Cell Transportation and Membrane

Osmosis 

Movement of water across a semi-permeable membrane from high to low water concentration.

Why Cells Are Small 

Smaller cells have higher surface area-to-volume ratio allowing faster nutrient and waste exchange.

Function of Cell Membrane 

Controls what enters and leaves the cell, maintaining homeostasis.

Cell Theory 

States that all living things are made of cells.

Fluid Mosaic Model 

Describes flexible, dynamic membrane structure made of lipids, proteins, and carbohydrates.

Phospholipid Bilayer 

Made of two layers of phospholipids with hydrophilic heads and hydrophobic tails.

Cholesterol Function 

Regulates membrane fluidity; prevents stiffness at low temps and excess fluidity at high temps.

Integral vs Peripheral Proteins 

Integral span the membrane for transport; peripheral sit on the surface and act as enzymes or anchors.

Glycoproteins and Glycolipids 

Aid in cell recognition and communication (e.g., CD4 glycoprotein targeted by HIV).

Diffusion 

Net movement of particles from high to low concentration until equilibrium is reached.

Energy Requirement of Diffusion 

No energy required; it is passive transport.

Facilitated Diffusion 

Passive movement through membrane proteins for large or polar molecules.

Factors Affecting Diffusion Rate 

Distance, temperature, solvent density, molecular size, membrane properties, concentration gradient.

Importance of Diffusion 

Allows oxygen and nutrients in, and carbon dioxide and waste out of cells.

Passive Transport 

Movement from high to low concentration without energy use.

Types of Passive Transport 

Simple diffusion, facilitated diffusion, osmosis.

Simple Diffusion Molecules 

Small, nonpolar molecules like O₂ and CO₂.

Facilitated Diffusion Molecules 

Large or polar molecules like glucose or ions.

Osmosis and Aquaporins 

Water moves across membranes quickly through aquaporin channels.

Active Transport 

Movement from low to high concentration using ATP energy.

ATP 

Adenosine triphosphate; releases energy when third phosphate bond is broken.

Sodium-Potassium Pump 

Moves 3 Na⁺ out and 2 K⁺ in using ATP.

Bulk Transport 

Movement of large materials using vesicles (endocytosis and exocytosis).

Endocytosis 

Cell engulfs materials into vesicles.

Types of Endocytosis 

Phagocytosis (solid intake), pinocytosis (fluid intake), receptor-mediated (selective uptake).

Exocytosis 

Releases materials from a cell, removes waste or secretes proteins.

Exocytosis in Plants 

Releases polysaccharides to build cell walls.

Simple Diffusion Summary 

High to Low; No energy; No protein; Example: O₂, CO₂.

Facilitated Diffusion Summary 

High to Low; No energy; Yes protein; Example: Glucose.

Osmosis Summary 

High to Low (water); No energy; Yes (aquaporin); Example: Water.

Active Transport Summary 

Low to High; Yes energy (ATP); Yes protein; Example: Na⁺/K⁺ pump.

Endocytosis Summary 

Into cell; Yes energy; No protein; Example: Amoeba eating.

Exocytosis Summary 

Out of cell; Yes energy; No protein; Example: Polysaccharide export.

What is 1

Chokesterol

What is 2

Membrane proteins

What is 3

Hydrophobic tail

What is 4

Hydrophilic head

What is 5

Phospholipid

What is 6

Carbohydrate chain

Molecule motion

Constant random motion.

Concentration gradient

Difference in concentration across a space.

Equilibrium

Equal concentration throughout a space.

Permeable

Allows all substances through.

Solution

Solute + solvent.

Hypotonic

Lower solute concentration.

Hypertonic

Higher solute concentration.

Isotonic

Equal solute concentration.

Hypo/Hyper/Iso prefixes

Refer to solute concentration.

Hypertonic environment

causes cells to lose water through osmosis

Hypotonic environment

causes water to move into cells through osmosis, leading to swelling and potentially bursting in animal cells (cytolysis) or turgor pressure in plant cells

Turgor pressure

Water pressure in plant cells.

Cytolysis

The animal version of Turgor pressure

The SHRINKING of plant cells when water leaves so the cell membrane pulls away from the cell wall is called

PLASMOLYSIS