2.2 Biological Molecules Flashcards

Question

explain the fatty acid chains on triglycerides

Answer 1

- fatty acid molecules have long 'tails' made of hydrocarbons (compound containing only hydrogen and carbon) - the tails are hydrophobic (repel water molecules), meaning that lipids are insoluble in water - they are also non-polar, as have a more even distribution of electrons (charge) - all fatty acids have basic structure, but it is the hydrocarbon tail that varies

Answer 2

O = C - R OH - (R= the variable hydrocarbon tail) 3 Cs attached to one OH and rest are just Hs

Answer 3

- synthesised by the formation of an ester bond between each fatty acid and the glycerol molecule ( ester bond forms between hydroxyl groups, and come together to form the O-C=O ester bond) - formed via a condensation reaction where water molecules is released, and is specifically called esterification - breaks down when each ester bond is broken in hydrolysis reaction where water is used up (3 water molecules for each ester bond)

Answer 4

saturated= don't have any double bonds between the carbon atoms in the hydrocarbon chain, so is "saturated" with hydrogen - such as fats in animals (CnH2n+1COOH) unsaturated= have at least one double bond between carbons in hydrocarbon chain, which causes the chain to kink - means that molecules can't pack close as easily, so liquid at room temp, such as oils in plants - use prefixes poly/mono as well to describe how many C=C

Answer 5

- also macromolecules - similar to triglycerides, but one fatty acid chain is replaced with a phosphate group - phosphate group is hydrophilic ( attracts water molecules) and the fatty acid chains are still hydrophobic

Answer 6

- in plants and animals, mainly used as energy storage molecules - in some bacteria (mycobacterium tuberculosis), used to store both energy and carbon - good for storage because: 1) the long hydrocarbon tails of the fatty acids contain lots of chemical energy (lots of energy is released when they're broken down). as a result, they contain about twice as much energy per gram as carbohydrates 2) they're insoluble, so don't cause water to enter the cells via osmosis, which would make them well. the triglycerides bundle together as insoluble droplets in cells as the fatty acid tails are hydrophobic, so they face inwards, shielding themselves from the water with the glycerol heads

Answer 7

- found in the cell membranes (controls what enter and leaves cells) of all eukaryotes and prokaryotes, making up the phospholipid bilayer 1)phospholipid heads are hydrophilic (due to phosphate group) and their tails are hydrophobic, so they form a double layer with their heads facing out towards the water on either side 2) the centre of the bilayer is hydrophobic, so water soluble substances cannot easily pass through it - and membranes act as a barrier to those substances

Answer 8

- has a hydrocarbon ring structure attached to a hydrocarbon tail - ring structure has a polar hydroxyl (OH) group attached to it - in eukaryotic cells, cholesterol molecules help to regulate the fluidity of the cell membrane by interacting with the phospholipid bilayer 1) small size and flattened shape to fit in between the phospholipid molecules in the membrane 2) at higher temperatures, they bind to the hydrophobic tails of the phospholipids, causing them to pack more closely together, so the membrane is less fluid and more rigid 2) in lower temperatures, the cholesterol prevents the phospholipids from packing too closely together, and so increasing the membrane fluidity

Answer 9

- made of the monomers amino acids - dipeptide is formed when 2 amino acids join together - polypeptide is formed when more then 2 amino acids join together - proteins are made of one or more polypeptides

Answer 10

- made of a carboxyl group ( -COOH) and an amino group ( -NH2) attached to a carbon atom - difference between amino acids is the variable R group they contain - all amino acids contain carbon, oxygen, hydrogen, nitrogen, and may also contain sulfur e.g glycine: H H2N- C -COOH (H= R group) H

Answer 11

- linked together by peptide bonds to form di and polypeptides - molecule of water is released during reaction ( bonding between the OH of COOH and the H of NH2), so is a condensation reaction - reverse is just adding water molecule to break peptide bond (hydrolysis reaction) - C-N bond is the peptide bond

Answer 12

- sequence of amino acids in a polypeptide chain - different proteins have a different sequence of amino acids in their chain - change in just one amino acid may change the structure of the whole protein

Answer 13

- hydrogen bonds form between the nearby amino acids in the chain, so the polypeptide chain does not remain straight and flat - coils into alpha helix or folds into a beta pleated sheet

Answer 14

- the coiled or folded chain of amino acids is often coiled or folded further - more bonds form between different parts of the polypeptide chain - the final 3D structure of proteins made of a single polypeptide chain

Answer 15

- the way in polypeptide chains are assembled together in proteins made of several polypeptide chains held together by bonds (e.g haemoglobin made of 4 polypeptide chains) - final 3D structure

Answer 16

- computer modelling can create 3D interactive images of proteins - useful for investigating the different levels of structure in a protein molecules

Answer 17

1) primary = peptide bonds between amino acids 2) secondary= hydrogen bonds 3) tertiary= several: - ionic bonds due to attraction between negative R groups and positive R groups on different parts of the molecule - disulfide bonds when two molecules of amino acid cysteine come close together, sulfur atom in one cysteine bonds to sulfur atom on another cysteine - hydrophobic and hydrophilic interactions ( when hydrophobic R-groups come close together in protein, they clump together, meaning that hydrophilic R-groups are more likely to be pushed to the outside, affecting the way the protein folds - weak hydrogen bonds that form between slightly positive hydrogen atoms in some R groups and slightly negative hydrogen atoms in other R groups 4) quaternary- influenced by all the bonds mentioned as it is dependent of the tertiary structure of the individual polypeptide chains being bonded together

Answer 18

- break up the ionic and hydrogen bonds, and the hydrophobic and hydrophilic reactions, so shape changes

Answer 19

- in globular proteins, the hydrophilic R-groups on the amino acids are pushed to the outside of the molecule, due to the H+H interactions in the tertiary structure - so they are soluble, so easily transported in fluids - are round and compact

Answer 20

1) HAEMOGLOBIN - carries oxygen around the body in red blood cells - is a conjugated protein (protein with a non- protein group (known as a prosthetic group) attached to it) - each of the 4 polypeptide chains have the prosthetic group haem attached to them, which contains iron which the oxygen can bind to 2) INSULIN- hormone secreted by the pancreas to regulate the blood glucose level - solubility is important, which means that it can be transported in the blood to the tissues where it acts - consists of 2 polypeptide chains, which are held together by disulfide bond 3) AMYLASE - enzyme that catalyses the breakdown of starch in the digestive system (most enzymes are globular) - made of a single chain of amino acids - secondary structure contains both alpha helix and beta pleated sheets

Answer 21

- insoluble, strong and rope shaped - structural proteins that are fairly unreactive (unlike many globular proteins)

Answer 22

1) COLLAGEN - found in animal connective tissues, such as bone, skin and ,muscle - very strong molecule - minerals can bind to collagen to increase its rigidity, for example in the bone 2) KERATIN - found in many external structures of animals, such as skin, hair, feathers, horns, nails - can be flexible (skin) or tough (nails) - dependent on degree of disulfide bonds 3) ELASTIN- found in elastic connective tissue ( skin, large blood vessels and some ligaments) - is elastic, so allows tissues to return to their original shape after they have been stretched

Answer 23

an atom with an electric charge

Answer 24

positive: cations negative: anion

Answer 25

- ion which does not contain carbon - important to biological processes

Answer 26

Ca2+ - involved in transmission of nerve impulses - release of insulin from the pancreas -act as cofactor for many enzymes, e.g. those involved in blood clotting, important for bone formation

Answer 27

Na+ - important in generating nerve impulses, for muscle contraction and regulating fluid balance in body

Answer 28

K+ - generating nerve impulses - muscle contraction - regulating fluid balance in body - activates essential enzymes for photosynthesis

Answer 29

H+ -affect pH of substances (H+>OH- means acid) - important for photosynthesis reactions occuring in thylakoid membrane in chloroplasts

Answer 30

NH4+ - absorbed by plants from soil and an important source of nitrogen (used to make amino and nucleic acids)

Answer 31

NO3- - absorbed from soil by plants and an important source of nitrogen (amino and nucleic acids made with)

Answer 32

HCO3- - act as buffer, to maintain pH of blood

Answer 33

Cl- - involved in chloride shift (help maintain pH of blood during gas exchange -act as cofactor in amylase enzyme - some nerve impulses

Answer 34

PO4(3-) - photosynthesis and respiration reactions -needed for synthesis of biological molecules such as nucleotides (ATP), phospholipids and calcium phosphate (strengthen bones)

Answer 35

OH- - affects pH of substance (OH->H+ means alkali)

Answer 36

1) REACTANT for loads of important chemical reactions, e.g. hydrolysis 2) SOLVENT, means substances can dissolve in it - most biological reactions take place in solutions, e.g. in cytoplasm 3) TRANSPORTS substances, easily as is a liquid and a solvent 4) TEMPERATURE CONTROL as high specific heat capacity and high latent heat, so acts as a coolant 5) HABITAT, means organisms can survive and reproduce in it as it helps with temperature control, is solvent and is less dense when freezes

Answer 37

- one atom of oxygen joined to two atoms of hydrogen by shared electrons

Answer 38

- the shared negative electrons from hydrogen are pulled towards the oxygen atom, meaning the other side of hydrogen atoms have a slightly positive charge - unshared electrons of oxygen give it a slight negative charge - so polar, partially + and - sides

Answer 39

- slightly negative oxygen atoms attract the slightly positive hydrogen atoms on other molecules

Answer 40

- SHC = energy needed to raise the temperature of 1g of substance by 1 degree - hydrogen bonds between water molecules absorb a lot of energy, takes lot of energy to heat up - doesn't experience rapid temperature change, so good habitat as temperature under water is more likely to be more stable than on land

Answer 41

-takes a lot of energy to break hydrogen bonds between water molecules - so high LHOE, lots of energy used up when evaporates - good for cooling things - some mammals sweat when too hot as when it evaporates, cools the surface of skin

Answer 42

- cohesion = attraction between molecules of the same type - water molecules are very cohesive, tend to stick together, because they are polar - helps water flow, so good for transporting substances - helps water to be transported up plant stems in the transpiration stream

Answer 43

- a lot of important biological reactions are ionic, e.g. salt ( one positively charged and one negatively charged atom or molecules) - water is polar, so slightly negative and slightly positive sides will be attracted to opposite charges ion - results in ion getting completely surrounded by water molecules, so dissolved - useful solvent for living organisms, e.g. in humans important ions dissolve in blood to be transported around body

Answer 44

- at low temperature, water freezes and turns into a solid - water molecules are held further apart in ice than in liquid because water molecules form 4 hydrogen bonds to other molecules - this makes lattice shape, so less dense, and reason to float - ice forms insulating layer in cold temperatures, and water below doesn't freeze - fish don't freeze and can move around

Answer 45

- test strip coated in a reagent - dipped in test solution - change colour if glucose present - colour can be compared to chart to give concentration of clucose - useful for testing urine

Answer 46

- iodine test - add iodine dissolved in potassium iodide solution - browney/orange to bluey/black

Answer 47

- biuret test - add drops of sodium hydroxide solution (needs to be alkaline) - add copper(II) sulfate solution - blue to purple

Answer 48

- emulsion test - add ethanol - shake for one minute - pour solution into water - clear to milky/ cloudy (NOT precipitate)

Answer 49

- general term for monosaccharides and polysaccharides

Answer 50

- monosaccharides and some disaccharides (maltose and lactose) add benedict's reagent to sample and heat in water bath to bring to boil (above 70 degrees) - blue to: green, yellow, orange, brick red - colour of precipitate changes - more accurate = filter and weigh precipitate

Answer 51

disaccharides (sucrose) - need to be broken down into monosaccharide - add dilute HCL and heat in water bath to be brought to a boil - neutralise with sodium hydrogencarbonate - carry out normal Benedict's test

Answer 52

- benedict's reagent - colorimeter - gives a quantitative estimate of how much glucose/ reducing sugar present in a solution

Answer 53

- device that measures the strength of a coloured solution by seeing how much light passes through - measures absorbance ( amount of light absorbed by the solution) - more concentrated the colour = higher absorbance

Answer 54

- measure the blue Benedict's solution left after the test - paler the solution, more concentrated the glucose - so higher the absorbance, lower the concentration of glucose

Answer 55

serial dilution 1) Line up five test tubes in a rack. 2) Add 10 cm* of the initial 40 mM glucose solution to the first test tube and 5 cm° of distilled water to the other four test tubes. 3) Then, using a pipette, draw 5 cm° of the solution from the first test tube, add it to the distilled water in the second test tube and mix the solution thoroughly. You now have 10 cm of solution that's half as concentrated as the solution in the first test tube (it's 20 mM). 4) Repeat this process three more times to create solutions of 10 mM, 5 mM and 2.5 mM.

Answer 56

1) Do a Benedict's test on each solution (plus a negative control of pure water, and when in colorimeter, set to 0 after). Use the same amount of Benedict's solution in each case. 2) Remove any precipitate — either leave for 24 hours (so that the precipitate settles out) or centrifuge them. 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 to make the calibration curve, showing absorbance against glucose concentration. Then you can test the unknown solution in the same way as the known concentrations and use the calibration curve to find its concentration.

Answer 57

a device that uses a biological molecule (e.g. enzyme) to detect a chemical - the biological molecule produces a signal (e.g chemical) which is converted to an electrical signal by a transducer - the electrical signal is then processed and used to work out other information

Answer 58

- used to determine the concentration of glucose in a solution - uses enzyme glucose oxidase and electrodes - enzyme catalyses the oxidation of glucose at the electrodes, which creates a charge and can be converted to an electrical signal by the electrodes - the signal is processed to work out the initial glucose concentration

Answer 59

- separating mixtures and identifying the components - components such as amino acids, carbohydrates, vitamins and nucleic acids

Answer 60

- paper - thin-layer: uae a layer of thin silica-gel on a rigid surface, such as glass or metal sheet

Answer 61

- mobile phase - stationary phase

Answer 62

- where the molecules can move - the liquid solvent (ethanol and water)

Answer 63

- where the molecules can't move - paper: chromatography paper - thin layer: silica gel, glass, plastic plate (0.1 to 0.3mm)

Answer 64

- mobile phase moves through or over the stationary phase - the components in the mixture spend different amounts of time in the phases: 1) longer in mobile = move faster and further - it is time spent in different phases that separates out the components - end up with chromatograph

Answer 65

1) Draw a pencil line near the bottom of a piece of chromatography paper and put a concentrated spot of the mixture of amino acids on it. It's best to carefully roll the paper into a cylinder with the spot on the outside so it'll stand up. 2) Add a small amount of prepared organic solvent (a mixture of butan-1-ol, glacial ethanoic acid and water is usually used for amino acids) to a beaker and dip the bottom of the paper into it (not the spot). This should be done in a fume cupboard. Cover with a lid to stop the solvent evaporating. 3) As the solvent spreads up the paper, the different amino acids (solutes) move with it, but at different rates, so they separate out. (this is due to difference in interactions with stationary phase and solubility in mobile phase of each amino acid) 4) When the solvent's nearly reached the top, take the paper out and mark the solvent front with pencil. Then you can leave the paper to dry out before you analyse it (see below). 5) Amino acids aren't coloured, which means you won't be able to see them on the paper. So before you can analyse them, you have to spray the paper with ninhydrin solution to turn the amino acids purple. This should also be done in a fume cupboard and gloves should be worn. (Note: you can't use ninhydrin to detect all biological molecules, only proteins and amino acids.) 6) You can then use R, values to identify the separated molecules:

Answer 66

- ratio of the distance travelled by the solute to the distance travelled by the solvent - always less than 1 -(DISTANCE TRAVELLED BY SOLUTE/DISTANCE TRAVELLED BY SOLVENT) - measure from point of origin to the vertical centre of the spot - look up Rf values in a database or table of known values

2.2 Biological Molecules Flashcards

(90 cards)