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Topic 2A- Cell Structure and
Division
Created

@February 10, 2025 8:27 PM

Class

Cells to Systems

Prokaryotes or Eukaryotes
Prokaryotic cells are single celled organisms
Smaller and simpler like bacteria
Eukaryotic cells are complex and includes animal and plants cells
Both cell types contain organelles

Plant Cell
Contains similar organelles as animal cells
Has cellulose cell wall for substance exchange with surrounding cells
Contains vacuole which has cell sap
Also chloroplasts

Algal Cells
Very similar to plant cells
Has the same organelles

Fungal Cells

Topic 2A- Cell Structure and Division

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Similar contents to plant cells
Cell walls are made of chitin instead of cellulose
No chloroplasts

Different Organelles
Cell- Surface Membrane
Found on animal cells and inside cell wall
Made of lipids and proteins
Regulates movement of substances in/out of cell
Contains receptor molecules allowing to respond to chemicals
Nucleus
Big organelle surrounded by nuclear envelope
Contains chromosomes made from nucleolus
Controls cell activities
Has DNA which contains instructions for protein synthesis
Mitochondrion
Has double membrane
Inner membrane is folded to form Cristae structures
Contents contain enzymes for respiration
Area of aerobic respiration for ATP production
High in numbers
Chloroplast
Found in plants and algae
Double membrane
Has membrane known as Thylakoid membranes which form grana

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Area of photosynthesis
Golgi Apparatus
Fluid filled sacs
Contains vesicles around the edges
Sorts and packages lipids and proteins
Makes lysosomes
Golgi Vesicle
Fluid filled sac in cytoplasm
Produced by golgi apparatus
Storage of lipids and proteins
Transports them out of cell
Lysosome
Round organelle surrounded by membrane
Contains hydrolytic enzymes to digest hostile cells
Ribosome
Small organelle floating freely or attached to rough endoplasmic
reticulum
Made of proteins and RNA
Produces proteins
Rough Endoplasmic Reticulum
Surface contains ribosomes
Processes proteins
Smooth Endoplasmic Reticulum
Contains no ribosomes
Makes lipids
Cell Wall

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Rigid structure surrounding cells in plants, algae and fungi
Made of cellulose in plants and algae
Made of chitin in fungi
Supports cells and prevents shape change
Cell Vacuole
Found in cytoplasm in plants
Contains cell sap
Surrounding membrane is known as Tonoplast
Maintains internal cell pressure
Isolates unwanted chemicals inside cell

Specialised Cell Organelle
Cells can become specialised in multicellular organisms carrying out
specific functions
Structure of cell makes it fit for function

Tissues, Organs and Organ Systems
Specialised cells can form tissues, group of cells working a specific task
Group of tissue forms organs
Different organs create the organ system

Prokaryotic Cell Structure
Cytoplasm
Contains ribosomes but can be smaller than those in eukaryotic cells

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Flagellum
Long- hair like structure
Rotates to create cell movement
Organelle isn’t in every prokaryote but some have more than one
No nucleus
DNA floats in cytoplasm
DNA is presented as long coiled strand and not attached to proteins
Plasma Membrane
Made of lipids and proteins
Substance regulation in and out of cell
Cell Wall
Supports cell structure
Made of murein, glycoprotein
Capsule
Made of secreted slime
Protects bacteria from immune system attack
Plasmids
Small DNA loops
Contains genes for antibiotic resistance
Can be passed to other bacteria
Not always present in prokaryotes

Viruses
Nucleic acid surrounded by protein
Smaller than bacteria

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Contains no plasma membrane, cytoplasm or ribosomes
Invades and reproduces inside other organisms
Has DNA or RNA
Coat called Capsid surrounds DNA core

Binary Fission
DNA and plasmids replicate
DNA can only replicate once but plasmids have unlimited chances
DNA loops migrate to opposite sides of cell as cell increases in size
Cytoplasm divides
Two daughter cells are produced, containing one copy of DNA but
different numbers of plasmids

Host Cell Replication
Viruses use attachment proteins to bind to complementary receptor
proteins
Different receptor proteins used depending on host cell
Viruses own DNA/RNA is injected into host mimicking a hijack
Using the host, viral molecules are able to replicate

Analysing Cell Components
Magnification
How big the image is compared to the specimen itself

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Resolution
Image quality

Optical Microscopes
Uses light to create image
Unable to view organelles smaller than 0
...
5k

Electron Microscopes
Electrons used for image
Higher resolution= More detailed image
Max resolution of 0
...
5mil
Scanning Microscopes/ TEMS
Uses electromagnets to transmit electrons through specimen
Denser areas absorbs more electrons, darker imagery
High resolution pics
Only works on thin specimens
Transmission Microscopes/ SEMS
Scans electron beam across specimen to form image
Shows specimen surface in 3D
Can be used on thick specimens
Lower quality images

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Cell Division: Mitosis
Parent cell dividing two genetically identical cells
Required in multicellular organism growth
Repairs damaged tissue

Mitosis Division Stages
Prophase
Chromosomes condense
Centrioles move to opposite sides of cell, forming spindle fibres
Nuclear envelope breaks down
Metaphase
Chromosomes become aligned in the centre and attach to spindle
Anaphase
Centromeres divide and separate chromatid pairs
Spindles contract, pulls chromatids to opposite ends of spindle
Telophase
Chromatids reach opposite sides of spindle
Strand uncoils and become chromosomes
Nuclear envelope forms around chromosome groups
Cytoplasm divides each containing daughter cells

Cancer- Uncontrolled Cell Division
Mitosis in controlled by genes
Uncontrolled cell division forms a tumour
Tumour invades surrounding tissue

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Cancer Treatment
G1
Chemotherapy drugs prevents enzyme synthesis
Prevents synthesis phase and forces cell to kill itself
S Phase
Radiation usage can damage DNA
If damage is severe enough, cell kills itself preventing tumour growth

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