Molecules Flashcards
Water is/can… (5)
- a reactant
- a solvent
- a habitat
- transports substances
- help with temperature control
Structure of water
There is one atom of oxygen joined by two hydrogen atoms as the shared negative hydrogen electrons are pulled towards the oxygen atoms. The unshared negative electrons on the oxygen give it a slightly negative charge, making it a polar molecule. It also contains hydrogen bonds due to the difference in charges
What is specific heat capacity
The energy required to raise the temperature of 1 gram of substance by 1 degree celcius
What do hydrogen bonds absorb
Lots of energy
Does water have a high or low specific heat capacity
High
What is high latent heat of evaporation
Lots of energy is used up when water evaporates
Does water have a high latent heat of evaporation
Yes due to the hydrogen bonds
What is cohesion
The attraction between molecules of the same type e.g two water molecules as they are polar
Why is cohesion useful
Helps water to flow so useful for transporting substances
What property does a polar molecule have
It is a good solvent so can dissolve
Why is ice less dense than water
Ice molecules are held further apart so ice is less dense than water therefore ice will float
What are carbohydrates made from
Polymers called Monosaccharides
What is a hexose monosccharide
Monosaccharide with six carbon atoms
Two forms of carbohydrates
Alpha and beta
What is the order of the alpha ring
Hydrogen on top and the hydroxyl underneath
What is the order of the beta ring
The hydroxyl is on top the hydrogen is on the bottom
What is a monosaccharide with 5 carbon atoms called
Pentose monosaccharide
What are monosaccharides joined together by
Glyosidic bonds
What three elements are carbohydrates made up of
Carbon, hydrogen and ocygen
For every carbon atom how many hydrogen and oxygen atoms are there
2 hydrogen atoms
1 oxygen atom
What happens during carbohydrate synthesis and it’s name
A hydrogen atom on one monosaccharide bonds to a hydroxyl group releasing a water molecule - called condensation
What happens during the reverse of carbohydrate synthesis and it’s name
A molecule of water reacts with the glycosidic bond breaking it apart - called hydrolysis
What is formed when two monosaccharides join together
Disaccharide
General term for mono/disaccharides
Sugar
More than two monosaccharides are
Polysaccharides
Starch is…
The main energy storage material in plants
Glycogen is…
The main energy storage material in animals
Cellulose is…
The major component of cell walls in plants
What is cellulose made from
Long, unbranched chains of beta glucose bonding by hydrogen bonds to form straight cellulose chains. There are fibres called microfibrils providing structural support
What do animals store excess glucose as
Glycogen
Structure of glycogen
Polysaccharide of alpha-glucose similar to amylopectin but with lots of side branches so stored glucose can be released quickly which is important for energy release and also very compact so good storage
What do plants store excess glucose as
Starch
What is starch a mixture of two….
Polysaccharides of alpha-glucose - amylose and amylopectin
What is amylose
A long unbranched chain of alpha-glucose. The angles of the glycosidic bonds give it a coiled structure like a cylinder. This makes it compact so is good for storage as you can fit more in to a small space
What is amylopectin
A long branched chain of alpha-glucose. Side branches allow the enzymes that break down the molecule to get at the glycosidic bonds easily, so glucose cannot be released quickly
What is starches solubility status
Insoluble in water so it doesn’t cause water to enter cells by osmosis making them swell making it good for storage
What are triglycerides
Complex macromolecules with a large molecular mass containing carbon, hydrogen and oxygen with one molecule of glycerol and three fatty acid tails
What do fatty acid molecules have
Long tails made of hydrocarbons that are hydrophobic and therefore insoluble in water. All fatty acids have the same basic structure but the hydrocarbon tail varies
What bonds do triglycerides contain
Ester bonds between fatty acid and glycerol molecules
How is each bond on a triglyceride formed
By a condensation reaction called esterification
How are triglyceride bonds broken
When ester bonds break due to hydrolysis reaction
What are saturated fatty acids
They do not have any double bonds between carbon atoms as the fatty acid is ‘saturated’ with hydrogen
What are unsaturated fatty acids
At least one double bond between carbon atoms causing the chain to kink
How does the structure of triglycerides relate to their functions
1) Long hydrocarbon tails of fatty acids contain lots of chemical energy which is released when they are broken down and therefore lipids contain twice the amount of energy per gram as carbohydrates
2) They are insoluble so don’t cause water to enter the cells by osmosis leading to swelling. Triglycerides bundle together as insoluble droplets as the fatty acid tails are hydrophobic, the tails face inwards shielding the water with their glycerol heads
How does the structure of phospholipids relate to their function
1) Phospholipid heads are hydrophilic and their tails are hydrophobic so form a double layer with heads facing out
2) The centre of the bilayer is hydrophobic so water soluble substances can’t easily pass through it
How does the structure of cholesterol relate to their function
Has a hydrocarbon ring structure (polar hydroxyl group) attached to a hydrocarbon tail. Helping to regulate the fluidity of the cell membrane.
1) Cholesterol has a small size and flattened shape allowing it to fit in phospholipid bilayer
2) At high temps they bind to hydrophobic tails causing them to pack more closely together helping the membrane to be less fluid and more rigid
3) At low temps prevents the phospholipids from packing too close together
What are proteins made from
Long chains of amino acids. They are the monomers as proteins are made up of one or more polypeptides
What do all amino acids have
Carboxyl group, amine group, R group
What do all amino acids contain
Carbon, oxygen, hydrogen and nitrogen some containing sulfur
What bonds link amino acids
Peptide bonds
What type of reaction is joining of amino acids
Condensation
What is the order of protein structure
Primary, secondary, tertiary, quaternary
What is a primary structure
Sequence of amino acids in the polypeptide chain, different proteins have different sequences of amino acids in their primary structure. A change in just one amino acid may change the structure of the whole protein.
What is a a secondary structure
Polypeptide chain doesn’t remain flat and straight. Hydrogen bonds form between nearby amino acids in the chain making it automatically coil into an alpha helix or beta pleated sheet.
What is a tertiary structure
Coiled or folded chain of amino acids often coiled an folded further. More bonds form between different parts of the polypeptide chain, many proteins made from a single polypeptide chain the tertiary structure forms the final 3D structure
What is a quaternary structure
Proteins that are made from several different polypeptide chains held together by bonds. It is the way these polypeptide chains are assembled together making it quaternary. Proteins made from more than one polypeptide chain, this is the final 3D structure.
What bonds hold together primary proteins
Peptide
What bonds hold together secondary proteins
Hydrogen
What bonds hold together tertiary and quaternary proteins
Ionic = attractions between negative R groups and positive R groups
Disulfide bonds = two molecules of cysteine coming close together the sulfur atom in one cysteine bonds to the sulfur in the other cysteine forming a disulfide bond
Hydrophobic/phillic interaction = hydrophobic R groups close together in the protein being close together tend to clump together. Hydrophilic R groups pushed to the outside affecting the proteins folding and structure.
Hydrogen bonds = weak bond forming between positive hydrogen atoms in some R groups and negative atoms in other R groups on the polypeptide chain
Features of a globular protein
- Hydrophilic R groups on the amino acids tend to be pushed to the outside of the molecule. Caused by hydrophobic/phillic interactions in tertiary structure
- They are soluble so easy to transport in fluids
What are the functions of haemoglobin the globular protein
Haemoglobin - carries oxygen around the body in RBC. Conjugated protein so has a non-protein group attached called a prosthetic group. Each of the four polypeptide chains in haemoglobin has a prosthetic group called haem which contains iron which oxygen binds to
What are fibrous proteins
Tough and rope-shaped proteins that are insoluble and strong. They are structural and fairly unreactive
What is the fibrous protein collagen
Found in animal connective tissue such as bone, skin and muscle. Mineral scan bind to the proteins to increase its rigidity
What are the functions of insulin the globular protein
Insulin - secreted by the pancreas to regulate the blood glucose level. Its solubility is important as it means it can be transported in the blood to the tissues where it acts. An insulin molecule consists of two polypeptide chains which are held by disulfide bonds
What are the functions of amylase the globular protein
Amylase - an enzyme catalyzes the breakdown of starch in the digestive system made from a single chain of amino acids. Secondary structure contains alpha helix and beta pleated sheet sections.
What is the fibrous protein keratin
Found in many of the external structures of animals such as skin, hair, nails, feathers and horns. It can be flexible (skin) or hard and tough (nails)
What is the fibrous protein elastin
Found in elastic connective tissue, such as skin, large blood vessels and some ligaments. It is elastic so it allows tissues to return to their original shape after they have been stretched
What is benedicts test for reducing sugars
1) Add benedicts reagent to a sample and heat it in a water bath
2) The colour will go from blue to brick red to indicate a positive test in the form of a coloured precipitate
3) The higher the concentration of reducing sugar the further the colour change goes
What is benedicts test for non reducing sugars
1) To be completed if reducing is negative
2) Add dilute hydrochloric acid and carefully heat in a water bath. Then neutralize it with sodium hydrogen carbonate
3) Carry out the benedicts test after
4) If the test’s positive it will form a coloured precipitate
How can glucose be tested
Using test strips coated in a reagent. The strips are dipped in a test solution and change colour if glucose is present. Colour change then compared to a chart. Used for urine testing of diabetes
How can starch be tested
Adding iodine solution to the test and if starch is present then the sample changes from browny-orange to dark blue-black
How to test for proteins
Using the biuret test:
1) The test solution should be alkaline so add sodium hydroxide solution
2) Add copper (II) sulfate solution
- If protein is present solution turns purple
- If no protein the solution will stay blue
How to test for lipids
Emulsion test:
Shake the test substance with ethanol for about a minute and then pour the solution into water
- If lipid present the solution will turn milky
How does colorimetry determine the concentration of a glucose solution
1) Benedicts reagent and a colorimeter to get a quantitive estimate of how much glucose (reducing sugar) there is in a solution
2) The colorimeter measures absorbance and the more concentrated the colour of the solution, the higher the absorbance
3) Paler solution = more glucose there was, higher glucose conc = lower the absorbance of solution
How to carry out the test for concentration of glucose (serial dilations)
1) Line up five test tubes in a rack
2) Add 10cm of the initial 40mM glucose solution to the first test tube and 5cm of distilled water to the other four test tubes
3) Then using a pipette draw 5cm of the solution from the first test tube, add it to the distilled water in the second and mix the solution thoroughly. Now have 10cm of solution that’s half as concentrated as the solution in the first test tube
4) Repeat this process three more times to create solutions of 10mM, 5mM and 2.5mM
How to determine the concentration of glucose solution following a serial dilation
1) Do a Benedict’s test on each solution using the same amount of Benedicts solution in each case
2) Remove any precipitate (leaving 24 hours or centrifuge)
3) Use a colorimeter (with a red filter) to measure the absorbance of the Benedict’s solution remaining in each tube
4) Use the results in a calibration curve
What are biosensors
A device that uses a biological molecule such as an enzyme to detect a chemical. The biological molecule produces a signal which is converted to an electrical signal by a transductor. The electrical signal is then processed and can be used to work out other infomation
Rf value of an amino acid =
distance travelled by solute / distance travelled by solvent
