Do Now
• What is a cell?
• What are some parts of cells?
• What is the function of a nucleus?
• What do lipids make in cells?
Chapter 5 - Cells
5.1
• Fundamental discovery – all living things
are made of cells
• Cells are the basic units of structure and
function in living things
• First lenses – merchants of fabric
• Quality of the weave
• 1600’s Holland – telescope - microscope
Anton Van Leeuwenhoek
• First microscope
• Dutch
• Tiny organisms in water
• Made detailed drawings
Robert Hooke
• English
• Interest from van Leeuwenhoek
• Thin slices of plant stems, wood and pieces
of cork
• Cork – tiny chambers  cells
• Dead cells
• Opened up the study of cells
Robert Brown
• Scottish
• Dark center near the center of the cell 
nucleus
Matthias Schleiden
• German
• All plants made of cells
Theodor Schwann
• All animals made of cells
• Swans are animals
Rudolf Virchow
• German
• All cells arise from the division of
preexisting cells
Cell Theory
1. All living things are composed of cells
2. Cells are the basic unit of structure and
function in living things
3. Cells come from preexisting cells
Cell Diversity
• Cells differ in size, shape, and internal
organization
• Your body has at least 200 types of cells
Size
• Range in size from .2 um to 1000 microns
• Most cells are between 5 to 50 um
• A cell is limited in size by the ratio between
its volume and its outer surface area
• Food, oxygen and other materials must
enter and exit through the cell’s surface
• The larger the cell the larger their surface
area needed to maintain it
• As a cell grow its volume increases more
rapidly that its surface area
• If a cell is to big the surface area is too
small
Size is limited by physical factors:
1. Flow of information
2. Flow of materials
5.2 Parts of the Cell
• Tasks of living cells – taking in food,
transforming food into energy, getting rid
of wastes and reproducing
Three Main Components of Eukaryotic
Cells
1. Cell membrane is the outer boundary
2. Cytoplasm lies inside the cell membrane,
contains water and salts, and surrounds
the organelles
3. Nucleus directs cell activities
Eukaryotic Cell
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Cell Membrane
• plasma membrane
• Separates the cell from the surrounding
environment
• Controls the movement of materials in and
out of the cell – lets some in and some out
• Protection
• Support
Structure of the Cell Membrane
• The two layers are made of lipids and
proteins are embedded in them
• Double layer = bilayer
Membrane Proteins
• Peripheral proteins – proteins attached to
the surface of the cell membrane
• Integral proteins – proteins that go through
the membrane – carbohydrates can be
attached to them
• Transport molecules through the lipid
bilayer (channels and pumps)
Fluid Mosaic Model
• Lipid molecules that form the membrane
are fluid
• The proteins are free to move about
• The cell membrane has fluid properties
Carbohydrates
• Attach to the proteins or lipids
• Function as Id cards – allows cells to
interact with one another
Cell Wall
• Surrounds cell membrane in plants
• Function – protection and support
• Made of 2 or more layers
Cell Wall
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• First layer – gluey substance called pectin
– holds cells together
• Primary cell wall – made of cellulose –
fibrous – elastic – stretches as it grows
• Third layer – only in woody plants
– secondary cell wall
– made of cellulose and lignin
– makes cellulose more rigid
Nucleus
• Large dark structure
• Prokaryotes – cells that do not have a nucleus
– Ex. Bacteria
• Eukaryotes – cells that have a nucleus and
membrane bound organelles
– Karyon – nucleus
– Pro – before
– Eu - true
Nucleus
• Information center
• Contains DNA
– Info. To make 1000’s of molecules
• Directs all activities
Nuclear Envelope (membrane)
• Consists of 2 membranes that surround the
nucleus
• Nuclear pores
– in nuclear envelope
– Small openings
– Allows molecules in and out
Nucleolus
• Small region in the nucleus
• Made of RNA and proteins
• Ribosomes (make proteins) made here
Chromosomes
• Are DNA’s wrapped around proteins
• Contain the genetic information
• Fig 8-8
Cytoplasm
• Area between the cell membrane and the
nucleus which contains the various
organelles
• Jellylike
• Contains many important structures
• Many of the substances need for cell
metabolism are dissolved in the cytosol
5.3 Cytoplasmic Organelles
Organelles
• Structures in the cytoplasm
• Tiny structures that perform a specialized
function in the cell
Mitochondria
• Powerstations
• Change chemical energy stored in food into
compounds that are more convenient to use
• Sites of chemical reactions that transfer energy
from organic compounds to ATP
• double membrane
• Smooth outer membrane serves as the boundary
between the mitochondrion and the cytoplasm
• The inner membrane is tightly folded, forming
cristae
• The cristae provide a large surface area on which
many biogeochemical reactions occur
• “powerhouse of the cell”
Chloroplast
• Trap energy of sunlight and convert it to
chemical energy
• 3 membranes – two envelope like – 3rd
radiant energy changed to chemical
(bonds)
• Only in plants
Chloroplast
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Ribosomes: Protein Factories
• Small particles that are the sites of protein
synthesis
• Spherical structure composed of proteins
and RNA
• Ribosomes can be attached to the ER or
remain free
• Smallest organelle
Endoplasmic Reticulum: Shippers
• ER
• Intercellular highway
• Complex network of sacs
• Transports materials through the inside of
the cell
Two types of ER
• Rough ER (RER)
– Ribosomes attached to its surface
– Protein synthesis in ribosomes
– Move into RER for modification and transport
• Smooth ER (SER)
– No ribosomes
– May store special enzymes and chemicals
Golgi Apparatus: Manufactures
• Looks like – flattened sac of membranes
piled one on the other
• Proteins sent here to be modified
(attaching carbs and lipids to them)
• Modifies, collects, packages and
distributes molecules made at one location
of the cell and used at another
Movement of materials – “eating”
• Endocytosis – (In) process where a cell
takes in large particle too big to enter
through the cell membrane
• Two types
– Pinocytosis – cell engulfs liquids
– Phagocytosis – cell engulfs large particles
•White Blood cells
Lysosomes: Clean-up Crews
• Small membrane bound structures that
contain chemicals and enzymes for
digesting certain materials
• Formed by Golgi apparatus
• Only in animal cells
• Break down organelles that are no longer
needed
Vacuoles and Plastids: Storage Tanks
• Vacuole
– saclike structure
– Stores water, salts, proteins and
carbohydrates
• Plastid – plant organelles
– Store food and pigments
– Ex. Chloroplast (chlorophyll)
– Leukoplasts – store starch
– Chromoplasts – store pigment
Cytoskeleton: Framework
• Most cells are capable of some movement
– inside or out
• Cytoskeleton is composed of a variety of
filaments and fibers that support cell
structure and drive cell movement
• Two types
Microtubules
• Hollow tubules made out of proteins
• Functions
– Provide support for cell shape
– Help move organelles and cytoplasm
– Play a role in cell division by forming
centrioles (animals only) – spindle fibers move
chromosomes
– Support and make up cilia and flagella
Cilia
• Short thread like structures
• Help unicellular cells move
• Move substances along the cell’s surface
(humans)
Flagella
• Long whip-like structures
• Move single celled organisms about
Microfilaments
• Long thin fibers that function in the
movement and support of the cell
• Move the cytoplasm – cytoplasmic
streaming
5-4 Movement of Materials
through the cell membrane
• Every cell is in a liquid environment
• Liquid environment makes it easier for
food, oxygen and water to move in and out
Diffusion – Passive Transport (No energy, No ATP)
• Molecules are in constant motion
• Tend to spread out randomly in space
• Molecules move from an area of greater
concentration to an area of lesser
concentration
• Diffusion – process by which molecules
move from greater to lesser
Equilibrium
• Concentration of substances on both sides
of the membrane are the same
• Molecules are still moving back and forth
but equally
• Molecules always try to get to this
Permeability
• Determines what moves across
• Permeable – substance can move in and
out
• Impermeable – substance can’t move
• Selectively permeable – some things can
pass some can’t – characteristic of
biological membranes
Osmosis – Passive Transport
• Diffusion of water molecules across a
selectively permeable membrane
• Water passes through cell membranes
rapidly
• Moves greater to lesser
• Hypotonic solution – Solution in which the
concentration of solutes is lower than
inside the cell
• Isotonic solution – Solution in which the
concentration of solutes in and outside the
cell is equal
• Hypertonic solution – solution in which the
concentration of solutes is higher than
inside the cell
Osmotic pressure
• Turgor pressure
• force exerted by water molecules hitting
the membrane
• Causes water to move
• High pressure to low pressure
Osmotic pressure – Problems for a cell
• Cytoplasm filled with salts, sugars and
proteins
• Cell has a low concentration of water
inside as compared to outside
• Water would continuously move in – cell
would burst
How cells deal
1. Ex. Cells in a fluid like blood not in water –
concentrations are equal
2. Plants and bacteria – cell wall keeps cell
from exploding even under high osmotic
pressure but they are very vulnerable
3. Pump it out
Ex. Unicellular organisms – paramecium – contractile
vacuole – pumps it out
Facilitated Diffusion
• Passive transport
• Movement occurs from greater to lesser
conc.
• Need a concentration gradient
• Molecules brought in by a carrier protein
• Fast, specific
• Facilitates or helps
Active Transport – 2 types
• Needs energy
• Move materials against a concentration
gradient
• Lesser to greater conc.
1. Protein Pumps
• Pump molecules into the cell  Ca, K, Na
• Need energy
• Sodium potassium pump
2. Endocytosis (In)
• Process of taking food into the cell by
surrounding it with the cell membrane
• Brings in large molecules, clumps of food
and whole cells
• Two Types
– Phagocytosis – large particles
– Pinocytosis – liquid, small particles
• Exocytosis – large molecules out of cell exit
5-5 Cell Specialization
• Specialization – cells are often uniquely
suited to perform a particular function in
an organism
Factory in Miniature
• Pancreas – cells produce digestive
enzymes
• Lots (100x) more ER and ribosomes
• More golgi apparatus too
Light Sensitive Cell
• Eye cells – one end lots of mitochondria,
the other end contains lots of sacs full of
rhodopsin which detects light and signals
the other cells  vision
5-6 Levels of Organization
• Cells  tissues  organs  organ system
 organism
Tissue
• Group of similar cells that perform a
similar function
• Animals have 4 types - muscle, nerve,
epithelial and connective
Organs
• Group of tissues that work together to
perform a specific function
Organ system
• Group of organs working together to
perform a specific function
• Humans – 11 systems
• The overall specialization and
interdependence of cells, is one of the
remarkable attributes of living things
The End