Cell Structure Flashcards Preview

Biology A Level > Cell Structure > Flashcards

Flashcards in Cell Structure Deck (26):
1

What is resolution?

The ability of an optical instrument to see or produce an image that shows final detail clearly.

2

optical microscopes

Use light
Lower resolution
Maximum resolution 0.2 micrometers
Good for look at whole cells or tissue
Maximum useful magnification of a light microscope about x1500

3

Disadvantages of optical microscopes?

Uses only optical light between 400 and 700 nm
Resolution limits magnification
Wave length of visible light ranges from 400 to 700 nm so structures closer than 200nm will appear as one objects
Ribosomes can't be examined as they are too small

4

Stages of using microscope

Start by clipping slide containing specimen onto stage
Select lowest-powered lens
Use coarse adjustment knob to move objective lens down to just above slide
Look down eyepiece and adjustment knob until clear image
If you need to see slide with greater magnification swap higher-powered objective lens and refocus

5

Calculating magnification

Total magnification= magnifying power of objective lens x magnifying power of eyepiece lens

6

Details about laser scanning microscope

Use laser beams to scan specimen tagged with fluorescent dye
Laser causes dye to fluoresce give off light. Light focused through pinhole onto detector. Detector hooked up to computer generated image. Image can be 3D
Pinhole any out of focus is blocked so microscope produce a much clearer image than normal light microscope
Can be used to look at objects at different depths in thick specimens

7

Electron microscopes are

Large and expensive
Need great deal of skill and training to use
Transmission and scanning
Higher resolution

8

Transmission electron microscopes

Specimen have to be chemically fixed by dehydrated and stained
Beams of electrons passes through specimen stained by metal salts some electrons pass through and are focused on screen or photographic plate
Form 2D black and white images
Can produce up to 2 million times some even 50 million times

9

Scanning electron

Electrons bounce off specimen surface
3D image with magnification from 15 x to x 200000
Image black and white computer programme adds colour

10

Calculations

I/MA
Um to convert to x 1000

11

Graticules

Little thing used to measure under microscope

12

Nucleus

Has nuclear envelope with double membrane
Has nucleolus between envelope and nucleus
Control centre of cell, contains instructions of cell

13

Rer/ ser

Rough endoplasmic reticulum- Coated with ribosomes, provides area to assemble amino acids into proteins
Smooth endoplasmic reticulum- no ribosomes, catalyse reactions involved in lipid metabolism

14

Golgi appartus

Membrane bound sacs
Protein modifying

15

Mitochrondrion

Site of ATP production during aerobic respiration
Self replicating abudent to in cells

16

Chloroplasts

Can be any size
Green
Allows photosynthesis

17

Vacuole

Filled with water and dilutes
Only plant cells have them

18

Lysosomes

Small bags
Engulf old cells and foreign matter

19

Cilia and undulipodia

On outside of cell surface

20

Ribosomes

Small
Some bound on RER to synthesis protein

21

Centrioles

Two bundles of microfibres
Mostly involved in cell division

22

Cytoskeleton

Like trains around the cell to allow things to move

23

Cellulose cell wall

Provides strength and support
Maintains cells shape
Contributed to strength and support of whole plant
Permeable and allow solutions

24

Protein synthesis

MRNA in gene (nucleus)
Leaves through nuclear pore
RER
Vesicle
Golgi appartus
Vesicles

25

Eukaryotes

Bacteria
Plasma membrane, cytoplasm, smaller ribosomes, DNA and RNA, smaller, no membrane bound organelles, walls made of peptidoglycan not cellulose naked DNA as loop
Some have waxy capule, small loops of DNA (plasmids), flagella, pili
Divide by binary fission

26

What is magnification?

The number of times appear, compared with size of the object.