Cells - Methods Of Studying Cells

Question 1

What are the three methods of studying cells?

Answer 1

Light microscopes.
Electron microscopes.
Cell fractionation and ultracentrifugation.

Question 2

How does a light microscope work?

Answer 2

It has a pair of convex glass lenses which first focus on a beam of light onto or through an object.

Question 3

What is the resolution of images from a light microscope?

Answer 3

0.2 um

Question 4

Why is the resolution of a light microscope so big?

Answer 4

Because it uses the wavelength of light which restricts the resolution because it’s long.

Question 5

What is the resolution of an electron microscope?

Answer 5

0.1 nm

Question 6

What is the equation for calculating magnification?

Answer 6

Magnification = size of image/size of real object.

Question 7

What is resolution?

Answer 7

The minimum distance apart that two objects can be distinguished a separate objects in an image.

Question 8

What are the two types of electron microscope?

Answer 8

Transmission electron microscope.
Scanning electron microscope

Question 9

How do electron microscopes work?

Answer 9

A beam of electrons that are focused by electromagnets inside a vacuum.

Vacuum is needed so that the particles in the air do not deflect the electrons out of the beam alignment.

Question 10

How does a transmission electron microscope work?

Answer 10

A beam of electrons passes through a thin section of a specimen. Areas that absorb the electrons appear darker on the electron micrograph that is produced.

Question 11

How does a scanning electron microscope work?

Answer 11

A beam of electrons passes across the surface and scatter. The pattern of scattering buildup a 3-D image depending on the contours of the specimen.

Question 12

What are the limitations of the electron microscopes?

Answer 12

– The whole system must be in a vacuum so living specimens cannot be observed.
– A complex staining process is required which may introduce artefacts to the image.
– Specimens have to be very thin particularly so that the electrons can pass through .
– SEM has a lower resolving power than TEM, but both have greater resolving power than a light microscope.

Question 13

What is cell fractionation?

Answer 13

The process in which different parts and organelles of a cell are separated so that they can be studied in detail. The most common method of cell fractionation is differential centrifugation.

Question 14

What is the process of homogenisation?

Answer 14

1. Cells are blended in a homogeniser forming a resultant fluid called the homogenate. This is then filtered to get rid of cell debris. This is then placed in a centrifuge and spun at low speed.
2. Heaviest organelles e.g. the nuclei form at the bottom where a thin pellet forms.
3. The fluid at the top called the supernatant is removed, leaving the pellet nuclei. The superation is then transferred to another tube and spend slightly faster.
4. The process continues so that each time the speed is increased the next densest organelle is sediment and separated out.

Question 15

The homogenate at the beginning has to be in an ice cold buffered isotonic solution why?

Answer 15

Ice cold: reduce the activity of enzymes that break down organelles
Buffered: to prevent organelle proteins including enzymes from becoming denatured
Isotonic: to prevent water from moving into the organelles via osmosis which would cause them to burst.

Question 16

In a plant cell, what is the most densest organelle to the least densest?

Answer 16

Nucleus
Chloroplast
Mitochondria
Lysosomes
Endoplasmic reticulum
Ribosomes

Question 17

What are the features of a eukaryotic cell?

Answer 17

They contain a nucleus and membrane found organelles.

Question 18

What is the role of the nucleus?

Answer 18

Nuclear envelope: double membrane containing 3000 nuclear ores which enables molecules to enter and leave.

Contains chromatin and nucleolus which is part of ribosome production. a granular like a jelly material called nucleoplasm makes up the bulk of the nucleus.

Question 19

What is the rough endoplasmic reticulum?

Answer 19

Series of flattened sacks enclosed by a membrane with ribosomes on the surface. RER folds and processes proteins made on the ribosomes.

Question 20

What is the smooth endoplasmic reticulum?

Answer 20

System of membrane bound sacs. SER produces and processes lipids.

Question 21

What is the Golgi apparatus?

Answer 21

A series of fluid filled, flattened and curved sacks with vehicles surrounding the edges. Golgi apparatus processes and packages, proteins and lipids. It also produces lysosomes.

Question 22

What is the mitochondria?

Answer 22

Found a double membrane called the envelope inner membrane is folded to form projections called cristae with a matrix on the inside containing all the enzymes needed for respiration it is the site of aerobic respiration.

Question 23

What are centrioles?

Answer 23

Hollow cylinders containing a ring of microtubules arranged at right angles to each other. Centrioles are involved in producing spindle fibres for cell division.

Question 24

What are the ribosomes?

Answer 24

Composed of two sub units and are the site of protein synthesis.

Question 25

What are the lysosomes?

Answer 25

They are vesicles containing digestive enzymes bound by a single membrane.

Question 26

What are the components of a prokaryotic cell?

Answer 26

Cell wall
Capsule
Plasmid
Flagellum
Pili
Ribosomes

Question 27

What is the capsule?

Answer 27

Protective slimy layer which helps the cell to retain moisture and adhere to surfaces.

Question 28

What is the plasmids?

Answer 28

Circular piece of DNA.

Question 29

What is the flagellum?

Answer 29

A tail like structure which rotates to move the cell.

Question 30

What is the Pili?

Answer 30

Hair like structure which attached to other bacterial cells.

Question 31

Viruses are nonliving so what do they consist of?

Answer 31

Nucleic acid enclosed in a protective protein Coke called the capsid sometimes covered with a lipid layer called the envelope.

Question 32

Viruses are nonliving so what do they consist of?

Answer 32

Nucleic acid enclosed in a protective protein Coke called the capsid sometimes covered with a lipid layer called the envelope.

Question 33

How are cells of multicellular organisms organised?

Answer 33

Groups of cells organised to form tissues.
Groups of tissues organised to form organs.
Groups of organs form organ systems.