Eukaryotic CELL STRUCTURE AND FUNCTION

• The Golgi apparatus is involved in the modification, sorting, packaging, and transport of proteins.
• Cells were first

  observed by Robert

  Hooke, who examined

  cork under a

  microscope.

  The structures

  were named from

  the Latin word

  cella for room.
• CELL THEORY

  The cell theory explains the importance

  of cells to life:

  All living organisms are made of

  cells.

  Cells are the smallest units of life.

  All existing cells are derived from

  other cells.

  All cells maintain homeostasis.
• Prokaryotes

  Smaller cells (0.1-0.5μm)

  No nucleus or organelles

  Always single-celled
• Eukaryotes

  Larger cells (10-100μm)

  Nucleus and organelles

  present

  Single or multicellular
• Surface area is the biggest limiting factor to cell size.

  Surface is needed for both nutrient absorption and waste removal.
• The largest

  human cells

  are eggs at

  about

  0.13mm

  (130um) in

  diameter.
• The smallest

  human cells

  are sperm at

  0.05mm

  (50um) in

  diameter.
• The plasma membrane is the barrier that

  surrounds all cells and forms their surface.

  Plasma membranes provide:

  Physical separation between the inner cell

  and external environments.

  Site of nutrient and waste exchange.

  Sensation of environmental changes or

  communication from other cells.

  Structural connection to neighboring cells.
• Phospholipids are the

  main component of

  plasma membranes.

  Hydrophobic fatty

  acid tails are

  insoluble in water.

  Hydrophilic

  phosphate heads are

  soluble in water.
• The phospholipids form a bilayer – a double-layer sheet where

  the hydrophobic tails congregate in the middle.

  Proteins enable communication, transportation, and adhesion.
• types of membrane proteins:
• Receptor is Respond to chemical signals, like hormones. Carrier: Transport materials across membranes. Enzymes: Increase the rate of membrane chemical reactions. Anchoring: Attachment to other cells. Recognition: identify the cell as "self” to the immune system.
• Membrane carbohydrates act as lubricants, adhesives, or part of the cell recognition system.
• Plasma membranes are selectively permeable,

  meaning only certain molecules can pass.
• Small nonpolar molecules (CO2, O2) are freely permeable.
• Large polar molecules (glucose, proteins, water) are impermeable without a protein channel.
• Diffusion is the passive movement of molecules from areas of greater to lower concentration.
• The concentration gradient is the gradually changing

  amount of the particle across a distance.
• Osmosis is the movement of water molecules through protein

  channels called aquaporins.
• Water molecules move towards areas with more solutes

  (salts, sugars).
• Hypertonic

  Higher concentration of solute outside of cell.

  Water moves out of cell.

  Cell shrivels.
• Isotonic

  Equal concentration of solute in and out of cell.

  Water moves in and out.

  No cell change.
• Hypotonic

  Lower concentration of solute outside of cell.

  Water moves in to the cell.

  Cell bursts.
• These bacteria have been exposed to a drug that punctures their

  membranes, allowing water to flow in uncontrollably until they

  burst.
• Facilitated Diffusion

  Protein channels allow the

  diffusion of molecules that would

  otherwise be impermeable.

  Passive: No energy required
• Active Transport

  Protein channels move

  substances against the

  concentration gradient.

  Active: requires energy.
• Vesicular transport uses membranous sacs to transport large amounts of material at once.
• Exocytosis moves material out of the cell.
• Endocytosis moves material in to the cell.
• Phagocytosis is a type of endocytosis where white blood cells

  engulf bacteria or viruses whole.
• Cytosol is the fluid found within cells containing nutrients,

  ions, and proteins.

  Organelles are individual structures that have specific jobs.
• The cytoskeleton is a network of protein filaments that give the

  cell structure and support its shape. Common cytoskeleton

  shapes include:
• Microvilli

  Fingerlike

  extensions that

  increase surface

  area.
• The cytoskeleton is a network of protein filaments that give the

  cell structure and support its shape. Common cytoskeleton

  shapes include:
• Centrioles

  Cylindrical

  structures that

  direct

  chromosomes

  during cell

  division..
• Cilia

  Long, slender

  extensions of

  plasma

  membrane that

  can move

  independently.
• Flagella

  Very long

  extensions of

  plasma

  membrane that

  can move

  independently.
• Proteins do all the work in a cell, and must be produced and

  maintained by a series of structures:
• Ribosomes

  Tiny particles

  made of RNA

  that build

  proteins.