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Basic Structure of a Cell
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Introduction to Cells Cells are the basic units of organisms Cells can only be observed under microscope
Basic types of cells:
Animal Cell Plant Cell Bacterial Cell
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Number of Cells
Organisms may be: • Unicellular – composed of one cell • Multicellular- composed of many cells that may organize
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Prokaryotes include bacteria & lack a nucleus or membrane-bound structures called organelles
Eukaryotes include most other cells & have a nucleus and membrane-bound organelles (plants, fungi, & animals)
Cells May be Prokaryotic or Eukaryotic
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Prokaryotes
Nucleoid region contains the DNA
•Cell membrane & cell wall
• Contain ribosomes (no membrane) to make proteins in their cytoplasm
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Eukaryotic Cell
Contain 3 basic cell structures:
• Nucleus
• Cell Membrane
• Cytoplasm with organelles
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Two Main Types of Eukaryotic Cells
Plant Cell Animal Cell
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Organelles
Very small size
Can only be observed under a microscope
Have specific functions
Found throughout cytoplasm
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Protect and support the enclosed substances (protoplasm)
Resist entry of excess water into the cell
Give shape to the cell
Cell wall
CELL WALL
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CELL WALL
Made of cellulose which forms very thin fibers
Strong and rigid Found in plant cells
Cell wall
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Living layer Controls the movement of materials into and out of the cell
Selectively permeable
Cell membrane
Cell or Plasma Membrane
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Lies immediately against the cell wall in plant cells
Made of protein and phospholipids
Selectively permeable
Cell membrane
Surrounding the Cell
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Jelly-like substance enclosed by cell membrane
Provides a medium for chemical reactions to take place
Cytoplasm
Cytoplasm of a Cell
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Contains organelles to carry out specific jobs
Examples: chloroplast & mitochondrion
Cytoplasm
More on Cytoplasm
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Controls the normal activities of the cell
Bounded by a nuclear membrane
Contains chromosomes
NUCLEUS
Nucleus
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Each cell has fixed number of chromosomes that carry genes
Genes control cell characteristics
Nucleus
More on the Nucleus
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Nucleolus
• Cell may have 1 to 3 nucleoli
• Inside nucleus
• Disappears when cell divides
• Makes ribosomes that make proteins
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Smooth & Rough Endoplasmic Reticulum
Smooth ER lacks ribosomes & makes proteins USED In the cell
Rough ER has ribosomes on its surface & makes proteins to EXPORT
RIBOSOMES • Small specks made of RNA.
• Found in cytoplasm or on the
endoplasmic reticulum
• Makes proteins
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Rod shape Site of Cellular respiration
Cell Powerhouse
Mitochondrion ( mitochondria )
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Active cells like muscles have more mitochondria Burn sugars to produce energy ATP
In Animal Cells:
Mitochondria
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Have a large central vacuole
Surrounded by tonoplast Contains cell sap Sugars, proteins,
minerals, wastes, & pigments
Plant Cell Organelles
Vacuole
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Contain the green pigment chlorophyll
Traps sunlight to make sugars (food)
Process called photosynthesis
Plant Cell Organelles
Chloroplast
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Golgi Bodies • Stacks of flattened
sacs
• Have a shipping side & a receiving side
• Receive & modify proteins made by ER
• Transport vesicles with modified proteins pinch off the ends
Transport vesicle
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Lysosome • Contain digestive
enzymes
• Break down food and worn out cell parts for cells
• Programmed for cell death (lyse & release enzymes to break down & recycle cell parts)
LYSOSOME • Small cylindrical
• Used during
mitosis
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Different kinds of plant cells
Onion Epidermal Cells
Root Hair Cell
root hair
Guard Cells
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mitochondrion
nucleus
glycogen
granule
cell
membrane
cytoplasm Animal cell
No cell wall or chloroplast Stores glycogen in the cytoplasm for food energy
vacuole
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Animal Cell Organelles
• Near the nucleus • Paired structures • Help cell divide
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Different kinds of animal cells
white blood cell
red blood cell
cheek cells sperm
nerve cell
muscle cell
Amoeba
Paramecium
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Similarities between plant cells and animal cells
Both have a cell membrane surrounding the cytoplasm
Both have a nucleus
Both contain mitochondria
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Differences between plant cells and animal cells
Animal cells Plant cells
Relatively smaller in size
Irregular shape
No cell wall
Relatively larger in size
Regular shape
Cell wall present
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Animal cells Plant cells
Vacuole small or absent
Glycogen as food storage
Nucleus at the center
Large central vacuole
Starch as food storage
Nucleus near cell wall
Differences between Plant Cells and Animal Cells
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STRUCTURE & FUNCTION
OF CELL MEMBRANE (pp. 59-60)
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Structure & function of cell membranes • Lipids = form foundation of membranes
– Separates inside of cell from outside
– Selectively permeable – how phospholipids
interact with H2O
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CELL MEMBRANE AS BARRIER
• Phospholipids = Phosphate
group + 2 fatty acids
– Polar head – phosphate
group – attracted to water
(hydrophilic)
– 2 Non-polar tails – fatty
acids – repelled by water –
interior of membrane
(hydrophobic)
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• Lipid bilayer = double layer
– Non-polar tails – interior – repels ions, polar
molecules (sugars, proteins)
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PROTEINS EMBEDDED IN LIPID
BILAYER • What keeps proteins within lipid bilayer?
– Some amino acids (remember, amino acids make up
proteins) are polar / non polar
– Non polar part = attracted to the interior of lipid
bilayer, but repelled by H2O on either side
– Polar part = attracted to H2O on either side of lipid
bilayer
– **DUAL ATTRACTION holds protein in lipid bilayer*
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Cell Membranes Contain Different Types
of Proteins 1. MARKER proteins – attached to carbohydrate on cell’s
surface (help other cells recognize their cell type (heart,
liver)
2. RECEPTOR proteins – recognize and bind to specific
substances
3. ENZYMES – involved in important biochemical reactions
4. TRANSPORT proteins – aid in the movement of
substances into and out of the cell