AGENDA

Standard Cell Membrane and Cell Transport Practice

STANDARD Students will analyze the nature of relationships

between structures and functions in living cells. Explain the role of cell organelles for both prokaryotic

and eukaryotic cells, including the cell membrane, in maintaining homeostasis.

Explain the impact of water on life processes.

HOMEOSTASIS “Homeo” – similar; the same “Stasis” – stable Homeostasis is the balanced internal condition of

cells Also called equilibrium Example: body temperature

CELL MEMBRANE The protective boundary that separates the cell

from its environment. Made up of phospholipids in a double layer

Phospholipid bilayer

lipid

phosphate

inside cell

outside cell

PHOSPHOLIPIDS

Contain 2 fatty acid chains (Made of C, H, and O) and a phosphate group

The head is polar and hydrophilic (water loving)

The tails are nonpolar and hydrophobic (water fearing)

CELL MEMBRANE Semi-permeable and Selectively permeable

Needs to allow some materials but not all to pass through the membrane

Controls what gets in or out; the membrane is selective

CELL MEMBRANE Fluid Mosaic Model

Fluid because individual phospholipids and proteins can move side-to-side within the layer, like it is a liquid

Mosaic because of the pattern produced by the scattered protein molecules when the membrane is viewed from above

CELL MEMBRANE Accessory Proteins

Transport proteins allow passage of hydrophilic substances across the membrane Channel proteins are a type of transport protein that have a

channel through which certain molecules or ions can pass Carrier proteins are a type of transport protein that binds to

molecules and changes shape to carry them across the membrane

CHANNEL PROTEIN

CARRIER PROTEIN

CELL TRANSPORT Two Types:

Passive Transport – does not require energy Active Transport – requires energy

CELL TRANSPORT Passive transport

The cell uses no energy Materials move from high concentration to low

concentration 3 types

Diffusion Facilitated diffusion Osmosis

DIFFUSION

Does not require energy on the part of the cell.

Movement of particles from an area of high concentration to low concentration

Continues until all molecules are evenly spaced

Example: oxygen diffusing into a cell and carbon dioxide diffusing out

FACILITATED DIFFUSION Does not require

energy on the part of the cell.

Uses transport proteins to move from areas of high concentration to low concentration

Examples: glucose or amino acids moving from blood into a cell

OSMOSIS Requires no energy on the part of the cell Diffusion of water and ONLY water Moves from high concentration to low

concentration

OSMOSIS Water is very important to life! Cell survival depends on balancing water uptake

and water loss. But the cell doesn’t control water movement through the cell membrane.

Three different solutions cells may be exposed to: Hypotonic Hypertonic Isotonic

HYPOTONIC SOLUTION

The solution has a higher concentration of water and a lower concentration of solute than inside the cell.

Water moves from the solution to the inside of the cell. The cell swells and may eventually burst.

hypo – Swells, envision the cell as an expanding “o”

HYPERTONIC SOLUTION

The solution has a lower concentration of water and a higher concentration of solute than inside the cell.

Water moves from inside the cell into the solution. The cell shrinks

hyper – shrinks; “r” in hyper, “r” in shrink

ISOTONIC SOLUTION

The concentration of water and solutes in the solution is equal to the concentration inside the cell.

Water moves equally in both directions and the cell remains the same size.

iso – equal, no change in the cell’s size

CELL TRANSPORT Active Transport

The cell uses energy Actively moves molecules to where they are needed Movement from an area of low concentration to an area

of high concentration – this is hard, requires work! 3 types:

Ion pumps Endocytosis Exocytosis

ION PUMP Requires energy Molecules move through a

transport protein from low concentration to high concentration

Example: the Sodium-Potassium pump pumps NA+ ions out and K+ in. This pump is very important in nerve cells to help respond to stimuli and transport impulses

ENDOCYTOSIS

Requires energy on the part of the cell. Endo – enter; taking bulky materials into a cell. Phagocytosis – “cell eating”

Forms food vacuole and digests food This is how white blood cells eat bacteria

EXOCYTOSIS Requires energy on the part of the cell. Molecules are moved out of the cell by vesicles

that fuse with the plasma membrane Exo = exit; forces material out of the cell

Examples: hormones or wastes released from cell