cellular processes. homeostasis the ability or tendency to maintain internal equilibrium....

Cellular Processes

Homeostasis

• The ability or tendency to maintain internal equilibrium.– Maintain – “keep”– Internal – “inside”– Equilibrium – “stable or balanced”

Why is maintaining homeostasis in our body important?

Why is it important for cells to maintain homeostasis?

Cell Membrane

• The “gateway” of the cell.• It regulates what goes in and what comes

out.• Thus is important in understanding how a

cell regulates homeostasis.

A Closer Look at the Cell Membrane

Phosphate head

Fatty Tails

2 layers

Phospholipid Bilayer

Why is the cell membrane also

called the phospholipid

bilayer?

How does the Phospholipid bilayer help maintain homeostasis?

• The membrane is selectively permeable.– “selects some substances to cross but not

others”

NO ENTRYENTER

How “things” get selected to come into and out of the cell…

DIFFUSION

OSMOSIS

ACTIVE TRANSPORT

DIFFUSION

• Movement of particles from an area of greater concentration to an area of lower concentration.

• Cell does not use energy to do this.• Diffusion stops when the two areas are equal.

(homeostasis)• FACILITATED Diffusion

– diffusion of large molecules through protein channels

OSMOSIS

• Diffusion of water• 3 types of solutions drive the force of

osmosis– Hypertonic solution (higher concentration of

solute that water)– Hypotonic solution ( lower concentration of

solute than water)– Isotonic solution (solute has same

concentration as water)

Osmosis

• 3 types of solutions drive the force of osmosis

Active Transport

• The movement of molecules against the concentration gradient. – Therefore it requires energy.– Energy is in the cell is called ATP

ATPRequiresEnergy

Types of Active Transport

• Endosytosis – “into the cell”– Phagosytosis – “cell eating”

• EX) White blood cells eat invading bacterial cells

– Pinocytosis – “cell drinking”

And how do cells let it out…

“Exit the cell”

Latin Roots• Phago – to eat• Pino – to drink• Exo – exit• Endo – enter• Iso – same/equal• Hyper – high• Hypo – low• Cyto – cell• Bi – two• Homeo - same