Many life forms consist of only one cell. unicellular
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Others consist of many cells multicellular
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Brachiating Gibbon Brachiating Gibbon
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Viewing and Studying Cells Microscopes Microscopes First
developed in 1600s First developed in 1600s Advances in technology
have advanced knowledge Advances in technology have advanced
knowledge Von Leewenhoeks microscope and drawings
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Produced early micrographs
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Todays microscopes
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Transmission Electron Microscopes Use a beam of electrons
instead of light Use a beam of electrons instead of light Very
large & expensive Very large & expensive Can not be used on
living specimens Can not be used on living specimens
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Scanning Electron Microscope (SEM) Uses a beam of electrons
Uses a beam of electrons Cannot be used on living organisms Cannot
be used on living organisms 3-D photographs 3-D photographs
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A cell is the smallest unit that can carry out all the
activities necessary for life. How Big is a... ?
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Cell sizes vary from the ostrich eggthe largest of cells
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To minute bacteria
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Most cells are microscopic
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Some might say that a cell is like a submarine
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A submarine is protected by a tough hull
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And a cell is protected by a cell membrane
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However.. A cell membrane is far more complex than a submarine
hull
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It has to allow.. food to enter the cell waste to leave the
cell
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The cell membrane helps maintain homeostasis in the cell.
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When cells are small, they work efficiently Their inner
structures are close to the membrane
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When cells are LARGE Their inner structures are further from
the membrane
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waste Large cells need more food and produce more waste food
waste This is difficult!
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As cells grow, their outer surface area is not large enough to
provide for enough food uptake and waste disposal
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So cells can not grow indefinitely
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so getting back to the idea of a submarine..
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All cells are surrounded by water
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Water is also present inside the cell H2OH2O H2OH2O
H2OH2OH2OH2O H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O
H2OH2O
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Lets look closely at water. Water H 2 O is 2 H atoms covalently
bonded with 1 oxygen atom
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Water is a polar molecule
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The charged ends of water molecules, attract other water
molecules
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These attractions are known as Hydrogen Bonds.
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Hydrogen bonds are important in nature. They cause water
molecules to stick together.
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Thats one reason why some insects can walk on water
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And some lizards can run on it
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So lets put all this together and see how water shapes the cell
membrane In a test tube, pour a layer of oil on top of some
water
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Even if you shake and mix it thoroughly, the water and oil
eventually return to two separate layers
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Hydrogen bonds cause the polar water molecules to cluster
together
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But lipids are nonpolar Not attracted to water Pushed away and
separated from the water
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The force of water pushing on the lipid layer is what shapes
the membrane
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3.2 Membrane Architecture
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Cell membranes act like a giant security system for a cell
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To understand how membranes work, you have to understand how
they are formed.
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Phospholipids are the basic building blocks of membranes.
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They form phospholipid bilayers Polar heads point toward water
inside and outside of the cell. Nonpolar tails are inside the
membrane away from the water.
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Lipid bilayers are fluid, not rigid Cells can exist in a
variety of shapes. Cells can be flexible.
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That leads to an important question How do necessary molecules
such as glucose get into the cell? How do necessary molecules such
as glucose get into the cell? Feed me !
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Membranes have protein gates which regulate the flow of
substances in and out of the cell.
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Membrane proteins have several functions
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Channel Proteins Allow the transport of substances into and out
of the cell Allow the transport of substances into and out of the
cell..like kidney cells that remove wastes Myocyte: Ion
Channels
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Receptor Proteins Transfer information from the outside
environment into the cell Transfer information from the outside
environment into the cell like brain cells..when you learn
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Surface Marker Proteins name tags AB +
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Membrane proteins often work together Marker proteins direct
cells in their development Channel proteins aid in cell functions
Channel and receptor proteins also allow communication between
cells!
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OK..so heres more questions How can proteins perform such
different tasks?
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How do the proteins fit into the lipid bilayer membrane?
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The answer lies in the structure of the protein
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Lets Review Proteins are made of long chains of amino acids
Proteins are made of long chains of amino acids Each of the 20
amino acids are different from each other Each of the 20 amino
acids are different from each other The arrangement of a.a.
ultimately determines protein structure The arrangement of a.a.
ultimately determines protein structure
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Charges on the protein chains cause them to bend, fold and
twist
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A proteins complicated structure determines its function.
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Membrane proteins have 3 basic sections. 2 Polar ends
Hydrophillic Form hydrogen bonds with water
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Middle. nonpolar coil Fits into nonpolar center of membrane Can
float and move within the membrane
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Congratulations! You passed through the cell membrane You
passed through the cell membrane You are now ready to dive into
cells You are now ready to dive into cells
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Inside the Cell Inside the Cell Chapter 3.3
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Two Types of Cells Prokaryotic Prokaryotic Prokaryotes
Prokaryotes Eukaryotic Eukaryotic Eukaryotes Eukaryotes
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Eukaryotic Cells vs. Prokaryotic Cells Eukaryotes Eukaryotes
Contain a nucleus Contain a nucleus Have double stranded DNA Have
double stranded DNA DNA forms chromosomes DNA forms chromosomes
Plants and Animals Plants and Animals Prokaryotes Prokaryotes Lack
a nucleus Lack a nucleus Have a single, circular strand of DNA Have
a single, circular strand of DNA DNA is not surrounded by a
membrane DNA is not surrounded by a membrane Bacteria Bacteria
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Lets Compare ProkaryotesEukaryotes No nucleus Nucleus No
membrane bound organelles Many organelles Most 1 -10 microns Many 2
-1,000 microns Evolved 3.5 billion years ago Evolved 1.5 billion
years ago Only bacteria Plants, animals, protists
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Like Characteristics ProkaryotesEukaryotes Cell membrane
Cytoplasm An internal fluid environment Cytoplasm Ribosomes
Location of protein synthesis Ribosomes
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Eukaryotes vs. Prokaryotes Complex vs. simple structure Complex
vs. simple structure Organelles
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Think of a cell as a factory..
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Each organelle is a separate department Each department has a
separate job Each department has a separate job
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Nucleus Control center of the cell Control center of the cell
Contains DNA Contains DNA Complete genetic set of instructions
Complete genetic set of instructions Humans = 23 chromosomes Humans
= 23 chromosomes Surrounded by a membrane Surrounded by a membrane
Has pores to allow movement in and out of membrane Has pores to
allow movement in and out of membrane Nuclear pores Nuclear
pores
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Nuclear Membrane
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Cells Manufacture and Release Energy Mitochondria Mitochondria
Animals and plants Animals and plants Chloroplasts Chloroplasts
Plants only Plants only
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Mitochondria Powerhouse of the cell Powerhouse of the cell
Convert energy stored in food to ATP Convert energy stored in food
to ATP Bound by a double membrane Bound by a double membrane Outer
membrane is smooth Outer membrane is smooth Inner membrane is
highly folded Inner membrane is highly folded
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Chloroplasts Plants use chloroplasts to make food from CO 2, H
2 O and solar energy Plants use chloroplasts to make food from CO
2, H 2 O and solar energy They contain the green pigment,
chlorophyll. They contain the green pigment, chlorophyll.
Photosynthesis Photosynthesis Found ONLY in plants Found ONLY in
plants
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Cells Maintain Homeostasis Endoplasmic reticulum Endoplasmic
reticulum Eukaryotes Eukaryotes Transport network Transport network
Golgi Apparatus Golgi Apparatus Packaging and distribution center
Packaging and distribution center
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Endoplasmic Reticulum (ER) A membrane system that is continuous
with the nuclear envelope A membrane system that is continuous with
the nuclear envelope Many different activities Some ribosomes are
attached to some parts of the ER Some ribosomes are attached to
some parts of the ER Appears rough rough ER If ribosomes are not
attached If ribosomes are not attached Appears smooth smooth
ER
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Endoplasmic reticulum
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Endoplasmic reticulum (ER) Transport system for many molecules
Transport system for many molecules Major manufacturing center of
the cell Major manufacturing center of the cell Proteins Proteins
Lipids Lipids Membranes for other organelles Membranes for other
organelles Packages some molecules for transport to Golgi bodies
Packages some molecules for transport to Golgi bodies
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Golgi Apparatus Packaging, Labeling and Shipping Center
Packaging, Labeling and Shipping Center Membrane system of vesicles
Membrane system of vesicles Assembly point for items to be exported
from the cell Assembly point for items to be exported from the cell
Packages and sorts proteins and polysaccharides Packages and sorts
proteins and polysaccharides Move through vesicles To plasma
membrane To other organelles Outside the cell The Post Office
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Golgi Apparatus
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Vacuoles Storerooms Storerooms Storage vesicles Storage
vesicles Food & water Food & water Digestion Digestion
Digestive Enzymes Digestive Enzymes Support Support Water
Regulation Water Regulation Contractile vacuoles Contractile
vacuoles
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Vacuoles
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Lysosomes special digestive vacuoles Where did the tail
go?
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Centrioles Found in pairs Found in pairs Help in cell division
Help in cell division Animal cells only Animal cells only
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Plant Cells
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Cell Wall Plant cells Plant cells Contains cellulose and
protein Contains cellulose and protein Provides strength Provides
strength Provides rigidity Provides rigidity
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Large Central Vacuole Nutrient, water and waste storage
Nutrient, water and waste storage May occupy 30*90% of cell volume
May occupy 30*90% of cell volume Helps plant stand upright Helps
plant stand upright
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Lets Compare
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Animal Cell vs. Plant Cell
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Theory of Endosymbiosis
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Evidence for Endosymbiosis Many bacteria and mitochondria are
the same size and have a set of double membranes Many bacteria and
mitochondria are the same size and have a set of double membranes
Mitochondria have their own ribosomes and DNA Mitochondria have
their own ribosomes and DNA Their ribosomes are structurally
similar to prokaryote ribosomes Their ribosomes are structurally
similar to prokaryote ribosomes Some organelles divide in a manner
similar to bacteria Some organelles divide in a manner similar to
bacteria