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proteins Flashcards

1
Q
A
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2
Q

what are proteins made of?
what’s it called when two amino acids join together ?
heats it called when multiple amino acids join together?

A

Monomers called amino acids
dipeptide
polypeptide-proteins are made up one or more polypeptides

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3
Q

what do all amino acids contain

A

carbon, oxygen,hydrogen and nitrogen and some have sulphur

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4
Q

what two groups are the same for every amino acid

A

amine and carboxyl

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5
Q

what chemical bond forms dipeptide and polypeptides

A

peptide bonds

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6
Q

what’s released during this reaction an what’s it called

A

water-condensation

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7
Q

where does the reaction take place

A

ribosomes-site of protein synthesis

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8
Q

what enzyme carries out the hydrolysis of this reaction

A

protease- adds water back to reaction breaking peptide bond

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9
Q

difference between polypeptide and protein?

A

to be a protein a polypeptide has to fold into a complex 3d shape correctly.
it carries out its functions as an enzyme or hormone and at this point we call it a protein molecule.

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10
Q

many proteins contain diff polypeptides what does this then form?

A

Large complex molecule.

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11
Q

what’s the primary structure for a protein

A

this is the sequence of amino acids in the polypeptide.diff proteins have a diff sequence of AA in their primary structure. A change in one amino acid may change the whole structure of protein.The amino acids are held together by peptide bonds.

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12
Q

If one amino acid affects the sequence and change the shape of the protein what would happen

A

it would prevent the protein from carrying out its function effectively

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13
Q

What happens in the secondary structures

A

Hydrogen bonds form between -NH and -CO groups of amino acids in chain. This makes it coil into a alpha helix or beta pleated sheet.

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14
Q

why do hydrogen bonds form

A

the oxygen atoms in the CO groups have a small negative charge and the Hydrogen atoms in the NH group have a small positive charge.These charges attract and hydrogen bonds form along polypeptide chains

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15
Q

what happens in the tertiary structure?

A

the coiled or folded chain of amino acids folded further and more bonds form along chain.

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16
Q

describe the bonds that form along the chain in the tertiary structure

A

ionic-attraction between negatively charged R groups and positively charged R groups.
disulphide- when two molecules of AA cystein come close tg the sulfur atom in one cysteine bonds to the other sulfur in other cysteine forming a disulphide bond.
hydrophilic and hydrophobic-when hydrophobic R groups are close together in protein they clump tg. So hydrophilic R groups pushed to outside which affects how protein folds to its final structure.
Hydrogen bonds-formed between slightly + charged r groups and slightly -charged r groups

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17
Q

what proteins have the tertiary structure a their last structure

A

ones made form a single polypeptide chain

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18
Q

what happens in quaternary

A

this is for proteins made from several diff polypeptide chains and the QS is how these chains are assembled. The QS Is determined by tertiary structure of the individual polypeptide chains being bonded tg. SO its influenced by all the bonds

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19
Q

Describe globular proteins

A

Round and compact.They are soluble and so easily transported in fluids

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20
Q

How are globular proteins soluble

A

The hydrophilic R groups on the amino acids are pushed to the outside of molecule and this is caused by hydrophobic and hydrophilic interactions in tertiary structure.

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21
Q

Name examples of three globular proteins

A

Hämoglobin
Insulin
Amylase

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22
Q

Describe Hämoglobin

A

Carries 02 around body in rbc.
It’s a conjugated protein so it has a protein with a prosthetic group.

Each of the 4 polypeptide( 2 alpha and 2 beta) chains in Hämoglobin has a prosthetic group called haem.

Haem group contains iron which oxygen binds to and bindings easier due to tertiary structure changing.

Water soluble so dissolved in plasma

23
Q

Describe insulin

A

Hormone secreted by pancreas. Helps to regulate blood glucose level. It’s soluble so it can be transported in blood to tissues where it acts. An insulin molecule consists of 2 polypeptide chains which are held together by disulphide bonds. Where they’re in pancreas 6 of these molecules bind to form a large globular structure.

24
Q

Describe amylase

A

Enzyme which catalyses breakdown of starch in digestive system. It’s made of a single chain of amino acids. Secondary structure contains alpha helix and beta pleated sheet sections.

25
Q

What’s a prosthetic group

A

Non protein part

26
Q

Describe fibrous proteins

A

Tough and rope shaped so can form long chains. They are also insoluble and strong. They’re structural and fairly unreactive

27
Q

Give three fibrous proteins

A

Collagen
Keratin
Elastin

28
Q

Describe collagen

A

Found in animal connective tissues like bone skin and muscle.
It’s very strong
Minerals can bind to protein to inc rigidity

29
Q

Describe keratin

A

Found in many external structures of animas like skin hair nails feathers and horns. Either flexible or tough

30
Q

Describe elastin

A

Found in elastic connective tissues such as skin, large blood vessels and some ligaments. It’s elastic so it allows tissues to return to Og shape after they’ve been stretched.

31
Q

How does Hämoglobin structure make it easier for oxygen to attach

A

When oxygen attaches the quaternary structure of proteins slightly chabges
Making it easier for oxygen to attach

32
Q

Amylase is an enzyme explaij how criticism the specificity of its shape is

A

Amylase is made of a single polypeptide chain and this chain folds to form a groove along surface which is active site.
Shape of active site means it fits perfectly to the substrate molecule
As the active site is perfectly shaped to fit substrate it makes amylase extremely soecific

33
Q

Describe and explain shape of collagen

A

Polypeptide chains wrap together to form a TRIPLE HELIX.
In the polypeptides every third AA is glycine and R group is H so glycine has smallest R group
So this allows collagen polypeptides to wrap tightly around each lther
As they wrap tightly around each other hydrogen bonds form between polypeptide chains

34
Q

What do the hydrogen bonds in collagen do

A

Help stabilise quaternary Structure of the protein

35
Q

How else is collagen so strong aside from its triple helix shape

A

Polypeptide chains held together by string crosslinks and there’s cross linking between diff helical molecules.
Collagen molecules are staggered to prevent weak spots

36
Q

How is keratin strong

A

Has a high number of AA cysteine which is shed to form disulfide bonds(string covalent bonds).

37
Q

How does it allow tissues to return to Og shape after stretcg

A

The hydrophobic regions would usually allow elastin strands to associate but when they’re stretched the strands move apart but remain attached at crosslinks.
After stretching the elastin molecules spring back tg

38
Q

What are lipids and name three types

A

Macromolecules containing carbon hydrogen and oxygen.
Triglycerides,phospholipids and cholesterol.

39
Q

Describe a tryglecride

A

They have one molecule of glycerol with three fatty acids attached to it. It’s synthesised by the formation of an ester bond between each fatty acid and glycerol molecule.

40
Q

Describe synthesis and breakdown of triglycerides

A

One triglyceride had three ester bonds. Each ester bond is formed by a condensation reaction (in which a water molecule is released). The process in which triglycerides are synthesised is esterification. Triglycerides break down when ester bonds are broken. Each ester bonds broken in a hydrolysis reaction ( in which a. Water molecule is used up)

41
Q

Describe breakage of ester bonds between fatty acids

A

Fatty acids have long tails made of hydrocarbons. The tails are hydrophobic. These tails make lipids insoluble in water. All fatty acids have the same basic structures but hydrocarbon tail varies

42
Q

Describe breakage of ester bonds between fatty acids

A

Fatty acids have long tails made of hydrocarbons. The tails are hydrophobic. These tails make lipids insoluble in water. All fatty acids have the same basic structures but hydrocarbon tail varies

43
Q

What are the two diff types of fatty acids and contrast

A

Saturated- don’t have double bonds between carbon atoms in hydrocarbon tails.it’s saturated with hydrogen. Straught chain molecules have many contact points.Higher mp solid at rtp.found in animals fats

Unsaturated- one double bond between carbon atoms which causes the chain the kink. Kinked molecules have fewer contact points.lower mp-liquid at room temp.Found in plant oils

44
Q

What are phospholipids

A

It has one phosphate group with glycerol and two fatty acids. The phosphate group is hydrophilic and fatty acids tails are hydrophobic

45
Q

What is cholesterol

A

Another type of lipid with a hydrocarbon ring structure attached to a hydrocarbon tail.The ring structure has a polar hydroxyl group attached to it.

46
Q

What’s the function of triglycerides

A

Energy storage molecule in animals and plants. Some bacteria used triglycerides to store both energy and carbon. Triglycerides are good for storage because long hydrocarbon tails of fatty acids contain lots of chemical energy which releases lots of energy when broken down.
Cuz of these tails lipids contain twice as much energy per gram as carbs.
Triglycerides are also insoluble so they don’t cause water to enter the cell by osmosis which makes it swell.
Triglycerides bundle tg as insoluble droplets in cells cuz fatty acid tails are hydrophobic - tails face inwards facing the selves from water w their glycerol heads.

47
Q

What’s the function of phospholipids

A

Forms phospholipid bilayer- component of membranes
Tails are hydrophobic so they splay outwards so it’s waterproofing eg skin
As the centre(tails) are HydroP water soluble substances can’t easily pass through it and membranes acts a barrier to those substances

48
Q

Are phospholipids and tryglycerides polymers

A

No they’re made from a small repeating unit so they’re macromolecules

49
Q

Function of cholesterol

A

Helps strengthen the cell membrane by interacting with phospholipid bilayer.
Cuz of its small and flattened shape it allows cholesterol to fit between phospholipid molecules in membrane making them more packed tg. This helps it more rigid and less fluid.

50
Q

Relate structure of tryglecrides to its function

A

High energy:mass ratio=high calorific value from energy storage
Insoluble hydrocarbon chain=no effect on osmotic water potential and used for waterproofing
Slow conductor of heat-thermal insulation
Less dense than water- buoyancy of aquatic animals

51
Q

How to test for proteins

A

Biuret test

Add equal volume of sodium hydroxide to make solution alkaline
Add drops of dilute copper(||) Sulfate and swirl to mix
Positive-blue to purple
Negative-purple to purple

52
Q

How to test for starch

A

Iodine text
Add iodine dissolved in potassium iodide to sample
Positive-brown orange to blue black
Negative-stays brown orange

53
Q

How to test for lipids

A

Emulsion test
Dissolve samples with ethanol
Add an equal volume of water and shake
Positive- cloudy white emulsion
Negative - colourless

54
Q

Test for sugars

A

Benedict’s

Reducing sugars-
Add benefits reagent and heat in a water bath that’s been brought to boil
Positive -it will form a coloured precipitate
negative -stays blue
Non reducing sugars-get new sample of solution
Add dilute hcl Then neutralise it with sodium hydrogencarbonate. and carefully heat in a water bath that’s been brought to boil.
Then do bennets test again
Positive-coloured precipitate
Negative-starts blue

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