Download Respiration releases chemical energy from organic

A2 Unit BY4: Metabolism, Microbiology and Homeostasis
Name:
Date:
Topic 4.2 Respiration Releases Chemical Energy From Organic Molecules – Page 1
From the syllabus:
Respiration releases chemical energy from organic molecules
(a) All living organisms carry out respiration in order to provide energy in the cell.
(b) Glycolysis as a source of triose phosphate, pyruvate, ATP and reduced NAD. The formation of
acetyl CoA. (The names of intermediates are not required.)
(c) The Krebs cycle as a means of liberating energy from carbon bonds to provide ATP and reduced
NAD with release of carbon dioxide. The role of reduced NAD as a source of electrons and protons for
the electron transport system. The energy budget of the breakdown of glucose under aerobic and
anaerobic conditions. Fat and amino acid utilisation.
Suggested Practical Activities: Demonstration of dehydrogenase activity using artificial hydrogen
acceptors, as illustrated by methylene blue or DCPIP or tetrazolium compounds.
l. Respiration
Completed
1.
2.
3.
Start of topic checklist for RESPIRATION RELEASES ENERGY FROM ORGANIC COMPOUNDS
Tick as appropriate:
RED: I do not know about this
AMBER: I have heard about this but have not learned this yet. I am unsure on this.
GREEN: I have heard about this and I have learned this. I am confident about this.
Topic
1. Respiration is a series of enzyme-catalysed reactions
which release chemical energy from organic molecules
in order to synthesise ATP.
2. The four main stages of the breakdown of a glucose
molecule to carbon dioxide are: glycolysis, link reaction,
Krebs cycle and electron transport chain.
3. Glycolysis is the phosphorylation of glucose, the
splitting of the 6C hexose phosphate formed into two
3C triose phosphate molecules and the oxidation of
each of these to 3C pyruvate with a small yield of ATP
and reduced NAD.
4. Glycolysis takes place in the cytoplasm and does not
require oxygen.
5. The link reaction involves the conversion of pyruvate to
acetate as a result of the loss of carbon dioxide followed
by the removal of hydrogen by the reduction of NAD
(oxidative decarboxylation); the acetyl then combines
with co-enzyme A. The link reaction takes place in the
matrix of the mitochondrion.
6. Each acetyl co-enzyme A enters the Krebs cycle, the coenzyme A is regenerated and the acetate fragment is
picked up by a 4C acid, to produce a 6C acid.
7. The Krebs cycle is a series of decarboxylations (removal
of carbon) and dehydrogenations (removal of hydrogen)
where the acetate fragment from the glucose molecule
is completely broken down and the 4C is regenerated
via 6C and 5C intermediates.
8. The function of the krebs cycle is a means of liberating
energy form carbon bonds to provide ATP and reduced
NAD (and FAD), with the release of carbon dioxide.
9. Reduced NAD (and FAD) deliver hydrogen to the
electron transport system in the inner mitochondrial
membrane so acting as triggers for this system.
10.Be able to describe the production of ATP via the proton
pump mechanism.
11.Define the terms aerobic and anaerobic respiration.
12. Understand the role of oxygen as the final electron
acceptor in the electron transport chain and explain the
formation of water.
13.Without oxygen the reduced NAD (and FAD) cannot be
reoxidised and therefore made available to pick up
more hydrogen, so under anaerobic conditions the link
reaction and Krebs cycle cannot take place.
14.Under anaerobic conditions glycolysis can take place as
the NAD transfers the hydrogen to pyruvate to form
lactate in animals and ethanol and carbon dioxide in
plants and Fungi, but there is only a small yield of ATP.
RED
AMBER
GREEN
15.Know the number of ATP molecules produced in each
stage of respiration and therefore the total for the
complete oxidation of glucose.
16.Not all the energy of the glucose molecule is captured in
ATP and there is a loss of heat energy.
17.Under certain conditions fats and proteins can be used
as respiratory substrates.
18.Glycerol is converted to a 3-carbon sugar which enters
the Krebs cycle via triose phosphate.
19.Long fatty acid chain molecules are split into 2C
fragments which enter the pathways as acetyl coenzyme A.
20.Proteins are broken down into their constituent amino
acids which are deaminated with the removal of the
NH2 group. This leaves an organic acid that can be fed
into the Krebs cycle.
21.Be able to describe and recognise similarities in
mitochondrial and chloroplast membranes in terms of
providing a proton gradient: proton pumps, ATP
synthetase, electrochemical gradient with high energy
electrons fuelling the pump.
A nucleotide is the basic unit or monomer from which nucleic acids are formed.
The nucleotide of DNA consists of three parts:

Deoxyribose (a pentose sugar)
What does ‘a pentose sugar’ mean?

Phosphate group (H3PO4)
What three elements does a phosphate group contain?

An organic nitrogen containing base.
If the base is described as ‘organic’ and nitrogen containing, what 2 elements must it
contain?
The three shapes shown by each of the parts are usually used when drawing a simple
diagram of DNA structure.
The deoxyribose sugar, phosphate group and organic base are joined together as shown
below to form a nucleotide.
A DNA nucleotide.
Label the three parts of the DNA nucleotide shown above.
All DNA nucleotides contain a phosphate group, deoxyribose sugar and organic base but they
do not all have the same base. Four different bases are found adenine, thymine, cytosine
and guanine.
The names of these four bases are usually abbreviated to the letters A, T, C and G. These 4
letters form the bases of the genetic code.
Pick one of the four bases and draw a nucleotide (using the shapes as described above) with
that base attached in the box below:
DNA nucleotides can be joined together to from a polymer, a polynucleotide.
This reaction produces water and is known as a __________________________ reaction.
Below is a simple diagram showing the polynucleotide structure of a single strand of DNA.
Between which 2 parts of the nucleotide (monomer) have
bonds been made in order to form a polymer molecule?
____________________________________________
A covalent bond forms between these 2 parts. What does a
covalent bond mean?
____________________________________________
Label all the parts on the diagram where there is a covalent bond.
We describe the structure as having a ‘sugar-phosphate backbone’.
This sugar phosphate backbone is very strong, it is a lot easier to
break the hydrogen bonds holding the base pairs together in DNA,
than it is the bonds between the sugar and phosphate group.
The structure of DNA is in fact a ‘double helix’, with two strands of polynucleotides (polymers
of nucleotides) antiparallel to one another (one runs in one direction and the other in the
opposite direction), these two strands are then twisted to form a helix. The two strands are
held together by hydrogen bonds that form between the organic nitrogen containing bases.
This creates an effect that looks like a ladder.
Hydrogen bonds can only form between adenine and thymine; and between guanine and
cytosine.
This is known as complimentary base pairing.
On the diagram above label the following;
 A deoxyribose sugar.
 A nitrogenous base.
 A hydrogen bond.
 The sugar-phosphate backbone.
DNA has two major functions – it needs to be replicated during the S stage of interphase
in preparation for mitosis or meiosis and contains genes, genes contain the information for
synthesizing proteins.
RNA.
Cells also contain another polynucleotide called
RNA (Ribonucleic acid). It has a number of
similarities and a number of differences with DNA.
Look at the diagram to the right and see if you can
list some of the similarities and differences in the
table below.
Differences
DNA
RNA
Similarities
There are three types of RNA. Messenger RNA (mRNA), Ribosomal RNA (rRNA) and Transfer
RNA (tRNA). Find out the functions of each type.
Type of RNA
Function
mRNA
tRNA
rRNA
Identify and label the three types of RNA below:
Organic bases are put into categories. Adenine and guanine are purine bases and thymine
and cytosine are pyrimidine bases.
Look at the diagram on the previous page.
How many carbon ring structures do pyrimidine bases contain?
How many carbon ring structures do purine bases contain?
This means that only a pyrimidine paired with a purine will fit in the space between the
sugar phosphate backbones.
Therefore adenine always pairs with _____________
And guanine always pairs with__________________
Looking at the diagram state how many hydrogen bonds form between:
Adenine and Thymine ___________________
Guanine and cytosine ____________________
Colour code the diagram: Pentose sugar
Hydrogen bonds
Pyrimidines
Purines
Blue
Yellow
Green
Red
DNA quiz
(The letter before each clue is the first letter of the answer - write the
answer in the space below each clue)
A.
The partner organic base to thymine in DNA. (7)
C.
The partner organic base to guanine. (8)
D.
Name of the sugar found in DNA. (11)
D.
Name given to the double stranded, twisted coil of two DNA molecules. (6) (5)
H.
Type of bonds holding together chains of DNA. (8)
N.
Charge carried by nucleic acid molecules. (8)
N.
DNA and RNA are both types of these. (7) (5)
N.
Each DNA molecule is made up of a chain of these. (11)
O.
Number of chains of nucleotides making up an RNA molecule. (3)
P.
Types of organic base made up of two rings of carbon and nitrogen atoms. (7)
P.
Types of organic base made up of a single ring of carbon and nitrogen atoms.
(11)
R.
Place in the cytoplasm where amino acids are assembled. (9)
U.
The partner organic base to adenine in RNA. (6)