Cells

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Cells
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Why are cells so tiny?

• Larger cells do not function as efficiently
• The surface is the only way cells interact with
  the environment
• Surface-area-to-volume ratio
• As cell size increases, volume grows much more
  rapidly

Cell radius (r) Surface area (4pr2) Volume ((4/3)pr3)
1 units 12.57 units2 4.189 units3
10 units 1,257 units2 4,189 units3
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Cell Theory

• Schleiden and Schwann
• Three principles
• All living things are composed of cells
• Cells are the smallest living things
• (Functional units of the body)
• Cells come from pre-existing cells

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Cell Types

• Prokaryotes
• Lack a nucleus and membrane bound organelles
• MUCH smaller than eukaryotes
• Bacteria
• Eukaryotes
• Have a nucleus and organelles
• Much bigger than prokaryotes

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Cell Organelles

• Cell membrane
• Semi-permeable
• Cytoplasm cell blood
• Fluid matrix surrounding nucleus
• Surrounded by a cell membrane
• Nucleus cell brain
• Contains chromatin (loosely coiled DNA)

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Endoplasmic reticulum

• Interconnected membranes forming canals and
  flattened sac-like spaces
• Functions
• Communications system
• Rough ER studded with ribosomes
• Involved in protein synthesis
• Smooth ER has no ribosomes
• Involved in synthesizing lipid

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Ribosomes

• Composed of protein and RNA
• May be free in the cytoplasm or attached to ER
• Function
• Involved in protein synthesis

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Golgi apparatus

• Stack of flattened membranes
• Function
• Package and transports proteins from the cell

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Mitochondria

• Cell powerhouse
• Contains its own DNA
• Capable of self-reproduction
• Composed of 2 membranes
• Contains enzymes used in cell respiration
• Function
• Produce ATP for cellular energy (cell respiration)

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Lysosomes

• Small sacs from the Golgi apparatus
• Contains enzymes capable of breaking down
  breaking down nutrients or toxins
• Function
• Digestion

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Centriole

• Twin hollow cylinders (centrioles)
• Function
• Involved in cell division

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Vesicles

• Tiny sacs formed by the cell membrane folding in
  and pinching off
• Function
• Intake or excretion of large materials
  (endocytosis and exocytosis)

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Microfilaments and Microtubules

• Tiny rods usually arranged in meshes or bundles
• Function
• Involved in cell movement
• Provides structure to the cell

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Cillia and Flagella

• Fine, long, threadlike organelles protruding from
  the cell surface
• Function
• Cell movement

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centrosome
Golgi apparatus
lysosome
vesicles
nucleus
mitochondria
flagella
smooth ER
rough ER
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Cell Membrane

• Selectively permeable (semi-permeable)
• Allows some substances in, excludes others
• Composed of phospholipid bilayer (containing
  cholesterol) and protein inclusions
• Fat soluble molecules pass through the lipid part
• Water soluble molecules must move through protein
  component
• Pores, channels or receptors

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Passive Transport

• Movement of a material into or out of a cell
  without the use of energy.
• Diffusion
• Osmosis
• Facilitated diffusion
• NO ENERGY REQUIRED

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Diffusion

• The process by which molecules move down a
  concentration gradient
• Move from area where there is more concentration
  to areas that are less concentrated
• Rate limited by concentration

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Facilitated Diffusion

• Diffusion using special carrier molecules to
  allow usually non-permeable molecules to pass
  through a selectively permeable membrane
• Example Insulin facilitates glucose movement
• Rate of passage is
• limited by the number
• of carrier molecules
• and concentration

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Osmosis

• The diffusion of water through a selectively
  permeable membrane which may not allow dissolved
  substances to pass
• May result in changing volumes on either side of
  the membrane
• Osmotic pressure
• The amount of pressure
• needed to stop osmosis

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Concentration Types

• Hypertonic
• A solution which has a greater concentration of
  solute particles than a given cell or solution
• Hypotonic
• A solution which has a lesser concentration
  solute particles than a given cell or solution
• Isotonic
• A solution which has an identical concentration
  of solute particles to a given cell or solution

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Filtration

• The forcing of permeable molecules through a
  membrane by hydrostatic pressure
• Example Blood pressure

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Active Transport

• The movement of molecules against a concentration
  gradient using cellular energy and carrier
  molecules
• Proton pump
• Sodium-potassium pump

ENERGY REQUIRED
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Bulk Passage

• Endocytosis
• The inward movement of molecules through a
  membrane by infolding and pinching off vesicles
• Pinocytosis taking in tiny droplets of liquid
• Phagocytosis taking in solid material
• Receptor Mediated molecule bonds with receptor
  protein
• Exocytosis

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Cell division

• Prokaryotes
• Binary fision
• DNA replicated in parent
• Parent divides
• Fast
• Eukaryotes
• Mitosis
• Complicated
• Lots of DNA
• Form chromosomes (compact structures, composed of
  DNA and histone proteins, that can be manipulated
  easily during cell division

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Cell cycle

• Interphase
• Period Inbetween cell division
• Majority of cells life
• Cell growth
• Protein synthesis

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Mitosis

• Cell division that Is Mighty Common
• Makes all cells EXCEPT gametes (reproductive
  cells)
• DNA is doubled then
• Cells divide once

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Prophase

• Cells Prepares to divide
• Chromatin condenses into chromosomes
• Nuclear membrane disappears

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Metaphase

• Chromosomes line up in the Middle
• Spindle Apparatus stretches from pole to pole

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Anaphase

• Sister chromatids move Away to opposite poles

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Telophase

• Cell Tears in two
• Nuclear membrane reforms
• Chromosomes disperse into chromatin
• Cytokinesis (cytoplasmic division) (separate
  phase?)
• Produces 2 identical daughter cells

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Cell differentiation

• Process by which cells develop different
  characteristics in structure and function
• Differences in outcome
• Directed by cells DNA
• Determined by cells position in the body and its
  chemical environment

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