How do we look at cells? Most cells are too small to see with
the naked eye, so how do we see them? Just how small is too
small?
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Microscope Power Line
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Compound Light Microscope Uses 1 or more lenses to produce
enlarged images Allows you to see living cells Magnifies up to
2,000 times
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Electron Microscopes Use beams of electrons, similar to your
television Cant see living cells, because specimens are put into a
vacuum Magnifies up to 200,000 times 2 types
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Thin slices stained with metal ions Heavily stained portions
absorb electrons Lightly stained portions the electrons pass
through, hitting a fluorescent screen and forming an image Black
and white images, color added Transmission Electron Microscope
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Scanning Electron Microscope Coated with layer of metal
Electrons bounce off onto a fluorescent screen 3-D black and white
images, color added
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Scanning Tunneling Microscope Uses voltage differences to
create digital images Allows you to see individual atoms in 3-D You
can see living organisms Magnifies up to 10 million times
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Cell Theory 1.All living things are made of one or more cells
2.Cells are the basic units of structure and function in organisms
3.All cells arise from existing cells
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What is a cell? All cells have all of the equipment necessary
to perform the essential functions of life All cells share several
common features There are 2 types of cells
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What features do all cells share? Cell membranethe outer
boundary that encloses the cell, protects it from its surroundings,
and regulates what leave and enters, including gases, nutrients,
and wastes Cytoplasmthe cell interior Ribosomesthe place where
proteins are made DNAprovides instructions
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What are the two types of cells? ProkaryotesEukaryotes
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The smallest and simplest cells, 1 15 m Lack a nucleus and
other internal compartments Lived at least 3.5 billion years ago An
example is a bacteria Prokaryotes
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Characteristics of Prokaryotes Grow and divide rapidly Some
need O 2, others dont Some make their own food No internal
compartments, so enzymes and ribosomes move about freely Single,
circular strand of DNA Cell wall
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Prokaryotic Cell Wall The cell wall is made of polysaccharides
with short amino acid chains attached Prokaryotes have to have a
cell wall, because they do not have an internal skeleton A
prokaryotes cell wall is to a bacteria as an insects exoskeleton is
to an ant
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Prokaryotes Capsules Some prokaryotes have capsules out side of
their cell walls Allow them to cling to almost anything, like skin,
teeth, and food How would this benefit them?
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Flagella Many prokaryotes have flagella, long threadlike
structure that protrude from the cells surface and enable movement
The flagella rotate to propel the prokaryote
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Eukaryotes Any organisms whose cells have a nucleus They also
have other internal compartments, called organelles Evolved about
1.5 billion years ago
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Nucleus, Organelles, and Cytoplasm The nucleus is an internal
compartment that houses the cells DNA Organelles are other internal
structures that carry out specific functions in the cell Cytoplasm
is everything inside the cell membrane but outside the nucleus
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Cilia are short, hair-like structures that protrude from cell
surfaces Flagella and cilia can propel cells or they can move
substances across a cells surface Cilia in lungs sweep mucus and
debris away and in your ears they conduct sound vibrations Flagella
and Cilia
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Cytoskeleton The cytoskeleton is a web of protein fibers It
holds the cell together and keeps cell membranes from collapsing
Anchored to cell membrane It links one region to another Anchors
nucleus and organelles to fixed locations 3 different
kindsmicrofilaments, microtubules, and intermediate filaments
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Microfilaments Long and slender, made of actin Network beneath
cells surface that is anchored to the membrane proteins Determines
the shape of the cell
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Microtubules Hollow tubes of tubulin Within the cytoskeleton,
microtubules act as the highway for transportation of information
from the nucleus out RNA/protein complexes are transported along
the tracks of microtubules by motor proteins
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Intermediate Filaments Intermediate filaments are thick ropes
of protein They make up the frame that allows ribosomes and enzymes
to be confined, which allows cells to organize complex metabolic
activities efficiently
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Cell Membrane Cell membranes are made up of phospholipids,
which are a phosphate group and two fatty acids Phospholipids are
made up of a polar head and two nonpolar tails Phospholipids form a
phospholipid bilayer
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Cell Membrane Cell membranes have selective permeability The
lipid bilayer allows lipids and substances that dissolve in lipids
to pass through Membrane proteins are also part of the membranesome
are for transport
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Cell Membrane There are several types of membrane proteins,
including: Marker proteins Transport proteins Enzymes Receptor
proteins Proteins move, because phospholipids are constantly in
motion
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Nucleus Houses most of the DNA, which controls the cells
functions Surrounded by a double membrane, called the nuclear
envelope or nuclear membrane The nuclear envelope is made of two
lipid bilayers Why do you think that there are 2?
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Nucleus Nuclear pores are small channels through the nuclear
envelope What are the pores for? The nucleolus is an area of the
nucleus where ribosomes are partially assembled Eukaryotic DNA is
tightly wound around proteins, and appears as a dark mass under
magnification most of the time
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Ribosomes Made up of dozens of proteins and RNA Cells make
proteins on ribosomes Some are suspended in the cytosol. These are
free ribosomes. Free ribosomes make proteins that remain in the
cell. Proteins that leave the cell are made on ribosomes on the
surface of the endoplasmic reticulum
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Endoplasmic Reticulum An extensive system of internal membranes
that move proteins and other substances through the cell The
membrane of ER is a lipid bilayer with embedded proteins
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Rough Endoplasmic Reticulum The Rough ER has ribosomes attached
It helps transport proteins made on the attached ribosomes The
proteins enter the ER and a small, membrane-bound sac, or vesicle,
pinches off Proteins made on ribosomes on the rough ER stay
separate from proteins made on free ribosomes
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Smooth Endoplasmic Reticulum The Smooth Endoplasmic Reticulum
lacks ribosomes, so it appears smooth under an electron microscope
The smooth ER makes lipids and breaks down toxic substances
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Golgi Apparatus A flattened, membrane- bound sac that serves as
the packaging and distribution center of the cell Enzymes in the
Golgi Apparatus modify proteins from the ER
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Lysosomes Lysosomes are small, spherical organelles th at
contain the cells digestive enzymes
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Mitochondria Organelle that uses organic compounds to make ATP,
the primary energy source of cells Cells with high energy
requirements, like muscle cells, may contain hundreds or thousands
or mitochondria
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Mitochondria The mitochondria has two membranes The outer
membrane is smooth The inner membrane is greatly folded, so that it
has a lot of surface area The two membranes form two
compartments
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Mitochondria The mitochondria also contain DNA and ribosomes,
because they make some of their own proteins Most mitochondrial
proteins are made in the cytosol
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Organelles Only Found in Plants Plants have 3 unique organelles
Cell wall Chloroplasts Central vacuole
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Cell Wall Plants cell membranes are surrounded by cell walls
Plant cell walls are made of proteins and carbohydrates, including
cellulose Helps support and protect the cells Connects cells to one
another
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Chloroplasts Chloroplasts are organelles that use light to make
carbohydrates from CO 2 and H 2 O Found in algae as well as plants
Surrounded by 2 membranes Contain their own DNA
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Central Vacuole The central vacuole stores water It may contain
ions, nutrients, and wastes It makes the cell rigid, when it is
full Enables plants to stand upright
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Lets Review We use microscopes to look at cells that are too
small to see with the naked eye The Cell Theory What is a cell?
What do all cells share? Prokaryotes vs. Eukaryotes Nucleus,
Organelles, and Cytoplasm, oh my! What separates plants from other
eukaryotes?
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The Cell CytoplasmRibosomes3. ER & Golgi apparatus 4.5.
Support/ structure 6. Power Plants 1.2. contains Function as
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How did eukaryotes and prokaryotes come to be so different?
Lynn Margulis
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Marguliss Other Causal Questions Why do mitochondria and
chloroplasts have their own DNA? Why do they have two membranes,
when other organelles only have one? Why do these organelles
reproduce separately from the rest of the cell?
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Endosymbiont Theory Margulis proposed that billions of years
ago, eukaryotic cells arose as a combination of different
prokaryotic cells The ancestors of mitochondria and chloroplasts
were once symbionts living inside larger cells They eventually lost
their independence and became organelles
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Endosymbiont Theory The theory answered each of Marguliss
questions They have their own DNA and reproduce separately because
they were once independent The inner membrane could be a remnant of
the old cell membrane and the outer membrane could be the cells
membrane surrounding the foreign cell Further evidence supports
Marguliss Theory
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Why arent organisms made of a few large cells? The human body
is made up of about 100 trillion cells Most of our cells are from
5m - 20m in diameter (There are 100 m in 1 mm)
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Surface Area-to-Volume Ratios 1.Calculate the surface area-to-
volume ratio of a cube with a side length of 2mm. 2.Calculate the
surface area-to- volume ratio of a cube with a side length of
1mm.
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Relationship Between Surface Area and Volume Side LengthSurface
area VolumeSurface area : volume ratio 1 mm6 mm 2 1 mm 3 6 : 1 2
mm24 mm 2 8 mm 3 3 : 1 4 mm96 mm 2 64 mm 3 3:2
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Why would the surface area to volume ratio be important? How
does the flatness of a single-celled Paramecium affect the cells
surface area-to- volume ratio? How would it affect the cells
ability to survive?
