else would it be for >:)
What is the reagent for a lipids test?
Emulsion test using ethanol and water.
What precautions and hazards can be found for the emulsion test?
Ethanol is flammable: do not do the test near a naked flame.
What is the method for the emulsion test?
Add ethanol (to emulsify), THEN water.
What are the results for the emulsion test?
Positive: a MILKY WHITE EMULSION forms on the top
Negative: nothingi happens.
Why is the emulsion test qualitative?
The more lipids are present the more opaque the emulsion will be, it is qualitiative only.
How can water be described? (importance)
Biologically important.
Is water a monomer or a polymer?
NO
What are the 2 types of bonding between molecules?
Ionic and covalent (chem flashbacks ewwww)
What is ionic bonding between?
Metals and non-metals.
How does ionic bonding work?
Metal donates electron to non metal.
What charges are gained in ionic bonding?
Metal becomes positive, non metal becomes negative.
What is covalent bonding between?
Non-metals only.
What happens in covalent bonding?
Atoms share electrons.
What is electronegativity?
Where some atoms attract electrons better than others.
Why does electronegativity happen?
Bigger nucleus means more protons to attract electrons with.
Is water more electronegative, or hydrogen?
WATERRRR
What is a polar molecule?
Molecule with a slight uneven distribution of charge.
How is water a polar molecule?
Electrons are pulled to the oxygen (becomes delta negative), while hydrogen becomes delta positive.
How would you describe an atom with a very slight charge?
Delta positive/negative.
What is hydrogen bonding? (in water)
Hydrogens get attracted slightly to the other oxygens.
What are properties of hydrogen bonding? (single/multiple)
Weak on their own, strong when there are lots.
What is cohesion?
When molecules attract each other.
How can you tell that water is cohesive?
It forms droplets.
How do the water molecules form up?
In a lattice structure.
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What is suface tension?
Intermolecular attraction at the surface of a liquid, agains a gas.
What is adhesion?
Water’s tendency to stick to surfaces (inside of tubes)
Give some properties of water? (9)
- Wide temp range as a liquid
- below 4 degrees is less dense than above
- high shc (4200j/kg degree)
- high latent heat of evaporation (100j/degree)
- polar
- is a reactant (photosynthesis/hydrolysis)
- has many hydrogen bonds
- transparent
- is a solvent
How do the properties of water aid its function? (6)
- Lower density cold water allows ice to float and currents to occur in the sea
- High SHC makes water a good buffer as there is no rapid temperature change.
- High latent heat of vapourisation allows sweat to absorb heat
- As it is a polar molecule it allows things to be dissolved into it.
- The many hydrogen bonds lead to properties of cohesion, adhesion and surface tension.
- As water is a solvent it allows for transpiration
