Unit 3: The Cellular Level of Organization

def of celll membrane (plasma membrane)

• Forms boundary of the cell

• Made of phospholipids and proteins 

Cell membrane creates 2 regions:

1) Intracellular region: inside the membrane

2) Extracellular region: outside the membrane

def of cytoplasm

 all material inside the membrane

Two components of cytoplasm: 

Two components of cytoplasm: 

1) Cytosol: the fluid part

Made of water (90%) & other chemicals such as proteins, oxygen,  etc 

2) Organelles: little organs

• Each performs specific function

Nucleus 

Function: 

Nucleus 

Function: 

1. Control center: directs cell’s activity

2. Contains DNA

Mitochondria 

Mitochondria 

Function: makes energy

Performs cellular respiration

Lysosome 

Function:

Lysosome 

Function: garbage disposal: destroys unwanted intracellular materials

Peroxisome 

Function:

Peroxisome 

Function: similar to lysosome but destroys only certain substances

Ribosome 

Function:

Ribosome 

Function: protein synthesis 

Not a membranous organelle 

Rough endoplasmic reticulum (ER) 

Structure

Rough endoplasmic reticulum (ER) 

Structure: a channel

• System extending from nucleus

  • Goes throughout the cytoplasm

• Has ribosome attached 

Funtions of rough ER

Functions: 

• Attached ribosomes make proteins 

• Proteins enter ER

• ER processes them 

• Proteins in ER are either secreted or become part of the cell membrane

what is the rough ER abundant in

cells that do a lot of secretion

Smooth endoplasmic reticulum (ER) 

Structure:

Smooth endoplasmic reticulum (ER) 

Structure: channel system extending from the Rough ER

functions of smooth Endoplasmic reticulum

Functions: 

1. Makes phospholipid and steroid hormones

2. Detoxifies

3. Muscles cells: stores/releases calcium

smooth Er is abundant in

Muscle cells + glands of ovaries/testes + liver cells 

Golgi complex 

Structure:

Golgi complex 

Structure: channel system in the cytoplasm

Golgi complex 

functions

Functions: modifies, packages, and distributes proteins for secretion or internal  use; forms lysosome 

Cytoskeleton 

Structure: 

Cytoskeleton 

Structure: 

1. network of protein filaments 

2. Extend throughout the cytoplasm

3. Not a membranous organelle 

Three types of filaments are part of cytoskeleton: 

Three types of filaments are part of cytoskeleton: 

1) Microfilaments: smallest filaments; made of protein called actin Functions: Cellular movement, cell shape, form microvilli 

2) Intermediate filaments: medium sized.  

Functions: provide mechanical strength; form cell junctions 

3) Microtubules: largest 

Functions: Movement of intracellular structures; Form cilia &  

flagella

are Cellular Projections found on cells

III. Cellular Projections 

Are not found on all cells 

Microvilli: finger like extensions of the membrane 

Made of: 

Function:

Locations?

Microvilli: finger like extensions of the membrane 

Made of:  microfilaments

Function: increase surface area of absorption

Locations? Simple columnar lining SI

what is Cilia:

Function:

Locations?

Cilia: hair like projections of cell surface 

Function: move extracellular material across cell

Locations? Trachea + oviduct + inner ear

Flagella: is:

Made of:

Function:

Location?

Flagella: tail like projections of cell surface 

Made of: of microtubules  

Function: move entire cells

Location? Sperm cell

Definition of membrane transport:

Definition of membrane transport: Movement of material across cell membrane

Can be passive (no energy required) or active (requires energy)

Example of passive transport

diffusion

Diffusion is

Diffusion is the movement of a solute from an area of high solute concentration   to an area of low solute concentration 

Two types of diffusion: 

Two types of diffusion: 

1) Simple:  no membrane protein needed for transport

Examples: O2 & CO2

Figure & animation of simple diffusion 

2) Facilitated: membrane proteins needed for transport

• Carries and channel proteins

Examples: glucose, Na+, K+

Active transport: is

the movement of a solute from an area of low solute concentration to an area of high solute concentration 

Two types of active transport: 

Two types of active transport: 

1) Primary active transport: example is Na⁺/K⁺ pump 

2) Secondary active transport: example is Na⁺/glucose pump 

Vesicular transport:

a special type of membrane transport where substances are  transported in a membranous vesicle 

Vesicular transport is used to move: 

1) A large amount of solute at one time 

2) Large molecules such as hormones and neurotransmitters 

Two types of vesicular transport: 

1) Exocytosis: substance exits the cell 

2) Endocytosis: substance enters the cell