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Biology > Proteins > Flashcards

Proteins Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

Chain of amino acids

A

Polypeptide

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2
Q

Tertiary structure

A

Twisted around

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3
Q

Different groups in amino acid structure

A

NH2 = amine group
R = R group (side chain)
CO2H = carboxyl group

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4
Q

Charges of groups and how they are held together in the secondary structure

A

-NH and -C=O on the ends of the chain
H = overall positive charge
O = negative charge
Opposite charges attract
2 groups form weak hydrogen bonds

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5
Q

Amino acid structure

A

N - C - C in middle

N attached to 2 hydrogen
C attached to R and H
C attached to H on top and O=H on bottom

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6
Q

How do the weak hydrogen bonds affect the secondary structure of the protein

A

Cause long polypeptide chain to be twisted into an alpha helix coil

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7
Q

Process called in which many amino acid monomers can be joined together

A

Polymerisation

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8
Q

Primary structure

A

—————-

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9
Q

What does the primary structure determine in the protein

A

Ultimate shape and function

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10
Q

Quaternary structure

A

Large number of proteins linked together, lots of twisted chains

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11
Q

How is a peptide bond formed

A

Combining the carboxyl group with an -H from another amino acid is lost
2 amino acids become linked when water is removed
Forming a peptide bond between amino acids

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12
Q

3 bonds in tertiary structure

A

Disulfide bond = strong
Ionic bonds = between carboxyl and amino groups, weak
Hydrogen bonds = weak

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13
Q

Secondary structure

A

VVVVV——-

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14
Q

What is the reaction called with the removal of water

A

Condensation reaction

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15
Q

Test for proteins

A

1) Place sample in test tube and add equal volume of sodium hydroxide solution
2) Add few drops of dilute copper solfate and mix
3) Purple = presence of peptide bonds, so presence of protein
Blue = no presence

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16
Q

What is changed among different amino acids

A

Their side group differs (R group)

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17
Q

Reaction that forms dipeptides and polypeptides

A

Condensation

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18
Q

Difference between dipeptide and polypeptide

A

Dipeptide = 2 amino acids
Polypeptides = many amino acids

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19
Q

What are fibrous proteins for

A

Structural function

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20
Q

What do globular proteins do

A

Metabolic functions

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21
Q

Describe fibrous proteins structure

A

Long chains which run parallele to one another
Linked by cross-bridges forming stable molecules

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22
Q

Describe each of the stages when forming a quaternary protein

A

1) Primary = sequence of amino acids determining protein’s shape and function
2) Secondary = polypeptide chain twisted into alpha helix due to hydrogen bonding because of different charges in amino acid
3) Tertiary = polypeptide helix twisted into compact structure with bonds disulfide, hydrogen, ionic
4) Quaternary = Many different polypeptide chains forming protein molecule

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23
Q

What type of chains can be contained in the quaternary structure of the protein formed

A

both protein and non-protein groups

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24
Q

What is chromatography

A

Technique to separate a mixture into its individual components
Relies on differences in solubility with different attractions to the mobiel and stationary phase

25
Q

Method of paper chromatography with amino acids

A

1) Use paper chromatography to separate amino acids
2) Spot placed on line at bottom of paper
3) Spots of known standard solutions placed on line beside unkown sample spot
4) Chromatography paper suspended in solvent
5) Amino acids separate depending on their charge and size
6) Compare unkown to known and math with chromatograms

26
Q

What are the two shapes that can form due to the secondary structure of a protein

A

Alpha helix
Beta pleated sheet

27
Q

Differencebetween alpha helix and beta pleated sheet

A

Alpha = H2 form every fourth peptide
Beta = protein folds so two parts of the polypeptide are parallel so H2 form between parallel peptide bonds

28
Q

How can hydrogen bonds break

A

High temps and ph changes

29
Q

What structure do the two types of proteins have

A

Fibrous protein = secondary
Globular protein = tertiary

30
Q

What bonds do secondary have

A

Peptide and hydrogen

31
Q

What bonds do primary have

A

Peptide

32
Q

What bonds do tertiary hav

A

Peptide hydrogen disulphide ionic and hydrophobic interactions

33
Q

Describe disfulfide bonds

A

Strong covalent
Form R groups
Disulfide bridges strongest but occur less frequently
Stabilise proteins
Broken by reduction

34
Q

Describe ionic bonds

A

Form between NH3+ and COO- when water removed
Ionic bonds are stronger than hydrogen bonds but not common
Broken by pH changes

35
Q

Describe h ydrogen bonds

A

Form between strong polar R group
Most common but weakest

36
Q

Hydrophobic interactions

A

Non-polar R groups within interior of proteins

37
Q

Name of protein test

A

Biuret test

38
Q

Describe globular proteins

A

Compact, spherical, soluble in H2O

39
Q

Why are globular proteins spherical

A

Non polar hydrophobic R group orientate towards centre of protein and polar hydrophilic R group orientates to outside

40
Q

How are globular proteins fit for their role

A

Orientation = water molecules can surround polar hydrophilic R group
Solubility = can be easily transported around organisms for metabolic reactions
Folding = enzymes and immunoglobins
Conjugated = contain prosthetic group

41
Q

Describe fibrous proteins

A

Long strands of polypeptide chains that have cross linkages due to H2 bonding
Little or no tertiary structure

42
Q

Why are fibrous proteins fit for their role

A

Insoluble = larhe number of hydrophobic R groups
Organised = highly repetitive
Good for structure e.g. collagen

43
Q

Compare globular and fibrous proteins

A

SHape: G is circular, F is long strands

AMino acid sequence: G is irregular and wide range of R groups, F is repetitive with limited range of R groups

Function: G is metabolic/ functional, F is structural

G is haemoglobin, enzymes, immunoglobulin, insulin. F is collagen, keratin, myosin, actin, fibrin

Solubility: G is soluble, F is insoluble

44
Q

What is collagen

A

Most structural protein found in vertebrates

45
Q

What does collegen form

A

Tendons cartilage ligaments bones teeth skin walls of blood vessels cornea on eeye

46
Q

Describe collagens structure

A

-Triple helix = 3 polypeptide chains held together close by H2 bonds
-Glycine = every third amino acid is glycine, contains H atom found inside polypeptide chains to form tight triple helix
-Fibrils = covalent bonds cross link R groups interacting triple helices when they are arranged parallele ot eachother
-Fibres = fibrils arranged together form fibres

47
Q

Collagens function

A

-Flexible structural protein form connective tissue
-H2 bonds in triple helix = very strong, withstand large pulling forces without stretching or breaking
-Staggered ends in fibrils = strength
-Stable = lots of proline and hydroxyproline amino acids so more stable as R groups repel eachother
-Length of collagen = too long to dissolve in water

48
Q

Uses of amino acids

A

Protein synthesis/ Building polypeptides
Respiration

49
Q

How does the secondary structure determines the proteins overall structure

A

H2 bonding between C=O and NH every 4 amino acids along the chain
Protein forms a righ thanded alpha helix
A beta pleated sheet forms by folding the chain back on itself in a zig zag plane
Both extend its 3D shape

50
Q

What is a prosthetic group

A

Non amino acid section of a protein
Covalently bonded to the polypeptide sections

51
Q

Describe haemoglobins structure

A

4 separate polypeptide chains bonded together
Each polypeptide bonded to a haem group which binds to O2

52
Q

Beneits of haemoglobins structure in mammals

A

Function = bind to O2 in lungs and release O2 at respiring tissues
Binding of O2 to one haem increases affinity of haemoglovin for O2
Changing shape of whole protein makes it easier to bind another O2 and harder to unbind
Haemoglobin can deliver O2 readily to tissues that require it most

53
Q

Define “r” group

A

Functional group

54
Q

If an amino acid is non-polar where will it be in a globular protein

A

Centre
Non-polar amino acids are hydrophobic and polar ones at the surface (in contact with water)

55
Q

Why is a sickle cell less soluble

A

Non plar amino acid at surface
Non polar do not interact with water

56
Q

How are dipeptides formed

A

Two amino acids joined by peptide bond
Condensation reaction occurs forming peptide bond
Between amine and carboxylic group of adjacent amino acids

57
Q

How are functional proteins different from a polypeptide

A

Polypeptide chains are primary structures
Functional proteins are formed from more than one polypeptide chains
Functional protein has tertiary or quaternary structure with hydrogen, ionic and disulfide

58
Q

How is a polypeptide formd

A

Condensation between many amino acids

59
Q

Why are cellular enzymes made from proteins

A

Shape relates to function
Structure determines by primary structure
Primary structure folds into tertiary which has a 3D shape
Shape of primary determines by bonds occur between amino acids within primary sequence
Bonds inclue hydrogen, ionic, disulfide
Order of amino acids changed affects bonds between amino acids altering the shape

Biology (57 decks)

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