1
Q
A scientist investigated the growth rate if the bacterium Bacillus sonorensis.
Describe how these bacterial cells replicate by binary fission.
A
-Replication of (circular) DNA
-Replication of plasmids
-Division of cytoplasm to produce daughter cells
2
Q
A scientist measured the mass of bacterial cells in picograms.
1 pg = 1 x 10^-12 g
Calculate how many grans are in 720 pg.
A
7.2 x 10^-10 g
3
Q
Suggest 2 ways in which the environmental conditions could be altered to increase the growth rate of bacteria.
A
- Increased glucose conc
- Increased respiration
- Increased oxygen conc
- Increased respiration
- Increased temperature
-Increased enzyme activity - Increased phosphate conc
- Increased ATP/DNA/RNA
- Increased nucleotide conc
- Increased DNA synthesis
4
Q
Describe the role of a centromere in the process of mitosis.
A
- Holds chromatids together
- Attaches chromatids to the spindle fibres
-Allows chromatids to move to opposite poles
5
Q
Mitosis is a cell process used by organisms throughout their lifetime.
Explain why mitosis is an important cell process.
A
- Allows for growth
- Can replace cells and repair tissues
- Produces genetically identical cells
- Asexual reproduction/cloning
6
Q
Describe what occurs during interphase to prepare a cell for division
A
- DNA replication
- Chromosome becomes two chromatids
- DNA is checked for errors
- Centrioles replicate
7
Q
Which organelle is not involved in the production and secretion of enzymes in eukaryotes?
-golgi apparatus
-ribosomes
-smooth endoplasmic reticulum
-vesicle
A
Smooth endoplasmic reticulum
8
Q
Which of the following cell structures are present in prokaryotic cells?
-lysosomes
-nucleus
-ribosomes
-starch grains
A
Ribosomes
9
Q
Which structures are found in animal and plant cells?
A
Cell membrane
Nucleolus
10
Q
Which of these cell components contain ribosomes?
-chloroplast
-mitochondrion
-smooth endoplasmic reticulum
-cytoplasm
A
chloroplast
mitochondrion
cytoplasm
11
Q
Which 3 organelles in eukaryotic cells
have a double membrane?
A
- Chloroplast
- Mitochondrion
- Nucleus
12
Q
What is the function of nucleoli?
A
Formation of ribosomes
13
Q
True of False?
Eukaryotic cells have linear DNA
A
true
14
Q
True or False?
Eukaryotic cells only have small (70s) ribosomes
A
False
15
Q
Where would cisternae be found in a cell?
A
Endoplasmic reticulum
Golgi apparatus
16
Q
Which 2structures are found in both chloroplasts and mitochondria?
A
- 70s ribosomes
- circular DNA
17
Q
True if False?
Differential staining is a common feature of electron microscopy
A
False
18
Q
What can differential staining distinguish between?
A
- Different organelles
- Different types of cells
- Different types of organisms
19
Q
What is meant by a microscope with high resolution?
A
The microscope can distinguish structures that are very close together
20
Q
A culture of human cells had its cell surface membranes removed, releasing the cell contents.
This material became contaminated by bacteria.
The material was then centrifuged, separating the various cell structures according to size and mass.
Which cell structure would be separated along with the bacteria?
A
Mitochondria
21
Q
What is meant by ultrastructure?
A
the internal structure of a cell depending on its function
22
Q
Describe the 5 structures of the nucleus and their functions
A
nuclear envelope - double membrane, controls entry and exit of materialas
nuclear pores - allow passage of large molecules eg mRNA
nucleoplasm - granular, jelly-like material
chromosomes- protein-bound, linear DNA
nucleolus - smaller sphere insidee which is the site of rRNA production and makes ribosomes
23
Q
What are the 3 functions of the nucleus?
A
- acts as the control centre of the cell through production of mRNA and rRNA = protein synthesis]
- retain genetic material of the cell in the form of DNA and chromosomes
- manufacture rRNA and ribosomes
24
Q
Describe the structure of endoplasmic reticulum
A
rough and smooth ER both have folded membranes called cisternae
rough have ribosomes on the cisternae
25
What are the 2 functions of the rough endoplasmic reticulum?
- provide a large surface area for the synthesis or proteins and glycoproteins
- provide a pathway for the transport of material, especially proteins throughout the cell
26
What are the 2 functions of the smooth endoplasmic reticulum?
- synthesise, store and transport lipids
- synthesis, store and transport carbohydrates
27
What is the structure of of th golgi apparatus?
- folded membranes making cisternae
- secretary vesicles pinch off from the cisternae
28
What are the fucntions of the golgi apparatus?
- add carbohydrates to proteins to form glycoproteins
- produce secretory enzymes
- secrete carbohydrates
- transport, modify and store lipids
- form lysosomes
- molecules are labelled with their destination
29
What do golgi vesicles do?
once modified in golgi apparatus, finished products are transported to cell surface in golgi vesicle where they fuse with the membranee and the contents is release
30
When are lysosomes formed?
when the vesicles produced by the golgi apparatus contain enzymes such as protease and lipases and lysozymes
31
What are lysosomes?
bags of digestive enzymes
32
What are the functions of lysosomes?
- hydrolyse pathogens in phagosomes
- completely beak down dead cells
- exocytosis - release enzymes to outside of cell to destroy material
- digest worn-out organelles for reuse of materials
33
Describe the structure of the mitochondria
- double membrane
- inner membrane extensions called cristae
- fluid centre called matrix
- loop of mitochondria DNA
- 70s ribosomes
34
What is the purpose of cristae in mitochondria?
extensions on inner membrane which provide large surface area for attachment of enzymes and proteins
35
What is the purpose of the matrix in mitochondria?
contains proteins, lipids, ribosomes and DNA that allows the mitochondria to control the production of its own enzymes
36
What is the function of mitochondria?
site of aerobic respiration
site of ATP production
DNA to code for enzymes needed in resiration contained here
37
Describe the structure of ribosomes
small, made up of two sub-units of protein and rRNA
38
Where are ribosomes found?
in cytoplasm or associated with rough endoplasmic reticulum
39
Difference between 80s and 70s ribosomes
80s - found in eukaryotic cells
70s - found in prokaryotic cells, mitochondria and chloroplasts, is smaller
40
What is the function of ribosomes?
site of protein synthesis
41
Describe the structure of a vacuole
filled with fluid surrounded by a single membrane called a tonoplast
plant vacuoles may contain mineral salts, sugars, amino acids
42
What are the functions of plant vacuoles?
- make cells turgid = provide support
- temporary store of sugars and amino acids
- pigments may colour petals to attract pollinating insects
43
Describe the structure of chloroplasts
- chloroplast envelope
highly selective double membrane
- grana
stacks of thylakoids which contain chlorophyll, where light absorption takes place
- stroma
fluid filled matrix containing starch grains, where synthesis of sugars takes place
- contains circular DNA
44
What is the function of chloroplasts?
site of photosynthesis
45
How have chloroplasts been adapted for carrying out photosynthesis (3)?
- granal membranes provide a large surface area for attachment of chlorophyll, electron carriers and enzymes
- stroma possesses all the enzymees needed to make sugars for 2nd stage of photosynthesis
- contain DNA and ribosomes so can easily maufacture proteins needed for photosynthesis
46
What is the structure of cell walls in plants and fungi?
plants - made of microfibrils of cellulose
fungi - made of chitin
- middle lamella cements adjacent cell walls together
47
What are the functions of the cellulose cell wall?
- to provide mechanical strength in order to prevent the cell from bursting under pressure from osmotic entry of water
-mechanical strength to the plant as a whole
- allow water to pass along it and so contribute to the movement of water though the plant
48
What are algae cell walls made of?
cellulose or glycoproteins
49
What is the function of plasma mebranes?
controls the entry and exit of molecules
50
What are the 7 differences between prokaryotic cells and eukaryotic cells?
- prokaryotic much smaller
- no membrane-bound organelles in pro
- pro has smaller ribosomes (70s), 80s in eu
- no nucleus in pro (single circular DNA in cytoplasm instead)
- cell wall made of murein in pro, cellulose in eu
- pro DNA not associated with proteins, eu are
- no chloroplasts in pro, only chlorophyll associated with membran surface
51
State the structures found in a bacterial cell
- cell wall
- capsule
- cell-surface membrane
- circular DNA
- plasmid
52
What is the role of the cell wall in a bacterial cell?
physical barrier that protects against damage and osmotic lysis
53
what is the role of a capsid in a bacterial cell?
- protection from other cells
- helps groups of bacteria to stick together for further protection
54
What is the role of the cell-surface membrane in a bacterial cell?
controls entry and exit of chemicals
55
What is the role of circular DNA in a bacterial cell?
possesses the genetic information for the replication of bacterial cells
56
What is the role of the plasmid in a bacterial cell?
possesses the genes that may aid the survival of bacteria in adverse conditions
eg produces enzymes that break down antibiotics
57
What does bacteria store food reserves as?
glycogen granules and oil droplets
58
Viruses are non-living and acellular. Define non-living
no metabolic reactions
cannot move, respire, replicate
no nutrition
59
Viruses are non-living and acellular. Define acellular
not made of cells
no cell membranes
60
What are the structures of a virus?
- genetic material
- capsid
- attachment protein
- lipid envelope
- matrix
- reverse transcriptase
61
What is the function of genetic material in viruses?
codes for viral protein
62
What is the functio nof the capsid in viruses?
protein coat that protects the genetic material
63
What is the function of attachment proteins on viruses?
bind to receptors on host cell being infected
64
What 3 things may a prokaryotic cell contain?
- one or moree plasmids
- capsule around the cell - slimy layer
- one or more flagella - for locomotion
65
Define magnification
how many times larger the image is compared to the object M=I/O
66
Define resolution
the minimum distance between two objects in which they can still be viewed as separate
67
What is the resolution in an optical microscope vs electron determined by?
optical - wavelength of light
electron - wavelegnth of beam of electrons
68
Explain an optical microscope
a beeam of light is condensed to create an image
- poorer resolution due to light having a longer wavelength
- lower magnification
- produces colour images
- can view living samples
69
What are the 2 advantages of an electron microscope?
1 - electron beam has a short wavelength = high resolving power
2 - beam can be focused using electromagnets as electrons are negative charged
70
What are the 2 types of electron microscopes?
- transmission electron microscope
- scanning electron microscope
71
Explain electron microscopes
a beam of electrons is condensed to create an image
electromagnets are used to condense the beam
- higher resolvin gpower as electrons have a short wavelength
- higher magnification
- black and white images produced
- sample must be in a vacuum = non-living only
72
Explain a transmission electron microscope
thin specimen stained and placed in vacuum
electrons focused onto specimen by condenser electromagnet
parts of specimen absorb electrons and appear dark, other parts electrons pass through
image produced on 2D black and whitee photomicrograph
73
What is the main disadvantage og optical microscopes?
poor resolution due to longer wavelengths of light
small organlles not visible
74
What are the 2 advantages of using a light mciroscope?
- living samples can be examined
- colour image is obtained
75
What are the 4 disadvatages to using an electron microscope?
- electons are absorbed by air so samples must be in a vacuum = non-living only
- image is black and white as samples must be stained
- specimen must be extremely thin
- image may contain artefacts
76
What are the advantages of using a scanning electron microscope over a transmission electron miscroscope?
the specimens do not need to be thin
as the electrons are not transmitting through
instead the electrons are beamed onto the surface and electrons are scattered in different ways = 3D image
77
Each time you change the objective lens on an optical microscope, what must you do?
the magnification changes
so you have to calibrate the eyepiece
to work out what the distance is between each division on the eyepiece graticule
78
What is used to calibrate the eyepiece graticule?
a stage micrometer
79
What are the steps to calibratin gan eyepiece graticule?
1 - line up the stage micrometer and eypiece graticule whilst looking through the eyepice
2 - count how many divisions on the eyepiece graticule fit into one division on the micrometer scale
3- each division on the micrometer is 10μm so this can bee used to calculate what one division on the eyepiece graticule is at that current magnification
80
What is cell fractionation?
process where cells are broken up and the different organelles are separated out
enabling individual organelle structures and functions to be studied
81
Before cell fractionation the solution is:
cold - reduces enzyme activity that might break down the organelles
isotonic - prevents organelles bursting or shrinking from osmotic gain or loss
buffered - so pH does not fluctuate and change structure of organelles or functioning of enzymes
82
What are the 2 stages of cell fractionation?
1 - homogenisation
2- ultracentrifugation
83
What is homogenisation?
cells are broken up a homogeniser
this releases organelles
in a cold, isotonic, buffered solution
fluid called homogenate
is filtered to remove any complete cells and large debris
84
What is ultracentrifugation?
filtrate spun at low speed in centrifuge
densest organelles (nuclei) forced to bottom and form sediment
fluid at top (supernatant) removed leaving sediment
supernatant transferred to be spun at faster speed
85
Order the eukaryotic organelles from most dense to least dense
nuclei
chloroplast
mitochondria
lysosomes
endoplasmic reticulum
ribosomes
86
How do eukaryotic cells divide?
cells enter cell cylce and divide by mitosis or meiosis
87
How do prokaryotic cells divide?
cells replicate by binary fission
88
Viruses do not underego cell division as they are non-living. How do viruses replicate?
viruses replicate inside the host cells they invade by injecting their ncleic acid into the ceell to replicate the virus particles
89
Describe binary fission
how prokaryotic cells divide
- circular DNA and plasmids replicate
- cytoplasm splits to create two daughter cells
- new cell walls formed
each daughter cell has one copy of the circular DNA but a variable number of plasmid copies
90
What are the 3 phasees that the cell cycle is comprised of?
1- interphase
2- nuclear division
3- cytokinesis
91
What is interphase?
longest stage in the cell cycle
organelles double, cell grows and DNA replicates
G1 - growth
S - DNA synthesis
G2 - growth and preparation for mitosis
92
What is mitosis?
4 stages:
prophase
metaphase
anaphase
telophase
one round of division
genetically identical diploid cells made
for growth and repair
93
What occurs in prophase?
- chromatin condenses into chromosomes and become visible
-nucleolus disappears
- centrioles move to oppostive poles
- spindle fibres develop
94
What occurs in metaphase?
- chrmosomes align along the equator of cell
- spindle fibres released from poles not attach to centromere and chromatid
95
What occurs in anaphase?
- spindle fibres retract and pull centromere
- chromosomes split and sister chromatids pulled to each pole
- requires ATP
96
What occurs in telophase?
- chromosomes now at each pole beocme longer and thinner
- spindle fibres disintergrate
- nuclear envelope and nucleolus reform
- chromosomes unwind into chromatin
97
What occurs in cytokinesis?
cytoplasm divids to create 2 new genetically identical cells
98
Why do cells divide by mitosis (3)?
- growth - ensures new cells are genetically identical to parent cells
- repair - identical to damaged cells
- reproduction - new organisms identical to parent
99
How do you calculate the mitotic index?
number of cells in mitosis / total number of cells
100
Drugs used to treat cancer usually disrupt the cell cycle by:
- preventing DNA from replicating
- inhibiting the metaphas estage by interfering with spindle formation
101
In practice, the theoretical resolving power of an electron microscope cannot always be achieved. Explain why not
the preparation of the specimens may not be good enough
a higher energy electron beam is required
this may destroy the specimen
102
List 3 carbohydrates that are absorbed by an epithelial cell of th small intestine
- glucose
- fructose
- galactose
103
A sperm cell swims a considerable distance carrying the male chromosome.
What 2 organelles would it need in abundance/well developed.
- mitochondria
- nucleus
104
A white blood cell engulfs and digests foreign material.
What 2 organelles would it need in abundance/well developed.
- golgi apparutus
- lysosomes
105
Liver cells manufacture proteins and lipids at a rapid rate.
What 2 organelles would it need in abundance/well developed.
- endoplasmic reticulum
- mitochondria
- ribosomes
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