Cell Structure and Organisation

Nucleus

Controls cells activities and holds the chromosomes

• Double membrane called nuclear envelope
• Envelope has pores which allows transport of mRNA in and out
• Nuceloplasm - contains chromatin and coils of DNA bound to histone protein
• Nucleolus - produces RNA to make ribosomes

Mitochondria

• double membrane - seperated by intermembrane space
• inner membrane folded inwards to form cristae
• matrix containing compounds and DNA allowing them to produce own protein

Site of aerobic respiration

Produces ATP

Metabollically active cells contain many mitochondria e.g. muscle cells

Endoplasmic Reticulum (ER)

• double membrane forming flattened sacs
• fluid filled spaces between called cisternae
• interconnected and allows transport of materials throughout cell

Rough ER

• Ribosomes on outer surface
• Transports proteins made by ribosomes

Smooth ER

• Lack of ribosomes
• Synthesis and transport of lipids

Ribosomes

• made up of one large and one small sub unit
• made in nucleolus from rRNA and protein
• used in protein synthesis

Golgi Body

• Rough ER is pinched off at ends forming vesicles
• Vesicles fuse to become golgi
• Proteins transported in vesicles - they are modified and packaged
• At other end, vesicles are pinched off
• Products secreted by exocytosis and vesicle fuse with membrane

Functions

• Produce secretory enzymes
• Secrete carbohydrates
• Produce glycoprotein
• Transport and store lipids
• Form lysosomes

Lysosomes

• small vacuoles formed when portions of golgi body are pinched off
• contain digestive enzymes
• remove worn out organelles and dangerous material e.g. bacteria
• reuse useful components

Centrioles

• during cell division, they divide and move to opposite poles of cell
• synthesise microtubules of spindle

located just outside nucleus in cytoplasm (centrosome)

Chloroplasts

• double membrane
• stroma - contains ribosomes, lipid, circular DNA, starch grains
• thylakoids - flattened sacs in stroma
• granum - many thylakoids
• chlorophyll found within thylakoids

Vacuole

• plant cells have large permanent vacuoles but animal cells have small ones
• single membrane (tonoplast)
• contain cell sap (provides osmotic system)
• water enters cell by osmosis, causing it to swell and it becomes turgid, keeping plants upright

Cellulose Cell Wall

• contains microfibrils embedded in a polysaccharide matrix
• permeable to water - strong to resist swelling so it can become turgid
• microfibirils provide mechanical strength

Plant

• cell wall and membrane
• chloroplasts
• large vacuole
• no centrioles
• plasmodesmata

Animal

• no cell wall, but has membrane
• no chloroplasts
• small vacuoles
• centrioles
• no plasmodesmata

Tissues

Group of similar cells, specialised in the same way

• Cilia epithelial - trachea
• Columnar epithelial - stomach / intestines
• Squamous epithelial - alveoli
• Cuboidal epithelial - kidney tubules

Organs

Aggregation of several tissues that perform a specific function e.g. heart, lungs etc.

Organ System

Aggregation of organs that together perform a specific function e.g. respiratory system, digestive system etc.

Prokaryotes

• no membrane bound organelles
• small ribosomes
• circular DNA free in cytoplasm
• no membrane
• cell wall made of peptidoglycan

Eukaroytes

• membrane bound organelles
• large ribosomes
• DNA in chromosomes
• cell wall made of cellulose (plants)

• causes diseases
• no membrane, metabolism or organelles
• made up of protein coat and nucleic acid
• invade host cel and take over nucleus and multiply

Bacteriophages (T2 phage)