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Biology AS Level OCR A Revision Notes (full AS course - new spec for 2017)£2.50
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Title: AS BIOLOGY B (2015) TOPICS 1 AND 2 ANSWERS
Description: These notes are appropriate for students in year 12 and 13 studying the new A LEVEL BIOLOGY B as of 2015 (pearson qualification). They cover all the answers needed to pass your A level biology exams. These answers are best paired with the questions document that is available separately on my account and helps students to self-test and self-check with the answers for optimal learning and memory recall. Please see other uploads for the remainder of the topics within this A level. Good luck!
Description: These notes are appropriate for students in year 12 and 13 studying the new A LEVEL BIOLOGY B as of 2015 (pearson qualification). They cover all the answers needed to pass your A level biology exams. These answers are best paired with the questions document that is available separately on my account and helps students to self-test and self-check with the answers for optimal learning and memory recall. Please see other uploads for the remainder of the topics within this A level. Good luck!
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TOPIC 1+2
EDEXCEL BIOLOGY
AS LEVEL
Topic 1: Biological molecules:
Questions and answers
1
...
Disaccharides?
Molecule containing two sugars
3
...
What are the types of monosaccharides?
Hexose e
...
glucose C6H1206, pentose E
...
ribose and deoxyribose and ribose
5
...
What is the structure of (hexose sugar) alpha glucose, beta glucose and pentose ribose (and
deoxyribose)
Alpha- -OH group (down, down, up, down)
© 2015 Produced by Zsara Finch
Beta- -OH group (up, down, up, down
...
How are disaccharides/polysaccharides formed?
Through concentration reactions
8
...
Explain the structure and function of glucose, starch, glycogen and cellulose
...
Hexose sugar= C6H1206
...
Energy supplier
...
Alpha glucose units, 1-6 glyosidic bonds
causing side branches so glucose is released quickly in active tissues
...
Cell wall in plants- very strong
...
What is an ester bond?
Formed in a condensation reaction (esterification) with a carboxyl group of a fatty acid and one
hydroxyl group of glycerol
11
...
12
...
13
...
What is an unsaturated lipid?
One double bond= monounsaturated fatty acid
2+ double ponds =polyunsaturated fatty acid
© 2015 Produced by Zsara Finch
2
TOPIC 1+2
EDEXCEL BIOLOGY
AS LEVEL
15
...
Fats store x3 energy than carbohydrates
...
Insulation: fatty sheath insulates nerve impulses so electrical impulses travel further
...
Fat has a low density, causing some organisms to float
...
How are phospholipids formed?
When glycerol combines with a phosphate group instead of a fatty acid by esterification
...
What do phospholipids contain?
Phosphate and glycerol
...
What is formed when hydrophobic tails are in the air and hydrophilic tails are in the water?
Monolayer
19
...
20
...
21
...
22
...
They join by a condensation reaction and a water molecule is lost
Peptide bonds form when 2 amino acids form (dipeptide)
R group isn’t involved
Polypeptide chains form, when folded, this becomes a protein
...
What are the roles of hydrogen, ionic and disulphide bonds in the structure of proteins?
Hydrogen bonds form by negative changes on the oxygen atom of the carboxyl group and
positive charges on hydrogen atom of amino groups
...
Disulphide bonds form when two cysteine molecules are close together in a polypeptide
...
They are strong, but less occurring
...
24
...
© 2015 Produced by Zsara Finch
3
TOPIC 1+2
EDEXCEL BIOLOGY
AS LEVEL
25
...
g
...
26
...
g
...
27
...
Most
common structural protein among animals
...
Hydrogen bonds
...
28
...
What is the difference between pyrimidines and purines?
Pyrimidines contain only one nitrogen containing ring whereas purines contain two
...
Purines consist of adenine and guaumine
...
How is DNA replicated?
Semi-conservatively
31
...
32
...
What does this model assume?
Assumes that DNA unzips and new nucleotide align along each strand
...
34
...
What is a gene?
A sequence of bases on a DNA molecule coding for a sequence of amino acids in a polypeptide
chain
36
...
What is the structure and role of TRNA?
found in cytoplasm
‘clover leaf’ complex shape
Hydrogen bonds between different bases
The anticodon- 3 bases expose to attach to mRNA at the ribosome
38
...
Triplets codes for 3 bases
Not all genome codes for proteins- lots are non-coding
...
What are the stages of protein synthesis?
40
...
What is a point mutation?
change in one/small number of nucleotides affecting a single gene
42
...
43
...
A change in one base in one codon changes a single amino acid in a chain of 147
amino acids, altering nature of proteins
...
44
...
45
...
© 2015 Produced by Zsara Finch
6
TOPIC 1+2
EDEXCEL BIOLOGY
AS LEVEL
46
...
47
...
48
...
49
...
50
...
51
...
What is a catabolic reaction?
Reaction that breaks down substances in a cell
53
...
What are extra-cellular enzymes?
Enzymes that catalyse reactions within the cell in which they were made
...
What is molecular activity?
Number of substrate molecules transformed per minute by a single enzyme molecule
56
...
57
...
This is
because kinetic energy increases and therefore collisions between molecules increases
...
pH affects the ionic bonds that holds protein molecules in shape
...
g
...
pH increases rate of reaction at optimum point
...
58
...
59
...
60
...
What is the cell theory?
Unifying concept that states that cells are a fundamental unit of structure, function and
organisation in all living organisms
...
What are complex organisms made up of and how are they organised?
Tissues- a group of similar cells- Organs- groups of different tissues- organ systems- organs
working together
...
What are prokaryotic cells made up of and what are their functions?
Nucleoid: contains DNA
Plasmids: small circular DNA
70S ribosomes: site of protein synthesis
Cell wall: supports and controls cell
4
...
S- synthesis of lipids and steroids
...
Golgi apparatus: modifies proteins synthesised in the cell
...
What are the different parts of the mitochondria?
6
...
What does it mean to be Gram positive/Gram negative and how can they be tested and
why?
Bacteria cells can be gram positive or gram negative
...
This is because gram positive bacteria have a thick outer layer of peptidoglycan, which absorbs
stain
...
The outer membrane
protects these bacteria from antibiotics e
...
penicillin
...
What do antibiotics do?
Some affect the bacteria cell walls, cell membrane and genetic material, enzymes or the
ribosomes
...
g
...
© 2015 Produced by Zsara Finch
9
TOPIC 1+2
EDEXCEL BIOLOGY
AS LEVEL
Mostly successful with gram positive bacteria, however there are some that effect the
phospholipid membrane in gram negative bacteria, however they do have serious side effects
...
What is the magnification equation?
Magnification = size of image /actual size of the object
10
...
11
...
Why is staining specimens important?
Highlights specific parts of a cell
13
...
What is the classification of viruses based on? Give examples
Based on their structure and nucleic acid types
...
What is lytic cycle?
a virus attaches to a receptor on a host cell
The virus injects its RNA/DNA into the cell
The viral DNA uses the hosts enzymes and ribosomes to copy its nucleic acid and proteins
The nucleic acid and proteins are assembled to make new viruses, which bursts out of the cell
and destroy it
...
What is the latency cycle?
Viral DNA inserted into the host cell chromosomes, where it lies for ears
No new viruses are produced in latent period
Viral DNA is activated and expressed, new viruses are formed and the host cell is destroyed
...
What are positive ssRNA viruses?
These are viruses that contain a single strand of RNA that is a sense strand
...
The proteins made include viral structural
proteins and an RNA polymerase, which is used to replicate the viral RNA
...
What are negative ssRNA viruses
Single, antisense strand of RNA
...
He virus important RNA replicase, which used free
bases in the host cell to transcribe the antisense RNA strand and produce a sense strand that can
be translated at the ribosomes
...
19
...
They have viral RNA as their genetic material
...
This viral DNA passes into the nucleus of the host cell where it is inserted
into the host DNA
...
New viral material is synthesised and the new viral particles leave the cell by exocytosis
...
20
...
This is done by:
target receptors by which viruses recognise their host cells
target enzymes
inhibit the protease enzyme which enable new virus particles to ‘bud’
21
...
22
...
23
...
What is the cell cycle and what does it consist of?
A regulated process in which cells divide into two identical daughter cells
...
25
...
Cytokinesis: cells separate
...
What are the stages of mitosis?
Prophase: chromosomes are coiled up and consist of two daughter chromatids joined at the
centromere
...
The
microtubules form between the spindles and attach to the centromere of the chromosomes as
they line up on the metaphase plate
...
They are drawn to opposite poles
by the microtubules
...
Nucleoli and centrioles and reformed
...
How does mitosis contribute to growth and repair?
Growth: permanent increase in an organism’s mass, size and number of cells
Dry mass: mass of body with all water removed
© 2015 Produced by Zsara Finch
11
TOPIC 1+2
EDEXCEL BIOLOGY
AS LEVEL
28
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BINARY FISSION: mitosis followed by splitting of an individual= 2 new individuals (bacteria)
PRODUCING SPORES: mitosis and production of asexual spores which are capable of growing
into new individuals (fungi)
REGENERATION: Regrow a body part ha has been lost- fragmentation, reproduced from
fragments of original body (starfish)
PRODUCING BUDS: Outgrowth by parent organism that develops in independent organism
(yeast, hydra plant)
VEGETATIVE PROPAGATION: plant forms structure by mitosis that develops into a fully,
differentiate, genetically identical plant (spider plant)
30
...
What are the stages of meiosis
FIRST DIVISION
interphase: chromatin not visible
...
prophase: chromosomes visible
...
Crossing over occurs here
...
Anaphase: centromeres do not divide
...
o
...
Cells have two chromosomes
...
prophase: centrioles replicate and move to new poles, 90 degrees to original ones
metaphase: new spindles form, chromosomes line up on metaphase plate
anaphase: spindle Fibres contract, centromeres split and chromatids move o opposite ends of
the cell
telophase: nuclear envelops reform
...
31
...
Crossing over: large, multi-enzyme complexes, ‘cut and join’ bits of materal and paternal
chromatids together
...
32
...
What are the types of mutation and what do they do?
Translocation: during chromosome separation in meiosis, one part of a chromosome may break
off and attach onto a different chromosome
...
34
...
e
...
35
...
E
...
chromosome 21 fails to separate- the game may be formed has 2 chromosome 21’s,
resulting in a zygote with x3 copies of the chromosome
...
g
...
How does sexual reproduction occur in mammals?
Gametogenesis
37
...
Draw and identify the parts of the sperm and the egg
...
How does fertilisation occur in mammals?
Gametes must meet and fuse
As sperm moves through the female reproductive tract, he acrosome region matures, releasing
enzymes to penetrate ovum
...
One sperm gets through to the surface membrane
...
40
...
Happens
when travelling down oviduct
...
41
...
Describe the stages of micro gametogenesis (pollen grain formation) and mega
gametogenesis (embryo sac formation)
Micro gametogenesis:
Microspore mother cell divides by meiosis to form 4 microspores (pollen grain)
...
There are two male gametes
produced by mitosis of the generative nucleus
...
Mega gametogenesis:
Megaspore mother cell formed my mitosis
Divides by meiosis to form 4 haploid cells
3 degenerate, and 1 survives and divides my mitosis 3 times to from a mature embryo sac
...
43
...
The tip of the tube contains hydrolytic
enzymes that digest tissue
...
The generative nucleus travels down, divides by mitosis to form 2 male nuclei, they pass into the
ovule
...
The other nucleus fuses with the egg to form a diploid zygote
...
CORE PRACTICAL 4
45
...
The other nucleus fuses with the egg to form a diploid zygote
Title: AS BIOLOGY B (2015) TOPICS 1 AND 2 ANSWERS
Description: These notes are appropriate for students in year 12 and 13 studying the new A LEVEL BIOLOGY B as of 2015 (pearson qualification). They cover all the answers needed to pass your A level biology exams. These answers are best paired with the questions document that is available separately on my account and helps students to self-test and self-check with the answers for optimal learning and memory recall. Please see other uploads for the remainder of the topics within this A level. Good luck!
Description: These notes are appropriate for students in year 12 and 13 studying the new A LEVEL BIOLOGY B as of 2015 (pearson qualification). They cover all the answers needed to pass your A level biology exams. These answers are best paired with the questions document that is available separately on my account and helps students to self-test and self-check with the answers for optimal learning and memory recall. Please see other uploads for the remainder of the topics within this A level. Good luck!