02 the plasma membrane
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Transcript of 02 the plasma membrane
A View of the Cell
The Plasma Membrane
A View of the Cell
Cells maintain homeostasis Depends on the movement of materials in and
out of the cell Nutrients, waste and ions
Two factors govern the movement of materials in and out of the cell Diffusion The plasma membrane
Diffusion
Diffusion is caused by the random motion of atoms and molecules Types of motion: vibrational, rotational and
translational
The diffusion of water through a membrane is called osmosis
Diffusion in a Cell
The direction a molecule travels depends on… The concentration gradient The function the molecule plays in cell
metabolism
3 situations exist between cells and their environment based on concentration Hypotonic Hypertonic Isotonic
Diffusion in a Cell
Diffusion in a Cell
The Plasma Membrane
The plasma membrane separates the cell from its environment and controls what passes through it
The fluid mosaic model The plasma membrane has a dynamic – ever changing
– structural composition A phospholipid bilayer Cholesterol Proteins
Phospholipids
The Role of Cholesterol
Cholesterol helps to maintain the proper fluidity of the membrane in cases of extreme temperature change
Cholesterol Rigidity Fluidity
Cholesterol Rigidity Fluidity
The Role of Proteins
Transport proteins Move needed substances or waste material
through the membrane
Methods of Cellular Transport
Passive Transport
Requires no cell energy
Diffusion
Osmosis
Active Transport
Requires the cell to expend energy
Used to get necessary metabolic chemicals
Particles move against the concentration gradient or are too large to pass through transport proteins
Passive Transport – Facilitated Diffusion
Channel proteins (a type of transport protein) create a passage or channel through which molecules can pass
Active Transport
Carrier proteins (a type of transport protein) bind with a molecule and uses energy to move it against the concentration gradient
Active Transport
When a molecule is too large to pass through the membrane…
…cells can absorb them by engulfing them Endocytosis Ex/ White blood cells, feeding
…cells can excrete or secrete them Exocytosis Ex/removal of waste, release of cellular product
(neurotransmitters, hormones, enzymes)
Endocytosis
To absorb a large molecule (or organism!) a cell can…
…completely engulf it Phagocytosis https://www.youtube.com/watch?v=aWItglvTiLc
Endocytosis
To absorb a large molecule a cell can…
…make a small pocket (called a vesicle) out of the membrane to store it Pinocytosis
Exocytosis
When a cell directs the contents of a vesicle out of the membrane into the extracellular space Waste = excretion Products = secretion