Cell Structure Flashcards
(90 cards)
1
Q
What is a cell?
A
the smallest structural and functional unit of an organism, which is typically microscopic and consists of cytoplasm and a nucleus enclosed in a membrane.
2
Q
How does wavelength affect the resolution of a microscope?
A
Light has a longer wavelength so objects are harder to distinguish between lowering the resolution
3
Q
how do you calculate magnification?
A
size of image / size of real object
4
Q
How do you calculate real object size?
A
size of image/magnification
5
Q
How do you calculate the image size?
A
magnification x size of real object
6
Q
how do you convert mm into um?
A
X1000
7
Q
how do you convert mm into nm?
A
X100,000
8
Q
how do you convert nm into mm?
A
/100,000
9
Q
how do you convert um into mm?
A
/1000
10
Q
What does resolution mean?
A
The minimum distance apart that two objects can be in order for them to appear as separate items
11
Q
What does magnification mean?
A
How many times larger the image is compared to the object
12
Q
What is the max. resolution of a light microscope?
A
0.2 um
13
Q
What is the max. resolution of an electron microscope?
A
0.1 nm
14
Q
Greater resolution means…
A
greater clarity; the image produced is more clear and precise
15
Q
What is cell fractionation?
A
A process where cells are broken up and the different organelles they contain are separated out
16
Q
Describe the solution cells are placed in before cell fractionation.
A
Cold, buffered, isotonic
17
Q
Why must the solution a cell is fractionised in be cold?
A
to reduce enzyme activity that might breakdown organelles
18
Q
Why must the solution a cell is fractionised in be isotonic?
A
to prevent organelles bursting or shrinking as a result of osmotic gain or loss of water
19
Q
Why must the solution a cell is fractionised in be buffered?
A
so the pH remains constant to prevent altering organelle structure or enzyme function
20
Q
What are the two stages of cell fractionation?
A
Homogenation and Ultracentrifugation
21
Q
What is homogenation?
A
When cells are broken up by a homogeniser
22
Q
What is the purpose of homogenation?
A
To release the organelles from their cells
23
Q
What is homogenate?
A
The fluid left over from cell homogenisation
24
Q
Why must the homogenate be filtered?
A
To remove unhomogenised cells and large pieces of debris
25
What is ultracentrifugation?
A process where cell fragments in a filtered homogenate are separated in a centrifuge
26
What is a centrifuge?
A machine that spins tubes of homogenate at very high speed in order to create a centrifugal force
27
Describe the ultracentrifugation process.
1. Homogenate is decanted into a tube and spun at a low speed
2. Heavier organelles are forced to the bottom of the tube forming a pellet or thin sediment
3. The supernatant is removed leaving the pellet or thin sediment
4. The supernatant is transferred to another tube and centrifuged again at a higher speed
28
What is the supernatant?
The remaining fluid at the top of the tube after centrifugation
29
What are the heavier cell organelles?
Nucleus, mitrochonria
30
What are the lighter cell organelles?
Ribosomes, lysosomes
31
How does an electron microscope have a higher resolution?
The electron beam has a shorter wavelength
32
How can an electron microscope be focused?
Using electromagnets, as electrons are negatively charged
33
Why must the object be placed in a vacuum when viewed under an electron microscope?
Electrons are absorbed or deflected by particles in the air preventing the object from being seen clearly
34
What are the two types of electron microscope?
Transmission (TEM) and Scanning (SEM)
35
What are pros of light microscopes?
Coloured dyes can be added to provide coloured/contrasted images
Livingcells can be viewed
No artefacts are produced
36
What are the cons of light microscopes?
```
Low resultion due to lights short wavelength
Low magnification (x1500)
Specimen needs to be thin
```
37
What are the pros of SEMs?
Higher resolution and magnification than a light microscope
Specimen sections don't need to be thin
Gives a 3D surface image of the cell
38
What are the cons of SEMs?
Image is not coloured
Living cells cannot be viewed
Artefacts may appear due to complicated preparation
Magnification and Resolution are lower than TEM
39
What are the pros of TEMs?
Highest resoltion and magnification (x1,500,000)
| Shows internal cell structure
40
What are the cons of TEMs?
Image is not coloured
Living cells cannot be viewed
Artefacts may appear due to complicated preparation
Specimen must be very thin
41
What is an artefact?
A structure or substance not normally present but produced by an external agent or action, such as a structure seen in a microscopic specimen after fixation that is not present in the living tissue
42
Name 3 cell features/organelles present in all eukaryotic cells
Nucleus, mitrochondria, smooth/rough er, ribosomes, golgi aparatus, lysosomes, cell suface membrane, cytoplasm
43
Name 3 cell features/organelles only present in plant cells
Vacuole, chloroplasts, cell wall
44
Name 3 cell features/organelles present in Eukaryotes but not Prokaryotes
Nucleus, mitrochondria, golgi apparatus, lysosome, Smooth/Rough ER
45
Name 3 cell features/organelles present in Proaryotes but not Eukaryotes
Capsule, Plasmids, Circular DNA, Flagella
46
Name 3 cell features/organelles present in all prokaryotic cells
Cytoplasm, cell-surface membrane, cell wall, capsule, plasmids, circular DNA, flagellum, ribosomes
47
What is the function of the nucleus?
Controls the activities of the cell and makes DNA, mRNA, tRNA and rRNA
48
What is the function of mitrochondria?
Location of aerobic respiration (Kreb's cycle and electron transport chain) to produce nATP and other metabollic intermidiates (eg. amino acids)
49
What is the function of the cell-surface membrane?
Provides structure to the cell and regulates substance movement into and out of the cell.
Also allows communication and recognition
50
What is the function of a chloroplast?
Site of photosynthesis, only present in plant cells
51
What is the function of the golgi apparatus?
Modifies and packages new proteins and lipids, produces golgi vesicles and lysosomes
52
What is the function of the golgi vesicle?
Stores lipids and proteins and transports them out of the cell
53
What is the function of lysosomes?
Contains digestive enzymes (lysozymes) for destroying worn-out organelles and engulfed products of endocytosis, digesting invading cells
54
What is the function of ribosomes?
Site of proteinsynthesis, translates mRNA into proteins
55
What is the function of the rough endoplasmic reticulum?
Folds and processes proteins produced by ribosomes
56
What is the function of the smooth endoplasmic reticulum?
Synthesises and processes lipids
57
What is the function of the cell wall?
Supports the cell and prevents the cell changing shape
58
What is the function of the cell vacuole?
Maintains pressure inside the cell and keeps the cell ridged to prevent the plant from wilting
Isolates unwanted chemicals in the cell
59
What is the function of the capsule?
Protects bacterium from attack by immune system cells
60
What is the function of plasmids?
Contain genes that can be passed between prokaryotes
61
What is the function of flagella?
Allows the cell to move
62
What is the function of attachment proteins?
Allows the virus to identify and attach to a host cell
63
What is the function of the capsid?
Contains the nucleic acids of the virus
64
What are the features of the nucleus?
Nucleolus, nuclear envelope, nuclear pores, nucleoplasm, chromatin
65
What are the features of the mitrochondria?
double membrane, cristae, matrix
66
What are the features of the cell surface membrane?
Bilayer of phospholipids, cholesterol, proteins, glycoproteins, glycolipids
67
What are the features of endoplasmic reticulum?
cisternae, lamellae, ribosomes (RER)
68
What are the features of chloroplasts?
stroma, grana, lamella, chloroplast envelope, thykaloid
69
What are the features of golgi apparatus?
cisternae, vesicles, lumen, transface, cisface
70
What is the function of the nucleolus?
manufactures RNA and ribosomes
71
What is the function of the nuclear envelope?
controls entry-exit of the nucleous
72
What is the function of the nuclear pores?
allows large molecule passage
73
What is the function of chromatin
consists of protein bound linear DNA
74
What is the function of the double membrane?
controls entry and exit of material
75
What is the function of cristae?
extensions of the inner membrane providing a large surface area for enzyme and protein
76
What is the function of the matrix?
contains lipids, proteins, ribosomes and DNA, allowing protein production
77
What is the function of the cisternae
Contains enzymes to prevent any redundant enzymatic activity
78
What is the function of the chloroplast envelope?
selects what enters and exists the chloroplast
79
What is the function of the grana (thylakoids)?
Contains chlorophyll for photosynthesis and light absoption
80
What is the function of the stroma?
a fluid filled matrix where the sugars are synthesised for photosynthesis
81
What are the differences between prokaryotes and eukaryotes?
PROKARYOTES - Baterium, 0.1-10 um (typically 1um) 70s ribosomes, cell wall made of murein or peptidoglycan, binary fission
EUKARYOTES - Animal plant or fungi, 10-100 um, 80s ribosomes, cell wall made of celluloseor chitin, mitosis and meiosis
82
What are the steps of binary fission?
1. Circular DNA and plasmids replicate
2. Cell enlarges and dna loops move to poles
3. Cytoplasm divides producing two daughter cells
83
What are the steps of viral replication?
1. Virus attaches to host cell via receptor proteins
2. Genetic material is released into cell
3. Genetic material replicated by host cell
4. Viral components assemble
5. Replicated viruses leave from host cell
84
What are the four stages of the cell cycle?
Mitosis, Gap Phase 1, synthesis/interphase, gap phase 2
85
Describe the steps of interphase
1. DNA unravels and is replicated
2. Organelles are replicated
3. ATP content is increased
4. Protein production increases
86
Describe the steps of prophase
1. Chromosomes condence into sister chromatids
2. Centrioles move to poles forming spindle fibres
3. Nuclear envelope breaks down and nucleolus disappears
87
Describe the steps of metaphase
1. Sister chromatids line up in centre of cell
| 2. Joined to spindle apparatus by centromere
88
Describe the steps of anaphase
1. The centromeres divide separating the sister chromatids into chromosomes
2. The spindle fibres contact pulling the chromatids to the poles
89
Describe the steps of telophase
1. The chromatids uncoil and become long and thin
2. The nuclear envelope forms again
3. The cytoplasm begins to divide
90
Describe the steps of cytokinesis
1. The cytoplasm divides
| 2. Two daughter cells are produced
