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Cells
Chapter 7
The size range of cells
Why are cells so small?
Small cells have a high surface
area to volume ratio which
allows more stuff to move in and
out of the cell
CELL THEORY
• Living organisms are composed of
one or more cells
• Cells are the smallest unit of life
• Cells come from other cells
ALL CELLS HAVE
• Plasma membrane
– Outer layer
• Cytoplasm
– Watery stuff inside
• DNA
– Genetic material
• Ribosomes
– Make proteins
TWO BASIC CELL TYPES
Prokaryotic Cells
• DNA in nucleoid region
• No membrane-bound
organelles
• No nucleus
• Small
• Bacteria
Plasma Membrane
aka: The Gate-keeper
Overview of an Animal Cell
Overview of a Plant Cell
Nucleus & Nuclear Envelope
Ribosomes
Endoplasmic Reticulum (ER)
Golgi Apparatus
Lysosomes
Sac of hydrolytic enzymes
Digests macromolecules
Breaks down dead organelles
pH ~ 5
Formation & Function of Lysosomes
Formation & Function of Lysosomes
Formation & Function of Lysosomes
The Endomembrane System
Mitochondria
Site of Cellular Respiration, Makes ATP
Chloroplast
Site of Photosynthesis
Converts energy from sunlight to chemical energy
stored in sugar
Central Vacuole: Plant Cells
Stores
Water
Waste
Nutrients
Makes plant cell
turgid
Peroxisomes
Produce and break down H2O2
Cytoskeleton
• Network of fibers
throughout cytoplasm
• Gives cell shape
• Holds organelles in
place
• Involved in movement
& changing shape
Motor Molecules & Cytoskeleton
•Changing shape
•Cilia movement
•Flagella movement
Organelles move along
microtubule or
microfilament
Ex: Vesicle transport
Centrioles
• Centriole: 9x3 ring of microtubules
• Involved in cell division
Structure of Eukaryotic Cilia/ Flagella
9x2 + 2 ring of microtubules
Covered in plasma membrane
Basal Body
Anchors cilia/ flagella to cell
9x3 ring of microtubules
Wave
Back and
forth
Dynein “walking” moves Cilia and Flagella
•Powered by ATP
•Dynein arms grip adjacent
microtubule
•Grip, pull, release – repeat
•Results in bending of microtubules
Microfilaments (actin filaments)
• Pulling force
– Muscle contraction
– Cytoplasmic streaming
– Pseudopodia
• Part of Extracellular
Matrix
– Support cell membrane
– Inside of cell membrane
Extracellular Matrix
Plant Cell Walls
• Protects cell
• Plasmodesmata
• Gives cell shape
– Cell to cell communication
• Prevents excessive uptake of
– Cytoplasm continuous from one
H20
cell to other
• Primary, secondary walls
• Middle lamella cements cells together
Cell Junctions in Animal Cells
Fuses membranes
Strong sheets
Pass ions and small molecules