Cytoplasmic Organelles

Centrioles•Made of microtubules.

•Small, paired, tiny structures near the nuclear envelope.

•Most active during cell division.

•They are not found in plant cells.

Cytoplasmic Organelles: Centrioles

Movement of Materials Through The Cell Membrane

For a cell to maintain its internal environment,

it has to be selective in the materials it allows to cross its cell membrane.

Transport: How molecules and fluids pass through the cell membrane.

Movement of Materials Through The Cell Membrane

Movement of molecules across the cell membrane depends on:

(A) concentration difference

(B) membrane permeability

(C) size and type of particle

(D) temperature and pressure

Movement of Materials Through The Cell Membrane

Three types of passive transport (i.e., no energy is required).

1. Diffusion: The process by which molecules of a substance move from an area of higher concentration of that substance to areas of lower concentrations.

Movement of Materials Through The Cell Membrane: Diffusion

Movement of Materials Through The Cell Membrane

2. Osmosis: The diffusion of water molecules

through a selectively permeable membrane from an area of higher concentration of water to an area of lower concentration of water.

It continues until equilibrium is reached.

Movement of Materials Through The Cell Membrane: Osmosis

Movement of Materials Through The Cell Membrane

3. Facilitated diffusion: The use of carrier proteins to move lipid insoluble substances through the cell membrane.

Like diffusion and osmosis, no energy is used, but a concentration difference must exist for movement to occur. Example, transport of glucose.

Movement of Materials Through The Cell Membrane: Facilitated Diffusion

Movement of Materials Through The Cell Membrane

Active TransportIt is an energy-requiring process.

It enables substances that do not diffuse into the cell to move against the natural flow.

That is, materials cross the plasma membrane against a concentration difference.

Movement of Materials Through The Cell Membrane

Three types of active transport

1. Individual molecules are carried through membrane-associated pumps.

These pumps depend on energy (ATP).

Movement of Materials Through The Cell Membrane

For example, the sodium-potassium pump. It ushers out sodium ions (Na+) and brings in potassium ions (K+) across the cell membrane.

These pumps are common in nerve and kidney cells.

Movement of Materials Through The Cell Membrane: Active Transport