Thread of Life Revision: OCR B salters

A revision booklet addressing all the points in the specification in sufficient detail. Some diagrams and mechanisms/structures may need to be drawn out, All of which can be found in revision guides, the OCR chemical ideas text book, exam datasheets or the chemical storylines textbook!

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How To Use this Booklet:
This booklet has been created by addressing all the points on the OCR B
salters specification for the section, what's in medicine. I advise reading
through the Book, highlighting or underlining words written in ALL
CAPITALS. I also suggest making a spider diagram or mind map to
summarise key points and help the information here stick in your mind. You
could also draw your own images by points on this book that may help you
to remember that point.…read more

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Use empirical rate equations of the from: rate = K[A]m [B]n where m
and n are integers. Carry out calculations based on the rate equation and
understand that the rate constant K increases with increasing
temperature.
SEE QUESTIONS FOR 10.3 FOR THIS SECTION!!!!
B) Describe the Characteristics of of enzyme catalysis including
specificity, temperature sensitivity, pH sensitivity and inhibition.
Enzymes are SPECIFIC because they have a precise tertiary structure which
exactly matches the structure of the SUBSTRATE- the molecule that is reacting.…read more

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Enzyme Kinetics:
Step1: E + S ES (intermediate)
Step 2: ES E + P
At LOW substrate concentrations, step ONE is the rate-determining step. Thus
the reaction is FIRST ORDER with respect to both enzyme and substrate.
However, enzymes are molecules with a large Mr so their molar concentrations
can be very small. As the substrate concentration rises, it becomes very much
greater than the enzyme concentration. The enzyme is then said to be
SATURATED with all the active sites occupied i.e.…read more

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Amino acids are BIFUNCTIONAL molecules- they contain both the amino (-NH2)
and carboxyl (-COOH) functional groups. When these functional groups are
attached to the same carbon atom, the amino acid is called an ALPHA ( )
AMINO ACID.
For all amino acids (EXCEPT GLYCINE for which R=H), -amino acids have four
different groups attached to the -carbon, so they can exhibit OPTICAL
ISOMERISM. A carbon with 4 different side groups attached to it are called
CHIRAL CARBONS.…read more

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When several amino acids are joined together in this way, a POLYPEPTIDE is
formed. PROTEINS are naturally occurring condensation polymers formed
when many amino acids join together!
Hydrolysis
When a peptide link or protein s REFLUXED with MODERATELY
CONCENTRATED ACID OR ALKALI for several hours, the C-N bond in the
peptide link is BROKEN. Under acidic hydrolysis conditions, the ­NH2 groups
are protonated to give ­NH3+ , whereas under alkaline hydrolysis conditions
the -COOH deprotonates to give ­COO-.…read more

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Sensitive to pH: pH affects the ratio of ­COO- to NH+ present in R groups. Small
changes of pH can affect the charges of the R groups present in the active site
itself, resulting in a decrease in activity. A change of pH of more than 2 units
causes the tertiary structure of the enzyme to break down, with the loss of the
active site. This is called DENATURATION.…read more

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Explain, using the structures in the Date Sheets, how phosphate units
join with deoxyribose to form the phosphate-sugar backbone in DNA.
The four bases present in DNA join by condensation with the
deoxyribose in the phosphate-sugar backbone. Two strands of DNA form
a double-helix structure through base pairing
DRAW OUT DIAGRAM FROM CHEMICAL STORYLINES PAGE 47.
(iii) Understand that various models were devised before the currently
accepted version was formulated.
Look up Rosalind Franklin, Linus Pauling and James Watson and Francis Crick.…read more

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L)Using the structures on the Data Sheets, describe and explain the
significance of hydrogen bonding in the pairing of bases in DNA, and
relate to the replication of genetic information; use the diagram on the
data sheet to explain how DNA encodes for an amino acid sequence in a
protein.
Chemists have found that the base pairing in DNA enables it to do two things:
One strand, with the aid of enzymes, can synthesise a complementary
copy of itself (i.e.…read more

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CYSTOSINE and GUANINE (C & G)
(M) Understand that DNA analysis can be used for `genetic
fingerprinting'; discuss the ethical issues of using and storing data from
human DNA analysis.
DNA DATABASES Since DNA is different in every individual (except identical
twins), DNA sequences can be used to identify individuals. A trace of blood,
skin or semen is all that is needed to extract the required DNA.
FOR: 1) Databases are useful in solving crimes now and in the future.…read more

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