Cell Structure and Function
Basic Unit of Life…
Objectives
• The learner will be able to:
– Tell what cells are.
– State the cell theory and identify the components of the cell theory.
– Identify the role of the cell wall and the cell membrane in the cell.
– Describe the functions of the cell.
– Explain how cells are organized in many-celled organisms.
– Describe diffusion, osmosis, active transport, and facilitated diffusion.
BEFORE ACTIVITY
Active Art
 Go to phschool.com
Type the code cbp-3072
Follow directions and take the quiz
at the end.
BEFORE ACTIVITY
Possible Sentences
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Cells
Eukaryotes
Prokaryotes
Unicellular
Multicellular
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Microscopic
Organelles
Nucleus
DNA
Organisms
History of the Cell
• The invention of the microscope made it
possible to discover and study cells.
– The scientists who contributed to the
microscope are:
• Hans and Zacharias Janssen
• Robert Hooke
• Anton Von Leeuwenhoek
History of the Cell
• Who discovered the cell and gave it its
name?
• Robert Hooke
• When did he discover the cell?
• 1663
• How did he discover the cell?
• Using his version of the Compound
Microscope.
• He was viewing a piece of cork.
History of the Cell (cont.)
Robert Hooke’s Compound
Microscope
Robert Hooke
Cell Overview
• Cells are the basic unit
of structure and
function in ALL living
things.
– Cell form parts of the
organs and perform
all functions for the
organ.
• All cells are
surrounded by a cell
membrane.
• All cells contain DNA
at some point in their
life.
• Most cells are made
up of tiny structures
called organelles.
• One square
centimeter of your
skin is made up of
more than 100,000
cells.
Development of the Cell Theory
• 3 German Scientists made important contributions to
our knowledge of the cell.
– Matthias Schleiden
– Theodore Schwann
They developed the
first two points of the
cell theory, but did not
explain where cells
come from.
– Rudolf Virchow discovered all cells come from
cells.
Cell Theory
• All living things are composed of
cells.
• Cells are the basic units of structure
and function in living things.
• All cells are produced from other
cells.
Prokaryotes vs. Eukaryotes
• All cells fall into two categories (eukaryotes and prokaryotes)
depending on whether they have a nucleus or not.
– Karyon means “kernel” or “nucleus”
Prokaryotes
Eukaryotes
•Cells that do not contain nuclei.
• pro- means before
•Genetic material is not contained in
a nucleus.
•They have all the characteristics of
life such as reproduction,
responding to the environment, and
growing.
•Ex. Bacteria
•Cells that contain nuclei.
• Eu- means true
•Contains dozens of structures
that are highly specialized
•Genetic material is contained
in the nucleus away from
everything else.
•Ex. Plants, Animals, Fungi,
and Protists
Keys to Understanding Cells
Anatomy Students need these!!!
• Cyt- : [cell] Ex. Cytoplasm fluid
(cytosol)
• Endo-: [within] Ex. Endoplasmic
reticulum (membranous structure
within the cell
• Hyper-: [above] Ex. Hypertonic
solutions have greater osmotic
pressure than body fluids.
• Hypo- : [below] Ex. Hypotonic
solutions have lower osmotic
pressure than the body fluids.
• Inter-: [between] Ex. Interphase is
the stage between divisions of a
cell.
• Iso- [equal] Ex. Isotonic solutions have
the same osmotic pressure as body
fluids.
• Mit- [thread] Ex. Mitosis is cell division
when thread-like chromosomes
become visible.
• Phag- [to eat] Ex. Phagocytosis takes
place when a cells takes in solid
particles.
• Pino- [to drink] Ex. Pinocytosis takes
place when a cell takes in tiny drops of
liquid.
• -som [body] Ex. Ribosomes are tiny
structures that consist of protein and
RNA.
Looking Inside The Cell
Looking
Inside
The
Cell
– Contains nearly all of the cell’s DNA,
– dense region
• Nucleus
which controls the cell’s activities.
– Enclosed in a double-layered (lipid)
membrane called the nuclear
envelope.
• Nuclear pores allow materials to move
in and out.
– Chromatin is found in nucleus.
• Consists of DNA and proteins.
• Condenses into chromosomes during
cell division (i.e. mitosis, meiosis)
• Nucleolus
found inside the
nucleus
– Ribosomes are
made in the
nucleolus and
leave through the
nuclear pores into
the cytoplasm
Looking Inside The Cell
• Cytoplasm: clear, thick,
gel-like fluid between
the cell membrane and
the nucleus; it is
constantly moving
– It contains networks of
membranes and
organelles suspended in
a clear liquid called
cytosol
• Cytoskeleton: a
network of protein
filaments (rods and
tubules) that help the
cell maintain its shape.
• In animal cells, the
microfilaments form
centrioles (used during
cell division)
Check Point
1) What structure separates the nuclear
contents from the cytoplasm?
2) What is produced in the nucleolus?
3) What is chromatin?
4) What structures are produced by the
cytoskeleton?
Looking Inside The Cell
• Ribosome: “factories” to produce
proteins; some are attached to
Endoplasmic Reticulum and other
float in the cytoplasm
• Endoplasmic Reticulum: passageways
that carry proteins and other
materials from one part of the cell to
another; similar to hallways of a
building
• Lipid components of the cell are
assembled here
Looking Inside The Cell
• Mitochondria: the “powerhouse” of the cell; converts
nutrients in food to energy for the cell.
– Surrounded by two membranes
• Golgi Apparatus: the cell’s “mail room”
– receive proteins from the endoplasmic reticulum and it
modifies, sorts, and packages them for storage or secretion
• Lysosomes: the “clean up crew” of the cell
– small, round structures containing enzymes that break down
lipids, carbohydrates, and proteins into small molecules to be
used by the cell.
– Breaks down old organelles
Looking Inside The Cell
• Vacuoles: water filled sac that stores food and other
nutrients needed by the cell.
– Plants have one large Central Vacuole
– Some animal cells have them and others don’t
• Chloroplasts: (only in a plant cell) large green structures
that capture energy from the sun and covert it into
chemical energy (food for the plant) in a process called
photosynthesis.
– Surrounded by two membranes
– Contains the green pigment chlorophyll
Cell Boundaries
• Cell Membrane: controls what substances enters and
leaves the cell; nutrients enter here and wastes leave
here.
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–
–
–
Provides protection and support
It is a double layered sheet called lipid bilayer
Also has proteins embedded in lipids
Selectively permeable (semipermeable) meaning it only allows
certain substances to enter or leave the cell.
• Cell Wall (only in plant cells): rigid layer of nonliving material
that surrounds the cell; it provides support and protection
– Composed mainly of cellulose, a tough carbohydrate fiber.
Movement Through Cell Boundaries
• Diffusion
– Particles move from an area of high concentration to an
area of low concentration.
– When the concentration of a solute is the same on both
sides of the membrane, the system (organism) has reached
equilibrium.
Movement Through Cell Boundaries
• Osmosis
– The diffusion of water across a semipermeable
membrane.
– Water moves across membranes until equilibrium is
reached.
• When equilibrium is reached (same strength inside and
outside the cell) the solution is isotonic (same strength).
• When the solution on one side of membrane is more
concentrated (stronger) other side , it is hypertonic.
• When the solution on one side of the membrane is less
concentrated than the other side, it is hypotonic.
Movement Through Cell Boundaries
• Osmotic Pressure
– Osmosis exerts pressure on the hypertonic side of the
permeable membrane.
– Cells are filled with salts, sugars, proteins, etc.; so, they
would always be hypertonic when placed in fresh water.
– Cells are never in fresh water because body fluids like
blood have the same concentrations of dissolved
materials. They are ISOTONIC!
– Plant cells and Bacteria come in contact with fresh water,
but the cell walls protect the membranes from bursting.
Movement Through Cell Boundaries
• Facilitated Diffusion
– The cell membrane has
protein channels that allow
certain molecule to pass into
and out of the cell.
– These channels are selective.
• Ex. Only glucose (sugar) can
pass through a channel made
for glucose.
• They are not “one-size-fitsall”
Movement Through Cell Boundaries
• Active Transport
– Requires energy
– Movement against the
concentration
– Accomplished by protein
“pumps” in the cell
membrane.
• Endocytosis: the
process of taking
material into the cell by
means of pockets on
the cell membrane.
– The pocket that is
formed during
endocytosis breaks away
from the membrane and
forms a vacuole.
Movement Through Cell Boundaries
• Phagocytosis
1. Extensions of cytoplasm surround
a particle and package it within a
food vacuole.
2. The cell engulfs it.
3. The vacuole breaks from the
membrane.
• Pinocytosis
1. Tiny pockets form along the
membrane.
2. The pockets fill with liquid.
3. The pockets form vacuoles.
• Exocytosis
– The membrane
of a vacuole
fuses with the
membrane
– Contents are
forced out of
the cell.
Cellular Organization
• Unicellular Organisms
– Single-celled organisms
– Carry out all characteristics of
life.
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•
•
•
Reproduce
Grow
Respond to the environment
Transform energy
– Ex. Yeast, Bacteria, and some
Alga
Cellular Organization
• Unicellular Organsims
– Organisms composed
(made) of many cells
– Depends specialized cells
cooperating with each
other.
– Cells develop specialized
tasks.
• Examples of Specialized
Cells…
– Red Blood Cells transport
oxygen.
– Muscles Cells specialized
for movement.
– Pancreatic Cells produce
proteins and enzymes for
digestion.
Levels of Organization
Organ Systems
A group of organs that work together to perform a
specific function.
Organs
Many groups of tissues that work
together.
Tissues
A group of similar cells that
perform a particular
function.