Download Chapter 4 Cell Structure and Function Section 1: The History of Cell

Chapter 4
Cell Structure and Function
Section 1: The History of Cell Biology
1. The Discovery of Cells
a. In 1665 Robert Hooke studied the bark of the cork oak tree using a
compound light microscope
i. He described what he saw as tiny little cell, similar to the cells that
monks lived in
ii. He also studied the cells of tree roots, stems, and ferns
b. In 1673 Anton van Leeuwonhoek, using a slightly stronger microscope than
Hooke, studied living cells
c. In 1838 Matthias Schleiden concluded that all plants were composed of cells
d. In 1839 Theodor Schwann concluded all animals were composed of cells
e. Rudolf Virchow concluded that all cells come from other cells
2. The Cell Theory
a. All living things are composed of one or more cells
b. Cells are the basic units of structure and function in an organism
c. Cells only come from the reproduction of existing cells
*All cells share characteristics that indicate that cells are related to other living things*
Section 2: Introduction to Cells
*There are at least 200 types of cells, ranging from flat cells to branching cells to round cells to
rectangular cells
1. Cell Diversity
a. Cells are very diverse in terms of shape, size, and internal organization
b. In biology form usually follows function….a cell’s function influences its shape
c. Shape and Size
i. Shape- the diversity in cell shapes reflects the different functions of
cells. Each cell has a shape that has evolved to allow the cell to
perform its function effectively
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Human nerve cell radiate out from the body of the cell and send signals quickly
throughout the body
Human skin cells are flat and overlap each other to protect the inside of the body from
the outside world
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Human red blood cells are round so they can flow easily through blood vessels and not cause
a blockage
ii. Size
1. Most cells are microscopic
2. Some are large enough to be seen with the naked eye
a. Example: the nerve cell in a giraffe extends from its
spinal cord to its foot (6 ½ feet)
b. Example: a human egg cell is about the size of a period
on this paper (.)
3. The size of a cell is limited by its surface area to volume ratio.
a. As a cell grows its volume increases at a faster rate
than its surface area
b. Cells need to take things in such as oxygen and
nutrients
c. Cells need to remove waste and carbon dioxide
4. If a cell were to become too large it would not be able to take
in enough nutrients and get rid of enough waste in order for it
to survive
5. Examples of surface area to volume ratio in the human body
a. Alveoli in your lungs
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b. Villi in your small intestines
c. Ruggae in your stomach
d. Folds in your brain
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2. Basic Parts of a Cell – despite the diversity among cells, three basic features are
common in all cell types
a. Plasma membrane
i. Covers a cell’s surface and acts as a barrier between the inside and
the outside of the cell
ii. All materials enter or exit through it
iii. It is also called the cell membrane and lipid bi-layer
b. Cytoplasm
i. It is the area that is within the cell membrane and includes the fluid,
cytoskeleton, and all the organelles except the nucleus
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ii. Cytosol is the soluble portion of the cytoplasm which includes
molecules and small particles, but not the organelles covered with
membranes
c. Control center
i. Cells carry coded information in the form of DNA for regulating their
functions and reproducing themselves
ii. In some cells the DNA floats freely and in other cells it is contained in
a membrane bound structure called the nucleus
3. Two Basic Types of Cells – Fossil evidence suggests that the earliest cells on Earth
were simple cells similar to some present day bacteria. As cells evolved, they
differentiated into two major types: prokaryotes and eukaryotes
a. Prokaryotes
i. Organisms that lack a membrane bound nucleus and membrane
bound organelles
ii. DNA is often located in a part of the cell called the nucleoid
iii. Prokaryotes are divided into 2 domains; Bacteria and Archaea
1. Domain Bacteria includes almost all the bacteria that exists in
the world
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2. Domain Archaea are microscopic organisms that live in
extremely harsh environments like hot springs and high saline
conditions
b. Eukaryotes
i. Organisms made up of one or more cells that have a nucleus and
membrane bound organelles
ii. The organelles carry out cellular processes just as human organs do
iii. Eukaryotic cells are generally much larger than prokaryotic cells
4. Cellular organization
a. Colonies
i. A colonial organism is a collection of genetically identical cells that
live together in a connected group. Colonial organisms are not truly
multi-cellular because few cell activities are coordinated.
ii. Example: Volvox a green algae
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b. True Multicellularity
i. As organisms evolved, their cells became more specialized and
eventually were unable to survive independently
ii. Groups of cells took on specific roles
1. Groups of cells functioning together are called a tissue
2. Groups of tissues functioning together to perform a particular
job are called organs
3. Groups of organs functioning together make up organ
systems
4. Several organ systems combine to make up an organisms
Section 4: Unique Features of Plant Cells
Plant Cells- Plants make their own carbon containing molecules (glucose) by taking
in atmospheric carbon dioxide during photosynthesis. Therefore they have 3
structures that are not found in animal cells to help them in this process
a. Cell Wall
i. It is a rigid layer that lies outside the cell’s plasma membrane
ii. It is made of cellulose, proteins and other carbohydrates
iii. Pores in the cell wall allow substances to enter and exit the cell
b. Central Vacuole
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i. It is a large, fluid filled organelle that stores water, enzymes,
metabolic waste, and other materials
ii. It can make up 90% of a plant cell’s volume and can push all of the
other organelles towards the outer edges of the cell
iii. The central vacuole is responsible for a plant standing upright or
wilting over
iv. Some plants have vacuoles that store other substances like toxins
1. The acacia tree stores poisons that provide a defense against
plant eating animals
2. Tobacco plants store the toxin nicotine
c. Plastids are organelles that are surrounded by a double membrane and
contain their own DNA
i. Chloroplasts
1. Use light energy to make carbohydrates from carbon dioxide
and water
2. Each chloroplast contains a system of flattened, membranous
sacs called thylakoids
3. Thylakoids contain the green pigment chlorophyll, the main
pigment that captures light energy
4. Chlorophyll can be found in plants, algae, and seaweed
ii. Chromoplasts
1. Plastids that contain colorful pigments and may or may not
take part in photosynthesis
2. They contain colorful pigments such as orange, red, purple,
and yellow
d. Comparing Cells
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i. Prokaryotes versus Eukaryotes- Prokaryotes lack a nucleus and
membrane bound organelles. They have a region called the nucleoid,
in which their genetic material is concentrated. They also lack an
internal membrane system
ii. Plant cells versus Animal cells- Plant cells contain a cell wall, a large
central vacuole, and contain a variety of plastids…all of which help
the plant to function
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