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Chapter 7 Notes
Section 1
Cells
Cells remained out of sight during
most of human history until the
invention of the first microscopes.
It was not until the mid 1600s that
scientists began to use microscopes
to observe living things.
The History of the Cell
 1.) In 1665 Robert Hooke used an early
compound microscope to look at a thin
slice of cork (plant material)
 It was composed of tiny empty chambers
that he called “cells”. (Figure 7-1, pg 169)
 We now know that cells are not empty but
contain living matter.
The History of the Cell
 2.) In 1674 Anton van Leeuwenhoek used
a single-lens microscope to observe pond
water and other things.
 3.) In 1838 Matthias Schleiden concluded
that all plant are made up of cells.
 4.) The following year Theodor Schwann
stated that all animals were make of cells.
The History of the Cell
 5.) In 1855 Rudolf Virchow concluded that
new cells could be produced only from the
division of existing cells.
 These numerous observations made it
clear that cells are the basic units of life.
Cell Theory
All living things are composed of
cells.
Cells are the basic units of structure
and function in living things.
New cells are produced from
existing cells.
Exploring the Cell
 Today‟s researchers use microscopes and
techniques more powerful than the
pioneers of biology could have imagined.
 When using a light microscope the light
limits the detail of images that can be
made.
 Electron microscopes are capable of
revealing details as much as 1000 times
smaller than those visible with light
microscopes.
 Transmission electron microscopes (TEMs) make
it possible to explore cell structures and large
protein molecules.
 Cells and tissues must be cut first into thin slices
before they can be examined.
 Scanning electron microscopes (SEMs) use a
pencil like beam of electrons to scan over the
surface of a specimen.
 Specimens do not have to be cut.
 A stunning three-dimensional image is produced
 Only nonliving preserved cells and tissue
can be visualized when using electron
microscopes.
 In the 1990s researchers perfected a new
class of microscopes that produce images
by tracing the surfaces of samples with a
fine probe. (Figure 7-3, page 172)
Types of Cells
 A typical cell ranges from 5 to 50 micrometers
in diameter.
 Cells have two characteristics in common
 1. surrounded by a barrier called a cell membrane.
 2. at some point in their lives they contain the
molecule that carries biological information (DNA).
 Cells fall into two broad categories, depending
if they contain a nucleus:
 1. Prokaryotes-Cells that do not contain nuclei
 2. Eukaryotes-Cells that do contain nuclei
Cell membrane
Cytoplasm
Cell membrane
Cytoplasm
Nucleus
Organelles
Prokaryotes
 Smaller and simpler than eukaryotic cells.
 Have genetic material that is not
contained in a nucleus.
 Some contain internal membranes.
 Grow, reproduce, and respond to the
environment.
 Ex. Bacteria
Eukaryotes
 Cells are generally larger and more
complex than prokaryotic cells.
 Generally contain dozens of structures and
internal membranes.
 Contain a nucleus in which their genetic
material is separated from the rest of the
cell.
 Ex. plants, animal, fungi, and protists.
Chapter 7 Notes
Section 2
Eukaryotic Cells
Eukaryotic cells are divided into two
parts
Nucleus
Cytoplasm
Portion outside the nucleus where
organelles reside
Nucleus
 Contains most of the cell‟s DNA
 DNA is the code for making proteins
 Surrounded by a double membrane called
the nuclear envelope
 Contains chromatin, which consists of DNA
bound to protein
 Condenses during cell division to form
chromosomes
 Nucleolus – small dense region in nucleus
where the assembly of ribosomes begins
Ribosomes
 Small particles of RNA and protein
 Are spread throughout the cell
 Are also attached to the rough endoplasmic
reticulum
 Ribosomes are the site of protein
synthesis
Endoplasmic Reticulum
 An internal membrane system
 Lipids, some proteins, and other materials
are assembled here
 Rough ER has ribosomes attached to allow
for protein synthesis
 Smooth ER has no ribosomes to allow for
lipid synthesis
Golgi Apparatus
 Appears as a stack of membranes
 Acts like a postman
 It changes, sorts, and packages proteins and
other materials
 Also delivers these “packages” to their final
destination
Lysosomes
 Small organelles filled with enzymes
 Act as a cleaning crew
 They break down lipids, carbohydrates, and
proteins so the cell can use them
 Also break down “old” organelles
 Also break down unneeded junk in cell such as
bacteria
Vacuoles
Saclike structures used for cell
storage
Stores water, salts, proteins, and
carbohydrates
Mitochondria
 “Powerhouse of the cell”
 Converts chemical energy stored in food
into a form that cells can use
 Has a double membrane
 One on the outside of organelle
 One folded up inside the organelle
 Contains its own DNA
Chloroplasts
 “Powerhouse for a plant cell”
 Converts energy from sun into chemical
energy during process of photosynthesis
 Contains its own DNA
Cytoskeleton
 A network of protein filaments
 Helps cell retain its shape
 Also helps in cell movement
 Two of the filaments are microfilaments
and microtubules
 Microtubules are very important in cell division
 As well as centrioles which help organize cell
division
Chapter 7 Notes
Section 3
Cell Boundries
 Cell Membrane All cells are surrounded by this thin, flexible
barrier.
 It regulates what enters and leaves the cell and
provides protection and support.
 Contains protein molecules that are embedded
in the lipid bilayer with carbohydrates attached.
 The Carbohydrates act like „chemical
identification cards‟.
Outside
of cell
Proteins
Carbohydrate
chains
Cell
membrane
Inside
of cell
(cytoplasm)
Protein
channel
Lipid bilayer
 Cell Wall Lie outside the cell membrane.
 Porous enough to allow water, oxygen, and
carbon dioxide through.
 The main function is to provide support and
protection for the cell.
 Plant cell walls are made mostly of cellulose
Measuring Concentration
 The cytoplasm contains a solution of many
different substances in water.
 The concentration of a solution is the
mass of solute in a given volume of
solution (mass/volume).
 EX: If you had 12 g of salt in 6 L of water, what
is the concentration.
Diffusion
 The process by which molecules of a
substance move from areas of higher
concentration to areas of lower
concentration.
 Particles will move until equilibrium is
reached.
 Does not require the cell to use energy.
Glucose
molecules
High
Concentration
Cell
Membrane
Low
Concentration
Osmosis
 If a substance is able to diffuse across a
membrane the membrane is said to be
permeable to it.
 Most biological membranes are selectively
permeable; some substances can pass
across and others cannot.
 Osmosis is the diffusion of water through
a selectively permeable membrane.
Osmosis
 When a solution has a higher solute
concentration than the cell, it is said to be
hypertonic. (“above strength”)
 When a solution has a lower solute
concentration than the cell, it is said to be
hypotonic. (“below strength”)
 When the concentration is the same inside
and outside the cell, it is said to be
isotonic. (“same strength”)
Osmotic Pressure
 For organisms to survive, they must have
a way to balance the intake and loss of
water.
 Sometimes the cell takes on too much
water and may burst.
 Large organisms are not in danger of this.
 Bacteria and plant cells are surrounded by a
tough cell wall that tries to prevent this.
Facilitated Diffusion
 Sugar glucose molecules cannot pass
through the membrane on their own.
 The cell membrane protein channels are said to
facilitate (help) the diffusion of glucose across
the membranes lipid bilayer.
Active Transport
 Materials move against a concentration
difference.
 This process requires energy and
transport protein “pumps”.
 Potassium, calcium and sodium move
across this way.
Endocytosis
 The process of taking material into the cell
by means of infoldings, or pockets, of the
cell membrane.
 Two types:
 Phagocytosis “cell eating”- Extensions of
cytoplasm surround a particle and package it
within a food vacuole. The cell then engulfs it.
(Amoebas)
 Pinocytosis-Tiny pockets form along the cell
membrane, fill with liquid, and pinch off to form
vacuoles within the cell.
Exocytosis
 The membrane of the vacuole surrounding
the material fuses with the cell
membrane, forcing the contents out of the
cell.
 EX: The removal of water by a contractile
vacuole.
Chapter 7 Notes
Section 4
Unicellular Organisms
 Only has one cell
 Can carry out all the essential functions of
life
 Grow, reproduce, respond to the environment,
etc.
Multicellular Organisms
Made of many cells that do different tasks
(cell specialization)
Examples
 Muscle cells are packed with dense fibers that
contract
 blood cells have special proteins that bind to
oxygen to transport it around the body
 nerve cells have the ability to transmit messages
throughout the body
Plants also have specialized cells
Examples:
 Guard Cells – monitor the plants internal conditions
Levels of Organization
Individual Cells  Tissues  Organs
 Organ Systems  Organism
Tissues
Groups of similar cells that perform
a specific function
Four main types
Muscle
Epithelial
Nervous
Connective
Organs
 Many groups of tissues working together
to perform a specific function
 Example
 The stomach is an organ made up of smooth
muscle tissue, epithelial tissue and nervous
tissue
Organ Systems
Many organs working together to
perform a specific function
Example
Digestion – includes the stomach, large
and small intestines, esophagus,
mouth, and pharynx, liver, and
pancreas
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