The cell

Cell theory:

All living things contain cells.

All cells come from other cells.

VirusesAre viruses living?

Influenza virus (an Orthomyxovirus)

According to cell theory no.

However they do contain organic molecules (DNA or RNA & protein) and can replicate themselves using a host cell, so some biologists say yes.

This demonstrates the rule, that for every rule in biology, we can usually find at least 1 exception

Prokaryotic cells

• Do they have a nucleus?• Do they have organelles?• How big are they?• Examples include

Escherichia coli bacteria Streptococcus pnemoniae

no

Very small - usually 1 – 10 m

no

Bacteria, blue green bacteria

Eukaryotic cells

• Do they have a nucleus?• Do they have organelles?• How big are they?• Examples include

yes

yes

Larger than bacteria – usually 20 – 500 m

Plants, animals, fungi, Protista

Cell membrane

Main function Controls entry and exit of substances

Cell wall

Main function Provides structure and support

Only found in plant cells

Cytoplasm

Main function Provides a medium for reactions & site for organelles

Nucleus

Main function Control centre – contains the genetic blueprint (genes) forcoding proteins, hence controls all cell activities

Nucleolus

Main function Site of RNA production & storage

Nuclear membrane

Main function Keeps DNA within nucleus

Endoplasmic reticulum

Main function Transport system, site for reactions to occur

Ribosomes

Main function Site of protein synthesisSome are found free in the cytoplasmMost are found attached to the endoplasmic reticulum

Mitochondria

Main function Site of aerobic respiration – energy production

Plastids

Chloroplasts

Main function Site of photosynthesis

Only found in plant cells

Golgi body

Main function Packaging for secretion

Vacuoles

Main function Storage of food and waterIn plants provides strength and structure to cell

Plant cells usually have 1 large oneAnimal cells usually have several smaller ones

Lysosomes

Main function Storage of wastesMost contain enzymes that break down substances

Contractile vacuole

Main function Pumps out excess water, hence maintaining water balance in the cell

Only found in some unicellular organisms

Centrioles

Main function Forms spindle during cell division

Only found in animal cells

Cytoskeleton

Microfilaments are thin fibres that are made mostly of the protein actin. Microfilament fibres can change length when supplied with energy by ATP, and so they allow cells to change shape. They also guide the movements of organelles within the cell. Interactions of actin and the protein myosin are important in contraction of muscle cells.

Intermediate fibres (intermediate filaments) are somewhat larger in diameter than are microfilaments, and are made of several different proteins. Intermediate fibres form a 3-D network throughout the cell that forms much of the framework of the cell and holds the organelles in position.

Microtubules are about 24 nanometers in diameter, somewhat thicker than microfilaments or intermediate fibres. Microtubules are hollow and composed largely of the protein tubulin. Microtubules help to position, anchor, and move organelles. They are also important in cellular reproduction and in the movements of cells. Microtubules are important components of both cilia and flagella, and of centrioles.

Cilia and flagella

Main function

Usually found in animal or Protist cells

Movement

Plant cells

Special features include: Cell wallChloroplastsLarge single vacuoleNo centrioles

Animal cells

Special features include: No cell wallNo chloroplastsVacuoles usually small and numerousCentrioles

What type of cell am I?

What type of cell am I?

plant

plantanimal

animalProkaryotic Prokaryotic

What type of cell am I?

What type of cell am I?

animal

animal

plant

plant

Label the cells

Label the cellsCell wall

Cell membrane Cell

membrane

nucleusnucleus

nucleolusnucleolus

Nuclearmembrane

Nuclearmembrane

Chromatin/DNAChromatin/DNA

mitochondrion

mitochondrion

cytoplasm

lysosome

chloroplast

centrioles

Golgi body

vacuole

Rough endoplasmicreticulum

cytoplasm

Smooth endoplasmicreticulum

Rough endoplasmicreticulum

ribosomes

vacuole

Smooth endoplasmicreticulum

Identify the organelles

Identify the organelles

Cell wall

Cell wall

nucleus

nucleus

mitochondrion

nucleolus

nucleolus

nucleolus

vacuole

vacuole

Nuclearmembrane

cytoplasmchloroplast

chloroplast

Rough endoplasmicreticulum

Nuclear pore

Identify the function of these• cell membrane

• cell wall

• cytoplasm

• nucleus

• nucleolus

• nuclear membrane

• mitochondria• Golgi body

Provides a medium for reactions & site for organelles

Controls entry and exit of substances

Provides structure and support

Control centre – contains the genetic blueprint (genes) forcoding proteins, hence controls all cell activities

Site of RNA production & storage

Keeps DNA within nucleus

Site of aerobic respiration – energy production

Packaging for secretion

Identify the function of these

• endoplasmic reticulum • ribosomes• lysosomes• centrioles• cilia/flagella• chloroplasts• vacuole• contractile vacuole

Transport system, site for reactions to occur

Site of protein synthesis. Some are found free in the cytoplasmMost are found attached to the endoplasmic reticulum

Site of photosynthesis

Storage of food and waterIn plants provides strength and structure to cell

Storage of wastesMost contain enzymes that break down substances

Forms spindle during cell division

Movement

Pumps out excess water, hence maintaining water balance in the cell