3.1 - 3.4 Studying cells Flashcards
(52 cards)
1
Q
Magnification =
A
Size of image/size of real
2
Q
Magnification
A
How many times bigger the image is when compared to the real object
3
Q
Resolution
A
The minimum distance apart that two objects can be in order for them to appear as separate items
4
Q
Cell fractionation
A
The process where cells are broken up and the different organelles they contain are separated out
5
Q
Before cell fractionation can begin, the tissue is placed in a solution. The solution is:
A
- Cold - to reduce enzyme activity breaking down organelles
- Isotonic - to prevent organelles bursting or shrinking due to osmosis
- Buffered - so that pH does not fluctuate, to avoid changes to enzymes or organelles (prevents denaturing)
6
Q
Describe the process of homogenation
A
- Cells broken up by a homogeniser to remove organelles from the cell
- Homogenate then filtered to remove debris
7
Q
Describe the process of ultracentrifugation
A
- Test tube of filtrate placed in a centifuge and spun at a slow speed
- Heaviest organelles fall to the bottom, forming a pellet
- Supernatant is removed
- Supernatant put in another tube, spun faster
8
Q
What order do the organelles come out in in ultracentrifugation?
A
- Nuclei
- Chloroplasts (plant cells only)
- Mitochondria
- Lysosomes
- ER
- Ribosomes
9
Q
How does a Transmission Electron Microscope work? (TEM)
A
- Electron gun produces beam of electrons
- Focused on specimen by a condenser electromagnet
- Beam passes through specimen
- Variation in electrons get through, produces image on screen (photomicrograph)
Resolving power = 0.1 nm
10
Q
What are the limitations of a TEM?
A
- System must be in a vacuum (no live specimens)
- Complex staining process
- Black and white image
- Image may contain artefacts
- Specimen must be very thin
11
Q
How does a Scanning Electron Microscope work?
A
- Beam of electrons from above
- Passed back and forth in a regular pattern
- Electrons are scattered by the specimen, depending on the contour of the specimens surface
- Analyse scattered electrons and secondary electrons
- 3D image produced
Resolving power = 20nm
12
Q
What advantages does a SEM have over a TEM?
A
- Thicker specimen
- 3D image
13
Q
What are the limitations of a SEM?
A
- In a vacuum (no live specimens)
- Complex staining process
- Image may contain artefacts
- Lower resolution than TEM
14
Q
Describe the structure of the nucleus
A
- Spherical, 10-20 nm diameter
- Nuclear envelope = Double membrane that surrounds the nucleus
- Nuclear pore = Hole in nuclear envelope that allows things in and out
- Nucleoplasm = Jelly like material
- Chromosomes = Made up of DNA
- Nucleolus = Makes ribosomal RNA and assembles ribosomes
15
Q
Describe the function of the nucleus
A
- Controls production of mRNA and tRNA
- Makes ribosomal RNA and ribosomes
- Houses DNA
16
Q
Describe the structure of mitochondria
A
- Rod shaped, 1-10um length
- Double membrane = controls in and out, inner membrane has cristea
- Cristea = Provide large SA for attachment of enzymes and other ribosomes
- Matrix = fluid filled inner space where DNA, proteins, lipids, ribosomes and enzymes for respiration are found
17
Q
Describe the function of mitochondria
A
Produce energy carrier molecule ATP
18
Q
Describe the structure of chloroplasts
A
- Disc shaped, 1um diameter, 2-10um length
- Chloroplast envelope = double plasma outer membrane
- Thylakoids = discs that contain chlorophyll
- Grana = stacks of 100+ thylakoids
- Stroma = fluid filled matrix where second stage photosynthesis takes place
19
Q
Describe the function of chloroplasts
A
- Granal membrane provides large SA for attchment of chlorophyll, electron carriers and enzymes for 1st stage photosynthesis
- Stoma fluid contains enzymes for 2nd stage photosynthesis
- Manufactures some proteins
20
Q
Describe the structure of Rough Endoplasmic Reticulum (RER)
A
- Sheet like membranes spread through cytoplasm
- Cisternae = tubules and flattened sacs
- Ribosomes = outer surface of membranes
21
Q
Describe the function of RER
A
- Provide large SA for protein and glycoprotein synthesis
- Provide pathway for transport of materials
22
Q
Describe the structure of Smooth Endoplasmic Reticulum (SER)
A
- Similar to RER
- No ribosomes
- More tubular
23
Q
Describe the function of SER
A
Synthesise, store and tranport lipids and carbohydrates
24
Q
Describe the structure of the Golgi apparatus
A
- Cisternae = stacks of membranes that make up flattened sacs
- Vesicles = small. hollow, rounded structures
25
Describe the function of the Golgi apparatus
- Produce glycoproteins, secretory enzymes and lysosomes
- Secrete carbohydrates
- Transport, modify and store lipids
26
Describe the structure of lysosomes
- Vesicles that contain enzymes
- 50+ lysozymes per lysosome (enzymes that digest certain bacteria cell walls)
- Up to 1um diameter
27
Describe the function of lysosomes
- Hydrolyse material ingested by phagocytic cells
- Exocytosis (release enzymes to outside cell to destroy surroung material)
- Digest wornout organelles for the reuse of chemicals
- Autolysis (completely break down dead cells)
28
Describe the structure of ribosomes
- Two types = 80S (found in eukaryotic, 25nm diameter)
= 70S (found in prokaryotic, smaller)
- 1 large and 1 small subunit
- Contain ribosomal RNA and protein
29
Describe the function of ribosomes
Protein synthesis
30
Describe the structure of the cell wall
- Lots of polysaccharides (eg cellulose)
- Middle lamella = glues cells together
31
Describe the function of the cell wall
- Provide strength to stop cell bursting
- Mechanical strength to plant as a whole
- Allows water to pass along it
32
Describe the structure of a vacuole
- Fluid filled sac
- Tonoplast = single layer outer membrane
- Contains mineral salts, sugars, amino acids, waste and sometimes pigments
33
Describe the function of a vacuole
- Supports herbaceous plants by making cells turgid
- Sugars and amino acids may act as a temporary food store
- Pigments may colour petals, attracting pollinators
34
What is the organisation order in an organism?
```
Organelle
Cell
Tissue
Organ
Organ system
Organism
```
35
What is the purpose of the cell wall of a bacterial cell?
- Physical barrier
- Excludes certain substances
- Protects against mechanical damage
- Protects against osmotic lysis
36
What is the purpose of the capsule of a bacterial cell?
- Protects bacterium from other cells
| - Helps groups of bacteria stick together for protection
37
What is the purpose of the cell-surface membrane of a bacterial cell?
- Differentially permiable layer, controls entry and exit of chemicals
38
What is the purpose of the circular DNA in a bacterial cell?
- Possesses genetic information
39
What is the purpose of a plasmid in a bacterial cell?
- Possesses genes that may aid survival in adverse conditions
40
Prokaryotic cells vs Eukaryotic cells - nucleus
```
P = No true nucleus
E = Distinct nucleus with a nuclear envelope
```
41
Prokaryotic cells vs Eukaryotic cells - proteins
```
P = DNA not associated with proteins
E = DNA associated with proteins called histones
```
42
Prokaryotic cells vs Eukaryotic cells - DNA
```
P = Some DNA in circular plasmids
E = No plasmids, linear DNA
```
43
Prokaryotic cells vs Eukaryotic cells - membrane
```
P = No membrane-bounded organelles
E = Membrane-bounded organelles
```
44
Prokaryotic cells vs Eukaryotic cells - chloroplasts
```
P = No chloroplasts
E = Chloroplasts in plants and algae
```
45
Prokaryotic cells vs Eukaryotic cells - ribosomes
```
P = Smaller ribosomes (70S)
E = Larger ribosomes (80S)
```
46
Prokaryotic cells vs Eukaryotic cells - cell wall
```
P = Cell wall made of murein
E = Cell wall made of cellulose (or chitin in fungi)
```
47
Prokaryotic cells vs Eukaryotic cells - capsule
```
P = Capsule
E = No capsule
```
48
Describe the passage of an amino acid through organelles, from the cytoplasm until it is excreted from the cell as a protein
- Cytoplasm
- RER
- Golgi body
- Lysosomes
49
Describe how to measure the length of something under a microscope
- Measure with eyepiece graticule
- Calibrate with stage micrometer
- Repeat and calculate the mean
50
Which organelles does a prokaryotic cell have?
- Cell wall
- Cell surface membrane
- Ribosomes
- Plasmid
- Nucleic acids
- Mitochondria
- Capsid
- Choloroplasts
- Cell wall (P)
- Cell surface membrane (P)
- Ribosomes (P)
- Plasmid (A)
- Nucleic acids (P)
- Mitochondria (A)
- Capsid (A)
- Choloroplasts (A)
51
Which organelles does a eukaryotic cell have?
- Cell wall
- Cell surface membrane
- Ribosomes
- Plasmid
- Nucleic acids
- Mitochondria
- Capsid
- Choloroplasts
- Cell wall (S)
- Cell surface membrane (P)
- Ribosomes (P)
- Plasmid (S)
- Nucleic acids (P)
- Mitochondria (P)
- Capsid (A)
- Choloroplasts (S)
52
What organelles does a virus have?
- Cell wall
- Cell surface membrane
- Ribosomes
- Plasmid
- Nucleic acids
- Mitochondria
- Capsid
- Choloroplasts
- Cell wall (A)
- Cell surface membrane (A)
- Ribosomes (A)
- Plasmid (A)
- Nucleic acids (P)
- Mitochondria (A)
- Capsid (P)
- Choloroplasts (A)
