Cell Structure and Function - Weebly...Cell Structure and Function Chapter 3 CELL THEORY 3.1 Key...
Transcript of Cell Structure and Function - Weebly...Cell Structure and Function Chapter 3 CELL THEORY 3.1 Key...
Cell Structure and Function
Chapter 3
CELL THEORY 3.1
Key Concept
• Cells are the Basic unit of life
Cell Theory
• Due to the invention and improvement of the microscope
• Many scientists contributed
Cell Theory
• A unifying concept of biology
Three Principles of C.T.
1. All organisms are made of cells.
Three Principles of C.T.
2. All cells are produced by other existing cells.
Three Principles of C.T.
3. The cell is the most basic unit of life.
All Cells
• Share certain characteristics: – cells tend to be microscopic
– all cells are enclosed by a membrane
– all cells are filled with cytoplasm
cell membrane
cytoplasm
Cell Types
• Two basic types of cells: – prokaryotic cells - eukaryotic cells
Prokaryotic Cells
• Examples: – bacteria
– blue-green algae
• Lack a nucleus
• No membrane-bound organelles
Eukaryotic Cells
• Examples: – plant cells
– animal cells
• Have a nucleus
• Have membrane-bound organelles
CELL ORGANELLES 3.2
Key Concept
• Eukaryotic cells share many similarities.
Cells Have an Internal Structure
• The cytoskeleton – supports and shapes the cell
– helps position and transport organelles
– provides strength
– assists in cell division
– aids in cell movement
Nucleus
• Stores genetic information
Endoplasmic Reticulum
• Make proteins and membranes
• Two types: – Rough ER
• contain ribosomes
– Smooth ER • no ribosomes
Golgi Apparatus
• Packages proteins for secretion outside of the cell
Ribosomes
• Link amino acids to form proteins
Vesicles
• Membrane-bound sacs that hold materials
Mitochondria
• Supply energy to the cell
Vacuole
• Fluid-filled sacs that hold materials
Lysosomes
• Contain enzymes to digest materials
Centrioles
• Tubes found in the centromeres – help divide DNA
– form cilia and flagella
Plant Cells
• Have cell walls – provides rigid
support
Plant Cells
• Have chloroplasts – convert solar energy to chemical energy
CELL MEMBRANE 3.3
Key Concept
• The cell membrane is a barrier that separates a cell from the external environment.
Cell Membranes
• Composed of two layers • Two major functions:
– forms a boundary between the inside and outside of the cell
– controls passage of materials
cell membrane outside cell
inside cell
Structure of C.M.
• Phospholipid bilayer • Other molecules are embedded in the
membrane • Called the fluid mosaic model
Selectively Permeable
• Allows only certain substances in or out
Some molecules
can cross the
membrane while
others cannot.
DIFFUSION AND OSMOSIS 3.4
Key Concept
• Materials move across membranes because of concentration differences.
Passive Transport
• Does not require energy input from a cell – allows molecules to move across a cell
membrane • Two types:
– diffusion – osmosis
Diffusion
• No energy required
• Moves from high to low concentration
Osmosis
• Diffusion of water molecules across a semi-permeable membrane
Types of Solutions
• Isotonic
• Hypertonic
• Hypotonic
Isotonic
• Equal concentration of dissolved particles
Hypertonic
• Higher concentration of dissolved particles outside the cell
Hypotonic
• Higher concentration of dissolved particles inside the cell
Transport Proteins
• Allow some molecules to pass through the phospholipid bilayer
• Called facilitated diffusion
HIGH
LOW
ACTIVE TRANSPORT, ENDOCYTOSIS, AND EXOCYTOSIS
3.5
Key Concept
• Cells use energy to transport materials that cannot diffuse across a membrane.
Active Transport
• Requires energy input from a cell – ATP
• Substances go from low to high concentration
• Occurs through transport protein pumps
• Used to maintain homeostasis
Active Transport
• Many models & mechanisms
ATP ATP
Endocytosis
• Transport of materials inside the cell – can be large material – or large quantities of materials
• Phagocytosis – cell eating
• Pinocytosis – cell drinking
Exocytosis
• Transport of materials outside the cell