Cell structure Flashcards
(43 cards)
1
Q
What is the equation for working out magnification?
A
Magnification = size of image / size of real object
2
Q
What is cell fractionation?
A
The process where cells are broken up and the different organelles they contain are seperated out
3
Q
What conditions are needed for cell fractionation, and why?
A
- Cold: to reduce enzyme activity that may break down the organelles
- Buffered: maintain pH so that protein structure does not change
- Isotonic: to maintain the same water potential so water doesn’t move in or out by osmosis
4
Q
What are the steps of cell fractionation?
A
- Homogenisation to break down the cells to release the organelles, resulting in a fluid called the homogenate
- Filtration to remove any excess cell debris
- Ultracentrifugation where the samples are spun in a centrifuge. The heaviest organelles ( the nuclei ) are forced to the bottom of the tube where they form a pellet, the fluid at the top ( the supernatant ) is removed. The supernatant is then transferred to a different tube and is spun at a higher speed
5
Q
What is the order of organelle separation?
A
Nuclei -> mitochondria ( and chloroplasts ) -> lysosomes -> endoplasmic reticulum -> ribosomes
6
Q
What is resolution?
A
The minimum distance that two objects can be distinguished apart in an image
7
Q
Why do light microscopes have low resolution?
A
As wavelength of light is too long, to distinguish between two objects with a small distance
8
Q
How do electron microscopes work?
A
- They use beams of electrons that are focused by electromagnets inside a vacuum environment
- The vacuum is needed so that particles in the air can not deflect the electrons
9
Q
How do transmission electron microscopes work?
A
- A beam of electrons pass through a thin section of a specimen
- Areas that absorb the electrons appear darker on the electron micrograph that is produced
10
Q
How do scanning electron microscopes work?
A
- A beam of electrons pass across a surface and scatter
- The pattern of the scattering builds up a 3D image depending on the contours of the specimen
11
Q
What are some limitations of using electron microscopes?
A
- Whole system must be in a vacuum, so living specimens can not be observed
- Specimens have to be very thin, particularly for TEM so that the electrons can pass through
- SEM has a lower resolving power than TEM, but both are still greater than light microscopes
12
Q
What is the structure of the nucleus?
A
- Nuclear envelope: a double membrane that controls the entry and exit of materials in and out of the nucleus
- Nuclear pores: allow the passage of large molecules
- Nucleoplasm: jelly-like material that makes up the bulk of the nucleus
- Chromosomes: consist of protein-bound, linear DNA
- Nucleolus: manufactures ribosomal RNA and assembles the ribosomes
13
Q
What is the structure of the mitochondria?
A
- Double membrane that controls entry and exit of materials
- Inner membrane is folded to form cristae that provide a large surface area for the attachment of enzymes and other proteins
- Matrix contains proteins, lipids, ribosomes and DNA that allows them to produce some of their own proteins
14
Q
What is the role of mitochondria?
A
- Site of aerobic respiration
- Produces ATP
15
Q
What is the structure of chloroplasts?
A
- Chloroplast envelope: double plasma membrane that is highly selective in what it allows to enter and exit the chloroplast
- Grana which are stacks of thylakoids
- Thylakoids contain chlorophyll
- Stroma: a fluid-filled matrix
16
Q
What is the function of chloroplasts?
A
To carry out photosynthesis
17
Q
What is the function of rough endoplasmic reticulum?
A
- Provide a large surface area for the synthesis of proteins and glycoproteins
- Provides a pathway for the transport of proteins throughout the cell
18
Q
What is the function of the smooth endoplasmic reticulum?
A
- Synthesise, store and transport lipids
- Synthesise, store and transport carbohydrates
19
Q
What is the difference between rough and smooth endoplasmic reticulums?
A
Rough has ribosomes, whereas smooth does not
20
Q
What is the function of the golgi apparatus?
A
- Add carbohydrates to proteins to from glycoproteins
- Modify proteins and lipids
- Transport lipids and proteins in vesicles
- Form lysosomes
21
Q
What are the functions of lysosomes?
A
- Hydrolyse material ingested by phagocytic cells
- Release enzymes outside of the cell to destroy material around it
- Digest worn out organelles so the useful chemicals that are made of can be re-used
- Break down cells after they have died
22
Q
What is the function of ribosomes?
A
Protein synthesis
23
Q
What are the two types of ribosomes?
A
- 80S, found in eukaryotic cells
- 70S, found in prokaryotic cells, mitochondria and chloroplasts, and are smaller than 80S
24
Q
What is the structure of cell walls?
A
- Consist of a number of polysaccharides
- Thin layer called middle lamella between adjacent cell walls
25
What are the functions of cellulose cell wall?
- Provide strength to prevent cell from bursting under the pressure created when water enters via osmosis
- Provide strength to plant overall
26
What are bacterial cell walls made of?
Peptidoglycan ( or murein )
27
What are fungi cell walls made from?
Chitin
28
What is the structure of a vacuole?
- A fluid-filled sac bounded by a single membrane called the tonoplast
- Contains a solution of mineral salts sugars, amino acids and wastes
29
What are the functions of a vacuole?
- Make cells turgid
- Contain sugars and amino acids that can act as a temporary food store
30
What are epithelial tissues?
- Sheet of cells that line the surfaces of organs
- Have a protective or secretory function
31
What are xylem?
- Hollow tubes in plants
- Used to transport water and mineral ions throughout the plant
32
What is the structure of bacterial cells?
- Cell wall made of peptidoglycan
- Capsule which protects bacterium from other cells
- Cell membrane
- 70S ribosomes
- Circular strand of DNA which possesses genetic information for replication
- Plasmids which possess genes that aid survival
33
What is the structure of a virus?
- Nucleic acids
- Capsid
- Lipid envelope which are derived from the host cell
- Attachment proteins
34
What happens during interphase?
- G1: cell increases in size and synthesises proteins
- S: genetic information is replicated into two identical copies of each chromosome
- G2: cell continues growing
35
What happens during prophase?
- Nuclear envelope dissolves
- Centrioles move to opposite poles of the cell
- Chromosomes condense
36
What happens during metaphase?
- Chromosomes line up on the cell equator
- Spindle fibres attach to them
37
What happens during anaphase?
- Sister chromatids are pulled to either pole of the cell
- The chromatids are now called daughter chromosomes
38
What happens during telophase?
- Nuclear envelope reforms
- Spindle fibres dissapear
39
What happens during cytokinesis?
Cell divides into two identical daughter cells
40
What is the process of binary fission?
- Circular DNA replicates and attaches to cell membrane
- Cell membrane grows between the two DNA molecules
- Cytoplasm divides into two
- New cell wall forms between the two molecules of DNA
- Produces two identical daughter cells
41
How do viruses replicate?
- Attachment proteins attach to host cell
- Nucleic acids are injected into host cell
- Host cell produces components of the virus, which are then assembled to form new viruses
42
What is cancer?
A group of diseases caused by uncontrolled growth and division of cells
43
How do chemotherapy drugs work to treat cancer?
- Prevent the DNA from replicating
- Inhibit the metaphase stage of mitosis by interfering with spindle formation
