7-2 Cell Structure

Cell Wall  Provides structure and protection for the cell  Mostly carbohydrates  Protein fibers reinforce  Found in plants, fungi, algae, and most bacteria 7-2

Cell Membrane  Regulates what goes in/out of a cell  Selectively permeable  Fluid Mosaic Model  Made up of a “mosaic” of different molecules  Molecules flow laterally Outside of cell Inside of cell (cytoplasm) Cell membrane Proteins Protein channel Lipid bilayer Carbohydrate chains 7-2

Cell Membrane  Lipid bilayer  Phospholipids have a polar head and non-polar tail  Polar head is attracted to water (hydrophilic)  Non-polar tail repels water (hydrophobic)  Proteins  Carbohydrates Proteins Protein channel Lipid bilayer Carbohydrate chains 7-2

Lipid Bilayer 7-2

7-2 Cell Transport

Diffusion  Diffusion is the natural movement of particles from an area of high concentration to a area of low concentration  Spontaneous (needs no energy)  Due to random particle motion and collisions  Concentration of solute will eventually reach equilibrium  No net diffusion but particles are still moving 7-3

Diffusion 7-3

Osmosis  Osmosis is the diffusion of water across a membrane  3 types of solutions: 1. Hypertonic- solution has a higher concentration of solutes than the cell 2. Isotonic- the concentration of solutes is the same inside and outside the cell 3. Hypotonic- solution has a lower concentration of solutes than the cell 7-3

Osmosis 7-3

Facilitated Diffusion  Uses integral membrane proteins  Channel or Carrier  High  Low concentration  Uses no energy  Molecule specific  Often for large or polar molecules 7-3

Active Transport  Low  High concentration  Against concentration gradient  Uses energy  Larger molecules use endocytosis (in) and exocytosis (out)  Types of endocytosis:  Phagocytosis (solid particles, mostly food)  Pinocytosis (liquids) 7-3

Cell Transport Passive Diffusion StandardFacilitated Channel Proteins Carrier Proteins Active Molecular Protein Pumps Bulk EndocytosisExocytosis

7-4 The Diversity of Cellular Life

Unicellular vs. Multicellular Organisms 7-4 UnicellularMulticellular Single cell The most common organisms Simple Reproduce quickly Many cells Great variety Cells perform different tasks (cell specialization) Evolved from unicellular organisms

Organization in a Multicellular Organism 7-4

Cell Specialization  Cells in multicellular organisms are specialized to perform specific functions  Unique shapes, proteins, and organelle makeup  Stem cells are undifferentiated “blanks” that can become many cell types 7-4