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Chapter 3A
 Cell Structure and Function
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 In 1665 Robert Hooke observed and named the first
cell.
 He observed cork cells, dead plant cells. Hooke only
observed the cell wall and empty space.
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 1674 Anton von Leeuwenhoek observed living cells- he
saw single celled organisms in a drop of pond water.
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 1838- Mathius Schleiden- proposed all plants were
made of cells.
 1839-Theodor Schwann- proposed all animals were
made of cells.
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 1855- Rudolf Virchow- states that cells come from the
reproduction of other cells.
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 Cell Theory
 1. All organisms are made of cells.
 2. The cell is the most basic unit of life. (structure and
function)
 3. All existing cells are produced by other living cells.
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 Cells have different structure for
different function.
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 Cells are enclosed in a membrane and have
cytoplasm- a liquid-like substance that contains
proteins, minerals…….
 Some cells have organelles.
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 Prokaryotic cells- do not have a nucleus or membrane
bound organelles. Bacteria
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Eukaryotic cells- they have a nucleus and membrane
bound organelles.
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 3-2 Cell Organelles
 Eukaryotic cells are highly organized.
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 The cytoskeleton is a network of proteins that criss-
cross the cell- it provides shape and support.
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 The Cytoplasm fills the space between the nucleus
and the cell membrane. It contains the fluid and
organelles
 The fluid part is the Cytosol.
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 The nucleus stores the genetic information or DNA
(deoxyribonucleic acid).
 DNA contains genes that are the instructions for
making proteins.
 The Nuclear envelope surrounds and protects the
nucleus.
 The nucleolus in the nucleus produces ribosomes
which make proteins.
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 The Endoplasmic reticulum or ER fills much of the
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cell. It is interconnected folded membranes.
The “intercellular Freeway”.
The folds increase the surface area.
Rough ER has ribosomes, so proteins are made here.
Smooth ER does not have ribosomes.
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 The Golgi Apparatus is stacks of membranes that
process, sort and deliver proteins.
 Some proteins stay in the cell, others move to other
cells.
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 Vesicles are membrane bound sacs that can move
through the cell.
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 Mitochondria- supply energy to the cell. They are the
site of Cellular Respiration . Mitochondria have a
double membrane and their own DNA- they may have
been taken in by larger cells.
 Cells that use a lot of energy have more mitochondria.
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 Vacuoles- in plant cells, the central vacuole stores
water, starch………….. It takes up most of the space in a
plant cell.
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 Lysosomes- in animal cells- they contain enzymes
that can break down old or damaged cells.
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 Cell Wall- in plant cells the cell membrane is
surrounded by a cell wall of cellulose.
 It provides structure and support.
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 Chloroplasts- in plant cells. The green organelles that
perform photosynthesis for the cell. Inside the
thylakoids provide more surface area. They have a
double membrane and DNA- they may have been
free-living.
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3-3 Cell Membranes
 The cell membrane is composed of the phospholipid
bilayer.
 A phospholipid has a polar phospholipid head and a
non-polar tail.
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 Cholesterol molecule strengthen the membrane.
 Proteins can extend through the phospholipid bilayer
or remain on the surface.
 Carbohydrates attach to the proteins to identify the
cell.
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 The cell membrane is selectively permeable- it allows
some material through, but prevents other material
from passing through.
 What molecules can pass through depends on the
molecules size, polarity and concentration.
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