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Biology Unit 4:
Cell Structure & Function
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Discovery of Cells
• 1600’s
• Robert Hooke
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• Discovery of light microscope
• Named box-like structures in
cork “cells”
1820’s: Rene Dutrochet• Cells are found in various parts
of organisms
1830’s: Robert Brown • All cells have a nucleus
• All plants are composed of cells
Matthias Schleiden
• All animals are composed of cells
Theodore Schwann
• All cells come from living cells
Rudulph Virchow
Cell Theory
Three parts:
• All living things are made of cells
• The cell is the basic unit of structure
and function in living things
• All cells come from existing cells
Unicellular Organisms
• Cell is the organism
• In terms of numbers
> dominate life on
Earth
Yeast
Volvox aureus
Chlamydomonas
Euglena
Multicellular Organisms
• Made up of many cells
• Great variety of organisms
• All depend on specialized cells
– Cells develop in different ways
to perform different tasks
– Ex: Red blood cells transport
oxygen throughout body
Red blood cells
Multicellular Organisms (cont.)
Levels of organization
• Cell - Ex: muscle cell
• Tissue - group of similar cells perform a
particular function
– Ex: muscle tissue
• Organ - group of tissues that work together
– Ex: stomach
• Organ system - group of organs that work
together to perform specific function
– Ex: digestive system
Muscle cell
Smooth muscle
tissue
Digestive System
Stomach
Types of Cells
• Eukaryotic
– Genetic material
contained in nucleus
– Plants, animals, fungi
and protists
• Prokaryotic
– Genetic material NOT
contained in nucleus
(*No nucleus*)
– Bacteria
The Eukaryotic Cell
Cell Structure
• Like a factory
• Two major parts: cytoplasm &
nucleus
• Organelles (“little organs”)
– Act like specialized organs
– Some structures developed from early
prokaryotes
• Ex: mitochondria & chloroplasts
Cytoplasm
• Gelatin-like material inside the cell
membrane, outside the nucleus
• Contains organelles
• Site of most cell activity
– Factory floor where products are
assembled, finished & shipped
Nucleus
• Control center of the
cell > boss or CEO
– Responsible for overall
function of factory
• Determines what
proteins will be made
• Contains hereditary
information > DNA
Nucleolus
• Small, dense
region of nucleus
• Assembly of
ribosomes begins
here
Nuclear Envelope
• Membrane around
nucleus only
• Has small pores
that allow
information and
ribosomes to move
in and out of
nucleus
Ribosomes
• Responsible for
assembling proteins
– Workers on assembly
line in factory
– Responds to orders
from boss > nucleus
• Located throughout
cytoplasm
Endoplasmic
Reticulum
• Site where lipid components of cell
membrane are assembled
– Also assembles proteins exported from cell
– Assembly line in factory
• Two types:
– Rough ER - appears bumpy due to
ribosomes on surface
– Smooth ER - No ribosomes
Endoplasmic
Reticulum
Golgi
Apparatus
• Prepares proteins and
other materials for storage
or use outside cell
• Like finishing & packing
department in factory
– Finishing touches put on
before ready to leave
factory
– Sorted & stored or shipped
outside of cell
Lysosomes
• Small organelles filled
with enzymes
• Maintenance crew for
factory
• Break down carbs, lipids
& proteins for use by cell
• Remove “junk” - waste
and dead material found
in cell
Vacuoles
• Saclike structures
that store nutrients
– water, salts,
proteins & carbs
• Storage rooms of
factory
Mitochondria
• Convert nutrients in
food into energy for
cell use
– Local power plant for
factory
– Source of energy
Chloroplasts
• Capture energy from
sunlight and convert it into
chemical energy >
photosynthesis
– Solar power source for factory
• Only in plant cells
– Chlorophyll > chemical that
causes plant cells to be green
Cytoskeleton
• Network of protein fibers that helps cell
maintain its shape
– Microtubules and microfilaments
– Support structure of factory (beams &
columns that support walls & roof)
• Also used to move cell membrane
Cell Membrane
• Phospholipid bilayer
• Regulates what enters & leaves the cell
– Like gate into the factory
• Provides protection & support
– Gives the cell its shape
Cell Wall
• Outside cell
membrane
• Provides protection
& support
• Present in plants,
algae, fungi and
many prokaryotes
* Never in animal cells
Plant Cell
Cell Wall (algae)
Cell Wall
prokaryote)
(bacteria >
Movement Across Cell
Boundaries
Diffusion
• Molecules spread into available
space
– across membrane
– from area of higher concentration
to area of lower concentration
– without use of energy > passive
transport
• Equilibrium - when
concentration is same
throughout a system
http://highered.mcgrawhill.com/sites/0072495855/student_vie
w0/chapter2/animation__how_diffusion
_works.html
Osmosis
• Diffusion of water
through a selectively
permeable membrane
– Membrane allows only
certain substances to
pass through
– Type of diffusion does not require use
of energy > passive
transport
How Osmosis Works
• Isotonic - “same strength”
– Same concentration on both sides
• Hypertonic - “above strength”
– Higher concentration outside cell
– Water leaves, cells shrink
• Hypotonic - “below strength”
– Lower concentration outside cell
– Water comes in, cells swell
http://www.tvdsb.on.ca/westmin/science/sbi3a1/Cells/Osmosis.htm
• http://highered.mcgrawhill.com/sites/0072495855/student_vie
w0/chapter2/animation__how_osmosis_
works.html
Facilitated Diffusion
• Movement of
specific molecules
across membranes
through transport
proteins
– Could not cross
without them
– Does not require
use of energy >
passive transport
• http://highered.mcgrawhill.com/sites/0072495855/student_vie
w0/chapter2/animation__how_facilitate
d_diffusion_works.html
Active Transport
• Cells move materials in direction
opposite diffusion
– Against concentration difference (gradient)
• Requires energy
• Small molecules or ions (K, Ca, Na)
carried by transport proteins or “pumps”
in membrane
Active Transport (cont.)
Larger molecules & clumps of material
transported by:
• Endocytosis - movement of materials
into cell through vesicles (pockets) of
cell membrane
– Phagocytosis- “cell eating”
– Pinocytosis- “cell drinking”
• Exocytosis - movement of materials out
of cell through vesicles
IV. Homeostasis
A. The Cell as an Organism
1. Unicellular organism- organism made up
of only one cell
a. Examples:
• Bacteria
• Yeast
• protists- amoeba, diatoms, plasmodium
b. Exhibit all 8 features of living things
c. All organisms must maintain
homeostasis
• Defined- relatively constant internal;
physical and chemical conditions
B. Multicellular Life
1. Cells in multicellular organisms do not
live on their own
2. They are interdependent- need to work
together
3. Need to communicate- send and receive
signals with each other
4. Cell specialization- different types of cells
play different roles
a. Some move- throat lining cells
b. Some react- nerve cells
c. Some produce substances- glandular cells
5. Levels of Organization
cells --> tissues --> organs --> organ systems -->
organisms
a. Tissue – is a group
of similar cells that
work together to
perform a function.
Examples of Tissues
Nerve Tissue
Nerve Cell
b. Organ – is
a group of
tissues that
work together
to do a job.
c. Organ
system- is a
group of
organs that
work together
to do a
certain job.
Examples of
organisms
Crow
Amoeba
d. Organism – is a
living thing that
can be made of one
or more cells.
Elephant
Bonobo
Hum
an
6. Cellular Communication
a. Cells in large organisms communicate
by means of chemical signals
b. The signals can either speed up or
slow down an activity of the cells that
are receiving them
c. Cellular junctions- hold cells together
in tight formations that allow for quick
signaling
• Ex: neuromuscular junction
d. Receptor- can be found on or in a cell; a
specific protein whose shape fits that of a
molecular messenger
• Ex: Hormones
Thyroid Hormone
Receptor
Careers that study cells and/or tissues
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Histologist- tissues/cells
Pathologist- infected tissues/cells
Oncologist- cancer cells
Embryologist- examines infertility
Geneticist
Veterinarian