Topic 2 Flashcards
(313 cards)
1
Q
Write the 4 groups found in an amino acid
A
- H group
- R group, residual group, side chain
- Amine group, NH2
- Carboxyl group, COOH
2
Q
Name the bonds found in the primary structure of a protein
A
Peptide bonds
3
Q
Are enzymes fibrous or globular prteins?
A
globular
4
Q
Which bond can be found in both secondary an tertiary structure of proteins?
A
Hydrogen
5
Q
Where in the cell are polypeptides made?
A
ribosomes
6
Q
What is a conjugates protein?
A
A protein containing a non-protein molecule/chemical or a prosthetic molecule
7
Q
State examples of a conjugated protein
A
- Haemoglobin
- Lipoprotein
- Glycoproteins
8
Q
Which 3 bonds can be found in the tertiary structure of a protein?
A
- Disulphide links
- Hydrogen bonds
- Ionic bonds
9
Q
State the structural similarities between fibrous and globular proteins
A
- Both contain primary structures
- Have hydrogen and peptide bonds
- Both are a long polypeptide chain
- Both made of amino acids
10
Q
Is fibrin a fibrous or globular protein?
A
Fibrous
11
Q
Are enzymes soluble or insoluble?
A
soluble
12
Q
What is the difference between the amino acid R groups on the outside of a globular protein and the amino acid R groups on the outside of a fibrous protein?
A
A R group on the outside of a globular protein will be polar and therefore hydrophilic, meaning the protein is soluble. A R group on the outside of a fibrous protein with be non-polar and therefore hydrophobic, meaning the protein is insoluble. This is because globular proteins have tertiary structure whereas fibrous proteins don’t`
13
Q
Which part of an amino acid is the variable group?
A
the R group
14
Q
Between which 2 groups does a peptide form?
A
N-H2 and the C=O
H-N-C=O
15
Q
Is haemoglobin a fibrous or globular protein?
A
Globular
16
Q
What is the key property difference between fibrous and globular proteins?
A
Globular are soluble, Fibrous are insoluble
17
Q
Between which type of R groups does an ionic bond form?
A
Delta positive charged and delta negative charged, polar R groups
18
Q
Name the two types of secondary structure
A
- alpha helix
- beta pleated sheet
19
Q
How many subunits are present in haemoglobin?
A
4
20
Q
Collagen is described as a _______ helix
A
triple
21
Q
Define primary structure of a protein
A
A specific sequence of amino acids joins together by peptide bonds (condensation) to form a polypeptide chain
22
Q
A disulphide bond forms between two R groups which contain_______
A
sulphur
-SH
the amino acid cysteine
23
Q
Name the four chemical elements that all amino acids contain
A
- C, H, O, N
24
Q
A protein with quaternary structure has more than one _______
A
polypeptide chain
25
Name proteins with a quaternary structure
- collagen
- haemoglobin
- insulin
26
What does a polypeptide need to do to form a protein?
Fold, become structured, into a more 3D shape
27
Is collagen soluble in water?
no
28
What does the enzyme amylase have on its surface which makes it soluble?
Polar R groups (hydrophilic)
29
Which non-protein group does haemoglobin contain that makes it a conjugated protein?
Haem group
30
State the key properties of collagen which make it good for its function
- Insoluble
- Fibrous protein allows for length to vary to the collagen fibres can adapt to the right size for their placement
- Lots of hydrogen bonds and strong peptide bonds make for **high tensile strength**
- some flexibility
31
When 2 amino acids form a dipeptide, which type of reaction takes place?
condensation
32
Define 'polypeptide'
A polymer made of many amino acids, joined by peptide bonds to form a long chain
33
If a polypeptide chain contains 150 amino acids, how many peptide bonds will it contain?
149
34
Draw a peptide bond
O-N**--**C=O
35
If a polypeptide contains 195 amino acids, how many molecules of water will be needed to fully hydrolyse it into amino acids?
194
36
Where in a cell does a polypeptide fold to form a functional protein?
In the lumen of the endoplasmic reticulum
37
What structural feature does an enzyme have which other globular proteins do not?
active site
38
What shape are globular proteins?
Spherical
39
What is the function of glycoproteins?
act as receptors on cell membranes
40
What is the function of haemoglobin?
to bind oxygen to red blood cells for transportation
41
Fibrous proteins have a _________ sequence of amino acids
repetitive
42
What is keratin?
A fibrous protein found in hair, nails, horns
43
List examples of fibrous proteins
- collagen
- fibrin
- keratin
44
Fibrous proteins have important _______ roles
structural
45
How are R groups positioned in a globular protein?
Polar groups on the outside, non-polar groups on the inside
46
Globular proteins have important roles in _____
metabolic reactions
47
List examples of globular proteins
- Enzymes
- Haemoglobin
- Thrombin, Fibrinogen, prothrombin
- insulin
48
Define tertiary structure
the further folding of the secondary structure into a **precise/specific** 3D shape
49
The primary structure determines _____________
the position of amino acid R groups
50
What is the monomer of proteins?
amino acids
51
Plants can make ___ amino acids and animals can make ______ amino acids
- all
- only some
52
What are essential amino acids?
the amino acids that animals must obtain from their diet
53
What id the dimer of amino acids called?
dipeptide
54
What holds together tertiary structures?
chemical bonds and hydrophobic interactions between R groups
55
What four types of R group are there?
- Nonpolar
- Polar
- Electrically charged - negative, acidic
- Electrically charged - positive, basic
56
How many different R groups are there and therefore the number of different amino acids?
20
57
State the function of cholesterol in the cell membrane
Cholesterol regulates the fluidity of the membrane
58
Which type of molecule forms the bilayer which is the cell membrane?
Phosopholipids
59
Is carbohydrate found on the inside or outside of the membrane?
outside
60
Describe the head of a phospholipid
- Hydrophilic
- Made of glycerol and a phosphate group
- Attached to two fatty acid chains
- Found on the surface of the bilayer
61
How many fatty acid tails are found in a phospholipid?
2
62
Where is cholesterol found in the cell membrane?
imbedded in the bilayer surface, in between the phospholipid tails
63
How many layers of phospholipids make up the cell membrane?
Two , therefore **bi**layer
64
What is the role of channel proteins in the cell membrane?
**Facilitated diffusion** -Channel proteins transport larger polar molecule through small water filled pathways
65
State 2 parts of the bilayer that water can pass through the bilayer.
- proteins
- phospholipids
66
State properties of cell membrane
- Fluid
- Flexible
- Bilayer
- Partially/selectively permeable
67
Which word described the fatty acid tails of a phospholipid and means 'water hating'?
Hydrophobic
68
Give one function of a membrane glycolipid
Act as a receptor, cell to cell recognition
69
Which molecules bind to carbohydrate and were used to prove that carbohydrate was only found on one side of the cell membrane?
Lectins
70
Are channel proteins transmembrane proteins?
Yes
71
Which technique helped scientists prove that proteins were embedded in the cell membrane rather than attached to the outside of it?
**Frozen fracture**
72
Molecules attached to the cell membrane which contain active are called ________
Enzymes
73
What type of protein is the CFTR protein?
Mucus
74
Do channel proteins span the membrane or are they only found on one side?
Span the membrane
75
Describe the evidence which supported the idea that the cell membrane is a bilayer.
Red blood cell membranes were digested and the lipids spread on the surface of water. The surface area that they covered on water was twice the surface area of the surface area of the red blood cell. Therefore there must be a double layer of lipid around the cell.
76
Give the function of a glycoprotein
Acts as a receptor, cell to cell recognition
77
Which chemical element do phospholipids contain that triglycerides do not?
Phosphorus
78
Which part of a phospholipid is hydrophobic?
The fatty acid tails, hydrocarbon chains
79
Name the aqueous environment found on the inside of a cell membrane?
Cell cytoplasm
80
Name the aqueous environment found on the outside of a cell membrane?
Tissue fluid
81
Why do phospholipids spontaneously form a bilayer?
- Most stable structure of phospholipids.
- Phosphate heads of phospholipids are hydrophilic – so they **attract** and interact with water on the membrane surfaces (both sides) Fatty acid tails of phospholipids are hydrophobic - so they **repel** and orientate themselves away from water inside the membrane
- Bilayer arrangement is due to the aqueous environment on both sides of the membrane (cytoplasm inside, tissue fluid outside)
82
What does 'fluid mosaic' mean in the term fluid mosaic model?
Fluid- 'sea' of phospholipids are able to move, fuse, pinch or change shape. Proteins are able to move
Mosaic- proteins interspersed through the bilayer, randomly scattered pattern
83
What are the differences between the ‘Davson-Danielli three layer sandwich’ model of the cell membrane and the present day ‘fluid mosaic’ model?
- FMM - Phospholipid head are on the outside
- FMM - Proteins are imbedded in the bilayer
- TLS - no carbohydrates present
- TLS - has no cholesterol
84
Describe the evidence which supports the idea that the cell membrane is fluid
- The proteins from the human cell and the mouse cell were able mix and therefore the proteins must be able to move across the fluid membrane
- Proteins in 2 different cells labelled with fluorescent markers each of a different colour, 2 cells are fused together, proteins intermix , so proteins must be able to move within the plane of the bilayer
85
Which monomers are the proteins found in the cell membrane made from?@
amino acids
86
State the function of a carrier protein
To move larger molecules **through** the bilayer via **facilitated diffusion** or **active transport** which requires **ATP**
- transport type depends on concentration gradient
87
What was the results of Davson and Danielli experiments?
In 1954, electron microscope images showed more detailed images of the cell membrane
- different layers could be seen in the cell membrane
88
What was the results of Gorter and Grendel experiments?
In 1924, red blood cell membranes contain enough phospholipids to cover the red blood cell twice
- Showed the cell membrane is a phospholipid bilayer
89
At first what were the dark outer layers and lighter inner layers thought to be?
- inner layer thought to be lipid
- outer layer thought to be protein
90
Explain the freeze fracture results
The freeze fracture showed ‘bumps’ in the centre of the membrane
- proteins are found embedded **in** the bilayer rather than either side
91
Explain the results of Frye and Edinin experiments
The proteins of two cells were labelled with different colour fluorescent markers and fused. The coloured markers intermixed
- the membrane is fluid which allows many proteins to move as the phospholipids move
92
What was the results of Unwin and Henderson experiments?
In 1984, some proteins can only be released from the cell membrane using strong detergents which dissolve the membrane. Others can be released more easily by increasing ionic strength
- found **intrinsic** proteins which are fully imbedded in the cell membrane and **extrinsic** proteins are loosely associated with the cell membrane
93
Explain the **Lectins**
results
Only bound to the outside of the cell membrane
- Carbohydrate is only found on the outside surface of the cell membrane
94
What are **lectins**?
Molecules which bind to carbohydrate
95
What are the 3 ways you can disrupt a cell membrane?
- Detergents, grab onto lipids
- extremes of temperature
- alchohol
96
Membranes enable ____________
Compartmentalisation
- allows for a concentration gradient to be created across membranes
97
How wide is the bilayer?
7nm
98
What is a micelle?
Spherical clusters with hydrophobic tails pointing into the centre
99
What components are in the fluid mosaic model?
- intrinsic/extrinsic proteins
- glycolipid
- glycoprotein
- transmembrane proteins
-channel proteins
-carrier proteins
- cholesterol
- phospholipid bilayer
100
Who came up with the three-layer protein-lipid sandwich model?
Singer and Nicholson in 1972
101
By which transport process does carbon dioxide pass through the cell membrane?
Diffusion
102
Are carrier proteins involved in facilitated diffusion?
Yes
103
Which three transport processes require energy in the form of ATP?
- endocytosis
- exocytosis
- active transport
104
Where exactly is the CFTR protein found in the body?
In the cell membrane of mucus producing cells in respiratory, digestive and reproductive systems
105
What does the CFTR protein transport?
Chloride ions
106
Through which two components of the cell membrane can water pass by osmosis?
- through channel proteins (aquaporins)
- Phospholipid bilayer
107
Define **facilitated diffusion**
the movement of molecules/ions from a region of high conc. to a region of low conc. down a concentration gradient **through** a channel/carrier protein in the membrane
108
Can lipid soluble molecules pass directly through a lipid bilayer?
yes
109
Compare simple diffusion to facilitated diffusion
- Both are the movement of substance down a concentration gradient
- Facilitated diffusion uses proteins and simple diffusion does not
- Facilitated always takes place through a membrane, diffusion doesn't always
110
State the key differences between active transport and facilitated diffusion
- Active transport uses ATP, f. diffusion doesn't
- Active transport transports substances against the conc.
gradient, f. diffusion goes down the conc. gradient
- active transport is only one way, f. diffusion is both
111
Explain the process of exocytosis
- this is the excretion of large molecules from a cell
- a vesicle within the cell that is carrying a substance moves towards the surface cell membrane
- the vesicle fuses to the cell membrane and then comes apart to release the molecules out of the cell
112
By which transport process would amino acids enter a cell, if there was a higher concentration of them outside the cell than inside?
Facilitated diffusion
113
Define **osmosis**
the net movement of **free** water molecules from a region of low solute conc. to a region of high solute conc. over a partially permeable membrane
114
Can ions pass directly through the lipid bilayer?
No as they are charged
115
Does facilitated diffusion require ATP?
No
116
Which type of proteins are involved in active transport?
specific carrier proteins
117
Describe how a white blood cell engulfs a bacterium
By endocytosis
- the cell membrane caves in to form a pocket around the bacterium (encloses the bacterium)
- the membrane comes back together and pinches off so the a vesicle is formed inside of the cell
118
Define **active transport**
the movement of molecules/ions against a conc. gradient by using carrier proteins and ATP
119
Compare osmosis and active transport
- Osmosis only moves water molecules
- Both transport molecule through a membrane
- active transport is against the conc. gradient, osmosis is down the conc. gradient
- Active transport requires ATP and carrier proteins
120
By which process does oxygen pass through the cell membrane?
simple diffusion
121
When equilibrium has been reached across a membrane, do the molecules stop moving?
No however there is no overall net movement, at the same rate
122
What does 'no net movement mean'?
The molecules are still moving but there isn't a favoured direction (conc. stays the same on both sides of the membrane) move at the same rate
123
When there is a large concentration difference between the inside and outside of a cell, does this lead to a fast or slow rate of diffusion
fast rate of diffusion
124
If a molecule is in high concentration outside a cell but does not enter a cell, what does this tell you about the permeability of the membrane to that molecule?
The membrane is impermeable to the molecule
125
Why can starch not diffuse out of plant cells, but glucose can?
Starch is too large a molecule to diffuse in between the cell membrane bilayer (also insoluble)
126
If water moves from an area of high concentration of free water in the air space of a leaf, through a stoma (pore) to an area of low free water outside the leaf (in the air), why is this not osmosis?
Because osmosis is over a partially permeable membrane. there was no membrane in this case so it was diffusion
127
What happens when the uptake of glucose into a cell as the concentration gradient becomes less steep?
glucose uptake slows down
128
Compare the processes of endocytosis and exocytosis
- Endocytosis is movement into a cell whereas exocytosis is movement out of a cell
- Both use vesicles and the cell membranes fluidity to move large (volumes of) substances
- both involved in bulk transport
- both require energy
- both involve membranes fusing
129
What do high ethanol concentrations do to phospholipids?
Dissolves the phospholipid
130
What do high temperatures do to membrane proteins?
Denature them
131
If there are 40 glucose molecules in a cell at the start of an experiment and there are 65 glucose molecules in the cell at the end of the experiment, calculate the percentage increase in glucose molecules in the cell over the course of the experiment
25/40= 0.625
x 100= 62.5%
132
What type of protein is the CFTR protein?
channel protein
133
What are the active transport processes?
- active transport
- exocytosis
-endocytosis
134
What are the passive transport processes?
- diffusion
- facilitated diffusion
- osmosis
135
What is a partially permeable membrane?
a barrier to some solutes but not water
136
What type of molecule does diffusion transport?
- non-polar, uncharged, lipid soluble, hydrophobic, small molecules
137
What type of molecule does facilitated diffusion transport?
charged, ions, hydrophilic, larger than CO2
138
What is ATP?
An energy transfer molecule used for all biological processes as an immediate source of energy#
- adenosine triphosphate
139
What are active transport proteins also known as?
( protein) Pumps
140
Name the sugar found in DNA
deoxyribose
141
State the name of the base which pairs with thymine in DNA
adenine
142
Which type of bond holds the two strands together in DNA?
hydrogen bond
143
State three parts of an RNA nucleotide
- pentose sugar (ribose)
- phosphate group
- organic base e.g. adenine, cytosine, guanine and uracil
144
Why is DNA replication described as semi-conservative?
In replication one strand of the DNA molecule will come from the original DNA double helix molecule and the other strand will have been newly formed from free mononucleotides
145
Which organic base is found in RNA but not DNA?
uracil in the place of thymine
146
Name the enzyme which joins mononucleotides in DNA replication
DNA polymerase
147
Name the sugar found in RNA
ribose
148
What is the function of DNA helicase in DNA replication?
to unwind, unzip, separate the 2 DNA strands
149
Is RNA single or double stranded?
single stranded
150
What is bonded to the pentose sugar in the DNA backbone?
A phosphate group
151
If 24% of the bases in a DNA molecule are adenine, what percentage of the bases will be cytosine?
26%
152
How many template strands are there in DNA replication?
2
153
Which base joins with cytosine in DNA?
guanine
154
Which organic base is found in DNA but not RNA?
thymine
155
Ina mononucleotide, is the base bonded to sugar or phosphate?
sugar
156
If 68% of the bases in a DNA molecule are adenine, what percentage of the bases will be uracil?
0% as uracil is not present in DNA molecules
157
Describe **complementary base pairing** in DNA
Each base in DNA has a specific base which it can pair up to
Cytosine - guanine (3 hydrogen bonds)
adenine - thymine (2 hydrogen bonds)
this is because A and C both have a two ring structure whereas G and T have a one ring. this means that each 'rung' is equal in the DNA so it is a uniform width
158
Give the structural differences between DNA and RNA
- DNA has thymine while RNA has uracil instead
- DNA is double stranded whereas RNA is single stranded
- DNA has the deoxyribose pentose sugar whereas RNA has the ribose pentose sugar
159
Why is DNA described as a **double helix**?
this is because each DNA strand twists into a helical shape and as there are two strand the helix is double
made of two strand wound together
160
Is DNA helicase an extracellular or intracellular enzyme?
intracellular
161
Is RNA a polynucleotide? Explain
Yes as RNA is made of many RNA mononucleotides joined together by phosphodiester bonds
162
Name the type of bond which joins mononucleotides in DNA
phosphodiester bonds
163
Name the type of reaction which takes place when DNA is broken down into mononucleotides
hydrolysis
164
Where in a cell does DNA replication take place?
Nucleus
165
If there were 200 bases in an RNA molecule, how many water molecules would be needed to completely break the molecule down into mononucleotides?
199
166
Name two nucleic acids
- deoxyribonucleic acid, DNA
- ribonucleic acid, RNA
167
Is DNA polymerase an extracellular or intracellular enzyme?
intracellular
168
In 'heavy' DNA, which isotope of nitrogen is present?
15N
169
Which part of a mononucleotide contains nitrogen?
organic base
170
In 'light' DNA, which isotope of nitrogen is present?
14N
171
If a DNA molecule consists of one strand made of 14N and one strand made of 15N, where in a tube will the band of DNA form, when centrifuged in a density gradient?
middle
172
In Meselson and Stahl’s experiment, where did the band/s actually appear in the tube after the first round of semi-conservative replication?
the middle
173
In Meselson and Stahl’s experiment, where did the band/s actually appear in the tube after two rounds of semi-conservative replication?
the middle and top
174
If one DNA molecule went through 5 rounds of semi-conservative replication, how many DNA molecules would be produced?
32
2 ^5
175
How many different RNA mononucleotides exist?
4
176
Name the 2 types/theories of how DNA replication takes place that were refuted by Meselson and Stahl’s experiments.
- Fragmentary (dispersive)
- conservative
177
What dictates the unique characteristics of an organism?
their genetic code
178
Define gene
A sequence of bases on a DNA molecule that codes for a specific sequence of amino acids in a polypeptide chain
179
What is the genome?
all the genes in an individual
180
What are purines?
Organic bases with a two ring structure
181
What are pyrimidines?
organic bases with a one ring structure
182
What is the function of DNA ligase?
acts as an enzyme to help close any gaps in the strand that don't have phosphodiester bonds
183
Who carried out the experiment containing light and heavy strand of DNA?
Meselson and Stahl
184
What bacterium did Meselson and Stahl use?
Escherichia coli, E.Coli
185
What is the conservative replication theory?
one DNA molecule has two original strands and one molecule has two 'new' strands
186
What is the fragmentary replication theory?
all DNA strands are made of a mixture of light and heavy DNA/ original nucleotides on new nucleotides
AKA dispersive replication
187
How did Meselson and Stahl separate the DNA?
using centrifugation, a centrifuge
188
How did Meselson and Stahl extract the DNA?
extracted the DNA from the bacteria using detergents
189
Name the product of transcription
mRNA (messenger RNA)
190
Which organic base is never found in mRNA?
Thymine
191
Where in a cell does transcription take place?
Nucleus
192
Which DNA strand, sense or antisense, is the template for making mRNA?
Antisense
193
Name the enzyme which is needed for transcription
RNA Polymerase
194
Does the whole DNA molecule unwind during transcription?
No, only the gene being transcribed
195
Name the sugar found in mRNA
Ribose
196
Is mRNA single or double stranded?
Single
197
Why is the genetic code described as degenerate?
A amino acid can be coded for by several triplet codes
198
If 499 mononucleotides are present in a molecule of mRNA, how many phosphodiester bonds will be present in the polynucleotide chain?
498
199
24% of the bases in a mRNA molecule are adenine, 35% are cytosine and 12% are guanine. What percentage of the bases in the mRNA molecule are thymine?
0%
200
How many template strands are there in transcription?
1
201
Which reaction joins the RNA mononucleotides in transcription?
Condensation
202
48% of the bases in a mRNA molecule are adenine, 32% are cytosine and 10% are guanine. What percentage of the bases in the mRNA molecule are uracil?
10%
203
If these three triplets of bases are found on the DNA antisense strand, which bases will be transcribed into the molecule of mRNA?
TTA CAG AGT
AAU GUC UCA
204
What is the role of RNA polymerase in transcription?
Creates phosphodiester bonds between the mononucluotides
205
What is the role of the antisense DNA strand in transcription?
To act as a template in which mRNA is built
206
Why is the genetic code described as ˋtripletˋ?
Every three bases will code for one amino acid
207
Describe the shape of a tRNA molecule
**clover leaf shaped**
Has an amino acid bonding site on one side and a specific anticodon the the bother side
208
Where in the cell does translation take place?
Cytoplasm at ribosome
209
Name the 4 key organelles/molecules that must be present for translation to take place
- ribosome (top and bottom)
- tRNA
- mRNA
- mononucleotides
210
If a tRNA molecule was hydrolysed, name the monomers that would be released
Mononucleotides
211
On which molecule would you find codons?
mRNA
212
On which molecule would you find anticodons?
tRNA
213
Name the type of bond that forms between a base in a codon and the complementary base of an anticodon
Hydrogen bond
214
How many bases does one codon consist of?
3
215
Name the type of bond that joins the amino acids in translation
Peptide
216
What is the product of translation?
Polypeptide chain
217
What does the ribosome need to attach to before translation can start?
The mRNA molecule
218
If there are 200 codons in a molecule of mRNA, how many amino acids is the polypeptide chain made from the mRNA likely to be made of?
200
219
In the process of translation what is carried by a tRNA molecule?
One specific Amino acid
220
What does the anticodon bind to?
The codon on the mRNA
221
What is determined by the sequence on codons on a mRNA molecule?
The sequence of amino acids in a polypeptide chain
222
Which cell organelle is made of rRNA?
Ribosome
223
How many bases are present in 70 mRNA codons?
210
224
What happens when a ribosome reaches a stop codon on a mRNA?
Can’t bind any new amino acid as there is no complementary tRNA so polypeptide chain is released
It detaches from the mRNA
225
Where is the cell are ribosomes found?
Attached to the endoplasmic reticulum
Forming rough ER
226
Define a **gene**
A section of organic bases in a specific sequence of DNA that codes for a specific sequence of amino acids in a polypeptide chain for a protein
227
Which molecule in the cell contains the genetic code?
DNA
228
Where does the polypeptide chain formed on the ribosome fold into a protein?
The lumen of the endoplasmic reticulum
229
Compare DNA replication with transcription
- Replication copies both DNA strands, transcription copies only one/antisense strand
- Replication makes double stranded DNA, transcription makes single stranded mRNA
- Replication uses the enzyme DNA polymerase, transcription uses RNA polymerase
- Replication uses the base thymine/mononucleotide containing thymine, transcription uses uracil/ mononucleotide containing uracil
230
What is the start codon?
AUG - methionine
231
What is a stop codon also known as?
A chain terminator
232
Define **activation energy**
The energy needed a reaction to occur
By causing bonds to {break / weaken / form}
Reduced by enzymes
233
Are enzymes fibrous or globular proteins?
globular
234
Name two extracellular enzymes which are involved in blood clotting
- thromboplastin
- thrombin
235
What is special about the active site, which makes it specific for a particular substrate?
The shape is specific/complementary to only one substrate. Lock and key model
236
Give one difference between extracellular and intracellular enzymes
Extra cellular enzymes are found and function outside the cell whereas intracellular enzymes are catalyse reactions inside the cell
237
Define **biological catalyst**
A catalyst made by an organism to lower the activation energy of reactions within the organism and to speed up the rate of reactions in the organism.
238
Name the 2 key environmental conditions that affect enzymes
- temperature
- pH
239
What forms as a transition state between the enzyme and substrate at the start of a reaction and the product/s at the end of a reaction?
Enzyme-substrate complex
240
Do enzymes increase or decrease the activation energy for a reaction?
decrease
241
What is similar about an active site and the substrate which fits into it?
They have the same shape/ a complementary shape
242
Name an intracellular enzyme which is involved in DNA replication
DNA polymerase, DNA helicase
243
What happens to an enzyme when it binds substrate in the induced fit theory?
The active site of the enzyme changes shape to conform around the shape of the substrate
244
What is meant by **enzyme specificity**?
A enzyme is specific to a single substrate with an active site specifically shaped to bind and accept that substrate
-Enzyme has an active site with a specific shape which **fits and binds** to the complementary shape of the substrate – lock and key hypothesis to form enzyme-substrate complex, so each enzyme is specific for only one substrate
245
What happens to pancreatic enzymes in a person with cystic fibrosis?
The are blocked by mucus in the pancreatic duct, they damage the pancreas and then are eventually broken down/destroyed
246
Is thrombin an extracellular or intracellular enzyme?
extracellular
247
Where are enzymes made in a cell?
ribosomes and fold in lumen of the endoplasmic reticulum
248
Name the transport process which moves a large quantity of enzymes out of a cell
exocytosis
249
Why would someone with cystic fibrosis be likely to have damaged insulin producing cells?
The digestive enzymes that are stuck in the pancreatic duct start to break down the pancreatic tissue which could result in the insulin producing cells being damaged
250
How would amylase lower the activation energy for the breakdown of starch into glucose?
by providing an alternate reaction route
- The way the substrate fits into the active site may put strain on some bonds so substrate distorted + bonds can be broken more easily
- Active sites can have acidic amino acids which provide an acidic environment or basic amino acids which form an alkaline environment – each of these may be favourable for a specific reaction
251
Name the substrate for the enzyme lipase
fats/trigylceride
252
Is DNA helicase an extracellular or intracellular enzyme?
intrcellular
253
How would you control the pH in an enzyme catalysed reaction?
Buffer solution
254
What is an **enzyme-substrate complex**?
the intermediate stage where the substrate has been bound the the enzymes active site. Where bonds are broken/made. activation energy is lowered
255
How would you control temperature in an enzyme catalysed reaction?
water bath
256
Name the 2 products formed when the enzyme lipase breaks down a triglyceride
- 3 fatty acids
- glycerol
257
Name the 2 products formed when the enzyme lactase breaks down the disaccharide lactose
- glucose
- galactose
258
Describe an **active site**
- specific to the shape of the substrate
- may change shape the mould around the substrate
- is where the substrate binds to an enzyme to be broken down/built up
- small depression with a specific shape to fit the substrate
259
When enzymes are exposed to temperatures above their optimum, what happens to them?
their active site starts to denature, resulting in them eventually becoming inactive
260
Why does the rate of a reaction increase as temperature increases?
The kinetic energy increases so there are more frequent substrate-active site collisions. this means more enzyme-substrate complexes meaning more product formed in given time
261
Why does the rate of an enzyme catalysed reaction decrease over time if a fixed volume of substrate is added at the start and no further substrate is added during the reaction?
Substrate eventually runs out as it is used up in the reaction
262
What makes an enzyme soluble in water?
the many polar r-groups on the outside of the protein
263
Which bonds may be present in the tertiary structure of an enzyme?
- hydrogen
- ionic
- disulphide
264
What happens to the rate of an enzyme catalysed reaction, as the enzyme concentration increases (assuming there is excess substrate)?
the rate of reaction increases proportionally
265
How would you measure the rate of an enzyme catalysed reaction if one of the products is a gas?
By collecting the gas in a gas syringe/measuring cylinder
266
Which part of an enzyme makes it specific for a particular substrate?
its active site
267
What is the difference between a **biological catalyst** and a chemical catalyst?
a biological catalyst is made by the organism to be used to speed up reactions in the organism, chemical catalyst is not
268
Where would you find hydrophobic amino acids in and enzyme?
On the inside/centre
269
Which parts of amino acids are joined by bonds in the enzyme tertiary structure?
the r-groups
270
What are the main types of mutation?
- point mutation (substitution)
- deletion
- duplication (insertion)
- inversion
271
What is a germ line mutation?
Occurs in the DNA of an ovary or testis cell that is dividing to form an egg or sperm
- passed on to future generations
- present in every cell
272
What is a somatic mutation?
A mutation that happens in all cells but gametes
- will die with the individual
- happens after conception
273
What is the process when the mucus is too watery?
- Na ions are actively pumped across the basal membrane
- Na diffuses through sodium channels in the apical membrane
- Cl diffuses down electrical (electrochemical) gradient through the gap junction
- water is drawn out of cells due to high solute concentration in tissue fluid
- water is drawn out of the mucus into the epithelial cell by osmosis
274
What is the process when the mucus is too sticky?
- Cl ions are transported via facilitated diffusion across the basal membrane
- Cl ions diffuse through open CFTR channels
- Na ions diffuse down the electrochemical gradient through the gap junction into the mucus
- high solute concentration in mucus draws water out of epithelial cells
- water is drawn j to the cell from tissue fluid by osmosis
275
What happens to the mucus if the CFTR is missing/non-functional?
Cl ions are pumped into the cell so solute increases. Na ions are continuously pumped out of the mucus through the permanently open Na channel. Water is continuously removed from the mucus by osmosis
276
What happens as a result of a mutation?
A change in the base sequence of DNA leads to different triplet/codon created leads to different R-group, different folding, different 3D specific shape. Leads to no function, no/faulty protein
277
What systems does CF effect?
Respiratory, digestive, reproductive
278
What is ficks law?
Rate of diffusion= (surface area X difference in conc)/thickness of gas exchange surface
279
How does CF cause problems in the lungs?
The sticky mucus is too difficult for cilia to move so the trapped pathogens stay. Increasing risk of infection. The extra mucus also increases the diffusion distance. The mucus can also cause blockages which reduces surface area
280
What problems does CF have on the digestive system?
The pancreatic duct becomes blocked by the sticky mucus, reducing digestive enzymes. This can lead to malabsorption syndrome. The pancreatic tissue can become damaged and insulin producing tissue due to the build up of enzymes leading to hard fibrous cysts
281
What is the effect or CF on the reproductive system?
Female: a mucus plug will develop in the cervix, impairing fertilisation rates
Male: vas deferens can be missing or can be blocked by mucus impairing the release of sperm
282
How are the lungs adapted for gas exchange?
- large surface area- lots of alveoli
- short diffusion distance- capillary and alveoli walls are thin
- steep concentration gradient maintained by ventilation and circulation
283
Enzymes are also known as...
biological catalysts
284
What is a catabolic enzyme?
An enzyme that breaks down large molecules into smaller units
285
What is an anabolic enzyme?
An enzyme that builds up substrates into a larger molecule
286
What is an isomerase enzyme?
An enzyme that does not build up or break down the substrate is simply altered
287
What is the initial rate of reaction?
the first rapid phase of the reaction that is used for comparison across enzyme controlled reactions
288
What is the saturation point?
The point where there is a limiting factor
289
What is the definition of a gene?
a sequence of bases on a DNA molecule that codes for a sequence of amino acid in a polypeptide chain
290
Define **locus**
the position of a particular gene pair on each of the chromosomes
291
Define homologous chromosomes
the chromosomes in a chromosomal pair
292
define **allele**
An alternative form of the same gene
found at the same locus on a chromosome
293
What is a genotype?
The combination of all alleles for one gene of the person
294
What are homozygous genotypes?
When both alleles are dominant/recessive
295
What are heterozygous genotypes?
When one allele is dominant and one is recessive
296
What is a phenotype?
The genotype that is expressed (the characteristic)
297
What is a dominant allele?
The allele that is always expressed
Will effect the phenotype of heterozygotes AND homozygotes
298
What is a recessive allele?
The allele that will only effect the phenotype of a homozygote
299
Carriers of CF have protection against what?
Typhoid
300
Define **monohybrid inheritance**
The inherited characteristic is controlled by only one gene
301
Define **incomplete dominance**
When neither allele is dominant and heterozygotes have an intermediate phenotype
- both alleles have an equal weighting in the expression
302
Define genetic testing
Identifying the abnormal allele of the gene in the DNA of any cells
303
Define genetic screening
Confirming the results of conventional tests to identify carriers and also to diagnose mutation in an embryo/foetus
304
What are the possible sources used for genetic testing?
- cheek cells and white blood cells from parents
- cells directly from a foetus or embryo
305
What are the 3 ways to test an embryo?
-Amniocentesis
- Chorionic villus sampling
- Non-Invasive prenatal Diagnosis (NIPD)
306
What is Amniocentesis?
Procedure: a needle is inserted into amniotic fluid to collect foetal cells that have fallen of the placenta or foetus
Time Frame:15-17 weeks
Risk: 1%
307
What is Chorionic villus sampling?
Procedure: small sample of placental tissue is removed, through wall of abdomen or vagina
Time Frame: 8-12 weeks
Risk: 1-2%
308
What is NIPD?
Procedure: analyses DNA fragments in the mothers blood plasma during pregnancy
Time Frame: 7-9 weeks
Risk: None
309
What is PGD?
testing before implantation
happens when there is a family history of a serious genetic condition
Procedure: couple undergo IVF so that embryo can be tested before transfer to the uterus- an early embryo can have a cell removed without causing harm
310
What is **autonomy**
the idea that people can make up there own minds about things but have a duty to take into account how their actions might affect others
311
Define co-dominance
When neither allele is dominant so BOTH phenotypes are FULLY expressed
312
How many separate strands of DNA are there?
46
313
What happens after cells for genetic testing have been collected?
The DNA is extracted and analysed to detects defective gene mutation
