Transcript Cells and Cell Organelles

Chapter7
Looking at cells
Where does cork come from?
• The bark of an oak
tree that grows in
Spain and Portugal
• The bark is dead
• All that is left are the
cell walls enclosing
air
Microscopes reveal cell
structure
• Robert Hooke , an
English scientist,
invented the
microscope in the
1600’s to view cork
• He named the “little
boxes” he saw,
“cells”
Anton van Leeuwenhoek
• 10 years after
Hooke’s findings
• Used a microscope to
view pond water
• He named the singlecelled organisms he
discovered
“animalcules”
The Cell Theory
• All living things are made of cells
• Cells are the basic units of structure and
function in organisms
• All cells arise from existing cells
Measuring the size of cell
structures
• Measurements are in
metric units
• International System of
Measurements (SI)
• Based on powers of 10
• Micrometers are onemillionth of a meter ( the
size of a bacterial cell)
Cells must be small
• Lower surface area to volume ratio = inability to
move substances across the membrane in large
enough numbers
• Higher surface area to volume ratio = greater
ability to exchange substances
Small is good!
Big is bad!
Common features of all cells
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Cell membrane
Cytoplasm
Cytoskeleton
Ribosomes
Genetic material
Prokaryotes do not contain
internal compartments
• No nucleus
• Smaller
• Ex: bacteria
Characteristics of bacteria
• Prokaryotes
• All have a cell wall surrounding the cell
membrane
• Some have flagella for movement
• DNA is circular instead of linear
• Some have a capsule for clinging
Eukaryotic cells are organized
• Have a nucleus
• Have other membrane enclosed
organelles
• Some have flagella or cilia for movement
Eukaryotes
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Larger
More complex
Many are highly specialized
Plants, animals, fungi, and many protists
Cell Organization
• Two divisions:
– Nucleus- eukaryotes only
– Cytoplasm- fluid portion of the cell outside the
nucleus
• Eukaryotes and prokaryotes
Organelles
• Specialized structures
• “Little organs”
Nucleus
• Controls cell functions
• Surrounded by a double membrane with
nuclear pores
• Contains DNA wound around proteins
• Wind up into chromosomes before division
takes place
Nucleus
• Nucleolus- where ribosomes are made
• Nuclear pores- allow materials in and out
Vacuoles
• Large, saclike, membrane-enclosed
structures that store materials such as
water, salts, proteins, and carbohydrates
Vacuoles
• Plants- large central vacuole, helps keep
leaves and flowers rigid
• Found in some unicellular organisms and
animals
– Contractile vacuole in paramecium
Vesicles
• In almost all eukaryotic cells
• Used for storage and movement
Lysosomes
• Small organelle filled with enzymes
• Digest old organelles, cellular “junk,” lipids,
proteins, and carbohydrates
• Type of vesicle, found in animal and some
plant cells
Ribosomes
• Made of RNA and protein
• Produce proteins
• Found in the cytoplasm (free) and rough
ER (attached)
Endoplasmic Reticulum (ER)
• A system of internal membranes that
moves proteins and other substances
through the cell
• Rough ER- has ribosomes on the surface
that create exported proteins
• Smooth ER- no ribosomes, makes lipids
for the cell membrane
– Detoxifies drugs
Golgi Apparatus
• Stack of flattened sacs
• Modifies, sorts, and packages proteins
made from the rough ER
• Sent into or out of the cell
Sources of Energy
• Mitochondria- animal and plant cells
• Chloroplasts- plant cells
Chloroplasts
• Converts sunlight into food energy in a
process called photosynthesis
• Double membrane
• Contains a green pigment called
chlorophyll
Mitochondria
• In eukaryotic cells
• Power plant of the cells
• Converts food energy into smaller units
the cell can more easily use
• Double membrane
Mitochondria
• Inherited only from your mother
• A way to trace the maternal lines of
animals
Endosymbiotic Theory
• Chloroplasts and mitochondria have their
own DNA and double membranes
• Theory states:
– These may have been independent
organisms at one time
– Create their own energy
– May have been beneficial once absorbed and
found to be beneficial
Unique features of plant cells
• Cell wall -surrounds the cell membrane, supports and
protects the cell
• Chloroplasts- green structures that absorb sunlight and
produce glucose
• Central vacuole- stores water and other substances,
when full makes a cell rigid
Cytoskeleton
• Network of protein filaments
• Gives cells their shape and internal
organization
– Helps to transport materials inside the cell
• Protein filaments
– Microtubules
– Microfilaments
Microfilaments
• Threadlike structures made of protein called
actin
• Make up a tough flexible framework that helps
support the cell
• Help cells move
– Amoebas- assemble and disassemble to help
them move
Microtubules
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Hollow structures
Made of protein tubulin
Maintains cell shape
Centrioles
– Makes spindle during mitosis to separate
chromosomes
Microtubules
• Make up cilia and flagella
– Used for swimming
• Arranged in a 9+2 pattern
• Small bridges between aid in movement
Cell Boundries
• Cell wall
• Cell membrane
Cell Wall
• Prokaryotes, plants, algae, fungi
– Animal cells do not
• Outside the cell membrane
• Strong supporting layer
• Porous- allows water, carbon dioxide and
oxygen to pass through
Cell Membrane
• Protects and supports cell
• Regulates what enters and leaves
• Phospholipid bilayer- to layers of lipids