• What are some of the tools scientists use to
observe very small things?
• Microscopes
Scientists
• Robert Hooke
studied nature by
using a light
microscope.
– Light microscopes
use optical lenses to
magnify objects by
bending light rays.
• Anton van
Leeuwenhoek was
the 1st scientist to
observe living cells.
What is a cell?
A cell is the smallest unit of life.
The cell theory states:
● All living things are made up of cells
● Cells are the basic units of structure
and function in living things
● New cells are produced from existing
cells
What is a theory?
Remember, a theory is not just a hunch, it is an
idea supported by a considerable amount of
experimental evidence.
Examples of Cells-Why are they
different?
The different shapes of cells reflect
their different functions.
• The long extensions that
reach out in various
directions from the nerve
cell allows the cell to send
and receive nerve
impulses(messages)
• The flat, plate-like shape of
skin cells suits their function
of covering and protecting
the surface of the body.
What limits cell size?
• Small cells can exchange substances(oxygen,
nutrients, and carbon dioxide) more readily
than larger cells because small objects have a
higher surface area to volume ratio.
• So, the cells divide!
There are 2 kinds of cells:
•
Eukaryotes – Have a
nucleus
•
• Examples of
Examples of
prokaryotes are
eukaryotes are plants,
bacteria
animals, fungus, and
protists
• Prokaryotes – Do NOT
have a nucleus
• Smaller than eukaryotes
•
More complicated
• Less complicated
Cells have specialized structures to carry out
functions. These are called organelles.
Cell Organelles:
• Nucleus – command
center of the cell.
The nucleus houses
and protects the cell’s
genetic material in the
form of DNA. ONLY
FOUND IN EUKARYOTES
Chromosomes are
structures in the nucleus
made of DNA and protein.
• Cytoplasm – the “gel”
material inside the cell
membrane but not in the
nucleus. The organelles
live inside the cytoplasm.
Cell Organelles
• Nuclear membrane- a
double membrane
that surrounds the
nucleus and is made
up of 2 phospholipid
bilayers.
• Nucleolus- within the
nucleus, where the
assembly (making) of
ribosomes begin.
Cell Organelles
• Cell membrane
(Plasma membrane) –
only allows certain
molecules to enter or
leave the cell. It also
provides protection
and support for the
cell.
Centriole-located near
the nucleus and helps
organize cell division.
Found in animal cells.
Cell Organelles
• Mitochondria – converts
food into energy (ATP) that
the cell can use. They are
the power centers of the
cell.
– ATP powers most of the
cells chemical reactions
– Highly active cells, such
as muscle cells, can
have hundreds of
mitochondria.
• Cytoskeleton – supports
the cell and helps to
maintain the shape.
– The same way tent poles
support the shape of a
tent.
Cell Organelles:
•
Endoplasmic Recticulum (ER) – makes lipids, proteins and other
materials that are exported (taken out) of the cell.
– Functions primarily as an intracellular highway, a path along
which molecules move from one part of the cell to another.
• Rough ER – part of the ER that makes proteins and
phospholipids.
• Once these proteins are made, they are later exported from
the cell or inserted into one of the cell’s own membranes.
• For example, ribosomes on the Rough ER make digestive
enzymes.
-Called “rough” because ribosomes are attached to the surface
and makes it look bumpy.
More Endoplasmic Reticulum
• Smooth ER – lacks ribosomes and thus has a
smooth appearance.
• Smooth ER builds lipids, such as cholesterol.
• In the ovaries and testes, smooth ER produces
the steroid hormones estrogen and
testosterone.
• In the skeletal and heart muscle cells, smooth
ER releases calcium, which stimulate
contraction.
• Smooth ER is abundant in the liver and kidney
cells, where it helps detoxify drugs and poisons.
Long term abuse of alcohol and other drugs
causes these cells to produce more smooth ER.
Cell Organelles:
• Ribosomes – small
particles of RNA and
protein that direct
protein synthesis in
the cytoplasm. They
build proteins by
following
instructions that
come from the
nucleus.
•
Cell Organelles:
Golgi Apparatus–
modifies, sorts and
packages the proteins
that come from the
Rough ER and either
stores them or ships
them out of the cell.
• Lysosome – removes
waste from the cell.
(Destroys cells that
are no longer
functioning properly.)
• Microtubules-holds organelles in place,
maintains a cell’s shape, and act as tracks that
guide organelles and molecules as they move
within the cell.
• Microfilaments- contribute to cell movement,
including the crawling of white blood cells and
the contraction of muscle cells.
Movement
• Cilia and flagella-hairlike structures that
extend from the surface of the cell, that helps
a cell MOVE.
• Cilia-Short, hair-like structures
• Flagella-Long, whip-like structures
Cell Organelles:
•
Chloroplasts – ONLY
FOUND IN PLANT CELLS
- captures energy from
sunlight and converts it into
chemical energy in plant
cells.
• Cell Wall – NOT FOUND IN
ANIMAL CELLS
- provides support and
protection for the plant cell.
-Contains a
carbohydrate called
cellulose.
Cell Organelles
• Vacuoles –saclike
structures used to
store materials
such as water,
salts, proteins, and
carbohydrates.
Balloon Demo
• How does the odor
pass through the
balloon?
– Molecules of the
substance pass
through the small
pores or dissolve in
the rubber.
– This is called
permeability.