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Biology Mrs Garland > Proteins > Flashcards

Proteins Flashcards

1
Q

what are proteins made of

A

Long chains of amino acids

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2
Q

what are amino acids

A

monomers from which proteins are made.

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3
Q

what is a dipeptide

A

who two amino acids join together

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4
Q

what is a polypeptide

A

when two or more amino acids join together.

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5
Q

What is the general structure for amino acids

A

NH2- amine group, COOH- carboxyl group and R- variable side chain

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6
Q

how do the 20 amino acids differ

A

differ only in their side group

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7
Q

how are amino acids linked together

A

by condensation reaction to form polypeptides. A molecule of water is released during the reaction .

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8
Q

What are

A
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9
Q

the bonds that are formed between the amino acids called

A

peptide bonds

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10
Q

what kind of reaction is it when the peptide bond is broken in a dipeptide.

A

hydrolysis

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11
Q

what are the four structural levels of proteins

A

Primary, secondary, tertiary, quaternary.

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12
Q

what is the primary structure of proteins

A

sequence of amino acids in the polypeptide chain

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13
Q

what is the secondary structure of proteins

A

the polypeptide chain doesn’t remain flat and straight.
-Hrogen bonds form between the amino acids in the chain.- making it automatically coil into an alpha helix or fold into a beta pleated sheet- this is the secondary structure.

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14
Q

what is the tertiary structure of proteins

A

coiled and folded further. more bonds form, including hydrogen bonds and ionic bonds(attractions between negative and positive charges on different parts of the molecule)

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15
Q

what is the quaternary structure of proteins

A

made of several different polypeptide chains held together by bonds. examples include haemoglobin, insulin and collagen, 3D shape

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16
Q

what is the structure and function of enzymes

A

usually roughly spherical in shape due to the tight folding of the polypeptide chains. They are soluble and often have roles in metabolism.g breaking down large food molecules- digestive enzymes. or help to synthesise large molecules

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17
Q

examples of proteins

A

Enzymes
Antibodies
Transport proteins
structural proteins

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18
Q

what is the structure and function of antibodies

A

ivolved in immune response, made up of two light(short) polypeptide chains and two heavy(long) polypeptide chains bonded together. Antibodies are variable regions- the amino acid sequences in these regions vary greatly

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19
Q

what is the structure and function of transport proteins

A

e.g channel proteins in cell membranes- contain hydrophobic and hydophilic amino acids which cause the protein to fold up and form a channel. These proteins transport molecules and ions accross a membrane

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20
Q

what is the structure and function of structural proteins

A

physically strong. Consist of long polypeptide chains lying parallel to each other with cross-links between them. Examples include keratin (hair and nails) and collagen( found in connective tissue)

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21
Q

what is the test for proteins

A

add sodium hydroxide solution because the test must be alkaline
then add copper sulphate solution, if present turns purple if not stays blue

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22
Q

what are enzymes

A

biological catalysts, they catalyse metabolic reactions at both cellular level and for an organisms as a whole

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23
Q

what is formed when a substate fits into an enzymes active site

A

an enzyme-substate complex

24
Q

how does an enzyme reduce the activation energy needed

A

if the two substrate molecules need to be joined, being attached to an enzyme holds them closer together, reducing any repulsion between the molecules so they can bond more easily.

If the enzyme is catalysing breakdown reaction, fitting into the active site puts a strain on bonds in the substate, so the substate molecule breaks up more easily.

25
Q

how is the induced fit model different to the lock and key

A

enzymes are specific and only bond to one particular substate. The substate has to make the active site change shape in the right way.

26
Q

what are the properties of enzymes

A

very specific- only catalyse one reaction.g maltase only breaks down maltose.- this is because only one complementary substrate will fit into the active site.
The active sites shape is determined by the tertiary structure.
If the tertiary stricture is altered in any way, the shape of the active site will change. If a mutatuion occurs in a gene the primary structure could be affected therefore effecting the tertiary structure.

27
Q

how is the primary structure of a enzyme determined

A

a gene

28
Q

how does temperature influence enzyme activity

A

more heat means more kinetic energy, so the molecules move faster. The enzyme is more likely to collide with the substrate molecules. energy of these collisions also increases, each collision is more likely to result in a reaction.

29
Q

how would too much temperature effect enzyme activity

A

rise in temp- enzyme molecules vibrate more.
if the temperature goes above a certain level, this vibration breaks some of the bonds that hold the enzyme shape. active site changes shape. enzyme and substrate no longer fit together.- enemy is denatured.

30
Q

how does Ph effect enzyme activity

A

All enzymes have an optimum pH value. Most work best at pH7(neutral). Exceptions include pepsin- acidic 2- found in stomach.
above and below optimum pH the H+ and OH- ions found in acidic ad alkalis can mess up the ionic bonds and hydrogen bonds that hold the enzymes tertiary structure in place. Making the active site change shape- denature.

31
Q

How does Enzyme concentration affect the Rate of reaction

A

The more enzyme molecules tare are in a solution, the more likely the substrate molecule is to collide with one and form n enzyme-substrate complex. increasing the concentratetion of the enzyme increases the rate of reaction.

If the amount of substrate is limited . comes to a point where there’s more than enough enzyme molecules to deal with all available substrate, so adding more enzyme has no effect

32
Q

why does the substrate concentration effect the rate of reaction up to a point

A

higher substrate conc- faster reaction; collisions between the substrate and enzyme more likely. only true up to a ‘saturation’ point. Active sites are full, adding makes no difference.

Substrate conc decreases with time, if no other variables trade of reaction will decrease over time. makes initial rate of reaction the highest.

33
Q

what are enzyme inhibitors

A

molecules that bind to the enzyme that they inhibit. can be competitive or non competitive.

34
Q

how do competitive inhibitors affect enzyme activity

A

have a similar shape to the substrate, compete with the substrate molecules to bind to the active site, but no reaction takes place, instead blocking the active site , so no substate molecule can fit in.
How much the enzyme is inhibited depends on the relative concentrations of the inhibitor and the substrate

35
Q

how do non-competitive inhibitors effect the rate of reaction

A

bind to the enzyme away from its active site, causes active site to change shape so the substrate molecules can no longer bind to it.

increasing conc of substarate won’t make any difference to the reaction rate.

36
Q

What is DNA

A

deoxyribonucleic acid is used to store genetic genetic info- all the instructions an organisms needs to grow and develop

37
Q

what is RNA

A

ribonucleic acid- similar to the structure of DNA , main function is to transfer genetic information from the DSNA to the ribosomes. Ribosomes read the RNA to make polypeptides (proteins) in a process called translation.

38
Q

what is a nucleotide made from

A

A pentose sugar (sugar containing 5 carbon atoms)
a nitrogen- containing organic base
a phosphate group

39
Q

what is the pentose sugar in a DNA nucleotide called

A

deoxyribose
each nucleotide has the same sugar and a phosphate group. the base on each nucleotide varies

40
Q

what are the four possible bases for a DNA nucleotide

A

Adenine, Thymine, cytosine and guanine

41
Q

what is the name of the sugar in a RNA

A

ribose sugar

42
Q

what are the four different bases n RNA

A

Adenine, Uracil ,cytosine and guanine

43
Q

what is the name of a polymer of nucleotides

A

polynucleotide

44
Q

what reaction forms polynucleotides

A

condensation between the phosphate group of one nucleotide and the sugar of another forming an ester bond

45
Q

what is the chain of sugar and phosphates known as

A

sugar-phosphate backbone

46
Q

what is it called when each base can only join with one particular partner

A

complementary base pairing

47
Q

what are the different complementary base pairings

A

adenine and thymine (A-T) and Cytosine and Guanine (C-G). Meaning there is always equal amounts of Adenine and thymine and Cytosine and Guanine

48
Q

what bonds form between A and T

A

two hydrogen bonds

49
Q

what bonds form between C and G

A

three hydrogen bonds.

50
Q

what word desbrides the way the two strands on polynucleotide strands twist to. form a double Helix

A

Antiparallel

51
Q

who discovered the double helix structure

A

Waste and Crick

52
Q

what enzyme splits the two strands in a semi conservative replication

A

DNA helicase- breaks the hydrogen bonds making the helix unwind

53
Q

what happens in stage 2 of DNA replication

A

original strand acts as a template, in leading strand enzyme primer produces a primer- short piece of DNA- this acts as the start point for dNA synthesis. Then DNA polymerase binds to the leading strand and walks along it adding complementary base pairings in 5’ to 3’ direction

54
Q

what are the two strands called

A

leading is top lagging is bottom

55
Q

what happens in stage 3 of DNA replication Numerous primers are made on lagging strand due to the direction being 3’ to 5’

A

DNA polymerase then adds a series of complementary bases in 5’ to 3’ direction using the different primers as a starting point, then the enzyme exonuclease removes all the primers, then another DNA polymerase fills in all the gaps left behind with DNA. Enzyme ligase then seals up the DNA in both strands.

56
Q

who validated semi conservative replication

A

Meselson and Stahl

DNA contains heavy nitrogen and light nitrogen

57
Q

how did meselson and Stahls experiment work

A

two samples of bacteria- one in a nutrient broth containing light nitrogen and one in a broth containing heavy nitrogen

Biology Mrs Garland (4 decks)

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