Download Chapter 3 The Basic Structure of a Cell

Basic Structure of a Cell
1
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
• Multicellularcomposed of many
cells that may
organize
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Cells May be Prokaryotic or
Eukaryotic
 Prokaryotes include bacteria &
lack a nucleus or membrane-bound
structures called organelles
Eukaryotes include most other cells
& have a nucleus and membranebound organelles (plants, fungi, &
animals)
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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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CELL WALL
Cell wall
Protect and support
the enclosed
substances
(protoplasm)
Resist entry of
excess water into
the cell
Give shape to the cell
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CELL WALL
Cell wall
Made of cellulose
which forms very
thin fibers
Strong and rigid
Found in plant cells
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Cell or Plasma Membrane
Cell membrane
Living layer
Controls the
movement of
materials into and
out of the cell
Selectively
permeable
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Surrounding the Cell
Cell membrane
Lies immediately
against the cell wall
in plant cells
Made of protein and
phospholipids
Selectively permeable
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Cytoplasm of a Cell
Cytoplasm
Jelly-like substance
enclosed by cell
membrane
Provides a medium
for chemical
reactions to take
place
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More on Cytoplasm
Cytoplasm
Contains organelles
to carry out
specific jobs
Examples:
chloroplast &
mitochondrion
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NUCLEUS
Nucleus
Controls the normal
activities of the cell
Bounded by a
nuclear membrane
Contains chromosomes
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More on the Nucleus
Nucleus
Each cell has fixed
number of
chromosomes that
carry genes
Genes control cell
characteristics
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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
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RIBOSOMES
• Small specks made of RNA.
• Found in cytoplasm or on the
endoplasmic reticulum
• Makes proteins
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Cell Powerhouse
Mitochondrion
( mitochondria )
Rod shape
Site of Cellular
respiration
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In Animal Cells:
Mitochondria
Active cells like
muscles have more
mitochondria
Burn sugars to
produce energy ATP
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Plant Cell Organelles
Vacuole
Have a large central
vacuole
Surrounded by tonoplast
Contains cell sap
Sugars, proteins,
minerals, wastes, &
pigments
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Plant Cell Organelles
Chloroplast
Contain the green
pigment chlorophyll
Traps sunlight to
make sugars (food)
Process called
photosynthesis
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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)
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LYSOSOME
• Small cylindrical
• Used during
mitosis
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Different kinds of plant
cells
Onion Epidermal Cells
Guard Cells
root hair
Root Hair Cell
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vacuole
cytoplasm
nucleus
mitochondrion
glycogen
granule
Animal cell
No cell wall or
chloroplast
Stores glycogen
in the
cytoplasm for
food energy
cell
membrane
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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
Amoeba
red blood cell
muscle cell
cheek cells
sperm
nerve cell
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
Relatively
larger in size
Irregular shape
Regular shape
No cell wall
Cell wall present
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Differences between Plant
Cells and Animal Cells
Animal cells
Plant cells
Vacuole small or
absent
Large central
vacuole
Glycogen as food
storage
Starch as food
storage
Nucleus at the
center
Nucleus near cell
wall
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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
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