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AH Biology > Proteins > Flashcards

Proteins Flashcards

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1
Q

What is the genome?

A

Total genetic material in a cell (complete set of DNA)

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2
Q

What is the proteome?

A

Entire set of proteins that can be expressed from a genome

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3
Q

What are non-coding RNA genes?

A

Genes that aren’t expressed as proteins in a particular cell type

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4
Q

Non-coding RNA genes are transcribed to produce…

A

tRNA
rRNA
RNA molecules that control the expression of other genes

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5
Q

The proteome is larger than… because…

A

The number of genes (particularly in eukaryotes) because more than one protein can be expressed from a single gene due to alternative RNA splicing

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6
Q

Factors that affect the set of proteins produced in a cell type…

A

Metabolic activity of cell
Cellular stress
Response to signalling molecules
Diseased vs healthy cells

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7
Q

Boundary around outside of eukaryotic cells?

A

Plasma membrane

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8
Q

Eukaryotic cells also have a… which..

A

System of internal membranes that increases the total area of the membrane available for vital metabolic processes

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9
Q

Endoplasmic Reticulum (ER)?

A

Forms network of membrane tubules continuous with the nuclear membrane

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10
Q

What are the 2 types of ER?

A

Rough (RER) - has ribosomes
Smooth (SER)- no ribosomes

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11
Q

What is the Golgi apparatus?

A

Series of flattened membrane discs

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12
Q

What are lysosomes?

A

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

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13
Q

What are hydrolases?

A

Enzymes that catalyse the cleavage of a covalent bond using water

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14
Q

Function of vesicles

A

Transport materials between membrane components

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15
Q

Membranes are made of…

A

Lipids and proteins synthesised in the ER

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16
Q

Where are lipids synthesised?

A

SER and inserted into its membrane by enzymes

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17
Q

Where are cytosolic proteins synthesised?

A

Cytosolic ribosomes and remain in the cytosol (liquid component of cytoplasm)

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18
Q

Examples of cytosolic proteins…

A

Enzymes for glycolysis
Enzymes that attach amino acids to tRNA at ribosomes during protein synthesis

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19
Q

Where are transmembrane proteins synthesised?

A

Begins at cytosolic proteins and completed inside ER

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20
Q

Transmembrane proteins carry a…

A

Signal sequence

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21
Q

What does a signal sequence do?

A

Halts translation and directs ribosome synthesising the protein to dock with the ER, forming RER

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22
Q

What is a signal sequence?

A

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

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23
Q

Why does protein pore remove cytosol particle and signal sequence after docking?

A

To allow translation to continue

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24
Q

As translation continues after docking…

A

The protein is inserted into the membrane of the ER

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25
What is post-translational modification?
When polypeptide chains have carbohydrates or phosphates added to them or are cleaved to form an active protein
26
What is the major modification?
Addition of carbohydrates
27
To form carbohydrates…
Enzymes catalyse the addition of various sugars in multiple steps
28
What are microtubules?
Structures that make the cell’s cytoskeleton and offer support and a means of transport
29
Where do vesicles that leave the Golgi apparatus take proteins?
Plasma membrane and lysosomes
30
Vesicles move along microtubules to…
Other membranes within cell and fuse with them
31
What are proteins transported by once they are in the ER?
Vesicles that bud off from the ER and fuse with the Golgi apparatus
32
How do molecules move through the Golgi discs?
In vesicles that bud off from one disc and fuse with the next in the stack
33
Due to their size, eukaryotes have a relatively small surface area to volume ratio so…
Plasma membrane is too small an area to carry out all the vital functions of the membrane
34
Examples of secreted proteins
Peptide hormones such as insulin and digestive enzymes such as trypsin
35
Many secreted proteins are synthesised as…
Inactivate precursors so require proteolytic cleavage to produce active proteins
36
What is proteolytic cleavage?
Type of post-translational modification where polypeptide is cut
37
What are amino acids?
Building blocks of proteins
38
Amino acid sequence determines…
Protein structure
39
What are proteins?
Polymers of amino acid monomers
40
Amino acids have the same… differing only in…
Basic structure, R group present
41
Amino acids are linked by… (occurs during translation at ribosomes)
Peptide bonds to form polypeptides
42
How is a peptide bond formed?
Enzyme causes condensation reaction between 2 adjacent amino acids (water is removed)
43
What kind of bond is a peptide bond?
Strong covalent bond
44
All amino acids contain an…
Amine (NH2) and acid group (COOH)
45
Name R groups
Acidic- hydrophilic, - , COOH Basic- hydrophilic, + , NH2 Polar- hydrophilic, slightly charged, CO, OH, NH2 Hydrophobic- hydrophobic, no charge, CH3
46
R groups vary in…
Shape, size, charge, hydrogen bonding capacity and chemical reactivity
47
Diversity of R groups accounts for…
The wide range of functions carried out by proteins
48
What is primary structure?
Sequence in which amino acids are synthesised into polypeptide
49
What is secondary structure?
Result of hydrogen bonding along backbone of protein strand
50
What is tertiary structure?
Final folded shape of the polypeptide and stabilised by interactions between R groups of amino acids
51
What are the interactions between R groups?
Hydrophobic interactions Ionic bonds London dispersion forces Hydrogen bonds Disulphide bridges
52
What is quaternary structure?
Spatial arrangement of subunits, only exists in proteins with 2 or more polypeptide subunits
53
Subunits are linked by…
Bonds between r groups of polypeptide chains
54
What are London dispersion forces?
Very weak attractions between electron clouds of atoms
55
What are hydrogen bonds?
Strong attractions between hydrogen atom and an electronegative atom (O2 or N2)
56
What are disulphide bridges?
Covalent bonds between R groups containing sulphur
57
What are ionic bonds?
COOH and NH2 groups ionise to become COO- and NH3+ which are strongly charged and attracted to each other
58
What are hydrophobic interactions?
As a polypeptide folds into its functional shape, the hydrophobic R groups are repelled by water so usually end up on the inside of the protein away from the surface
59
What is a prosthetic group?
Non-protein subunit bound tightly to protein and necessary for its function
60
Ability of haemoglobin to bind oxygen is dependent upon...
non-protein haem group (prosthetic group)
61
Effect of increasing temperature on interactions between R groups
Disrupts interactions that hold the protein in shape so protein begins to unfold and eventually denatures
62
Effect of changing pH on interactions between R groups
As pH increases/decreases away from optimum, the normal ionic interactions between charged groups are lost which gradually changes the conformation of the protein until it denatures
63
What is a ligand
A substance that can bind to a protein
64
Binding sites on surface of protein will have...
Complementary shape and chemistry to ligand
65
Mechanism used to regulate protein activity
Conformational change
66
What is an allosteric enzyme?
Enzyme whose activity is regulated by altering its conformation, contain a second type of binding site (allosteric site)
67
Where does a substrate bind?
Active site
68
Where does a substance other than the substrate bind?
Allosteric site
69
What does a modulator do?
Regulate the activity of an enzyme by binding to the allosteric site, change conformation of enzyme which alter affinity of active site for substrate
70
A positive modulator...
Increases the enzyme's affinity for the substrate, increasing activity
71
A negative modulator...
Decreases the enzymes affinity for the substrate, decreasing activity
72
Many allosteric proteins consist of...
Multiple subunits so have quaternary structure
73
What does allosteric mean?
'other shape' Refers to proteins that have interactions between spatially distinct sites (on same protein)
74
What happens when a ligand binds to a protein binding site?
Protein changes conformation so function changes
75
What is phosphorylation?
When a phosphate group is added or removed from the protein, common form of post-translational modification
76
A large subset of proteins is... when first synthesised so require...
Inactive, post-translational modification to become activated
77
What do protein kinases catalyse?
The transfer of a phosphate group from ATP to other proteins, the terminal phosphate of ATP is transferred to specific R groups
78
What do protein phosphatases catalyse?
The transfer of a phosphate group from protein to ADP to generate ATP (reverse reaction)
79
What allows binding of ligands?
R groups not involved in protein folding
80
What does phosphorylation do to a protein?
Conformational changes which can affect protein's activity
81
Haemoglobin is made of...
4 polypeptide subunits (haem groups)
82
What is co-operativity?
When changes in binding at one subunit alter the affinity of the remaining subunits (shown by allosteric proteins)
83
What causes the activity of allosteric enzymes to vary greatly?
Small changes in substrate concentration
84
Binding of a substrate molecule to one active site of an allosteric enzyme...
Increases the affinity of the other active sites for binding of substrate molecules
85
Haemoglobin shows co-operativity in...
binding and release of oxygen
86
What happens when an oxygen molecule binds to one subunit of haemoglobin?
Conformation of the subunit changes
87
what happens when an oxygen molecule is release from haemoglobin?
Decrease in affinity of other subunits to maximise the release of oxygen where it is needed e.g. working tissues
88
When temperature is increased and pH reduced in actively respiring tissues

AH Biology (13 decks)

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