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adv biology > 1.2 proteins > Flashcards

1.2 proteins Flashcards

1
Q

what is the proteome?

A

the entire set of proteins expressed by a genome

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2
Q

why is the proteome larger than the genome?

A

due to alternative splicing and post-transational modification (more than one protein being produced by a single gene)

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3
Q

what is the name for genes that do not code for a protein?

A

non-coding RNA genes

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4
Q

which genes are included in non-coding RNA genes?

A

those that are needed to transcribe tRNA, rRNA, and other RNA molecules that directly control the expression of other genes

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5
Q

the set of proteins expressed by a given cell
type can vary over time and under different
conditions. what are some factors that affect this?

A

metabolic activity
cellular stress
response to signalling molecules
diseased vs healthy cells

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6
Q

eukaryotes have a relatively small surface area : volume ratio. what does this mean?

A

the plasma membranes of these cells are too small to carry out the vital functions required

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7
Q

what is present in eukaryotic cells to account for the small plasma membrane?

A

a system of internal membranes to increase the total surface area

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8
Q

what are the endoplasmic reticula? (ER)

A

a network of membrane tubules that are continuous with the nuclear membrane

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9
Q

what are the golgi apparatus?

A

a series of flattened membrane discs

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10
Q

what are lysosomes?

A

membrane-bound organelles that contain a variety of hydrolases that digest
proteins, lipids, nucleic acids and
carbohydrates

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11
Q

what is the role of vesicles?

A

transport materials between membrane compartments

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12
Q

where are lipids made before being inserted into the membrane?

A

in the SER

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13
Q

in which type of ribosome are all proteins made?

A

in the cytosolic ribosomes

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14
Q

what happens once cytosolic proteins are synthesised?

A

they remain in the cytosol (liquid part of the cytoplasm)

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15
Q

what is the purpose of the signal sequence carried by transmembrane proteins?

A

to halt translation and direct the ribosome synthesising the protein to dock
with the ER, forming RER

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16
Q

what is a signal sequence?

A

a short stretch of amino
acids at one end of the polypeptide that
determines the eventual location of a protein
in a cell

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17
Q

what happens after docking?

A

translation continues and the protein is inserted into membrane of the ER

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18
Q

what happens once proteins have been synthesised at the ER?

A

they are transported to the Golgi apparatus by vesicles that bud off of the ER

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19
Q

how do molecules move through the Golgi?

A

in vesicles that come from one disc and fuse to another

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20
Q

what happens at the Golgi apparatus?

A

post-translational modification

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21
Q

what is classed as major protein modification?

A

the addition of sugars in steps to form carbohydrates (catalysed by enzymes)

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22
Q

what happens once post-translational modification is completed?

A

vesicles take the modified proteins to the plasma membrane and lysosomes, which bind to the membrane and allow the proteins to be released

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23
Q

how to vesicles move from one structure to another?

A

along microtubules, fusing to other membranes within the cell

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24
Q

what are examples of secreted proteins?

A

peptide hormones and digestive enzymes

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25
Q

what are the steps of the secretory pathway?

A

1) translation in RER, proteins enter lumen
2) proteins move through Golgi and packaged into vesicles
3) vesicles fuse to pm and proteins are released

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26
Q

many proteins are synthesised as inactive precursors. what is required to produce active proteins from them?

A

proteolytic cleavage

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27
Q

what is proteolytic cleavage?

A

another type of post-translational modification

28
Q

what is an example of secreted proteins that require proteolytic cleavage?

A

digestive enzymes

29
Q

what are factors that are different between R groups?

A

size, shape, charge, H bonding capacity, chemical reactivity

30
Q

are peptide bonds strong?

A

oui oui

31
Q

how are amino acids classified?

A

according to their R group

32
Q

what are the 4 amino acid classifications?

A

basic
acidic
polar
hydrophobic

33
Q

what are the characteristics of acidic R groups?

A

donates a H+ ion
negatively charged

34
Q

what are the characteristics of basic R groups?

A

accepts H+ ions
positively charged

35
Q

what are the characteristics of polar R groups?

A

include oxygen and nitrogen in the side chain

36
Q

what are the characteristics of hydrophobic R groups?

A

do not include oxygen and nitrogen in the side chain

37
Q

what is the primary protein structure?

A

the order in which the amino acids and synthesised into a peptide

38
Q

what is the secondary protein structure?

A

where hydrogen bonding in the backbone of the protein forms alpha helices, beta pleated sheets and turns

39
Q

what is tertiary protein structure?

A

refers to the overall folding of the peptide and its final shape, stabilised by many different interactions between the R groups

40
Q

describe hydrogen bonds

A

weak, between hydrogen and electronegative atom (NOF)

41
Q

describe ionic bonds

A

strong, between positive and negative ions

42
Q

describe LDFs

A

very weak

43
Q

describe hydrophobic interactions

A

strong, reversion to avoid water

44
Q

describe disulfide bridge

A

strong, between two R groups containing sulfur

45
Q

what is the purpose of prosthetic groups?

A

to give the protein added function

46
Q

in which type of protein structure are prosthetic groups found?

A

in the tertiary structure

47
Q

what is an example of a prosthetic group?

A

haem group on haemoglobin is essential for oxygen binding

48
Q

describe quaternary structure

A

exists in proteins with several connected polypeptide subunits. it is a description of the spatial arrangement of the subunits

49
Q

how do increasing temperatures affect proteins?

A

it disrupts the interactions that hold the protein in shape, causing the protein to unfold, eventually becoming denatured.

50
Q

how does pH affect proteins?

A

it affects the charges of acidic and basic R groups
as pH strays from its optimum, the normal ionic interactions between charged groups are lost, which changes the conformation of the protein until it becomes denatured

51
Q

what is a ligand?

A

a substance that can bind to a protein

52
Q

what happens when a ligand binds to a protein binding site?

A

conformational change

53
Q

what happens in allosteric enzymes?

A

modulators bind at secondary binding sites which are separate from the active site

54
Q

what occurs during cooperativity?

A

binding of one subunit changes the affinity of the remaining subunits

55
Q

what is an example of cooperativity?

A

the binding and release of oxygen to haemoglobin - binding of one increases affinity for the others

56
Q

what happens when temperature in haemoglobin increases or pH decreases?

A

the affinity is lowered and oxygen binding is reduced

57
Q

what happens in actively respiring tissue?

A

affinity for oxygen decreases, releasing it into the tissue

58
Q

what does the binding of an activator to an active/allosteric site do?

A

increases the affinity of the other active site for binding

59
Q

what happens when a modulator binds to an allosteric site?

A

they change the conformation and alter the affinity of the active site for the substrance

60
Q

how can the addition or removal of phosphates affect proteins?

A

can cause reversible conformational changes in proteins, affecting protein activity

61
Q

what is phosphorylation of proteins a form of?

A

post-translational modification

62
Q

what is kinase?

A

an enzyme that catalyses phosphorylation

63
Q

what is phosphatase?

A

an enzyme that catalyses dephosphorylation

64
Q

are proteins activated or inhibited by phosphorylation?

A

either

65
Q

how does adding a phosphate group alter a protein?

A

it adds negative charges
interrupts original ionic interactions and creates new ones

adv biology (13 decks)

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