Chapter 3 - Cells Flashcards
(72 cards)
1
Q
What is the equation for magnification?
A
Magnification = size of image / size of real object
2
Q
What is magnification?
A
Magnification is how many time bigger the image is
3
Q
What is resolution?
A
Resolution is the minimum distance between 2 objects without appearing blurred
4
Q
What is cell fractionation?
A
Cell fractionation is the process where cells are broken up and the different organelles they contain are separated out.
5
Q
What 3 conditions are required for cell fractionation?
A
- cold - to reduce enzyme activity that might break down the organelles
- isotonic - to prevent organelles bursting or shrinking as a result of osmotic gain or loss of water
- buffered - so that the pH does not fluctuate to not affect enzymes or organelles
6
Q
What are the 3 stages of cell fractionation?
A
- Homogenation
- Filtration
- Ultracentrifugation
7
Q
What is homogenation?
A
Cells are broken up by a homogeniser (blender) to open the cell membrane up and release organelles
8
Q
What happens during filtration?
A
The homogenate is filtered to remove any complete cells and large pieces of debris that may sink to the bottom
9
Q
What is ultracentrifugation?
A
- Organelles are spun at a low speed so the heaviest organelles form a pellet at the bottom on the centrifuge (spinning machine)
- The supernatant (residue liquid) is remove and respun at a faster speed to seperate organelles further
10
Q
Order the organelles from heaviest to lightest
A
- nuclei
- chloroplasts
- mitochondria
- lysosomes
- endoplasmic reticulum
- ribosomes
11
Q
How do light microscopes work?
A
A beam of light is passed through convex glass lenses to magnify the object
12
Q
What are 3 disadvantages of the light microscope?
A
- some organelles cannot be seen due to longer wavelength
- the specimen has to be very thin
- staining is needs to distinguish organelles
13
Q
What are 2 main advantages of electron microscopes?
A
- electrom beam has a short wavelength, so it has a high resolving power
- electrons are negatively charge, so higher focus through use of electromagnets
14
Q
What is the magnification and resolution of a light microscope?
A
1500x
0.2um
15
Q
What is the usual magnification and resolution of an electron microscope?
A
2,000,000x
0.1nm
16
Q
What is a transmission electron microscope?
A
- beam of electrons with use of EM radiation show image
- very high resolution
- 2D image
- no colour
- internal parts of organelles can be seen
17
Q
What is a scanning electron microscope?
A
- focused beam of electrons which reflect off the surface of structures
- 3D image
- sampels do not need to be thin
18
Q
Why do electron microscope need to be in a vacuum?
A
Air particles would interfere with beams of electrons so the specimens must always be dead
19
Q
What is the photomicrograph?
A
Photograph of an image produced by a microscope
20
Q
What are 5 disadvantages of electron microscopes?
A
- cannot be living material
- image is only 2D (TEM)
- specimen must be very thin (TEM)
- specimen take a long time to prepare
- image may contain artefacts, blocking organelles from view (TEM)
21
Q
What type of microscope would be sued to study replication of E.coli bacteria?
A
Light microscope because it is living.
22
Q
RDR
What are 3 roles of nucleus?
A
- control centre via production of mRNA + tRNA
- contain genetic material of cells
- produces ribosomes and ribosomes RNA
23
Q
What are 5 components of the nucleus?
A
- nuclear envelope - double membrane controlling exchange of substnaces
- nuclear pores - allow passage of molecules in and out of nucleus
- nucleoplasm - jelly material
- chromomes
- nucleolus - small sphere that makes ribosomes RNA
24
Q
What are 3 components of mitochondria?
A
- double membrane - control exchange of substances
- cristae - extensions of inner membrane to increase SA
- matrix - remainder liquid containing mitochondrial DNA and enzymes
25
What are 3 components of chloroplasts?
* chloroplast envelope - double membrane
* grana - stroage of thylakoids (contain chlorophyll)
* stroma - fluid matrix when sugar synthesis occurs (photosynthesis)
26
What 3 ways are chloroplasts adapted to their function?
* grana provide large SA for chlorophyll attachments
* stroma contains many enzymes
* chloroplasts contain DNA and ribosomes to make more photosynthetic enzymes
27
What is the rough endoplasmic reticulum?
* ribosomes present on surface + cisternae
* provides large SA for protein + glycoprotein synthesis
* provides pathway for transport of materials
28
What is the smooth endoplasmic reticulum?
* cristernae + no ribosomes - more tubular shape
* **lipid** synthesis, transport and storage
* **carbohydrate** synthesis, transport and storage
29
What is the structure of the golgi apparatus?
Flattened sacs (cristernae) with small rounded hollow structures (vesicles)
30
What are 5 functions of the golgi apparatus?
* add carbohydrates to proteins to form glycoproteins
* produces secretory enzymes
* secretes carbohydrates
* forms **lysosomes**
* modifies + labels **proteins** and **lipids**
31
What are 4 functions of lysosomes?
* hydrolyses material ingested by phagocytic cells
* **exocytosis** - releases enzymes outside cells to destroy materials
* digests worn out organelles - contain useful chemicals
* **autolysis**
32
What is **autolysis**?
A process where cells are broken down after they die
33
Describe the structure in ribosomes in all types of cells
80S - eukaryotic cells
70S - prokaryotic cells
consists of 2 subunits
34
What is the structure of a cell wall?
Microfibrils of cellulose embedded in a matrix
Middle lamella to join nearby cells together
35
What are cell walls in fungi made of?
Chitin (nitrogen based polysaccharide)
35
What is the structure of a vacuole?
* tonoplast - single membrane
* contains salts and sugars - used as a food source
36
What is a bacterial cell wall used for?
| + what is it made of
Protects cell against mechanical damage and osmitic lysis
Made of **peptidoglycan** (murein) - sugars + amino acids
37
What is the function of a capsule in a bacterial cell?
Prevents **desiccation** (drying out) and protects cell from viruses and antibiotics
38
What is a nucleoid?
Circular loop of DNA in bacteria that can't form chromosomes
39
What is the function of a flagella in a bacterial cell?
used for **locomotion** powered by protein motors
40
What is the function of a mesosome in a bacterial cell??
increases SA for enzymes
41
What is the function of **pilia** in a bacterial cell?
used in bacterial conjugation (DNA transfer)
42
What is **fungi** made up of?
Fungi is **eukaryotic** and have most of the organelles in plant cells, but do not have chloroplasts
43
What is the structure of a virus?
* contain nucleic acids - RNA or DNA
* capsid - protein coat
* lipid envelope
* attachment proteins - used in virus replication
* reverse transcriptae - found in capsid
44
# (3)
What are the roles of a capsid?
* protects nucleic acids from digestion by enzymes
* contains special sites to attach to a host
* provides proteins to allow virion to penetrate host cell
45
What is mitosis?
Mitosis is cell division where 2 genetically-identical daughter cells are produced
46
What happens during **interphase**?
DNA is replicated
Chromosomes are not yet formed
47
What happens during **prophase**?
* chromosomes condense and become visible
* nuclear envelope + nucleolus starts to break down
* centrioles move to poles of cellsand produce spindle fibres
48
What happens during **metaphase**?
* nuclear membrane has disappeared
* spindle fibres attach to centromeres and align chromosomes along equator
49
What happens during **anaphase**?
* spindle fibres pull centromeres apart
* chromatid are pulled to opposite ends of the cells
* cell starts to elongate
50
What happens during **telophase**?
* cell starts to divide
* nuclear envelope and nucleolus reforms
51
What is a **centriole**?
Tubular proteins that create spindle fibres
52
What happens during **cytokinesis**?
Cytoplasm and cell membrane splits into 2 daughter cells
53
What are the uses of mitosis?
* growth
* repair
* reproduction
54
What are the 3 stages of the cell cycle?
| + which is the longest
1. Interphase - resting phase as no division occurs
2. Nuclear division - nuclear divides into 2 or 4
3. Cytokinesis - cytoplasm divides to produce new cells
55
What are the 3 stages of interphase?
* G1 - organelles replicate and cell growths
* S - DNA synthesis
* G2 - energy stores replaced and cell growths again
56
What is **cancer**?
| + what causes it
Uncontrolled cell division caused by mutations
57
What are 3 sources of cancer treatments?
* Chemotherapy - prevents synthesis of enzymes required for DNA replication
* Radiotherapy - damages DNA so it can't pass the checkpoints in S phase
* Drugs - prevent spindle fibres from forming so mitosis cannot occur
58
What factors affect rate of cell division?
* Nutrients
* Oxygen
* Hormones
* Genes
* Risk factors - UV exposure, carcinogens
59
Why do tumours have a low blood supply?
The demand for oxygen cannot be kept up by the rate of mitosis
60
What is melalin?
Melalin is a pigment that reflects UV radiation
61
What is **metastasis**?
tumours spread out and form secondary tumours
62
What is **apoptosis**?
cells force to kill itself when it doesn't pass cell cycle checkpoints
63
What are the stages of binary fission?
1. The circular DNA in the cells replicates and both copies attach to the cell membrane. Plasmids also replicate.
2. The cell membrane then begins to grow between the two DNA molecules and begins to pinch inwards, dividing the cytoplasm in two.
3. A new cell wall forms between the two DNA molecules dividing the original cell.
4. The identical daughter cells each have a single copy of the circular DNA and a variable number of copiesof the plasmids.
64
What are the stages of virus replication?
1. They attach to host cell with attachment proteins
2. Nucleic acid is injected into host cell
3. Host cell replicates nucleic acid
4. Viruses form
65
What is in a lysosome?
H+ pump maintains acidic conditions to produce hydrolase enzymes
66
How do bacteria store excess food?
Food reserve granule suspended in cytoplasm
67
What is the role of **mitochondria**?
| active transport?
provides ATP and is the site of aerobic respiration
energy from respiration can be used for active transport against concentration gradient
68
How does DNA condense into chromosomes?
Histone proteins coil around the DNA and tighten it into chromosomes
69
How do lysosomes engulf phagocytes?
They fuse with a vesicle to release hydrolytic enzymes
70
What is the difference between eukaryotes and prokarytoes in terms of cell membranes?
Prokaryotes lack membrane-bound organelles
71
