Unit 2 Module 1 continued

2.1.15 Nucleotides coding molecules

Nucleic acids in living

organisms

What does DNA stand for?

Where is DNA found in a human cell?

Nucleotides are monomers of

nucleic acids

Which three components make up a

nucleotide?

What type of reaction links these

together?

Nucleotides common

features

List the five nitrogenous bases found in

nucleotides.

Draw and label a simple diagram of a

nucleotide.

Joining nucleotides together

Which parts of two consecutive

nucleotides attach to each other?

What forms the backbone of a nucleic

acid?

Which groups will be left over at either end of the polymer?

From nucleotides to nucleic

acids

What is the identity of the sugar

molecule in DNA and RNA? DNA: RNA:

Organic bases are either Which bases are purines and which are Adenine: Cytosine: Uracil:

purines or pyrimidines pyrimidines? Thymine: Guanine:

2.1.16 DNA information storage

DNA is a stable

polynucleotide

How many polynucleotide strands create one DNA molecule?

What holds these polynucleotides together?

Why is it important that DNA is a stable molecule?

Hydrogen bonding

and base pairing getting it right

What does antiparallel mean?

What are the base pairing couplets in DNA?

Each polymer strand does not lie flat, but coils up into what

shape?

The two chains twist around each other, giving what final shape to a DNA molecule?

Making copies

Francis Crick, co-discoverer of DNA

Describe the sequence of events which occur when a DNA

molecule is replicated.

1)

2)

3)

4)

Why is DNA replication described as semi-conservative?

Which part of the DNA molecule contains the genetic code?

Fill in the sequence of bases which would be found on this

DNA strands complementary strand. T-T-C-C-G-A-C-A-G-T

If the top strands sugar-phosphate backbone runs from left to right, which way does the other ones run?

If 17% of a DNA molecules bases are thymine, what

percentage are cytosine?

2.1.17 Reading the instructions

RNA is different

Give two ways in which the structure

of RNA monomers differs from the structure of DNA monomers.

How is the structure of the final RNA molecule different to a DNA molecule?

The base-pairing rules apply

What are the base pairing couplets in

RNA?

Which base never appears in RNA?

Give the sequence of RNA bases that is complementary to this DNA strand.

DNA: A-T-T-A-G-A-C-C-G-T-G RNA:

Three forms of RNA What are the three types of RNA?

What are the instructions for?

What do the sequences of bases on

DNA code for?

What does the term gene mean?

Explain the functions of the three types of RNA in protein synthesis.

mRNA:

rRNA:

tRNA:

Place the following statements in the

order which correctly describes the

sequence of events which leads to protein synthesis.

1. An mRNA strand is formed through base pairing. 2. tRNA leaves the ribosome.

3. mRNA attaches to a ribosome.

4. The amino acid joins the growing polypeptide chain. 5. The gene for a particular protein is exposed.

6. The DNA double helix is unzipped.

7. The ribosome moves along the mRNA strand. 8. tRNA holding an amino acid attaches to the ribosome.

9. The new strand leaves the nucleus.

Quick quiz True or false?

1) Uracil is a purine. 4) Purines break down into uric acid, which causes gout.

2) Cytosine is complementary to guanine. 5) Nucleic acid bases always contain nitrogen. 3) The two strands of a DNA molecule are identical. 6) Ribose is a six carbon sugar.

2.1.18 Enzymes are globular proteins

All enzymes are proteins

Glyoxalase 1

A short recap: define the following terms.

Substrate:

Globular

Hydrophilic:

Secondary

Why are enzymes described as specific?

What feature of an enzyme allows it to bind to its substrate?

The active site is a tiny part

of an enzyme

What is the job of most amino acids in an enzyme?

What is an enzymes active site?

Catalysts in nature What is a catalyst?

Why are enzymes often used as industrial catalysts?

Substrate and product Write down a word equation for the reaction catalysed by

lactase.

?

2.1.19 Inside and out where enzymes work best

Organisms vary considerably What types of conditions might change

the shape of a protein?

Enzymes and endotherms Why is regulating body temperature worthwhile for birds and mammals?

Nutrition and digestion enzyme locations

What is a heterotroph?

What is the difference between intracellular and extracellular

enzymes?

Even autotrophs (organisms which dont need to digest) contain enzymes.

Why might this be?

Enzymes and protection

Why do white blood cells contain enzymes which can break down

substances?

What are white blood cells digestive enzymes contained in?

2.1.20 Enzyme action

Falling apart and staying

together

Draw a diagram showing the activation energy

for a reaction.

What is the reason for boiling non-reducing

sugars in acid, when testing for their presence?

How do enzymes increase the rate of a reaction?

From one stable molecule to

another Why do cells need enzymes in order to live?

Not just shape more about fit

Why is enzyme action compared to a lock and key?

What happens after the key has entered the

lock?

Holding it all together the induced fit hypothesis

Carbonic anhydrase, an enzyme in blood

How is the substrate held in place within the

active site?

What name is given to the enzyme while its

substrate is bound?

Why do the products leave the active site?

What is the name for this theory of enzyme

action?

A carbonic anhydrase molecule takes about one s (microsecond) to catalyse its reaction. How

many reactions would be catalysed per minute

by 1000 enzyme molecules?

2.1.21 Enzymes and temperature

Heat and kinetic energy

When a substance is heated, what

happens to the kinetic energy of its molecules?

What two effects does this have on collisions between molecules?

So what effect does heat have on

enzyme activity?

Heat, vibration, breaking

bonds and denaturation

Why can heat break bonds within an enzyme?

What happens if an enzymes bonds begin to break?

Why does this impair the enzymes

activity?

What is the name of this process?

Speeding up and slowing down optimum temperature

What is the meaning of the term optimum temperature?

In what type of habitat might an organism need enzymes with

particularly high optimum

temperatures?

How might those enzymes differ from

normal ones to cope with the

temperature?

On the reverse of this sheet, plot a graph using the data on the next page, and determine what the optimum temperature of this

enzyme is:

Temperature / C Rate of reaction / mol product

formed per minute

0 0

10 5

20 19

30 40

40 58

50 31

60 3

2.1.22 Enzymes at work pH effects

What is pH? What does pH measure?

What pH range is acidic?

pH and bonds

What are hydrogen ions attracted to?

How can hydrogen ions alter the shape of an enzyme?

pH and active sites How will hydrogen ions interfere with

substrate binding to the active site?

Optimum pH varies between enzymes

Why does a change from the optimum pH affect the rate of a reaction?

pH and location What is the optimum pH for the

enzyme pepsin?

A UV spectrometer can be used to measure the rate of a reaction. The products of some reactions absorb UV light by recording how quickly this absorbance changes, the spectrometer can calculate how quickly the concentration of the product is changing. This produces data like that in

the table to the left.

2.1.23 Enzymes at work concentration effects

Increasing the substrate concentration

In figure 1, why does increasing the

substrate concentration above a certain level no longer increase the

rate of reaction?

Why is it important to only record the initial rate of reaction?

Increasing the enzyme

concentration

Describe the sequence of events which

occurs when enzyme concentration is

increased for a fixed concentration of substrate.

1)

2)

3)

Initial reaction rate

What happens to the reaction rate as

the reaction proceeds?

When should the reaction rate be measured in order to give fair results?

Limiting factors Define the term limiting factor.

Enzyme and substrate

concentrations in cells

Why can enzymes be kept at much

lower concentrations than substrates?

How might a cell reduce an enzymes activity?

2.1.24 Enzymes at work inhibitors of action Inhibitors of enzyme-

controlled reactions What is an enzyme inhibitor?

Competitive inhibitors

Ampicillin is a competitive inhibitor

of bacterial enzymes

How do competitive inhibitors work?

How can competitive inhibition be overcome?

How does this work?

Non-competitive inhibitors

How do non-competitive inhibitors differ from competitive ones?

How do non-competitive inhibitors

reduce enzyme activity?

What effect will increasing the

substrate concentration have on the

rate of reaction?

How might you test whether an

inhibitor is competitive or non-competitive?

Why might non-competitive inhibitors

be deliberately produced by the cell?

Permanent inhibitors How do permanent inhibitors differ from reversible inhibitors?

2.1.25 Enzymes at work coenzymes and prosthetic groups

Enzymes shaping up

What is a cofactor?

What three types of cofactor exist?

Coenzymes

The iron-containing haem group is a

vital part of haemoglobin

Where do coenzymes bind to their enzyme?

How are coenzymes similar to

substrates?

How are coenzymes similar to

enzymes?

Why is vitamin B3 essential for human

health?

What is a prosthetic group?

What can prosthetic groups contribute to a protein?

Which metal ion is vital to the

function of carbonic anhydrase?

What is the purpose of the reaction catalysed by carbonic anhydrase?

How can inorganic ions affect reaction rates?

What two features of an enzyme can

inorganic ions affect?

Which halide ion is vital to the

function of amylase?

2.1.26 Interfering with enzymes poisons and drugs

Deadly poisons

Why is potassium cyanide deadly?

Would increasing the concentration of

oxygen a patient breathed save them from

cyanide poisoning? Explain your answer.

Replacement enzymes and cystic fibrosis

Why are enzyme tablets prescribed to cystic

fibrosis sufferers?

Why must these tablets resist acid?

Ethylene glycol poisoning

Ethanol and ethylene glycol.

Competitive inhibitors often have similar shapes to the substrates

they inhibit.

Where is ethylene glycol found?

Why is it dangerous?

What is given as a treatment for ethylene

glycol poisoning?

How does this help?

Snake venom an enzyme and

toxin cocktail

List four components of snake venom and explain how they help the snake kill its

prey.

1)

2)

3)

4)

Quick Quiz True or False?

1. Enzymes increase reaction rate by increasing the stability of the products. 2. Competitive inhibitors have a similar shape to an enzymes substrate. 3. Higher hydrogen ion concentration gives higher pH readings. 4. Increasing enzyme concentration increases reaction rate. 5. The pH of the human stomach is around 2. 6. Prosthetic groups are polypeptides. 7. Carbonic anhydrase converts CO2 to carbonic acid. 8. Heat is a measure of the kinetic energy of a substances molecules.

?

2.1.27 Investigating enzyme action 1

What can we investigate? How can you measure the rate of an

enzyme-catalysed reaction?

Dependent and independent

variables

What is the difference between

dependent and independent variables?

If you record the rate of a reaction at different pH levels, which variable is

dependent?

What can you do to the independent variable to increase the accuracy of

your results?

What needs to be controlled?

In an enzyme-catalysed reaction, which variables are particularly important to

control?

What is the best way to regulate temperature?

Why is using enzyme in living tissue

less accurate than using purified enzyme?

How can pH be regulated?

Timescales, rate and control

tests

Why might using high enzyme

concentrations make getting accurate

results difficult?

What is the relationship between time

and reaction rate?

Which variable always goes on the y-axis of a graph?

What is the purpose of a control test?

2.1.28 Investigating enzyme action 2

Following an enzyme-

controlled reaction

Why is it best to record the initial rate

of reaction?

How can you do this?

Sketch a graph and label it to show how you would measure the initial rate

of a reaction.

How do you calculate the gradient of a

tangent?

Examples of enzyme investigations

Write a method for an investigation

into the effect of pH on amylase

activity.

2.1.29 Enzymes and metabolism an overview

Catalytic power Why is it vital to control the power of enzymes?

Control of metabolic sequences

Explain how end-product inhibition works.

Some enzymes are crucial to

life

Why is ATP synthase vital for life?

Write a word equation for the conversion of ADP to ATP.

Inborn errors of metabolism

What is the cause of problems with the bodys proteins?

Which protein does not work correctly

in sufferers of phenylketonuria (PKU)?

If undiagnosed, what does this

condition lead to?

Phenylalanine is an essential amino acid. How might this affect the way

PKU sufferers are treated?