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SB1 Revision Notes

Microscope

Hooke’s

Van Leeuwenhoek

Modern (light)

Electron

When?

1965

 

Use Hooke’s

1930s

Magnification

X30

X270

X1500

X2,000,000

Resolution

 

0.00014mm

0.0001mm

0.0000002mm

How?

Not powerful

Bad quality lenses

2 lenses

Very small lenses

Single-lens microscope

Found animalcules

Stains

Better lenses + light sources

Beam of electrons instead of light

Most detail of the cell

 

Resolution = smallest distance 2 points can still be seen as 2 points

Total magnification = magnification lens 1 x magnification lens 2

 

Prefix

Effect on unit (from a metre)

Example

milli-

¸1,000

Millimetres (mm)

micro-

¸1,000,000

Micrometres (mm)

nano-

¸1,000,000,000

Nanometres (nm)

pico-

¸1,000,000,000,000

Picometres (pm)

 

1.     Specimen placed on a transparent, 1mm thick glass slide

2.     Iodine added as a stain so it can be seen

3.     Thinner glass cover added on top to flatten the sample; placed on a stage; held in place with clips

 

4 lenses in total: 1 eyepiece, 3 objectives: 4x, 10x, 20/40x (convex lenses)

Circular area of the image on a microscope = field of view

 

 

Part of animal cell:

Purpose:

Nucleus, cells with nucleus = eukaryotic

-        Controls the cell and its activities

-        Contains chromosomes which contain DNA

Cell membrane

-        Thin bag controls what enters and leaves

-        Separates cells from one another

Cytoplasm

-        Watery jelly where most activities occur

-        Contains ribosomes (make proteins)

Mitochondrion

-        Where aerobic respiration occurs

-        Creates glucose for energy

 

 

Part of plant cell:

Purpose:

Cell wall

-        Made of cellulose

-        Supports and protects cell

Chloroplasts

-        Contain chlorophyll

-        Where photosynthesis occurs for energy

Vacuole

-        Stores cell sap as food

-        Keeps cell firm + rigid in replace of skeleton

 

Specialised cells = cells that have differentiated to perform specific roles

 

Digestion

Part of system

Purpose

Adaptions

Small intestine

Cells in lining absorb food molecules

Have microvilli to increase surface area to absorb more food + faster

Pancreas

Cells make enzymes needed to digest food in the small intestine

Enzymes are proteins so the producing cells have lots of ribosomes

Small intestine

Muscle cells squeeze food along

Muscle cells need lots of energy so have many mitochondria

 

Reproduction

Sexual reproduction: two gametes fuse to make a fertilised egg cell that becomes an embryo

All other nuclei contain 2 copies of each chromosome (46 total = diploid), gametes have 1 set of each (23 total = haploid) so when they combine they make 1 complete cell

 

Part of egg cell

Adaptations

Cell membrane

Fuses with sperm cell membrane

Becomes hard after 1 sperm enters

Cytoplasm

Packed with nutrients for energy + growth materials when fertilised

Jelly coat

Protects cell

Hardens after 1 sperm enters

Nucleus

Haploid

 

Part of sperm cell

Adaptations

Shape

Streamlined for swimming

Nucleus

Haploid

Acrosome tip

Contains enzymes to break down egg jelly coat

…