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AH Biology > Unit 1: KA2 - Proteins > Flashcards

Unit 1: KA2 - Proteins Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

Define the term proteome

A

The proteome is the entire set of proteins expressed by a genome

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2
Q

Why is the proteome larger than the number of genes?

A

because more than one protein can be produced from a single gene as a result of alternative RNA
splicing

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3
Q

What are genes that do not code for proteins called?

A

Non-coding RNA genes

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4
Q

What are non-coding RNA genes transcribed to produce?

A

tRNA
rRNA
RNA molecules that control the expression of other genes.

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5
Q

When can the proteins of a cell type vary?

A
  • Over time
  • metabolic activity
  • Cellular stress
  • response to signal molecules
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6
Q

What is the benefit of intracellular membranes

A

increases total surface area of membrane for cellular functions

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7
Q

Name the 4 internal membranes

A
  • Endoplasmic reticulum
  • Golgi apparatus
  • vesicles
  • Lysosomes
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8
Q

Describe the Endoplasmic reticulum.

A

A network of membrane tubules continuous from the nuclear membrane
Involved in synthesis of proteins and lipids
Smooth ER lacks ribosomes
Rough ER has ribosomes on the cytosolic face

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9
Q

Describe Golgi Apparatus

A

A series of flattened membrane discs

Involved in transport and modifications of proteins

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10
Q

Describe lysosomes

A

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

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11
Q

Describe Vesicles

A
  • Small membrane enclosed compartments

- Transport materials between compartments

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12
Q

Where are lipids synthesised?

A

smooth Endoplasmic reticulum

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13
Q

Where do proteins start synthesis?

A

Rough endoplasmic reticulum

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14
Q

Describe the synthesis of cytosolic proteins.

A

Synthesised fully in the cytosolic ribosome.

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15
Q

Describe the synthesis of Transmembrane proteins

A

Transmembrane proteins carry a signal sequence, which halts translation and directs the ribosome synthesising the protein to dock with the ER, forming RER.
Translation continues after docking and the protein is inserted into the membrane of the ER.

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16
Q

What is a signal sequence?

A

A signal sequence is 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

Where do proteins go once they have entered the ER

A

Once the proteins are in the ER, they are transported by vesicles that bud off from the ER and fuse with the Golgi apparatus.

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18
Q

What happens to proteins in the Golgi apparatus?

A

They undergo post-translational modifications

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19
Q

What is a major modification made to proteins?

A

Addition of carbohydrate groups.

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20
Q

How do proteins travel through the Golgi apparatus?

A

In vesicles that bud off from one disc and fuse to the next one in the stack.

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21
Q

Where do vesicles take proteins after the Golgi apparatus?

A
  • They fuse with the plasma membrane and release the protein.
    Lysosomes
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22
Q

How do vesicles travel?

A

The move along microtubules to other membranes and fuse with them within the cell.

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23
Q

Describe secreted proteins’ pathway.

A
  • Translated in ribosome on RER
  • enter the Endoplasmic reticulum’s lumen
  • They move through the golgi apparatus in vesicles and packaged in secretory vesicles
  • They then move to the plasma membrane and fuse with it, releasing the protein
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24
Q

What are many secretory proteins synthesised as and why?

A

inactive precursors, so they do not become active in an inappropriate place and cause damage.

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25
Q

Describe proteolytic cleavage and its use.

A

The process of breaking peptide bonds between amino acids in protein.
Turns inactive precursors into active proteins

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26
Q

What is an example of a secretory protein that must undergo proteolytic cleavage?

A

digestive enzyme.

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27
Q

What determines a protein’s structutre?

A

amino acid sequence

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28
Q

What are proteins?

A

polymers of amino acid monomers.

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29
Q

What is the only difference between amino acids?

A

The R group.

30
Q

How are amino acids linked?

A

peptide bonds

31
Q

What is resultant from the diversity of R groups?

A

The wide range of functions carried out by proteins

32
Q

What are the 4 amino acid classes?

A
  • acidic
  • Polar
  • hydrophobic
  • Basic
33
Q

Describe an Acidic amino acid

A

Key component of R group: COOH
Negatively charged
Hydrophilic

34
Q

Describe a basic Amino acid.

A

Key component of R group: NH2
positively charged
hydrophilic

35
Q

Describe a Polar amino acid.

A

Key component of R group: OH

Hydrophilic

36
Q

Describe a Hydrophobic amino acid.

A

Key component of R group: Hydrocarbon

Hydrophobic (duh)

37
Q

What is the primary structure?

A

The primary structure is the sequence in which the amino acids are synthesised into the polypeptide.

38
Q

What causes secondary structure?

A

Hydrogen bonds along the backbone of the protein strands.

39
Q

Name the 3 secondary structures.

A
  • α-helix
  • β-sheet
  • Turn
40
Q

Describe an α-helix.

A

Hydrogen bonds between oxygen and hydrogen form the helix

41
Q

Describe a β-sheet.

A

Polypeptide chains are linked together in a side by side formation with hydrogen bonds.
They can be: Antiparallel, Parallel or mixed.

42
Q

Describe a Turn.

A

Reverses the direction of the polypeptide chain.

43
Q

What is a tertiary structure?

A

The polypeptide chain folds.

44
Q

In what 5 ways can a tertiary structure be stabilised?

A
  • Hydrophobic interactions
  • Ionic bonding
  • Hydrogen bonds
  • London dispersion forces
  • disulphide bridges.
45
Q

Describe quaternary structure.

A

Quaternary structure exists in proteins with two or more connected polypeptide subunits.
It refers to the spatial arrangement of the subunits.

46
Q

what is a prosthetic group?

A

A non-protein unit tightly bound to a protein and are necessary for its function.

47
Q

What are the two factors that can influence the interactions of R groups?

A
  • Temperature

- pH

48
Q

How does temperature influence protein structure?

A

Increasing temperature disrupts the interactions that hold the protein in its tertiary shape, causing the protein to unfold..

49
Q

How does pH influence protein structure?

A

As pH increases or decreases from the optimum, the normal ionic interactions between the charged particles are lost, changing the conformation.

50
Q

What is a Ligand?

A

A ligand is a substance that can bind to a protein

51
Q

Where do ligands bind to proteins?

A

Free R-groups with complimentary shapes and chemistry.

52
Q

What effect does a ligand have on a protein

A

it causes a conformational change.

53
Q

What is an allosteric protein?

A

A protein with a second site known as an allosteric site.

54
Q

What structure do allosteric proteins have?

A

quaternary.

55
Q

Describe allosteric interactions.

A

a ligand binds to an allosteric site of an enzyme and alters its affinity for the substrate.

56
Q

What are the ligands that bind to allosteric enzymes and what do they do?

A

Positive and Negative modulators.

They regulate the enzyme’s affinity for the substrate by altering the active site.

57
Q

Describe cooperativity.

A

many allosteric proteins with multiple subunits (quaternary structure) show cooperativity in binding. Binding at one unit increases the other binding sites’ affinities.

58
Q

give an example of cooperativity

A

In haemoglobin, changes in binding of oxygen at one subunit alter the affinity of the remaining subunits for oxygen.

59
Q

What two factors affect binding to oxygen?

A

Temperature

pH

60
Q

How do temperature changes affect binding to oxygen?

A

Increase- affinity decrease

decrease- affinity increase

61
Q

What do allosteric reactions occur between?

A

spatially distinct sites.

62
Q

How do pH changes affect binding to oxygen?

A

increase- affinity increase

decrease- affinity decrease

63
Q

Describe how actively respiring tissue creates the perfect conditions for oxygen delivery to cells.

A
  • It produces heat, allowing the release of oxygen from haemoglobin.
  • It produces CO2, which reacts with with water, forming carbonic acid, decreasing the pH, allowing the release of oxygen from haemoglobin.
64
Q

What does the addition or removal of phosphate cause in proteins?

A

A reversible change

65
Q

What is the addition of phosphate a common form of?

A

post-translation modification

66
Q

What is Kinase’s function?

A

It catalyses phosphorylation of proteins

67
Q

What is phosphatase’s function?

A

It catalyses dephosphorylation of proteins

68
Q

What does phosphorylation do to a protein

A

it causes a conformational change, altering the proteins activity. Either activating or deactivating it.

69
Q

What happens in phosphorylation?

A

The terminal phosphate of ATP is transferred to a specific R group.

70
Q

What does phosphorylation/dephosphorylation regulate?

A

The activity of many cellular proteins, such as enzymes and reporters.

71
Q

Why is it important for the system to be able to return the target protein to its inactive state?

A

so the sensitivity of the target protein is restored and the target protein is able to respond again.

AH Biology (13 decks)

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