Cell Structure

Cells: What we Already Know

• All living things are made of 1 or more cells.

• Single-celled organisms include Paramecium, amoeba, chlamydomonas and yeast.

• These can carry out all the functions of living things.

• Cells vary in shape.

Cells: What we Already Know

• Cells are small because diffusion of substances in and out becomes very difficult when they become larger.

• Also it is easier for a single nucleus to handle a smaller cell.

• Cells can be divided into 2 types:– Prokaryotes – before the nucleus– Eukaryotes – true nucleus

General Characteristics of Cells

• Cytoplasm and Nucleoplasm– a jelly-like substance surrounded by a

membrane. – The portion of jelly outside the nucleus

is called cytoplasm.– The portion inside the nucleus is called

nucleoplasm.

General Characteristics of Cells

• Size and Shape– These are related to function.– Some cells like white blood cells can

change shape as they move about.

General Characteristics of Cells

• Cell Structure– Suspended in the cytoplasm are various

organelles. – Intracellular fluid, called cytosol, consists

mainly of water. In this are dissolved amino acids, sugars and other substances used to make bigger molecules.

– Structural proteins, enzymes and ions used to maintain a balanced biochemical environment are also present.

General Characteristics of Cells

• Organelles– The inside of cells are divided into small

compartments so different functions can go on at specific places in the cell at the same time.

– The compartments are called organelles, each has a different function.

Plant Cell

Animal Cell

Prokaryote Cell

Animal Cells Plant Cells•Plasma Membrane•Microvilli•Nucleus •Endoplasmic reticulum•Ribosomes•Golgi body•Lysosomes •Vacuoles•Peroxisomes•Mitochondria•cytoskeleton

•Centrioles•Cilia•Flagella

•Plastids•Chloroplasts•Cell walls•Large vacuole

Cell Membrane

• This separates the cell from the environment and maintains stable cell environment by controlling entry and exit of substances.

• It is selectively/partially permeable

Cytoplasm

• A jelly-like substance found between the cell membrane and the nuclear membrane.

• Holds the organelles in place• Contains dissolved substances and is

the site of many chemical reactions.

Mitochondria

• The site of respiration – energy production in the cell.

Golgi Apparatus

• This modifies proteins made by the ribosomes then packages them up and secretes them.

Endoplasmic Reticulum

• A transport network within the cell • Smooth ER is the site for lipid

synthesis (sER) • Rough ER is the site for protein

synthesis. (rER)

Ribosomes

• These can be associated with ER to form rough ER or free in the cytoplasm.

• The site of protein synthesis.

Nucleus

• This is the control centre for cell – it contains genetic material.

• Surrounded by a nuclear membrane.• The nuclear membrane has a

number of nuclear pores so substances can enter and leave the nucleus.

• Contains a nucleolus where RNA is made.

The Nucleus

Vacuoles

• These are found in plant cells• Storage sac for chemicals or water.

Lysosomes

• These are specialized vacuoles containing enzymes

Centrioles

• Found only in animal cells.• forms spindle fibre in cell division

Chloroplasts

• These are found in plant cells.• The site of photosynthesis.

Cell Wall

• This is found in plant cells and is made of cellulose.

• It provides a rigid support for the cell and prevents it from expanding too much.