Cells and Tissues

Organelles

These are specialized structures in cells that perform specific functions

Cytoplasm

Jelly-like substance that holds organelles

Cell Membrane

A structure that encloses the cytoplasm

Cell

Smallest unit of life

Cell Membrane

It is the outermost component of a cell

Cell Membrane

It forms a boundary between material inside the cell and outside

Intracellular

Materials inside the cell

Extracellular

Materials outside the cell

Cell Membrane

It acts as a selective barrier

Cell Membrane

It acts as an active barrier separating intracellular fluid (ICF) from extracellular fluid (ECF)

Cell Membrane

It plays a dynamic role in cellular activity by controlling what enters and what leaves the cell

1. Mechanical barrier

2. Selective permeability

3. Electrochemical gradient

4. Communication

5. Cell signaling

5 Functions of the Cell Membrane

Mechanical barrier

Cell membrane function:

It separates two of the body’s fluid compartments

Selective permeability

Cell membrane function:

Determines manner in which substances enter or exit the cell

Electrochemical gradient

Cell membrane function:

Generates and helps to maintain the electrochemical gradient required for muscle and neuron function

Communication

Cell membrane function:

Allows cell-to-cell recognition and interaction

Cell Signaling

Cell membrane function:

Cell membrane proteins interact with specific chemical messengers and relay messagws to the cell interior

1. 75% phospholipids

2. 5% glycolipids

3. 20% cholesterol

3 Components of Lipid Bilayer

1. Phosphate heads

2. Fatty acid tails

2 Parts of the Phospholipid Bilayer

Phosphate heads

These are polar (charged), so are hydrophilic (water-loving)

Phosphate heads

These face internal and external environments

Fatty acid tails

These are nonpolar (no charge), so are hydrophobic (water-hating)

Fatty acid tails

These create a hydrophobic region within the bilayer

5% glycolipids

These are lipids with sugar groups on outer membrane surface

20% cholesterol

It increases membrane stability

Phospholipid

It is the major structural component of the cell membrane

Membrane Proteins

These allow cell communication with environment

Membrane Proteins

These make up about half the mass of plasma membrane

Membrane Proteins

Most of these have specialized membrane functions

Membrane Proteins

Some of these float freely, and some are tethered to intracellular structures

1. Integral Proteins

2. Peripheral Proteins

2 Types of Membrane Proteins

Integral Proteins

Type of membrane protein:

Firmly inserted into membrane

Integral Proteins

Type of membrane protein:

Most are transmembrane proteins (span membrane)

Integral Proteins

Type of membrane protein:

Have both hydrophobic (lipid tails) and hydrophilic regions (water)

Integral Proteins

Type of membrane protein:

Function as transport proteins (channels and carriers), enzymes, or receptors

Peripheral Proteins

Type of membrane protein:

Loosely attached to integral proteins

Peripheral Proteins

Type of membrane protein:

Include filaments on intracellular surface used for plasma membrane support

Peripheral Proteins

Type of membrane protein:

Function as:

• Enzymes

• Motor proteins for shape change during cell division and muscle contraction