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3.1 Cell Theory
Plant cells have cell walls and chloroplasts.• A cell wall provides rigid support.
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3.1 Cell Theory
Plant cells have cell walls and chloroplasts.• A cell wall provides rigid support.• Chloroplasts convert solar energy to chemical energy.
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3.1 Cell Theory
KEY CONCEPT The cell membrane is a barrier that separates a cell from the external environment.
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3.1 Cell Theory
Cell membranes are composed of two phospholipid layers.
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3.1 Cell Theory
Cell membranes are composed of two phospholipid layers.• The cell membrane has two major functions.
cell membrane
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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
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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
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3.1 Cell Theory
Cell membranes are composed of two phospholipid layers.
![Page 9: Unit 3 Cell Membranes, Diffusion, And Osmosis](https://reader033.vdocuments.mx/reader033/viewer/2022061419/554e9569b4c90573338b5094/html5/thumbnails/9.jpg)
3.1 Cell Theory
cell membrane
Cell membranes are composed of two phospholipid layers.• The cell membrane is made of a phospholipid bilayer.
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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
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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
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3.1 Cell Theory
Cell membranes are composed of two phospholipid layers.
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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.
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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.
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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.
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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
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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
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3.1 Cell Theory
KEY CONCEPT Materials move across membranes because of concentration differences.
Diffusion and Osmosis
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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
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3.1 Cell Theory
Diffusion and osmosis are types of passive transport.
• Molecules diffuse down a concentration gradient.
Diffusion and Osmosis
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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
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3.1 Cell Theory
Diffusion and osmosis are types of passive transport.• There are three types of solutions.
• isotonic
• hypotonic
• hypertonic
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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
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3.1 Cell Theory
KEY CONCEPT Cells use energy to transport materials that cannot diffuse across a membrane.
Active Transport, Endocytosis, and Exocytosis
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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.
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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
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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