Biology Module 2 - An Introduction to Cells

Alexander Fleming

• Discovered antibiotics

• Found mold on his petri dish & noticed a zone around the mold where bacteria didn’t grow (Penicillium notatum), leading to the development of penicillin.

Antibiotics

Chemicals produced by other organisms that ward off bacteria.

Cell Theory

1. All living things are made of cells.

2. Cells are the basic unit of structure in organisms.

3. All cells come from other cells.

Prokaryotic cells

• “Pro” means before

• “Kary” means nucleus

• Lack internal membrane-bound organelles

• No nucleus

• Only has membrane, cytoplasm, ribosomes (genetic material)

• Much smaller than eukaryotic cells

• Single-celled

• 1-5 um in diameter

Eukaryotic cells

• “Eu” means true

• Membrane-bound organelles, including nucleus

• Larger

• Often multicellular

• 10-100 um in diameter

Bacterial Cell Walls

• Bacteria have cell walls

• Made of peptidoglycan

• Help bacteria survive in water

• Antibiotics interfere with cells walls

Peptidoglycan

• Polymer of sugars and amino acids

• Tough, mesh-like

• Forms the cell wall of most bacteria

• Provides strength for bacteria & maintains shape

• Antibiotics like penicillin destroy this layer to kill harmful bacteria

Nucleus

• Encloses the cell’s DNA

• Interpreting genetic instructions take place here

• Surrounded by the nuclear envelope

Endoplasmic Reticulum (ER)

• Network of membrane-covered “pipes”

• Rough ER

  • Protein synthesis

  • Rough bc it is studded by ribosomes

• Smooth ER

  • Lipid synthesis

  • Detoxification

Golgi Apparatus

• Stacked membranous discs

  • Packages and transports proteins

Protein Production Pathway

Nucleus → ER → Golgi apparatus

Mitochondria

• Extract energy from food

  • Convert energy into a useful form

Chloroplasts

• Plants & algae have them

• Sites of photosynthesis

  • Capture & conversion of sunlight energy into a usable form

Lysosomes

• Full of digestive enzymes

• Break down worn-out cell parts or molecules

Cytoskeleton

• Network of protein fibers

• Function include cell support, cell movement, and movement or structures within cells

Cell membranes

• 2 Main components

  • Phospholipid bilayer

  • Proteins

Phospholipid bilayer

A double layer of special fat molecules that forms the main part of every cell membrane.

• Semipermeable - only lets certain things through easily

Diffusion

Movement of molecules along a concentration gradient from high concentration to low concentration

Concentration Gradient

Difference in how clumped up molecules are in two areas.

Passive Transport

• Always high → low; never requires energy

• Simple diffusion

• Facilitated diffusion

Simple Diffusion

Small, neutral, nonpolar molecules

Facilitated Diffusion

• Larger, charged, polar molecules

  • Require help from a transport protein

Active Transport

• Active = energy required

• Moves things AGAINST the concentration gradient

  • Low → high concentration

Osmosis

Diffusion of WATER across a membrane

• Water moves from high → low concentration

• Solute moves from low → high concentration

Tonicity

Compares concentration of solute inside/outside the cell.

Hypertonic solution

• Higher solute concentration outside cell

• Water flows out of the cell

Hypotonic Solution

• Lower solute concentration outside cell

• Higher solute concentration inside cell

• Water flows into the cell

Isotonic Solution

• Solute concentration is equal on both sides of the membrane

• Water flows equally in both directions