unit 3 cell membranes, diffusion, and osmosis

3.1 Cell Theory

Plant cells have cell walls and chloroplasts.• A cell wall provides rigid support.

3.1 Cell Theory

Plant cells have cell walls and chloroplasts.• A cell wall provides rigid support.• Chloroplasts convert solar energy to chemical energy.

3.1 Cell Theory

KEY CONCEPT The cell membrane is a barrier that separates a cell from the external environment.

3.1 Cell Theory

Cell membranes are composed of two phospholipid layers.

3.1 Cell Theory

Cell membranes are composed of two phospholipid layers.• The cell membrane has two major functions.

cell membrane

3.1 Cell Theory

Cell membranes are composed of two phospholipid layers.• The cell membrane has two major functions.

– forms a boundary between inside and outside of the cell

cell membrane outside cell

inside cell

3.1 Cell Theory

Cell membranes are composed of two phospholipid layers.• The cell membrane has two major functions.

– forms a boundary between inside and outside of the cell

– controls passage of materials

cell membrane outside cell

inside cell

3.1 Cell Theory

Cell membranes are composed of two phospholipid layers.

3.1 Cell Theory

cell membrane

Cell membranes are composed of two phospholipid layers.• The cell membrane is made of a phospholipid bilayer.

3.1 Cell Theory

cell membrane

Cell membranes are composed of two phospholipid layers.• The cell membrane is made of a phospholipid bilayer.• There are other molecules embedded in the membrane.

protein

cholesterol

proteincarbohydratechain

protein channel

3.1 Cell Theory

cell membrane

Cell membranes are composed of two phospholipid layers.• The cell membrane is made of a phospholipid bilayer.• There are other molecules embedded in the membrane.• The fluid mosaic model describes the membrane.

protein

cholesterol

proteincarbohydratechain

protein channel

3.1 Cell Theory

Cell membranes are composed of two phospholipid layers.

3.1 Cell Theory

Cell membranes are composed of two phospholipid layers.• The cell membrane is selectively permeable.

Some molecules can cross the membrane while others cannot.

3.1 Cell Theory

Cell membranes are composed of two phospholipid layers.• The cell membrane is selectively permeable.

Some molecules can cross the membrane while others cannot.

3.1 Cell Theory

Chemical signals are transmitted across the cell membrane.• Receptors bind with ligands and change shape.• There are two types of receptors.

3.1 Cell Theory

Chemical signals are transmitted across the cell membrane.• Receptors bind with ligands and change shape.• There are two types of receptors.

– intracellular receptor

3.1 Cell Theory

Chemical signals are transmitted across the cell membrane.• Receptors bind with ligands and change shape.• There are two types of receptors.

– intracellular receptor– membrane receptor

3.1 Cell Theory

KEY CONCEPT Materials move across membranes because of concentration differences.

Diffusion and Osmosis

3.1 Cell Theory

Passive transport does not require energy input from a cell.

• Molecules can move across the cell membrane through passive transport.

• There are two types of passive transport.

• osmosis

• diffusion

Diffusion and Osmosis

3.1 Cell Theory

Diffusion and osmosis are types of passive transport.

• Molecules diffuse down a concentration gradient.

Diffusion and Osmosis

3.1 Cell Theory

Diffusion and osmosis are types of passive transport.

• Osmosis is the diffusion of water molecules across a semipermeable membrane.

Diffusion and Osmosis

3.1 Cell Theory

Diffusion and osmosis are types of passive transport.• There are three types of solutions.

• isotonic

• hypotonic

• hypertonic

3.1 Cell Theory

Some molecules can only diffuse through transport proteins.

• Some molecules cannot easily diffuse across the cell membrane.

• Facilitated diffusion is diffusion through transport proteins.

Diffusion and Osmosis

3.1 Cell Theory

KEY CONCEPT Cells use energy to transport materials that cannot diffuse across a membrane.

Active Transport, Endocytosis, and Exocytosis

3.1 Cell Theory

Active transport requires energy input from a cell and enables a cell to move a substance against its concentration gradient.

• Passive transport requires no energy from the cell.

• Active transport is powered by chemical energy (ATP).

• Cells use active transport to maintain homeostasis.

• Active transport occurs through transport protein pumps.

3.1 Cell Theory

A cell can import and export large materials or large amounts of material in vesicles during the processes of endocytosis and exocytosis.

• Cells use energy to transport material in vesicles.

• Endocytosis is the process of taking material into the cell.

• Phagocytosis is a type of endocytosis.

Active Transport, Endocytosis, and Exocytosis

3.1 Cell Theory

A cell can import and export large materials or large amounts of material in vesicles during the processes of endocytosis and exocytosis.

• Cells use energy to transport material in vesicles.

• Exocytosis is the process of expelling material from the cell.

Active Transport, Endocytosis, and Exocytosis