Cell Size and Plasma Membrane

Metabolism

The process by which the body converts the food and drinks you consume into energy

Cell Size

• Cellular metabolism depends on the cell size

• Cellular waste must leave

• Dissipates thermal energy

• Nutrients and other resources must enter

Surface Area to Volume

• Size dictates function

• Cells need a high sa/v ratio to optimize exchange of materials through plasma membrane (higher efficiency)

High sa/v

• Efficient at transport

• Smaller cell

Low sa/v

• Efficient at storage

• Larger cell

Parts of a phospholipid

• A: hydrophilic head

• B: hydrophobic tails

• 1: phosphate group

• 2: glycerol

• 3: saturated fatty acid chain

• 4: unsaturated fatty acid chain

Plasma membrane

• Separates internal cell environment from external environment

• Made primarily of phospholipids

Amphipathic

• Having both hydrophilic and hydrophobic regions

• Phospholipids form a bilayer to avoid their hydrophobic tails from interacting with water while hydrophilic heads face water on both sides

Fluid mosaic model

• Many macromolecules held together by weak hydrophobic interactions which allow the cell membrane to move and shift

• Temp affects fluidity

• Unsaturated/kinked tails prevents tight packing of phospholipids

Cholesterol

• Lipid helping to maintain fluidity at high and low temps

• Reduces movement at high temps

• Reduces tight packing of phospholipids at low temps

Peripheral proteins

• Proteins not embedded into the lipid bilayer

• Loosely bonded to surface

Integral proteins

• Proteins embedded into the lipid bilayer (Integrated)

• Can by hydrophobic, hydrophilic or both

• Determined by A groups (side chains)

• Hydrophilic regions make up interior of channel or pore, exposed to cytosol

• Hydrophobic regions makeup up surface of protein and interact with fatty acids on interior

Glycolipids

• Important for cell to cell recognition

• Carbohydrates bonded to lipids

Glycoproteins

• Important for cell to cell recognition

• Carbohydrates bonded to proteins

Hydrophillic

• Attracted to water

• Charged or polar

Hydrophobic

• Not attracted to water/ repels

• nonpolar or no charge

Selective permeability

• The ability to regulate the substances that enter and exit

• Due to hydrophobic interior (nonpolar hydrophobic tails)

Polar

• Molecule with uneven distribution of electrons/electrical charge

• Hydrophilic

Nonpolar

• Molecule with even distribution of electrons/electrical charge, neutral

• Hydrophobic

Charged

Being either positive or negative in polarity