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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
TWO BASIC CELL TYPES
Prokaryotic Cells
• DNA in nucleoid region
• No membrane-bound organelles
• No nucleus• Small• Bacteria
Plasma Membraneaka: The Gate-keeper
Overview of an Animal Cell
Overview of a Plant Cell
Nucleus & Nuclear Envelope
Ribosomes
Endoplasmic Reticulum (ER)
Golgi Apparatus
LysosomesSac of hydrolytic enzymes
Digests macromoleculesBreaks down dead organelles
pH ~ 5
Formation & Function of Lysosomes
Formation & Function of Lysosomes
Formation & Function of Lysosomes
The Endomembrane System
MitochondriaSite of Cellular Respiration, Makes ATP
ChloroplastSite of Photosynthesis
Converts energy from sunlight to chemical energy stored in sugar
Central Vacuole: Plant Cells
StoresWaterWasteNutrients
Makes plant cell turgid
PeroxisomesProduce and break down H2O2
Do not bud from the Endomembrane System
Cytoskeleton
• Network of fibers throughout cytoplasm
• Gives cell shape
• Holds organelles in place
• Involved in movement & changing shape
Motor Molecules & Cytoskeleton
Changing shapeCilia movementFlagella movement
Organelles move along microtubule or microfilamentEx: Vesicle transport
Centrosomes & Centrioles• Pair of centrioles w/in centrosome
– Centriole: 9x3 ring of microtubules
• Microtubules grow out of centrosome
• Most plant cells lack centrioles
Structure of Eukaryotic Cilia/ Flagella9x2 + 2 ring of microtubulesCovered in plasma membrane
Basal BodyAnchors cilia/ flagella to cell9x3 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• Gives cell shape• Prevents excessive uptake of
H20• Primary, secondary walls
• Plasmodesmata– Cell to cell communication– Cytoplasm continuous from one
cell to other• Middle lamella cements cells
together
Cell Junctions in Animal Cells
Fuses membranesStrong sheets
Pass ions and small molecules