Edexcel IGCSE Biology Cell Structure

This page contains the detailed and easy notes for Edexcel IGCSE Biology Cell Structure for revision and understanding Cell Structure.

Edexcel IGCSE Paper 1: Complete Revision Summary

 Cell Structure

 

Eukaryotic Cells – Plants and Animals

Prokaryotic Cells – Bacteria

EUKARYOTICPROKARYOTIC
Nucleus is present.Nucleus is absent.
All membrane bound organelles are presentMembrane bound organelles are absent.
DNA is enclosed in the nucleusDNA lies naked in the cytoplasm.
They are multicellularThey are mostly unicellular
DNA is linearDNA Is circular
Ribosomes are bigRibosomes are small
They are big cellsThey are small cells.
Example: Plants and AnimalsExample: Bacterial Cell

Animal Cells

NUCLEUS
  • It is the brain of the cell
  • It controls the activities of the cells
  • It contains DNA which holds our genetic information.
RIBOSOMES
  • It is the site for protein synthesis.
  • They are involved in making of proteins and enzymes required by the cell
CYTOPLASM
  • Jelly like fluid which fills the cell.
  • It is the site where all the chemical reactions of the cells take place as it contains all the major enzymes
CELL MEMBRANE
  • It the membrane that surrounds the cells
  • It controls what goes in and out of the cell.
MITOCHONDRIA
  • It is the powerhouse of the cell
  • It produced energy for the cell as it is the site for aerobic respiration

Plant Cell

PERMANENT VACUOLE
  • It is filled with cell sap.
  • It gives rigidity to the cells and makes the cell turgid
CELL WALL
  • Made up of cellulose.
  • It is the layer outside of the cell membrane
  • It supports the plant and maintain its shape.
CHLOROPLAST
  • It is the site for photosynthesis
  • It contains a green pigment, chlorophyll which absorbs light and prepared food.

 

Plant versus Animal Cell

ORGANELLEPlant CellAnimal Cell
NucleusPresentPresent
Cell MembranePresentPresent
MitochondriaPresentPresent
RibosomesPresentPresent
CytoplasmPresentPresent
Cell WallPresentAbsent
Permanent VacuolePresentAbsent
ChloroplastPresentAbsent

 

Bacterial Cell

Cell Wall
  • No cellulosic
  • made up of peptidoglycan
Circular DNA
  • No nucleus
  • Single DNA loop found naked in the cytoplasm
Plasmid
  • Extra chromosomal materials
  • They are in the form of small rings
  • They give special properties to bacteria like antibiotic resistance
Pilli
  • Hair like structures
  • Found on the surface
  • That helps bacteria to reproduce
Capsule
  • Slime layer
  • that protects the bacteria
Flagellum
  • Tail like structure
  • Helps the bacteria to move.

 

BACTERIAL VERSUS PLANT VERSUS ANIMAL CELLS

SPECIALISED ANIMAL CELLS

Special cells which have some extra features that allows them to perform specific functions

NERVE CELL

Function is to send electrical impusles round the body

  • Dendrites – They are hair like structures that receives the impulses
  • Axon – Long stalk the transmits the nerve impulses
  • Synapse – They transmit impulses from one neurone to another

MUSCLE CELL
  • Functions is to contract to bring about the movement of different parts of the body
  • They are made up of special fibres which helps them to contract and relax
  • Contain special proteins that allows them to contract and relax
  • They have loads of mitochondria which provides them energy to contract
  • They can store special storage carbohydrate called glycogen which acts as fuel for the muscles

SPERM CELL

Functions is to swim to the egg and fertilize it

  • Flagella – Helps it to swim to large distances
  • Mitochondria – Provides Energy to swim
  • Nucleus – Contains genetic information
  • Acrosome – Contains Hydrolytic enzyme to break the egg wall and penetrate inside the egg to fuse with the egg nucleus

Specialized Plant Cells

 

MICROSCOPES

Are the devices that use to see the cells which we cannot see by our naked eye.

MAGNIFICATION

The property of the microscope to enlarge the object.

RESOLUTION

The property of the microscope to distinguish between two closed placed objects.

Light and Electron Microscopes

LI&HT MICROSCOPESELECTRON MICROSCOPES
Uses beam of light to focus on the object.Use beam of electron.to focus on the object.
It is easy to handleIt is not easy to handle
It is small and compactIt is big and non portable
It does not require much expertise to handleIt requires proper training to handle
It can view the live samplesSamples have to be dead
No special sample preparations are requiredSpecial sample preparations ace required
Lower resolving power – 0.2μmGreater resolving power 0.5nm
Small magnifying power – x1000 -1500Greater magnifying power – x100000
Can form colour imagesForm 2D or 3D black and white images

 

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References:

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