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biology - 1.2 Flashcards

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AP® Biology flashcards Biology 101 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 number of genes, particularly in eukaryotes?

A

More than one protein can be produced form 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 do non-coding RNA genes include?

A

Those that are transcribed to produce tRNA, rRNA and RNA molecules that control the expression of other genes.

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5
Q

What are some factors which affect the set of proteins expressed by a given cell type?

A

The metabolic activity of the cell, cellular stress, the response to signalling molecules, and diseased versus healthy cells.

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6
Q

What do eukaryotic cells have which increases the total area of membrane?

A

A system of internal membranes.

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7
Q

Because of their size, what do eukaryotes have?

A

A relatively small surface area to volume ratio. Their plasma membrane is therefore too small an area to carry out all the vital functions carried out by membranes.

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8
Q

What does the endoplasmic reticulum (ER) form?

A

A network of membrane tubules continuous with the nuclear membrane.

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9
Q

What is the Golgi apparatus?

A

A series of flattened membrane discs.

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10
Q

What are lysosomes?

A

Membrane-bound organelles containing a variety of hydrolases that digest proteins, lipids, nucleic acids and carbohydrates.

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11
Q

What do vesicles do?

A

They transport materials between membrane compartments.

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12
Q

Where are lipids and proteins synthesised?

A

In the ER

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13
Q

What is the difference between RER and SER?

A

Rough ER has ribosomes on its cytosolic surface while smooth ER lacks ribosomes.

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14
Q

Where is lipids synthesised and where do they go?

A

In the SER and inserted into its membrane.

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15
Q

Where does the synthesis of all proteins begin?

A

In cytosolic ribosomes.

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16
Q

What is completed in cytosolic ribosomes?

A

The synthesis of cytosolic proteins and these proteins remain in the cytosol.

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17
Q

What do transmembrane proteins do?

A

They carry a signal sequence, which halts translation and directs the ribosome synthesising the protein to dock with the ER, forming the RER.

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18
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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19
Q

What does translation do after docking?

A

It continues and the protein is inserted into the membrane of the ER.

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20
Q

Once the proteins are in the ER, what happens to them?

A

They are transported by vesicles that bud off from the ER and fuse with the Golgi apparatus.

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21
Q

What happens as proteins move through the Golgi apparatus?

A

They undergo post-translational modification.

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22
Q

How do molecules move through the Golgi discs?

A

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

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23
Q

What do enzymes do in the Golgi apparatus?

A

They catalyse the addition of various sugars in multiple steps to form carbohydrates.

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24
Q

What is the major modification?

A

The addition of carbohydrate groups.

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25
Q

What do vesicles that leave the Golgi apparatus do?

A

They take proteins to the plasma membrane and lysosomes.

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26
Q

What do vesicles move along?

A

Microtubules to other membranes and fuse with them within the cell.

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27
Q

Where are secreted proteins translated and what do they do?

A

In ribosomes on the RER and enter its lumen.

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28
Q

What are examples of secreted proteins?

A

Peptide hormones and secreted enzymes.

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29
Q

What happens to secreted proteins once they enter the lumen of the RER?

A

They move through the Golgi apparatus and are then packaged into secretory vesicles.

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30
Q

What do secretory vesicles do?

A

They move to and fuse with the plasma membrane, releasing the proteins out of the cell.

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31
Q

What are many secreted proteins synthesised as?

A

Inactive precursors and require proteolytic cleavage to produce active proteins.

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32
Q

What is proteolytic cleavage?

A

Another form of post-translational modification.

33
Q

What are one example of secreted proteins that require proteolytic cleavage to become active?

A

Digestive enzymes.

34
Q

What determines protein structure?

A

Amino acid sequence.

35
Q

What are proteins?

A

Polymers of amino acid monomers.

36
Q

How are amino acids linked?

A

By peptide bonds to form polypeptides.

37
Q

What structure do amino acids have?

A

The same basic structure, differing only in the R group present.

38
Q

How do R groups of amino acids vary?

A

In size, shape, charge, hydrogen bonding capacity and chemical reactivity.

39
Q

How are amino acids classified?

A

According to their R groups: basic (positively charged); acidic (negatively charged); polar; hydrophobic

40
Q

What does the wide range of functions carried out by proteins result from?

A

The diversity of R groups.

41
Q

What is the primary structure?

A

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

42
Q

What results in regions of secondary structure?

A

Hydrogen bonding along the backbone of the protein strand - alpha helices, parallel or anti-parallel beta-pleated sheets, or turns.

43
Q

What does the polypeptide fold into?

A

A tertiary structure.

44
Q

What is the tertiary conformation stabilised by?

A

Interactions between R groups; hydrophobic interactions; ionic bonds; London dispersion forces; hydrogen bonds; disulfide bridges

45
Q

What are disulfide bridges?

A

Covalent bonds between R groups containing sulfur.

46
Q

Where does quaternary structure exist?

A

In proteins with two or more connected polypeptide subunits.

47
Q

What does quaternary structure describe?

A

The spatial arrangement of the subunits.

48
Q

What is a prosthetic group?

A

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

49
Q

What is the ability of haemoglobin to bind oxygen dependent upon?

A

The non-protein haem group.

50
Q

What can interactions of the R groups be influenced by?

A

Temperature and pH.

51
Q

What does increasing temperature do?

A

It disrupts the interactions that hold the protein in shape; the protein begins to unfold, eventually becoming denatured.

52
Q

What are the charges on acidic and basic R groups affected by?

A

pH

53
Q

As pH increases or decreases from the optimum, what happens?

A

The normal ionic interactions
between charged groups are lost, which gradually changes the conformation of the
protein until it becomes denatured.

54
Q

What is a ligand?

A

A substance which can bind to a protein.

55
Q

What can allow binding to ligands?

A

R groups not involved in protein folding.

56
Q

What will binding sites for ligands have?

A

Complementary shape and chemistry to the ligand.

57
Q

As a ligand binds to a protein binding site, what happens?

A

The conformation of the protein changes which causes a functional change in the protein.

58
Q

Where do allosteric interactions occur?

A

Between spatially distinct sites.

59
Q

What does the binding of a substrate molecule to one
active site of an allosteric enzyme do?

A

It increases the affinity of the other active sites for binding
of subsequent substrate molecules.

60
Q

Why is the increase in affinity of other active sites of biological importance?

A

The activity of allosteric enzymes can vary greatly with small changes in substrate concentration.

61
Q

What do many allosteric protein consist of?

A

Multiple subunits (have quaternary structure)

62
Q

What do allosteric proteins with multiple subunits show?

A

Cooperativity in binding, in which changes in binding at one subunit alter the affinity of the remaining subunits

63
Q

What do allosteric enzymes contain?

A

A second type of site, called an allosteric site.

64
Q

What do modulators regulate?

A

The activity of the enzyme when they bind to the allosteric site.

65
Q

Following the binding of a modulator, what happens?

A

The conformation of the enzyme changes and this alters the affinity of the active site for the
substrate

66
Q

What do positive modulators do?

A

Increase the enzyme’s affinity for the substrate.

67
Q

What do negative modulators do?

A

Reduce the enzyme’s affinity for the substrate.

68
Q

What does the binding and release of oxygen in haemoglobin show?

A

Cooperativity.

69
Q

What does changes in binding of oxygen at one subunit alter?

A

The affinity of the remaining subunits for oxygen.

70
Q

What lowers the affinity of haemoglobin for oxygen?

A

A decrease in pH or an increase in temperature, so the binding of oxygen is reduced.

71
Q

What will reduced pH and increased temperature in actively respiring tissue do?

A

It will reduce the binding of oxygen to haemoglobin
promoting increased oxygen delivery to tissue.

72
Q

What can the addition or removal of phosphate cause?

A

Reversible conformational change in proteins. This is a common form of post-translational modification.

73
Q

What do protein kinases do?

A

Catalyse the transfer of a
phosphate group to other proteins.

74
Q

Where is the terminal phosphate of ATP transferred to?

A

Specific R groups.

75
Q

What do protein phosphatases catalyse?

A

The reverse reaction, transfer of a phosphate group from other proteins.

76
Q

What does phosphorylation bring about?

A

Conformational changes, which can affect a protein’s activity. The activity of many cellular proteins, such as enzymes and receptors, is regulated in this
way.

77
Q

What can phosphorylation do to some proteins?

A

Some proteins are activated by
phosphorylation while others are inhibited.

78
Q

What does adding a phosphate group do?

A

It adds negative charges. Ionic interactions in the unphosphorylated protein can be disrupted and new ones created.

advanced higher biology (33 decks)

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