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Ribosomes (~ 22 nm)

Small organelles often attached to the RER
but also found free in the cytoplasm

Site of protein synthesis

Not membrane bound

A large protein subunit and a small
ribosomal RNA (rRNA) subunit form the
functional ribosome

Subunits bind with mRNA (copy of gene) in
the cytoplasm

This starts translation of mRNA for protein
synthesis (assembly of amino acids into
proteins)
80S in eukaryotes
Larger (22 nm)
Composed of 60S + 40S subunits

Links amino acids to make polypeptide
(protein)

70S in prokaryotes
Smaller (18 nm)
Composed of 50S + 30S subunits
Free ribosomes make proteins used in the
cytoplasm. Responsible for proteins that go
into solution in cytoplasm or form important
cytoplasmic structural elements
S = Svedberg unit - sedimentation
coefficient (rate of sedimentation under
centrifugal force in a sucrose gradient)

Ribosomal ribonucleic acid (rRNA) is made
using the DNA in the nucleolus
Two types of ribosomes exist
1S = 10-13 s
Larger units sediment faster
1
Mitochondria (1µm in diameter and 2- 7µm in length)

Double membrane structure – inner
membrane is folded - folds are termed
cristae; can divide to make more
mitochondria in more active cells

Power house of the cell – site of production
of ATP – the universal energy carrier; free
energy from energy rich molecules (e.g.
glucose) is stored in the form of ATP

Cristae provide a large surface area for
attachment of proteins and enzymes required
for the later stages of aerobic cell respiration
(electron transport and oxidative
phosphorylation)

Matrix – contains enzymes involved with the
Krebs cycle; synthesis of lipid and
phospholipids; contains DNA and RNA ;
contains ribosomes – able to manufacture
some of their own proteins (enzymes)

Cells with a high metabolic activity (e.g. heart
muscle cell; plant root cell) have many well
developed mitochondria – i.e. with more
cristae and enzymes, to provide large
amounts of ATP
Stalked particle in inner membrane
– site of ATP production
Cross
section
2
Chloroplast (4-6 µm in diameter and 4-10 µm in length)

Only in photosynthesizing cells (plants) and
some protoctists

Double membrane envelope with a third internal
membrane system (thylakoid membrane
system) in the stroma

Thylakoids – site of light dependent
reactions - are membrane bound structures
containing the light absorbing pigment
chlorophyll, and arranged in the form of stacked
flattened discs (grana), joined by connecting
membranes (lamellae) and surrounded by fluid
(stroma) – large surface area

Stroma – fluid containing enzymes for making
organic compounds (e.g. glucose ) by light
independent reactions; contains DNA,
ribosomes, and lipid droplets

Using light energy, the inorganic reactants,
CO2 and H2O are converted to organic chemical
energy (glucose) and O2 – light energy is
transformed into chemical energy in glucose

Photosynthesis
6CO2 + 6H2O
C6H12O6 + 6O2
Intergranal
lamella
Starch grain
 Chloroplasts are moved around
plant cells by the cytoskeleton– to
maximise light absorption
3
Flagella (Undilipodia) and Cilia

Flagella (longer) and cilia (shorter) are
cylindrical hair like extensions that stick
out from the surface of cells.

They are made of protein microtubules,
covered with an extension of the plasma
membrane

Flagella (one or few) move organisms
through a liquid medium– e.g. bacteria,
spermatozoa, protozoa

Cilia (large numbers on a cell) – move
cells through a fluid medium (e.g.
paramecium), or,
Paramecium – a ciliate
move fluid past the cell - e.g. ciliated cells in
trachea to move mucus, with trapped
material (e.g. bacteria, dust) towards the
throat

Each flagellum (or cilium) is made up of
a cylinder that contains 9 microtubules
arranged In a circle, with 2 microtubules
in a central bundle – a 9+ 2 arrangement.

Microtubule function requires energy (ATP)
Trypanosome (a flagellate) – a protozoan
4
- causes sleeping sickness
9 + 2 arrangement
The motor protein dynein
has “arms” that can push
one doublet ahead of the
other
5
Plant Cell Walls

Covers outside of cell surface membrane of plant cells

Made of cross-linked chains of cellulose (polymer of beta-glucose) molecules, crosslinked by hydrogen bonds

Forms sieve like network of strands – confers strength and shape

Held rigid by internal pressure (in vacuole) – gives turgidity - gives support to plant and
prevents cell from bursting (due to high internal osmotic pressure)
Plant cell “ghosts”
(cell contents removed
– cellulose cell walls
remain)
6
Cooperation between organelles – illustrated by protein synthesis and secretion
1
DNA contains the gene for insulin – DNA is located in the nucleus
2
DNA unwinds (using the enzyme helicase); a mRNA copy of the gene (e.g. for
insulin) is made by transcription
3
mRNA leaves the nucleus through a nuclear pore and attaches to a ribosome on
the rough endoplasmic reticulum (or with free ribosomes)
4
Ribosome translates mRNA into protein; protein enters lumen of RER; insulin
assumes a tertiary (3D) shape (conformation)
5
Vesicles containing insulin are pinched off from RER – vesicles transport insulin to
Golgi apparatus.
6
Vesicles fuse with the Golgi apparatus (cis face) and release insulin into the lumen
7
Golgi apparatus processes and packages insulin into secretory vesicles for secretion
8
Secretory vesicles (formed from the trans face) move to the plasma membrane
9
Secretory vesicles fuse with the plasma membrane and release (secrete) insulin by
exocytosis
Organelles involved – nucleus, ribosomes, RER, vesicles, and, plasma membrane
7
Nucleus
4
3
Protein is
secreted
(expelled) by
exocytosis
2
9
1
Plasma
membrane
6
5
8
7
Ribosomes on RER generally synthesize proteins destined for secretion (export) –
e.g. the hormone insulin in pancreatic endocrine cells. Free ribosomes make proteins
required for intracellular function
8
Destination proteins (“address proteins”) are present in membranes of vesicles
“Address proteins” are embedded in membranes of vesicle in order to direct vesicles
to their particular destinations .
•
Destinations (target organelles) have complementary receptors to address
proteins
•
Shape of receptor and address protein are complementary
COPI proteins coat vesicles that transport materials from the Golgi to the rough
endoplasmic reticulum
COPII proteins coat vesicles that transport materials from the RER to the Golgi
9
Cytoskeleton

Interconnected system of fibrous proteins (fibers) in the cytoplasm - between
organelles – not a rigid structure - assembled or dismantled in seconds

Enables cell movement – e.g. white blood cells, amoeba; enables intracellular
movement of organelles (e.g. chloroplasts, vesicles, centrioles),proteins,
translocation of mRNA from nucleus to ribosomes in cytoplasm in protein synthesis

Provides mechanical strength to cells and shape; holds organelles in place;
maintains cell shape (e.g. red blood cells)

Forms the spindle during cell division to move chromosomes / chromatids – termed
microtubules – composed of tubulin – require ATP to drive movement
10
Prokaryotic Cells (Bacteria & Blue-green Algae)
Kingdom – Prokaryotae (“before nucleus”)
•
Small (0.5 - 5µm); unicellular - simple; little internal organisation; reproduce by binary
fission
•
No membrane bound organelles present (e.g. nucleus, mitochondria, etc)
•
Single circular chromosome (“nucleoid”) – suspended freely in cytoplasm – not
membrane bound; “naked” - no proteins (histones) associated with DNA.

May contain plasmids – small, extra chromosomal pieces of circular DNA
•
Mesosome (one or more) – infolding of cell membrane; increases surface area for
location of vital enzymes (e.g. respiratory enzymes for energy production;
photosynthetic membrane – containing photosynthetic enzymes)
•
Ribosomes - 18 nm (22 nm in eukaryotes)
•
Cell wall present – composed of mucopeptide (murein)
•
Flagella – sometimes present - for movement;
•
Pili – extensions of cell membrane – for attachment (to other cells or surfaces),
involved in “sexual” reproduction
•
Slime layer (polysaccharide or polypepide) – for attachment to surfaces ; protection
against desiccation
•
Capsule – for additional protection
Forms colonies containing individual cells –
never tissues or multicellular organisms
11
A generalised bacterial cell (a prokaryotic cell)
plasma
membrane
Size ~ 18 nm
12
Differences between Prokaryotic and Eukaryotic Cells
Feature
Prokaryotic (bacteria)
Eukaryotic (plant/animal/fungi)
Size
Small cells – 0.5 - 5µm
Large cells – 20 – 40 µm and larger
Capsule (protection)
Present
Absent
Cell wall
Present (peptidoglycan /
murein)
In fungi (chitin); in plants (cellulose);
NOT in animals
Plasma (cell)
membrane
Present
(cell surface membrane only)
Present
(cell surface membrane + membrane
bound organelles)
Vacuole
Absent
Present (plant cells only)
Temporary in animal cells
Absent
Absent
Absent
Absent
Absent
Small ribosomes (70S),
always free in the cytoplasm
(size 18 nm)
Only in plant cells (has DNA)
Present
Present
Present (+ ribosomes)
Present (+ DNA)
Larger ribosomes (80S)
- size 22 nm; free in cytoplasm and
attached to rough ER
Cytoplasm
- Chloroplast
- Lysosomes
- Golgi Apparatus
- E Reticulum
- Mitochondria
- Ribosomes
13
Nucleus
- Nuclear envelope
- Nucleoli
- Chromosomes
(DNA)
Absent
Absent
Absent
Single and circular
(+ Plasmid)
No histones (DNA is “naked”)
Present (true nucleus)
Present
Present
Many and linear
(No plasmids)
DNA is associated with histones
Lipid droplets /
glycogen granules
Present
Present
Centrioles (organise
spindle fibres for cell
division)
Absent
Only in animal cells
Some plant cells?
Flagella (undulipodia)
(if present)
Sometimes present
Sometimes present
(None in plant cells)
Single microtubule
Microtubules in 9 + 2 arrangement
Present
Absent
Pili
14
Bacterial flagella

Bacterial flagella are structurally different to eukaryotic flagella.

They are composed of a spiral of protein (flagellin)

The flagellum is anchored into the plasma membrane by a basal body – allowing it to
rotate

Energy (ATP) is used to rotate the disc which spins the flagellum, thus creating
movement
15
√=Present
x = Not present
S=Sometimes present
Eukaryotic and Prokaryotic cells - Summary
Cell wall
Chloroplasts
Nuclear membrane
Cell surface membrane
Ribosomes
(not membrane bound)
Plant Cell
(Eukaryotic)
√
√
√
√
√
(22 nm)
Animal Cell
(Eukaryotic)
x
x
√
√
√
(22 nm)
Bacterial Cell
(Prokaryotic)
√
x
x
√
√
(18 nm)
Centrioles
Mesosome
Pili
Flagella (undulipodia)
Mitochondria
Golgi body
Endoplasmic reticulum
Vacuole
Glycogen granules
Starch granules
Lipid droplets
Plasmids
Plasmodesmata
Capsule
x
x
x
x
√
√
√
√
x
√
√
x
√
x
√
x
x
S
√
√
√
S
√
x
√
x
x
x
x
S
S
S
x
x
x
x
√
x
√
√
x
S
16
A*
Examination
Questions
&
Answers
17
Qs 1
The figure shows an organelle from a ciliated cell as seen with an electron microscope
a) Name the organelle
b) State the function of this organelle
c) State why ciliated cells contain relatively large numbers of these organelles
d) Calculate the actual length of the organelle as shown by the line AB in the figure
Express your answer to the nearest micrometre (µm). Show your working
An image drawn to the same magnification as the figure could be produced using a light
microscope.
e)
Explain why such an image would be of little use when studying cells
18
Ans 1
a) Mitochondrion
b) Site of aerobic respiration; release energy (produce ATP by aerobic respiration);
provide energy (ATP) for movement of cilia
c) Require large amount of energy for movement of cilia
d)
Use formula:
M=I/A
A = I /M
Actual size = Image size / 20 000
Image size (I) - measure the image size (line AB) in mm and convert to
micrometres
Line AB = 100 mm = 100 000 micrometres
Substitute in formula:
A = 100 000 / 20 000 = 5 µm
19
Qs 2
State one function of each of the following.
a)
b)
c)
d)
Mitochondrion.
Centriole.
Lysosome.
Chloroplast.
Ans 2
a)
aerobic respiration / respiration using oxygen
provides / produces , ATP ; releases / provides , energy
AVP ; e.g. Krebs cycle, protein synthesis , ornithine cycle, regenerate NAD, lipid
cycle, oxidative phosphorylation, oxidation of fats (beta oxidation)
b)
ref spindle / microtubules / cytoskeleton ;
synthesis urea
Ignore mitosis
c) contains / has / provides , digestive / hydrolytic / named , enzymes; digestion / destruction
/ breakdown , of , cell / organelle / foreign body / pathogen / bacteria / unwanted material /
unwanted structure ; DO NOT CREDIT engulfs / removes
d) photosynthesis / light absorption / ATP production / NADPH production / carbohydrate
production / named carbohydrate production ; ALLOW traps light lipid / protein , synthesis ;
20
Qs 3
The hormone insulin is a protein. It is produced in the human pancreas. Once insulin
molecules have been produced they are secreted through the cell membrane into the blood.
Describe the sequence of events involved in the production of an insulin molecule until it
passes through the cell membrane.
Ans 3

DNA unwinds (enzyme – unwindase / DNA helicase); complementary base pairing occurs
– transcription; mRNA formed from DNA template (enzyme RNA polymerase)

mRNA is translocated to cytoplasm through nuclear pores; m RNA attaches to ribosomes
on RER

Specific activated amino acids translocated to ribosomes from cytoplasm by tRNAs as
specified by codons on mRNA

Amino acids linked via peptide bond (enzyme – transpeptidase) until mRNA is translated
into a protein (insulin)

Insulin detaches from ribosomes and enters the lumen of the RER - assumes a 3D
(tertiary) structure

Vesicles containing insulin are formed - vesicle fuse with the Golgi body (cis face); insulin
is further modified in Golgi body – e.g. addition of carbohydrate. Insulin is enclosed in
vesicles produced by Golgi body – vesicles budded off from Golgi body (trans face)

Vesicles fuse with cell membrane and release insulin to the exterior by exocytosis
21
Qs 4
Organisms can be classified based on observable features.
Using the information below, label the five bacteria (1 to 5) with the correct letter
 Bacterium P has a single flagellum to enable it to move whilst bacterium Q has
several flagella.
 Only bacterium R has visible plasmids and bacterium S has a mesosome
 Bacterium T has a slime capsule
1
2
4
3
5
Ans 4
1-R
2–S
3 -P
4-T
5-Q
22
Qs 5
The drawing shows some bacterial cells.
The drawing has been magnified 6000 times.
a) Calculate the actual length, in micrometres, of cell A.
Show your working
A capsule surrounds each of these cells.
The main chemical constituent of this capsule is a nitrogenous polysaccharide.
b) List the elements present in this compound.
c) Give one way in which:
i)
The genetic material in cell A would differ from that in an animal cell;
ii)
The distribution of membranes in this bacterial cell would differ from
the distribution of membranes in a plant cell.
23
Ans 5
a)
Measure length of cell A = 33 mm = 33 000 um (illustrated measurement)
Use formula – M = I / A;
A=I/M
A = 33 000 / 6000 = 5.5 um
Answer = 5.5 µm
b) Nitrogen, Carbon, Hydrogen and Oxygen
c)
i)
In bacterial cell (cell A)
DNA/genetic material is naked and not in
a membrane-bound nucleus
ii)

DNA is not associated with proteins (histones)

DNA in loop (circular)

DNA in plasmids (extra chromosomal DNA)
In bacterial cell

No membrane-bound organelles (e.g. mitochondria; endoplasmic reticulum)

Bacteria only have a plasma membrane

Have mesosomes (infoldings of plasma membrane – location of respiratory
enzymes)
24
Qs 6
The cells in the human body and in plants
are eukaryotic cells.
a) State what is meant by a eukaryotic cell
The different organelles within a cell may
be seen using an EM
The figure is of an electron micrograph
of a plant cell showing cell organelles.
The organelle labelled D is shown at a
higher magnification.
b)
c)
Name the organelles labelled A to C
State one function of each of the
organelles labelled D to F.
The figure is an EM showing a lymphocyte
d)
Use the scale bar to calculate the actual
diameter of the cell along the line X---Y.
Show your working and give your answer to
the nearest whole number
25
Ans 6
a)
A cell that has, membrane bound organelles /nucleus
b)
i)
A
B
C
Nucleus
Nucleolus
Vacuole
ii)
D
E
F
Production of ATP / site of aerobic respiration
Supports cell
Production of glucose /site of photosynthesis
c)
Measure length of X-----Y - e.g. 10 cm = 100 mm = 100 000 µm
Scale bar = 1 cm = 10 mm = 10 000 µm
Use formula
A=I/M
= 100 000 / 10 000 = 10
Answer = 10 µm
26
Qs 7
Leucocytes and palisade mesophyll cells are examples of eukaryotic cells.
a) Complete the table below to compare the structure of a leucocyte and a palisade
mesophyll cell. Give two structural differences and two structural similarities.
Leucocyte
Palisade mesophyll cell
Structural differences
Structural similarities
The figure is a diagram of a leucocyte
The structures labelled A, B and C are involved
in protein synthesis and secretion.
b) Outline the roles of these structures in the
production of protein.
The figure below is an electron micrograph of an erythrocyte.
c) Describe how the structure is related to its function.
27
Ans 7
a)
Structural
differences
Structural
similarities
Leucocyte
Palisade mesophyll cell
No cell wall
Cell wall
No chloroplast
Chloroplast
No large permanent vacuole
Large permanent vacuole
Centriole
No centriole
Cytoplasm / cytoskeleton; Vesicles Nucleus /nuclear
membrane
Cell surface / plasma membrane; SER / RER
Ribosomes same size; Mitochondria ; Golgi apparatus
b)
A
B
C
Packages / modifies proteins (for secretion or use within cell)
Contains the genetic code for the protein / produces ribosomes
Produces the protein / transports protein / produces vesicles
c)




Biconcave / large surface area to volume ratio for maximum rate of
diffusion / absorption / gas exchange
Haemoglobin for transport of oxygen
Few organelles / no nucleus, allow it to take on flat / thin / biconcave
shape; enable a greater volume for haemoglobin
Small size / flexible, to squeeze through capillaries
28
Qs 8
a)
State two advantages of using an electron microscope to study cells
b)
Outline how a sample of tissue may be prepared for the electron microscope
The figure shows a mitochondrion, as seen using an electron microscope
c)
Calculate the actual length of the mitochondrion. Show your working
Mitochondria are not found in prokaryotic cells
d)
State four other ways in which prokaryotic cells differ from eukaryotic cells
29
Ans 8
a)
EM provides high magnification
EM has high resolution / resolving power
b)
o
o
o
o
o
o
o
c)
Specimen dead / killed, as in a vacuum
Fix in, glutaraldehyde and osmic acid
Dehydrate in alcohol / acetone / propanone; embed in resin / araldite
Section, with ultramicrotome / extremely thin / freeze fracture
Stain / provide electron scattering capability / electron dense mordant
Shadow, with, heavy metal / osmium / uranium / lead / mercury / gold
Mount on copper grid – spaces to allow electrons to penetrate
Length of image (I) = 60 mm = 60 000 µm; A = I / M = 60 000 / 40 000 = 1.5 µm
d)










Prokaryotic cell
Smaller
DNA circular
No nucleus / free DNA
No associated proteins with DNA
Smaller 70S / 18 nm ribosomes
No ER
No membranous organelles
Cell wall (murein)
No 9+2 flagella
No mitosis / meiosis
Eukaryotic cell









Larger
Nucleus / DNA in nucleus
DNA with proteins in chromosome
Larger / 80 S / 22 nm, ribosomes
Membrane bound organelles
(e.g. lysosome)
Cell wall not always present
(not murein)
9 + 2 flagella
Mitosis / meiosis
30
Qs 9
The figure shows an electron micrograph of a cell
a)
i)
State two features of the cell
shown that indicates it is eukaryotic
ii)
The line A-------B represents 20 µm
Calculate the magnification of the cell shown. Show your working
Microtubules and microfilaments are part of the cytoskeleton
b)
Suggest two roles of the cytoskeleton in the type of cell shown
The cells of a multicellular organism are usually specialised to perform a particular function
c)
Name the process in which a cell becomes specialised
Neutrophils are phagocytic blood cells that can engulf and digest foreign cells found in the
blood
d)
Describe how the ultra structure of a neutrophil is specialised to enable it to perform this
function
31
Ans 9
a) i)
Nucleus / nuclear envelope / nuclear membrane / nucleolus / Membranebound organelles (e.g. endoplasmic reticulum)
ii)
Measure scale bar = 90 mm = 90 000 µm
Use formula:
M=I/A
90 000 / 20 = (x) 4500
b)





c)
Provides strength / stability / support (cell)
Determines shape / changes shape / moves membrane (for endo / exoctytosis
Movement of organelles (e.g. lysosomes; chloroplasts) / RNA / protein
/ chromosomes / chromatids
Attach to organelles and hold organelles in place
Make up, centrioles / spindle fibres
Differentiation
d)







Many lysosomes / vesicles containing hydrolytic enzymes
Many microfilaments / microtubules - intracellular transport; mitosis
Many ribosomes / (a lot of) rough endoplasmic reticulum – protein synthesis
Many mitochondria – energy from aerobic respiration
(lots of) Golgi – modification of proteins and secretion; formation of vesicles
(many) receptor sites on cell surface /plasma membrane
Multi-lobed nucleus – allows flexibility / diapedisis
32
Qs 10
The Figure is a photomicrograph of cells from a leaf of Canadian pondweed, Elodea canadensis, which
lives in fresh water.
a) Use the scale bar to calculate the magnification of the photomicrograph.
Show your working.
A leaf of Canadian pondweed, which had been kept out of water for a short time, was seen to have
wilted (its cells were no longer turgid).
b) Explain, in terms of water potential, what would happen to its cells if the leaf
were then placed in distilled water with a water potential (Ψ) of 0
33
Qs 10 (continued)
A student wanted to find out more about the structures labelled A. Use of an electron
microscope revealed that each structure labelled A is surrounded by two membranes.
c) Name structure A.
d) Suggest a function of these membranes around structure A.
Some cells of Canadian pondweed were broken open using a liquidiser and some of the structures
labelled A were released intact.
e) What would happen to an intact structure A if it were then placed into distilled
water with a water potential (Ψ) of 0?
34
Ans 10
a) Measure scale bar = 20 mm = 20 000 um
M = I / A = 20 000 / 10
Magnification = 2000 X
b) Water will enter by osmosis, down a water potential gradient
From high water potential to low water potential
Cells / vacuoles, get bigger / swell / expand / increase in volume
Cell membrane / cytoplasm / cell contents, presses against cell wall
Water potential increases until equilibrium
Cell wall, stops it from bursting / resists expansion
c) Chloroplast
d) separates organelle from cell
allows reactions to take place in isolation
permits / controls / allows , what can , enter / exit
e) (organelle) will take up water (by osmosis)
burst - because there is no wall (to restrict
expansion) / membrane not strong
enough
35
Qs 11
The table below contains statements about four biological molecules.
a)
Complete the table, using a tick or a cross, to indicate whether the statement does or
does not apply to each of the biological molecules.
The first one has been done for you.
36
Ans 11
37
Qs 12
The Table compares the structures of prokaryotic and eukaryotic cells.
a) Complete the table.
As chromosomes / chromatin, OR,
associated with proteins / histones
(diameter of cell) 20 – 40 µm)
Ribosomes about 18 nm in diameter
Cell wall always present
The cytoskeleton is an important component in the cytoplasm of all eukaryotic cells.
b) Name one structure, associated with the cytoskeleton, which can bring about cell
movement.
c) Suggest two processes inside cells that rely on the cytoskeleton for movement.
38
Ans 12
a)
In table
b)
flagellum / cilium / microtubule / microfilament / undulipodium
c)
(movement inside cells of)

chromosomes / chromatids (in cell division)

(cytoplasm in) cytokinesis

organelles / named organelle (e.g. chloroplasts)

RNA (in protein synthesis)

proteins
39
Qs 13
The diagram is of a bacterium as seen using
an electron microscope
The bacterium contains DNA, as do other
eukaryotic cells
(a) State two other ways in which the
structure of the cell in the figure above
is similar to a typical animal cell
(b) Describe how bacterial DNA differs
from that found in eukaryotic cells
Some bacteria similar to that shown in the figure can cause disease. Antibiotics are given to
patients who are suffering from diseases caused by bacteria. Examples of the mode of action
of two antibiotics are given below
(c)
Antibiotic 1
binds to the enzyme RNA polymerase in bacteria, preventing
transcription
Antibiotic 2
prevents the formation of peptide cross links between
peptidoglycan chains in the cell wall
Explain why the prevention of transcription leads to the death of bacteria
(d) Suggest how the action of antibiotic 2 on cell walls leads to the death of bacteria
40
Ans 13
a)






Cell membrane
Cytoplasm
Ribosomes
Fat droplets / glycogen granules
RNA / tRNA / mRNA
No vacuoles
b) DNA is




Circular/not linear; not associated with protein / no histones
A single unit of nuclear material
Not membrane bound / not in nucleus
Replicated more quickly





No formation of mRNA
No translation (linking of amino acids)
No protein synthesis; no enzyme synthesis
No essential proteins made; no new cell structures
No reproduction




Weak wall formed
Antibiotic affects growing bacteria / when wall is forming
Cell bursts due to high internal osmotic pressure
Cannot reproduce
c)
d)
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Qs 14
The diagram shows some of the cell
structures involved in the secretion of an
extracellular enzyme.
(a) Identify A, B, C, and D.
(b) Outline the role of each of the above structures in this process.
Ans 14
a) A = nucleus; B = ribosome/RER; C = (RER) vesicle; D = Golgi body
b)

(nucleus) contains DNA which codes for the enzyme; DNA code is transcribed to
messenger RNA

mRNA attaches to ribosomes; code on mRNA translated into the polypeptide

polypeptide is transported through cell to Golgi body in vesicle of rough
endoplasmic reticulum

polypeptides in Golgi body combined / modified to form enzyme; carried in Golgi
vesicles to cell surface; for secretion/exocytosis
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Qs 15
The diagram shows a cell from the proximal (first) convoluted tubule in the nephron of the kidney.
(a)
Label two features on the diagram that help the cell to take up glucose from the
glomerular filtrate.
(b)
Explain how the two features of the cell help in the uptake of glucose from the
glomerular filtrate.
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Ans 15
a) Labels:
mitochondrion
microvilli / brush border
b) microvilli/brush border
increases surface area for uptake of glucose/
enables greater uptake of glucose/ref to larger amount of carrier protein present
mitochondria
provide ATP (energy);
for active transport of glucose (into intercellular fluid)
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QsQ16
The diagram shows the structure of a chloroplast.
a) Name structures labelled A to E on the diagram.
b) Describe where in the chloroplast:
the light dependent reaction takes place.
the light independent reaction takes place.
c) Describe three similarities in the structure of chloroplasts and mitochondria.
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Ans 16
a) A = double membrane
B = starch grain
C = granum / grana
D = stroma
E = lipid droplet
b)
Light dependent reaction – granum / thylakoid membranes/quantosomes
Light independent reaction - stroma
c) Any three of:
both have double outer membrane
large internal surface area / many internal membranes
contain DNA / ribosomes
contains lipid droplets
in mitochondria catalyses oxidative phosphorylation;
in chloroplasts catalyses (cyclic / non cyclic) photophosphorylation
enables both to synthesise proteins/polypeptides;
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Qs 17
The table below describes the structure and function of organelles in eukaryotic cells.
Complete the table by
filling in the empty boxes
A, B, C, D and E
Ans 17
A - ribosome manufacture/synthesis of ribosomal RNA
B - mitochondria
C - increase surface area for attachment of enzymes/for electron transfer chain/oxidative
phosphorylation
D - lysosomes
E - lipid / steroid synthesis / transport
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Qs 18
The diagram below shows an electron
micrograph of a cell.
a) Name the parts labelled A, B, C, D, E
and F.
b) What evidence can be seen in the
diagram that suggests that the cell is:
i) metabolically active and involved in secretion of enzymes.
ii) involved in production or modification of lipids
Ans 18
a) A. Golgi body; B. Centriole; C. Nucleolus; D. double nuclear membrane; E. mitochondrion; F. rough
endoplasmic reticulum
b) i) Any three of:
presence of many mitochondria
large rough ER with ribosomes
presence of microvilli / Golgi body
large nucleus
(ii) presence of much smooth endoplasmic reticulum
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Qs 19
The table below refers to a
Bacterial cell, a liver cell and a
palisade mesophyll cell and to the
structures which may be found
inside them.
If a feature is present in the cell,
place a tick in the appropriate box
and if a feature is absent from
the cell, place a cross in the
Appropriate box.
Ans 19
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Qs 20
The diagram below shows the structure of
a mitochondrion
a) Name structures A to E.
b) State where the following are situated in
the mitochondrion.
(i) The enzymes involved with oxidative phosphorylation and electron transport.
(ii) The enzymes involved with the Krebs cycle.
(iii) Why does the mitochondrion contain RNA?
c) The magnification of the diagram is 130,000 times. Calculate the actual length of the
mitochondrion.
Express your answer in um. Make your measurements along the axis XY
Ans 20
a) A = outer membrane; B = inner membrane; C = ribosomes; D = crista; E = DNA
b) i) Cristae
ii) Matrix
iii) Synthesises of proteins / polypeptides - e.g. Enzymes
c) XY = 112 mm = 112,000 µm;
112,000 / 130,000 = 0.86 µm
50