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• 1- How would you describe a cell?

• 2- What are parts of a cell or organelles you remember from previous classes?

Cell Theory •  1- All living things . •  2- Cells are . •  3- Cells come from .

So many different kinds of cells!

•  Size •  Shape • Organization

Cell Size

Head of a pin = 2 mm Human hair = 200 µm Plant cell = 100 µm Animal cell = 10 µm

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Cell shape •  Significant variation

in cell shape among species and within the same organisms

•  Shape is tied directly to function

Cell organization

• Differences in organization can occur at the level of the cell or at the level of a tissue

•  At the cellular level: – What kinds of organelles? – What kind of cytoskeletal organization?

•  At the tissue level: – How are the cell organized relative to each

other?

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Variability in cell function •  Protection (Epidermis) • Communication (Nervous system) • Reproduction (Reproductive system) •  Keeping us healthy (Immune system) • Chemical exchange (Cardiovascular

system, Respiratory system)

Cell Chemistry •  Even with all this variability, cells still have

basic chemistry in common – Genetic material (RNA, DNA)

• Nucleotides

– Proteins • Amino acids

• Cells use this genetic information and proteins to reproduce independently

Eukaryotes and Prokaryotes

•  Eukaryotes •  Prokaryotes

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Prokaryotes •  Incredibly diverse group of cells! • No nucleus •  Size: tend to be smaller than eukaryotes •  Shape: spherical, rodlike, corkscrew •  Tough protective coat (cell wall) • Rapid growth rate

Bacteria vs. Archaea Bacteria •  Single celled •  Cell wall •  Circular DNA •  No nuclear membrane •  E. coli, salmonella,

anthrax

Archaea •  Simple organisms without

a nuclear membrane •  Replicate their DNA and

protein differently than bacteria

•  Extreme conditions

Some interesting prokaryotes

Bacteria - Photoautotrophs

Bacteria - Chemoautotrophs

Archaea- Methanogens

Archaea- Thermophiles

Eukaryotes

•  Typically bigger than prokaryotes •  Have nucleus and membrane-bound organelles

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Figure 1-29 Essential Cell Biology (© Garland Science 2010)

The cell membrane •  Function

– Barrier to outside world – Regulates movement of molecules from the

outside of the cell to the inside – Signaling (lipid rafts)

•  Key components – Phospholipids – Integral membrane proteins (all the way through) – Peripheral membrane proteins

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Phospholipids

•  Form bilayer • Head group = POLAR • Hydrocarbon tails =

NONPOLAR • Most things that want

to get through need an escort

Cytoplasm

• Cellular material that lies between the cell membrane and the nucleus

•  LOTS of fun stuff happens here! – Site of RNA processing on free ribosomes – Houses all the organelles

The nucleus •  Function

– Contains cellular DNA – Site of transcription (DNA to RNA)

•  Key components – Nucleolus – Nuclear envelope – Nuclear pores (regulate transport into and out

of nucleus) – Chromatin (DNA + histone proteins)

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Figure 1-22 Essential Cell Biology (© Garland Science 2010)