Proteins Flashcards
Mainly just pages 32 - 35 in the textbook
1
Q
Are proteins large or small molecules?
A
Large (and complex) biological molecules.
2
Q
How many major groups can proteins be placed into? (based on their functions)
A
Seven major classes based on functions.
3
Q
Name the 7 types of protein:
A
Enzymes Structural proteins Defensive proteins Transport proteins Contractile proteins Storage proteins Signal proteins
4
Q
There are millions of different proteins, although they are all made up of the same “building-blocks” AKA Amino Acids.
Roughly how many kinds of amino acid are there?
A
Approximately 20.
5
Q
State the use of enzyme amylase.
A
Catalyses the digestion of starch.
6
Q
State the use of enzyme ATPase.
A
Catalyses the breakdown and formation of ATP.
7
Q
What is an enzyme?
A
A protein that acts as a biological catalyst to control biochemical reactions.
8
Q
What is a structural protein?
A
A protein which forms part of the body of an organism.
9
Q
Name a structural protein.
A
Collagen, it makes up hairs and ligaments.
Keratin, the major component of hair.
10
Q
Which protein group does Keratin fall into?
A
Structural protein, it is the major component in hair.
11
Q
State the use of insulin:
A
Controlling the blood glucose levels.
12
Q
Which category of protein does Insulin fall into?
A
Signal proteins
13
Q
What are signal proteins?
A
Proteins that carry messages around the body.
14
Q
What are contractile proteins?
A
Proteins involved in movement.
15
Q
Which protein group do actin and myosin fall into?
A
Contractile proteins, they are the proteins which enable muscle contraction.
16
Q
Name the contractile proteins which are responsible for muscle contraction:
A
Actin and myosin
17
Q
What are storage proteins used for?
A
Storage proteins serve as biological reserves of metal ions and amino acids (essentially just storage).
18
Q
What is the function of the storage protein, albumen?
A
the protein that forms the white of eggs.
19
Q
What are defensive proteins?
A
Proteins such as blood antibodies that fight infections.
20
Q
Which protein grouping does a lymphocyte cell fall into?
A
Defensive proteins, it is a white blood cell which fights infection.
21
Q
Which protein group does haemoglobin belong to?
A
Transport proteins, it carries oxygen in the blood.
22
Q
What are transport proteins?
A
Transport proteins are proteins that transport substances across biological membranes
23
Q
Amino acids have two functional groups, what are they?
A
Amino group (-NH2) Carboxyl group (-COOH)
24
Q
What is the functional ending for the Amino group?
A
- NH2
25
What is the functional ending for the Carboxyl group?
- COOH
26
How is the amino group joined to the alpha carbon?
Covalently bonded.
27
What is the name given to the central carbon atom?
The Alpha Carbon.
28
What is the simplest amino acid?
Glycine (H - A single Hydrogen atom).
29
Amino acids are amphoteric, what does this mean?
They have both acidic and basic properties when they dissociate in water.
30
Which functional group gives amino acids their acidic properties?
Carboxyl group, which can donate a proton so the molecule becomes negatively charged when in an alkaline solution.
31
Which functional group gives amino acids their basic properties?
Amino group, which can take up a proton so the molecule becomes positively charged in an acidic solution.
32
What is the name given to ions with both positive and negative charges?
Zwitterions.
33
What do buffer systems do for the body that is necessary for survival?
They keep the pH levels of the blood and other fluids within tolerable levels.
34
How do amino acids act as buffers?
They have the ability to donate or receive protons which means they tend to resist changes in pH when a base or acid is added.
35
When two amino acids combine, what is the product called?
dipeptide
36
How is a dipeptide formed?
a condensation reaction between the carboxyl group of one amino acid and the amino group of another.
37
What bond links the two amino acids in a dipeptide?
a peptide bond, (between the carboxyl group of one and the amino group of the other).
38
How is a polypeptide chain formed?
Amino acids join through peptide bonds in a chain with a bond at both the carboxyl group and the amino group.
39
What are proteins made up of?
One or more polypeptide chains: they are essentially made up of amino acid monomers.
40
What do simple proteins consist of?
amino acids only.
41
What do conjugated proteins contain which simple proteins do not?
A non-amino acid part called a prosthetic group.
42
The shape of a protein is determined by up to four levels of structure. Name each of the levels:
Primary structure
Secondary structure
Tertiary structure
Quaternary structure
43
What is the primary sequence of a protein?
The sequence of amino acids that make up its polypeptide chain(s).
44
What are the elements that appear in amino acids?
```
Carbon
Hydrogen
Oxygen
Nitrogen
(Some also containing Sulfur).
```
45
What holds together amino acid chains?
Strong peptide bonds.
46
The structure of a protein determines how it works, but what determines the structure of the protein?
The order of the amino acids.
47
What shape is a globular protein?
a protein with a roughly spherical shape.
48
What type of protein are haemoglobin, insulin and many other hormones a type of?
Globular proteins.
49
What is the primary structure of a protein?
The order in which the amino acids are arranged in a polypeptide chain.
50
If one single change occurs to an amino acid in a sequence it can lead to bad consequences.
Give an example of this:
A particular change in a single amino acid for the protein, Haemoglobin, (the main oxygen carrying blood protein), causes a serious blood disorder known as Sickle-cell anaemia.
51
What is the secondary structure of a protein?
Folding and coiling into either an alpha-helix or a beta-pleated helix.
52
Is it possible to have regions of alpha-helix coiling and beta-pleated sheets in the same polypeptide chain?
Yes, they can mix and match.
53
In the secondary structure of a protein, what determines the shape of the helix or sheet?
Regularly spaced hydrogen bonds formed between the C=O group of one monomer and the N-H group of another.
54
What is the tertiary structure of a protein?
The overall 3-D shape of the polypeptide chain.
55
What are the two main classifications of tertiary structures for proteins?
Fibrous Proteins
| Globular Proteins
56
Which type of protein is typically insoluble in water and physically tough?
Fibrous Proteins (condone structural proteins)
57
What is the main use for fibrous proteins and what makes them good at this job?
Mainly structural applications, they are good for this use as they are typically insoluble in water and physically tough.
58
Is silk a fibrous protein, or a globular protein?
Fibrous.
59
What is the main function of the structural protein silk?
It is used as threads in spiders web's.
60
Describe the structure of fibrous proteins:
Parallel polypeptide chains cross-linked at intervals to form long fibres or sheets.
61
What specific design feature makes globular proteins soluble in water?
They have their hydrophobic groups on the inside of the molecule and the hydrophilic groups facing outwards.
62
Which of the four structures determines the function of the final protein?
The tertiary stage: the precise structure of the 3-D shape determines the specific function.
63
What process occurs if the bonds holding the protein in shape are broken?
Denaturation
64
During denaturation, what happens to the primary structure of the protein?
The primary structure is retained.
65
During denaturation what happens that changes the function of the protein to make it significantly less effective?
The polypeptide chains unravel and lose their specific shapes.
66
Is denaturation a reversible process?
Almost never
67
List some factors that can cause a protein to denature?
Temperature, pH, salt concentrations
68
How does frying an egg show the process of denaturation?
The egg white heats up and denatures due to the high temperatures, this causes the transparent protein packed area around the yolk to irreversibly solidify and become white and opaque.
69
What happens to an insoluble, fibrous protein when it becomes denatured?
It loses its structural strength.
70
What happens to a soluble, globular protein when it has denatured?
The shape is changed dramatically and it becomes inactivated.
71
What is the quaternary structure of a protein?
Referring to the way that polypeptide chains are arranged in the protein
72
How does the quaternary structure of the fibrous protein, collagen, benefit its function as a structural protein?
It consists of three helical polypeptides that are super-coiled to form a rope-like structure with great strength.
73
All amino acids have 3 'groups' off the alpha carbon. Name these groups.
+ Amine group (NH2)
+ Carboxyl group (COOH)
+ Chemically Variable "R" group.
74
Summarise what happens in a condensation reaction.
The two amino acids are joined to form a dipeptide with the release of a water molecule.
75
What is the scientific name for two amino acids that have been bonded / joined (in a condensation reaction.)
Dipeptide.
76
Is a peptide bond a Condensation or Hydrolysis reaction.
Condensation - there is water formed as a result of the bond formation.
77
What makes each of the amino acids in proteins unique?
The chemically variable "R" group.
78
What does the "R" stand for in the amino acid structure?
The chemically variable group.
79
What is the primary structure?
The order of amino acids in the polypeptide chain.
80
What determines the primary structure?
The order of nucleotides in DNA and RNA
81
What type of bond joins neighbouring amino acids together?
A peptide bond.
82
How are di- and polypeptides broken down?
Hydrolisis
83
What is the tertiary structure held by?
Ionic bonds and disulfide bridges
84
What are disulfide bridges?
Bonds formed between sulfur containing amino acids.
85
Explain the importance of the amino acid sequence in protein folding:
The distribution of attractive and repulsive charges on the amino acids determine how the protein is organised and folded, (therefore also determines its biological function).
86
Why do channel proteins often fold with non-polar R groups to the channel's exterior and polar R groups to its interior?
Because the interior of a plasma membrane is a hydrophobic environment. Channel proteins span the membrane, and fold in such a way that the non-polar (hydrophobic) R groups align to the outside, and polar (hydrophilic) R groups form a channel on the inside. This channel allows water soluble molecules to cross the membrane.
87
Why does denaturation often result in the loss of protein functionality?
Denaturation is the process of a protein losing its shape, this disrupts the active site of the protein and thus its ability to carry out its biological function.
88
T / F - Proteins account for more than half the dry weight of most cells.
True - they are large and very abundant in cells.
89
Which bonds maintain the secondary structure?
Hydrogen bonds.
90
In a Beta-Pleated Sheet, what joins the two peptide chains?
Hydrogen bonds.
91
T / F - Disulfide bridges/bonds can be broken down by heavy metals, pH or temperature extremes and some solvents.
True.
92
What are the properties of globular proteins?
- Easily water soluble
- Tertiary structure critical to function
- Polypeptide chains folded into a spherical shape
93
What is the scientific name for antibodies?
Immunoglobulins.
94
Insulin, RuBisCo and Haemoglobin are types of what protein?
Globular
95
What are the properties of Fibrous proteins?
- Water insoluble
- Very tough physically; may be able to supple or stretch
- Parallel polypeptide chains in long fibres or sheets.
96
Skin tissue contains a large amount of the fibrous protein elastin, suggest its function:
The elastic properties allow tissues to resume their shape after stretching.
97
RuBisCO is the most abundant protein in the world. State what its use is:
It catalyses the first step of carbon fixation for photosynthesis.
98
Where in the cell do condensation reactions occur?
Ribosomes (Protein!)
99
Are Non-Polar bonds Hydrophilic or Hydrophobic?
Non-Polar = Hydrophobic.
100
Are Polar bonds Hydrophilic or Hydrophobic?
Polar = Hydrophilic.
101
Is Ethane a Hydrophilic or Hydrophobic molecule?
Hydrophobic, (Only C-H bonds)
102
Is Ethanol a Hydrophilic or Hydrophobic molecule?
Hydrophilic, (O-H bond)
103
What type of bonds are Non-Polar?
C - H bonds and all elemental bonds.
104
What is the monomer for a protein chain?
Amino Acids
105
In an amino acid structure, what is the R?
The variable group.
106
What is the amino group in an amino acid?
NH2
107
What is the carboxyl group in an amino acid?
COOH
108
What is the central carbon in an amino acid?
The Alpha Carbon.
109
Amino acids are amphoteric, what does this mean?
They can react as both an acid or a base. (As they have both an acid and base groups)
110
Why is it significant for survival that amino acids can act like buffers?
It resists pH changes which means that blood pH and other things can stay constant.
111
Amino acids are zwitterions, what does this mean?
A zwitterion is a molecule that has both acidic and basic groups. (The amino acid has an amino and carboxyl group.)
112
How does a zwitterion such as an amino acid resist pH changes?
The molecule can gain or lose hydrogen ions which allows it to absorb or release pH changes when an acid / base is added.
113
What is formed in a reaction between two amino acids?
Dipeptide.
114
What two products are formed in a condensation reaction between two amino acids.
A dipeptide and a water molecule.
115
What type of reaction joins amino acids together?
Condensation reactions.
116
What is the name of a long chain of amino acids joined together through peptide bonds?
A polypeptide chain.
117
What is a simple protein?
A protein that contains only amino acids.
118
What is a conjugated protein?
A protein containing a non-amino acid group known as a prosthetic group.
119
What is the name for a protein that has only amino acids?
A simple protein.
120
What is the name for a protein containing a prosthetic group (non-amino acid group)?
A conjugated protein.
121
Where do condensation reactions occur?
In the ribosomes.
122
Suggest where a polypeptide chain is created and why this might be?
In the ribosomes because they are proteins and protein synthesis occurs in the ribosomes.
123
What is the primary structure and what determines it?
The primary structure is the sequence of amino acids, determined by the sequence of DNA bases.
124
What is the secondary structure and what determines it?
The secondary structure is the proteins folding and coiling into either an alpha-helix or a beta-pleated sheet. Determined through hydrogen bonds.
125
What are the two forms that are created in the secondary structure?
Alpha-Helix.
| Beta-Pleated Sheet.
126
What is the tertiary structure and what determines it?
The tertiary structure is the 3D folding of a polypeptide chain. Determined by various bonds with varying strengths.
127
What are the bonds that are formed in the tertiary structure?
- > Hydrogen Bonds
- > London forces / hydrophobic interactions
- > Ionic bonds
- > Disulfide bridges
128
What is the strongest kinds of bond that a protein forms?
Disulfide bridges.
129
Bacteria living in high temperatures such as near lava springs contain many of what type of bonds, which type of bond is this and suggest why?
Disulfide bridges as they are the strongest bond and therefore are least affected by temperature and are harder to denature.
130
Are polar bonds hydrophobic or hydrophilic?
Hydrophilic
131
Are non-polar bonds hydrophobic or hydrophilic?
Hydrophobic
132
Are hydrocarbons such as ethane hydrophobic or hydrophilic?
Hydrophobic, they contain only non-polar (C-H) bonds.
133
Would a water molecule be hydrophobic or hydrophilic?
Hydrophilic as the H-O bonds are polar.
134
Name the non-polar bonds.
C - H bonds and all elemental bonds.
135
In a water molecule (H20) where are the charges and what are they?
The oxygen atom pulls the electrons more strongly than hydrogen meaning there is more e- near the oxygen. This means the oxygen has a slight negative charge and the hydrogen's have a slight positive charge.
136
Which of the following molecules contains amino acids?
- ATP
- Cellulose
- Glycogen
- Haemoglobin
Haemoglobin.
137
The alpha helical form of a polypeptide chain is caused by the presence of what in a molecule?
- Disulphide bridges
- Glycosidic bonds
- Hydrogen bonds
- Peptide bonds
Hydrogen bonds.
138
At which level/s of protein structure do London forces occur?
Tertiary and Quaternary
139
Which level of protein structure is encoded in DNA?
Primary.
140
What does a haemoglobin molecule contain?
Four polypeptide chains each with one attached haem group.
141
Name a complex globular protein with non-proteins substances in.
Haemoglobin.
142
Which property of amino acids allows them to act as buffers?
They contain both amino and carboxyl groups, (which allows them to absorb or release H+ atoms).
143
Where are polypeptides synthesised?
Ribosomes.
144
What is COOH group?
Carboxyl group.
145
What is the NH2 group?
Amine group.
146
What is a simple protein?
A polypeptide chain with only amino acids.
147
There are roughly 20 amino acids that are common in all organisms, what is different in each amino?
The only difference is the chemically variable "R" group.
148
What test is used for proteins?
The biuret test.
149
Name the type of bond formed between the joined pair of amino acid molecules.
Peptide bond.
150
Describe how a peptide bond is formed between two amino acids to form a dipeptide: (2)
- Condensation reaction,
| - Between amine and carboxyl groups.
151
The secondary structure of a polypeptide is produced by bonds between amino acids, describe how: (2)
- Hydrogen bonds,
- Between NH and C=O group,
- Forming alpha-helices or beta-pleated sheets.
152
Two proteins have the same number and type of amino acids but different tertiary structures, explain why: (2)
- Different sequence of amino acids / primary structure,
| - Forming bonds in different places.
153
Which amino acid has the R group of one Hydrogen atom?
Glycine.
154
What is the formula for the R group of glycine?
Just a single Hydrogen.
155
In the formation of a disulfide bridge, what molecule is released?
H2 (gas)
156
Is the formation of a disulfide bridge a condensation or hydrolysis reaction?
Neither, H2 gas is released.
157
Water is a polar molecule, Where does the slight negative and positive charge lie in the molecule?
The oxygen atom pulls electrons more strongly than the hydrogen atoms and this results in a slight negative charge around the oxygen and a slight positive charge around the hydrogens.
158
Is ethanol polar or non-polar?
Polar (O-H).
159
Is ethane polar or non-polar?
Non-Polar (all C-H).
160
Are polar bonds hydrophilic or hydrophobic?
Polar = Hydrophilic.
161
Is ethanol hydophilic or hydrophobic?
Ethanol = Polar = Hydrophilic.
162
Are non- polar bonds hydrophilic or hydrophobic?
Hydrophobic.
163
Is ethane hydrophilic or hydrophobic?
Ethane = hydrocarbon = non-polar = hydrophobic.
164
All hydrocarbons are hydrophilic? or hydrophobic?
Hydrophobic as they contain only non-polar C - H bonds
165
What does the biuret test determine?
The presence of peptide bonds (in a protein).
166
What type of results foes a biuret test give?
Quantitative results.
167
In a biuret test, what colour solution shows no peptides are present?
Blue solution.
168
In a biuret test, what colour solution shows peptides are present?
Pink solution.
