Name: ____________________________ Period: __________ Date: _______________

Notes: Cell Boundaries (Chapter 7-3)

I. Structure

a. All cells are bound by a cell membrane. It consists of:

i. Phosopholipid bi-layer

ii. Proteins

iii. Carbohydrates

iv. Cholesterol (a kind of lipid)

b. Cell Walls lay outside the cell membrane. They are rigid and made of

carbohydrates. Present in cells of:

i. Plants

ii. Fungi

iii. Bacteria

c. Semipermiable - they allow certain things across, but restrict other things

II. Movement across the cell membrane

a. Diffusion: The movement of a molecule, or atom from an area of high concentration to

an area of low concentration until equilibrium is reached

i. Equilibrium means equal concentrations on both sides of the membrane

ii. This naturally occurs and normally no energy is required

b. Osmosis: the movement of water across a semi permeable membrane

i. Isotonic solution : The same concentration of solute on both sides of the

membrane

ii. Hypotonic Solution : outside solution has a lower concentration of solute than

inside the cell (Higher concentration of water outside the cell)

Result: water moves into the cell

iii. Hypertonic Solution : outside solution has a higher concentration of solute

than inside the cell (Lower concentration of water outside the cell) Results:

Water moves out of the cell

c. Facilitated Diffusion

i. Movement of a molecule across a membrane when protein channels are

required is called facilitated transport

ii. Sometimes molecules are too large to pass or they are charged and can’t pass

through the membrane without help

1. When a protein channel helps a molecule this is called facilitated

diffusion.

2. Protein channels are specific for one kind of molecule

3. Facilitated diffusion is fast and specific.

d. Active Transport:

i. Movement of molecules from low concentration to high

concentration (opposite of diffusion).

ii. Molecular transport

1. Used for small ions such as Ca, K and Na.

2. Requires Energy (ATP)

3. Involves changes in protein shape

iii. Endocytosis (“endo” means in)

1. For transport of large molecules into the cell

2. Occurs with pockets of the cell membrane that fold into the cells

creating a vacuole (pocket surrounded by lipid bilayer) that is released

into the cytoplasm

a. Phagocytosis: “cell eating”- cells take up particles and form a

food vacuole

b. Pinocytosis: “cell drinking”- cells take up liquid from the

surrounding environment

iv. Exocytosis (“exo” means out)

1. Release of materials from the cell