Cell Structure & Function Cell Structure & Function

Introduction to CellsEukaryotic CellsProkarytoic Cells

Introduction to CellsIntroduction to Cells

History – Robert Hooke (1600’s) first described

cells in thin sections of cork that he examined under microscope

– Robert Brown (1820) first to describe that a nucleus seemed to be associated with all cells (at least eukaryotic cells)

Introduction to CellsIntroduction to Cells

History (continued)– Theodore Schwann & Matthias

Schleiden (1839) advanced cell theory»All organisms are composed of cells»The cell is the basic unit of life»All cells arise from preexisting cells

Introduction to CellsIntroduction to Cells

Cell Types– Prokaryotic– Eukaryotic

Sizes– Prokaryotic 0.2 to 2.0

microns– Eukaryotic 10 to 100

microns

Introduction to CellsIntroduction to Cells

Size Determinants– Cell surface to volume relationships

govern cell size– The smaller the cell the more

efficiently materials can be transported into and within the cell

– Cell must also be large enough to deal with information and metabolic requirements

Introduction to CellsIntroduction to Cells

Introduction to CellsIntroduction to Cells Common Components to All

– Plasma membrane – phospholipid bilayer that controls movement of substances into and out of cells

– Ribosomes – site of protein synthesis – note ribosomes have both RNA & protein

– Cytoplasm –matrix on interior of cell consisting of water soluble proteins and other materials

– Nuclear material – DNA/Protein complex that stores information

» Prokaryotic – circular» Eukaryotic – linear and in chromosomes

Eukaryotic CellsEukaryotic Cells

Eukaryotic Cells– Larger than prokaryotic– More complex than prokaryotic– All multicellular organisms composed

of eukaryotic cells– Eukaryotic cells composed of many

internal structures called organelles

Eukaryotic CellsEukaryotic Cells Endosymbiotic theory (Lynn Margullis – 1967) Evidence:

– Mitochondria & chloroplasts replicate via binary fision

– Mitochondria & chloroplasts have circular DNA– Mitochondria & chloroplasts have 70S (bacterial

ribosomes)– Mitochondria & chloroplasts start protein

synthesis in the same way as prokaryotic cells– Mitochondria & chloroplasts DNA sequences of

similar genes show greater relationships to prokaryotic genes

Eukaryotic CellsEukaryotic Cells

Nucleus Mitochondria Chloroplast Endoplasmic

reticulum (R & S) Golgi body

Lysosome Peroxisome Centrioles Vacuoles Flagella & cilia

Eukaryotic CellsEukaryotic Cells

Eukaryotic CellsEukaryotic Cells

Eukaryotic CellsEukaryotic Cells

Nucleus– Regulates growth

and reproduction of cell

– Contains DNA and chromosomes

Nucleolus – Ribosomal RNA

synthesis

Eukaryotic CellsEukaryotic Cells

Mitochondria – Energy production

in cell– Contains its own

DNA (circular)

Eukaryotic CellsEukaryotic Cells

Endoplasmic reticulum (rough and smooth)– Site of protein

synthesis in cells– Start of protein

export process– Connected to

nuclear pores and Golgi body

Eukaryotic CellsEukaryotic Cells

Golgi body– Sorting center for

proteins in cell– Produces vesicles

which fuse with plasma membrane

Eukaryotic CellsEukaryotic Cells

Lysosome– Only in animal

cells– Production of

intracellular digestive enzymes

– Involved with phagocytosis

Eukaryotic CellsEukaryotic Cells

Peroxisomes– Peroxisomes are small rounded

organelles found free floating in the cell cytoplasm.

– Contain at least 50 enzymes and are separated from the cytoplasm by a lipid bilayer single membrane barrier.

– Produce hydrogen peroxide which is toxic but is rapidly degraded by catalase

Eukaryotic CellsEukaryotic Cells

Flagella & cilia– Involved with

motility of cells– Composed of

microtubules

Eukaryotic CellsEukaryotic Cells

Vacuoles– Found only in plants– Large central organelle in plant cells– Regulates water in plant cells

Eukaryotic CellsEukaryotic Cells

Chloroplast– Site of

photosynthesis in plant cells

– Has own DNA (circular)

– Found only in plants

Eukaryotic CellsEukaryotic Cells Endosymbiotic theory (Lynn Margullis – 1967) Evidence:

– Mitochondria & chloroplasts replicate via binary fision

– Mitochondria & chloroplasts have circular DNA– Mitochondria & chloroplasts have 70S (bacterial

ribosomes)– Mitochondria & chloroplasts start protein

synthesis in the same way as prokaryotic cells– Mitochondria & chloroplasts DNA sequences of

similar genes show greater relationships to prokaryotic genes