1A - Biological Molecules Flashcards

Question

What make up proteins

Answer 1

Protein monomers = amino acids A dipeptide is formed when two amino acids join A polypeptide is formed when more than two a.a.s join Proteins consist of one (or more) polypeptides

Answer 2

Amino acids have the same general structure.. - a carboxyl group (-COOH) - amine/amino group (-NH2) - H group - R group (known as a variable side group) All living things share a bank of 20 a.a. types The only difference between these 20 amino acids is what makes up their R group (Glycine is the only a.a. without a C in its side group - just a H atom) **diagram no.4**

Answer 3

Amino acids are linked by condensation reactions to form polypeptides —> a water molecule is released during reaction The bonds performed between a.a.s are *peptide bonds* The reverse reaction happens during digestion **diagram no.5**

Answer 4

Proteins are big complex molecules Their structures can be described in four levels (These levels are a protein’s primary, secondary, tertiary and quaternary structures) —> primary structure -the sequence of amino acids on the polypeptides chain

Answer 5

The polypeptide chain doesn’t remain straight and flat —>*hydrogen bonds* form between aas in chain This makes it automatically coil into an α helix or fold into a β pleated sheet

Answer 6

The coiled/folded aa chain is often coiled/folded further. More bonds form between diff parts of the polypeptide chain —> including H bonds OR —> Ionic bonds - Attractions between + and - charges on different parts of molecule Disulfide bridges also form whenever two molecules Of the amino acid *cysteine* come close together - the Sulfur atom in one cysteine bonds to the Sulfur in the other .. for proteins made from a single polypeptide chain the tertiary structure forms their final 3D structure

Answer 7

Some proteins are made of several different polypeptide chains held together by bonds. The quaternary structure is the way these polypeptide chains assemble together. For proteins made from multiple polypeptide chains (Haemoglobin, insulin, collagen) The quaternary structure is the proteins final 3D structure

Answer 8

Shake the sample with ethanol so it dissolves Then pour solution into water Any lipid will show as a milky emulsion (more lipid, the more noticeable milky colour is)

Answer 9

Make solution alkaline so add a few drops of NaOH Will turn purple if proteins present Or will stay blue if not

Answer 10

• enzymes Roughly spherical due to light folding of polypeptide Are soluble and often have roles in metabolism - eg. Some break down large food molecules and others help synthesise large molecules • antibodies Involved in immune response Made up of two light/short polypeptide chains And two long/heavy chains bonded together - antibodies have variable regions - aa sequences in these regions vary lots • transport proteins - channel proteins (cell membranes) have both hydrophobic and phillic aas - causing protein to fold up forming a channel (transport molecules/ions across membranes) . • structural proteins - physically strong consisting of long chains - lying parallel to each other with cross links between —> these include keratin (hair/nails) and collagen (in connective tissue)

Answer 11

- make different known sugar concentrations - use colorimeter to measure absorbance of each conc - plot calibration curve on graph - find conc of sample from using curve

Answer 12

They catalyse metabolic reactions at a cellular level (respiration) And and for whole organism like digestion - enzymes can affect structures (eg. Collagen, connective tissues,) - and function (like respiration) - can be intracellular (in cells) or extra cellular - enzymes are globular proteins - and have an active site with specific shape (part of shape substrate binds to) Enzymes are highly specific due to tertiary struc

Answer 13

In chemical reactions, a specific amount of energy need to be supplied to chemicals Before the reaction can start —> this is activation energy (often as heat) - Enzymes lower amount of activation energy needed - Making reactions start with a lower temperature needed (speeds up rate of reaction) an *enzyme-substrate complex* is formed (always marking point) When a substrate fits into the active site — WHY do enzymes lower it - if two substrates need to join, being attached to the enzyme - hold them closer together , reducing any repulsion between so can bond easier - if enzymes catalyses a breakdown reaction, fitting into active site buts strain on substrate bonds - so substrate can break up with less energy **diagram no.6 for act energy graph**

Answer 14

It’s the fact that enzymes only work with substrates that fit in the active site Enzymes are the lock and substrates, the key But new evidence shows enzyme substrate complex changes shape slightly to complete fit Locking substrate even more tightly to enzyme (induced fit model)

Answer 15

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 in the right way too Substrates are never complimentary at the start

Answer 16

Enzymes are very specific, usually catalysing one reaction Eg. Maltaise = maltose, sucrase = sucrose - because only one complimentary substrate will fit into active site The active site’s shape is determined by enzyme’s tertiary structure (wch is determined by primary) - each diff enzymes has a unique tertiary so diff active site - if substrate doesn’t match, enzyme substrate complex won’t form and no catalysing - If tertiary is altered at all, active site will change, so substrate cant fit - No enzyme substrate complex and no catalysing (can’t carry function) Can be altered by a mutation in the gene that determines primary, diff enzyme produced

Answer 17

Rate of an enzyme controlled reaction increases When temperature increases - more heat = more KE so molecules are faster - making enzymes more likely to collide with substrates - energy of reaction increases too - meaning more successful collisions likely to result in a reaction If temp ends up too high, reaction stops

Answer 18

- rise in temperature makes the enzyme’s molecules vibrate more - if the temperature goes above a certain level, the optimum, this vibration breaks some of the bonds that hold enzyme shape - the active site changes shape and the enzyme and substance no longer form enzyme substrate complex - atp, is denatured and doesn’t function as catalyst

Answer 19

All enzymes have an optimum pH Most human enzyme optimum are at pH7 neutral - but pepsin eg is at pH 2 - useful as found in stomach Above and below pH optimum , the H+ and OH- ions found in acids and alkalis Can mess up ionic and hydrogen bonds that hold tertiary structure in place —> active site changes shape so enzyme denatures

Answer 20

The more enzymes molecules in a solution The more likely collisions are with substrate To form enzyme substrate complex —> hence increases rate of reaction But if substrate amount is limited It comes to a point where there’s more than enough enzymes So adding more enzymes has no further effect

Answer 21

Higher the substrate concentration the faster reaction —> more substrate molecules increases chance of collisions so more active sites used - Only true up to saturation point. - After that all active sites full Substrate concentration decreases with time during a reaction (unless more added/variables changed) - rate of reaction will decrease over time - makes initial rate of reaction at start the highest

Answer 22

Substances that directly/indirectly interfere with functioning of active site of an enzyme, reducing activity Two types of enzyme inhibitors are - competitive inhibitors (bind to active site) - non-competitive inhibitors (bind to enzyme at position other than active site)

Answer 23

Have a molecular shape similar to substrate —> allowing them to occupy active site —> hence competing with substrate for available active sites It’s the difference between the concentration of inhibitor and substrate concentration that determines the effect on enzyme activity. - substrate concentration increase = inhibitor effect reduces - inhibitor isn’t permanently bound and another molecule takes its place when it leaves - eventually all substrates will occupy an active site, - but greater inhibitor conc , the longer this takes .. Eg. An important respiratory enzyme acts on succincate Another compound (malonate) inhibits enzyme as It has a very similar shape to succinate, easily combining with enzyme And blocking succinate. Also, another eg. Is transpeptidase with penicillin

Answer 24

Attached themselves to the enzyme at a binding site (not active site) The inhibitor then alters active site shape, then substrates can’t occupy anymore —> enzyme can’t function As substrate and inhibitor aren’t competing for the same site An increase in substrate conc doesn’t increase inhibitor effects

Answer 25

—> A series of reactions where each step is catalysed by an enzyme There are hundreds of different metabolic pathways in a cell These are highly structured. The enzymes controlling a pathway Are attached to the membrane of an organelle in a precise sequence. Inside each organelle, optimum conditions for the enzyme may be provided. - to keep a steady conc of a particular chemical in a cell - the same chemical often acts as an enzyme inhibitor at the start of a reaction (READ TEXTBOOK IF DONT UNDERSTAND)

Answer 26

The end product inhibits enzyme A - If the conc of the end product increases above normal - There will be greater inhibition in enzyme A - as a result less end product is produced and it’s conc returns to normal - if conc of end product falls below normal - there will be less to inhibit A - so more end product will be produced and conc will be normal This is end product inhibition (not competitive) And is negative feedback

Answer 27

They’re globular proteins, Which act as biological catalysts By lowering the activation energies of chemical reactions. In all enzyme related questions, mention.. - all above and - enzyme substrate complexes are made - enzymes distort bonds in substrate - the substrate is complimentary to the active site