Cell Theory

Robert Hooke

• First described cell from his observations of cork slices

• First to used word “cell”

• 1665

Antonie Van Leeuwenhoek

• Discovered microscopic animals in water

Schleiden and Schwann

• stated all organisms are made of one or more cells

Virchow

• All cells come from division of pre-existing cells

What are the 3 statements of cell theory

• All living things are made of one or more cells

• The cell is the basic unit of life

• All cells come from division of pre-existing cells

What are cells and what do they do

• Smallest living things that exist at a cellular level

• Carry out all processes associated with life

What do molecules do in cells

• Molecules in cells are considered part of it

• They carry out biomechanics reactions

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how big are cells

• small ones are 0.3 micro metres

• most are 10 micro metres

• Big ones can be up to cm’s long (Ex. Algal cells and chicken egg)

What are eukaryotic cells and what do they contain

• complex

• Multi and unicellular

• Has: Cell membrane, Nucleus, Organelles, and Cytoplasm

Cell membrane

• Thin layer which separates cell’s interior and its environment

  
  

Nucleus

• Control centre of cell

• Contains DNA (blueprint of life)

Organelles

• Small bodies with specific structures and functions within cell

Cytoplasm

• Liquid substance where organelles are located

Nucleus function and structure

• Large and located in centre of cell

• Surrounded by nuclear envelope

• Contains nucleoplasm, chromosomes, and nucleolus

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Nuclear envelope

• Double layer membrane with pores

• Selectively permeable for intake/release of molecules

Chromosomes

• Genetic code

• In to form of Chromatin when not near cell division

Nucleolus

• Dark staining areas in nucleus

• Usually spherical

• Makes rRNA (which makes ribosomes)

Ribosomes

• Small dense-staining granules

• Makes protein

• Found on rough ER

• Found floating in cytoplasm in groups

Polysomes

• a cluster of ribosomes in cytoplasm

Rough ER

• ER covered in ribosomes

• Protein synthesis

Smooth ER

• no ribosomes

• Lipid and steroid synthesis

Vacuoles

• Filled with water and waste

• Small vacuoles are called vesicles

Vacuoles in plants

• One large central vacuole which may occupy 90% of the cell’s volume

• Gives rigidity to cell

• Makes cytoplasm a thin layer against the cell membrane (better gas exchange)

• stores waste products of metabolism

Vacuoles in animal cell

• Digest food

• Elimination of water

Vesicles

• small vacuoles

• Used to transport stuff in cytoplasm

Golgi body

• Temporary storage for material produced in cell (especially from the ER)

• Packages materials in vesicles that are later distributed in cell or sent out for excretion

Lysosomes

• Vesicles of hydrolytic enzymes in cell

• Produced by Golgi body

• Destroys old and malfunctioning cell parts

• May destroy cell if it is damaged or malfunctioning

Mitochondria structure

• Double membraned structure

• Inner membrane highly folded into Cristae (increases surface area)

  
  

Cristae

• where enzymes are arranged to carry out certain reactions

Mitochondria function

• Powerhouse of the cell

• Cellular respiration (makes ATP)

Cellular respiration

C6H12O6 (glucose) + 6O2 —> 6CO2 + 6H2O + ATP

Plastids

• Found ONLY in plant cells

• 3 types: Chloroplast, Chromoplast, Leucoplast

Chloroplast

• Site of photosynthesis

• Gives plants the green colour through chlorophyll

Chromoplast

• Stores other pigments other than chlorophyll (e.g., orange in carrot, red in tomato, etc.)

Leucoplast

• stores starch in potatoes

Microfilaments

• Thin solid fibres of protein

• Skeleton of cell

Microtubules

• Larger than microfilaments

• Made of tubulin

• Found in cilia, flagella, and centrioles

• Skeleton for cell

Flagella/Cilia

• Cilia- Short and many hairlike structures

• Flagella- Long and few hairlike structures

• Both used for locomotion and generating current (Movement of cell)

• “9+2” arrangement (9 doublets surrounding 2 singlets)

Centrioles

• “9 + 0” arrangement

• Produce basal bodies of cilia/flagella

• Usually 2 centrioles in either side of nucleus

• Found in ALL animal cells

Fluid Mosaic Model

• Cell surrounded by a layer of phospholipids and proteins

• Selectively permeable membrane

• Hydrophilic head faces outwards, Hydrophobic tail faces inwards

• Proteins, carbohydrates, and cholesterol span throughout which creates the “mosaic”

• Refer to a diagram to study this.

  
  

Cell wall

• Found in ONLY plant cells

• Made of cellulose (type of sugar)

• Very rigid and difficult to digest

• Semi-permeable (lets small molecules through and not large ones)

Plants vs Animal cells

• Plant cells: Cell wall, Plastids, Large central vacuoles

• Animal cells: Centrioles

Prokaryotes

• Unicellular (single cell organism)

• Lacks membrane bound organelles

• lacks nucleus

• Usually has Circular DNA

• Ex. Bacteria’s and Blue-green algae

Eukaryotes

• Multi and Unicellular (multi or single celled)

• Has membrane bound organelles and nucleus

• Genetic material in the form of chromosomes

• Ex. Planes, Animals, Fungi, etc.