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proteins Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

describe the formation of a peptide bond

A

condensation reaction

between amine group on one AA

and carboxylic acid group of another AA

forming a water molecule

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2
Q

describe how hydrogen bonds form within secondary structure of proteins

A

oxygen is relatively negative and hydrogen is relatively positive

oxygen and hydrogen are attracted to each other

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3
Q

alpha keratin is composed of alpha helices

explain why alpha keratin has a more regular structure than the quaternary protein haemoglobin

A

secondary structures are simple repeating structures

globular protein haemoglobin has a tertiary structure formed from complex folding of a secondary structure

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4
Q

compare and contrast the role of R-Group interactions in the formation of tertiary and quaternary structures of proteins

A

R-groups on AA interact

tertiary – interact within the protein molecule determines its shape

quaternary – interact between protein molecules holds molecules together

both involve the same interactions

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5
Q

what’s a peptide bond

A

formed between amino acids

covalent

carboxylic group of one AA interacts with amine group of another AA in a condensation reaction

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6
Q

what’s a protein

A

polypeptides (and macromolecules) made up of amino acids (monomers)

sequence, type and number of amino acids determines the protein’s shape (and its function)

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7
Q

what determines a different amino acid?

A

the R-group

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8
Q

how many different AA are commonly found in cells?

how many of these are essential?

A

20

9 and can only be obtained from what we eat

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9
Q

how is protein synthesised?

A

peptide bond between amino acids

condensation reaction:
amine group interacts with carboxylic group of another AA

forming a dipeptide/polypeptide

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10
Q

what is the production of polypeptides catalysed by?

A

enzyme peptidyl transferase (present in ribosomes)

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11
Q

describe the formation of a primary structure of a protein

A

sequence of amino acids bonded by covalent peptide bonds

DNA of a cell determines the primary structure of a protein by instructing the cell to add certain amino acids in specific quantities in a certain sequence

this affects the shape and function of the protein

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12
Q

describe the formation of a secondary structure of a protein

A

occurs when (weak) negatively charged nitrogen and oxygen atoms

interact with the weak positively charged hydrogen atoms

forming hydrogen bonds between polypeptide chains

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13
Q

describe the formation of alpha helic

A

hydrogen bonds form within AA chain

pulling the chain into a coiled shape

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14
Q

describe the formation of a beta pleated sheet

A

formed by parallel polypeptide chains that form hydrogen bonds

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15
Q

describe tertiary structure of a protein

A

folding of a protein into its final shape

coiling/folding of sections into a protein’s secondary structure brings r-groups of different AAs closer together to interact

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16
Q

what interactions are seen in tertiary structure

A

weak hydrophilic/hydrophobic interactions
between polar and non-polar r-groups

hydrogen bonds (weakest)

ionic bonds
formed between oppositely charged r-groups

disulfide bonds
covalently forms between AAs that contain sulfur

17
Q

describe a quaternary structure

A

results from association of more than 1 polypeptide chain (subunit) working as a functional macromolecule

protein subunits can be identical or different

18
Q

what’s the difference between hydrophobic and hydrophilic proteins?

A

proteins are assembled in the aqueous environment of the cytoplasm

so the way a protein folds depends on whether the r-groups are hydrophilic or hydrophobic

philic groups – outside the protein
phobic groups – inside of molecule shielded from water in cytoplasm

19
Q

what enzyme catalyses the break down peptide bonds?

A

protease – catalyses break down of peptides into their constituent AA

20
Q

a conjugated protein is held together by many different types of bond

which bond is not formed when a conjugated protein folds into its quaternary structure?

A

peptide

21
Q

what are the properties of globular proteins?

A

compact

water soluble

usually roughly spherical

22
Q

how are globular proteins formed?

A

found where proteins fold into their tertiary structure

where the hydrophobic r-groups are kept away from aqueous environment

hydrophobic r-groups on the outside of the protein

this is essential for regulating many of the processes necessary to life

23
Q

what’s an example of a globular protein

A

insulin

involved in blood glucose regulation

hormone, therefore has to fit into specific receptors on membrane

water soluble, so it’s able to be transported in the blood

24
Q

what’s a conjugated protein?

A

a globular protein which contains a non-protein, prosthetic group

25
Q

what’s a cofactor?

A

metal ions and molecules derived from vitamins that form prosthetic groups

26
Q

what’s an example of a conjugated protein?

A

haemoglobin

quaternary protein made from 4 polypeptides, consisting of

2 alpha, and 2 beta subunits

each subunit contains a prosthetic haem group

the haem group consists of iron (II) ions which combine reversibly with oxygen

27
Q

describe the formation and function of catalase

A

enzyme

quaternary protein containing 4 haem prosthetic groups

iron (II) ions allows catalase to react with hydrogen peroxide to increase the rate of reaction

(hydrogen peroxide is a common byproduct of metabolism and causes damage to cells when it accumulates)

28
Q

what’s a fibrous protein?

A

formed from long, insoluble molecules

which is due to high proportion of amino acids with hydrophobic r-groups in their primary structure

the amino acid sequence in primary structure is usually repetitive

which makes the structures of fibrous proteins more organised and stronger

29
Q

describe the formation and function of keratin

A

fibrous protein

has large proportion of cysteine
(sulfur-containing amino acid)

many strong disulfide bonds (disulfide bridges)
results in forming strong, inflexible, insoluble materials

30
Q

having a high degree of disulfide bonds leads to what

A

flexibility

31
Q

describe the formation and function of elastin

A

fibrous quaternary protein found in elastic fibres

made from tropoelastin (stretchy molecule)

gives blood vessels the elasticity to expand when needed, or go back to their normal size

32
Q

describe the formation and function of collagen

A

fibrous protein

connective tissue found in skin, tendons, ligaments and nervous system

most are made up of 3 polypeptides wound together in long and strong rope-like structure (gives flexibility)

33
Q

describe the secondary structure of a protein

A

secondary structure of a protein is held together by hydrogen bonds

that form between the amine group of one amino acid and the carboxyl group of another

These hydrogen bonds cause the polypeptide chain to coil

into an alpha helix/beta pleated sheet

34
Q

how are amino acids made in:

plants

and animals

A

made in autotrophic green plants as products of photosynthesis which are assembled into proteins

heterotrophic organisms gain amino acids from plants through food chains

35
Q

describe the difference between simple and conjugated proteins?

A

simple contain amino acids in their structure

conjugated contain amino acids plus a prosthetic group

36
Q

what are the three ways the charges on a protein resulting from the pH effect may influence its behaviour

A

charges on active site affects capability of enzyme to join with its specific substrate

at iso-electric point (IEP) the protein carries equal numbers of opposite charges
which attract, making the protein clump together and ppt.
at other pHs the proteins carry like charges which repel molecules
which increase the solubility

at extreme pHs the protein molecules may carry huge numbers of like charges
which may exert a large repulsive force which breaks apart the hydrogen and ionic bonds holding the 3D structure together
leads to denaturation since structure and functional ability is lost

37
Q

state three properties of a fibrous protein different from a globular protein

A

insoluble

strong

unreactive

biology (14 decks)

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