CELLULAR STRUCTURES & Active and Passive Transport
1. Passive membrane transport does not require the
THEIR FUNCTIONS cell to expend energy.
2. Active membrane transport does require the cell
Cell Structure to expend energy, usually in the form of ATP.
Organelles – specialized structures in cells that perform Types of Passive Transport
specific functions
1. Diffusion – movement of substances in a solution
ex: nucleus, mitochondria, ribosomes from high concentration to a low concentration
Cytoplasm – jelly-like substance that holds organelles Solutes – dissolved
Cell membrane – plasma membrane; encloses the Solvent – predominant liquid or gas that dissolve solute
cytoplasm
Concentration gradient – difference in the concentration of
Extracellular – substances outside the cell a solute in a solvent between two points divided by their
distance
Intracellular – substances inside the cell
2. Osmosis – diffusion of water (a solvent) across a
Functions of the Cell selectively permeable membrane from higher water
− Smallest units of life concentration to lower water concentration
− Cell metabolism and energy use
− Synthesis of molecules Osmotic pressure – force required to prevent movement of
− Communication water across cell membrane
− Reproduction and inheritance
- depends on the difference of solution concentrations
Cell Membrane Structure inside a cell relative to outside the cell.
Fluid-mosaic model – the model used to describe the cell Hypotonic – has a ↓ concentration of solutes and ↑
membrane structure. concentration of water
- less tone or osmotic pressure
The membrane contains phospholipids, cholesterol, - water moves by osmosis into the cell, causing it to
proteins, and carbohydrates. swell.
Phospholipids Lysis – when cell swells, then rupture
- form a bilayer that contains 2 regions: polar and
nonpolar. Isotonic – same solute concentrations
Phospholipid Structure Hypertonic – ↑ solute concentration and ↓ water
Polar region – exposed to water (hydrophilic) concentration
Nonpolar region – facing the interior of the membrane - water moves by osmosis from the cell causing it to
(hydrophobic) shrink
Movement through the Cell Membrane Crenation – cell-shrinking
Cell membrane – has selective permeability, which allows 3. Facilitated Diffusion – diffusion by passing through
only certain substances to pass in and out of the cell. cell membrane channels or through carrier molecules
- moves from an area of higher concentration to an
higher concentrations inside the cell area of lower concentration; does not require ATP
- enzymes, glycogen, and potassium
higher concentrations outside the cell Leak and Gated Channels
- sodium, calcium, and chloride 2 classes of cell membrane channels:
Cell Membrane Passage 1. Leak channels – constantly allow ions to pass
O2 and CO2 – can pass directly through the cell through; always open
membrane’s phospholipid bilayer. 2. Gated channels – limit the movement of ions
- some substances use protein channels, such as Na+ across the membrane by opening and closing
- route of transport depends on the size, shape, and Carrier molecules – proteins within the cell membrane
charge of the substance involved in facilitated diffusion
- some substances require carrier molecules, such as - water soluble molecules or ions across the
glucose membrane.
- some substances require a vesicular transport
labd
1. Passive membrane transport does not require the
THEIR FUNCTIONS cell to expend energy.
2. Active membrane transport does require the cell
Cell Structure to expend energy, usually in the form of ATP.
Organelles – specialized structures in cells that perform Types of Passive Transport
specific functions
1. Diffusion – movement of substances in a solution
ex: nucleus, mitochondria, ribosomes from high concentration to a low concentration
Cytoplasm – jelly-like substance that holds organelles Solutes – dissolved
Cell membrane – plasma membrane; encloses the Solvent – predominant liquid or gas that dissolve solute
cytoplasm
Concentration gradient – difference in the concentration of
Extracellular – substances outside the cell a solute in a solvent between two points divided by their
distance
Intracellular – substances inside the cell
2. Osmosis – diffusion of water (a solvent) across a
Functions of the Cell selectively permeable membrane from higher water
− Smallest units of life concentration to lower water concentration
− Cell metabolism and energy use
− Synthesis of molecules Osmotic pressure – force required to prevent movement of
− Communication water across cell membrane
− Reproduction and inheritance
- depends on the difference of solution concentrations
Cell Membrane Structure inside a cell relative to outside the cell.
Fluid-mosaic model – the model used to describe the cell Hypotonic – has a ↓ concentration of solutes and ↑
membrane structure. concentration of water
- less tone or osmotic pressure
The membrane contains phospholipids, cholesterol, - water moves by osmosis into the cell, causing it to
proteins, and carbohydrates. swell.
Phospholipids Lysis – when cell swells, then rupture
- form a bilayer that contains 2 regions: polar and
nonpolar. Isotonic – same solute concentrations
Phospholipid Structure Hypertonic – ↑ solute concentration and ↓ water
Polar region – exposed to water (hydrophilic) concentration
Nonpolar region – facing the interior of the membrane - water moves by osmosis from the cell causing it to
(hydrophobic) shrink
Movement through the Cell Membrane Crenation – cell-shrinking
Cell membrane – has selective permeability, which allows 3. Facilitated Diffusion – diffusion by passing through
only certain substances to pass in and out of the cell. cell membrane channels or through carrier molecules
- moves from an area of higher concentration to an
higher concentrations inside the cell area of lower concentration; does not require ATP
- enzymes, glycogen, and potassium
higher concentrations outside the cell Leak and Gated Channels
- sodium, calcium, and chloride 2 classes of cell membrane channels:
Cell Membrane Passage 1. Leak channels – constantly allow ions to pass
O2 and CO2 – can pass directly through the cell through; always open
membrane’s phospholipid bilayer. 2. Gated channels – limit the movement of ions
- some substances use protein channels, such as Na+ across the membrane by opening and closing
- route of transport depends on the size, shape, and Carrier molecules – proteins within the cell membrane
charge of the substance involved in facilitated diffusion
- some substances require carrier molecules, such as - water soluble molecules or ions across the
glucose membrane.
- some substances require a vesicular transport
labd
