Transcript Introduction to Biology Chapter 3 Notes: Cell Structure

Introduction to Biology
Chapter 3 Notes:
Cell Structure and Function
Mr. Grivensky/Mr. Rutkoski
3-1 Early Microscopes
 In the 1600s, a Dutch glassmaker
named Anton van Leeuwenhoek
discovered that if he placed several
magnifying lenses at the proper
distances from each other he could
greatly magnify small objects.
van Leeuwenhoek is given credit
for creating the first microscopes
“Cell Theory Scientists”
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Robert Hooke, an English physicist, at about the same time
as Leeuwenhoek, was using a microscope to observe
flowers, insects, and slices of cork.
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In 1665, Hooke published a book of his drawings and
named the chambers he observed in plant samples, “cells”.
He chose this name because they reminded him of the tiny
rooms in a monastery, which are also called cells.
Hooke believed that only plants were made up of cells, as
did most scientists of his time and nearly 200 years later.
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In 1839, a German biologist, Theodor Schwann found that
animal tissues also had cell-like structures which lead him
to the conclusion that animals were made up of cells also.
..more “Cell Theory Scientists”
 Around the same time as Schwann made his
discovery, Robert Brown, a Scottish biologist had
found that cells had a structure near the center. We
now call this structure the nucleus.
 German biologist, Matthias Schleiden, suggested that
the nucleus played a role in cell reproduction.
 In 1855, German physicist, Rudolf Virchow, studied
cell reproduction further and proposed that animal
and plant cells were produced by the division of
existing cells.
Cell Theory
 The discoveries of these scientists are
summarized in the cell theory.
 Cell Theory states that:
 A. All living things are composed of cells
 B. Cells are the smallest working units of
living things
 C. All cells come from preexisting cells by
cell division
Modern Microscopes
 Compound light microscope
 Uses more than one lens to
magnify objects
 Can magnify an image up to
1000 times
 These are what we use at
Wyoming Area
 Cells and organisms can be
studied while they are still
alive
Electron Microscopes: TEM
 Use magnets to focus a beam of electrons,
much like a television
 The beam of electrons can be used to
examine a sample
 Electron microscopes can magnify 1000x
larger than a light microscope (100,000
times)
Transmission Electron Microscope (TEM)
 Shines a beam of electrons through a
sample, and then projects the image onto a
fluorescent screen
Electron Microscopes: SEM
Scanning Electron Microscope (SEM)
 Uses a beam of electrons to scan the
surface of a sample. The SEM collects the
electrons that bounce off the sample, and
forms an image on a television screen
 Both, TEMs and SEMs can only observe
nonliving specimens. These specimens
must be sliced very thin for use in a TEM,
and the SEM only shows the outer surface
of the specimen
SEM & TEM Photos
SEM
TEM
Scanning Probe Microscope
 In the early 1980s, the scanning
probe microscope was invented
 It does not use any lenses, and
instead traces the surface of an
object with a probe
 These microscopes have been used to
photograph molecules and atoms.
3-2 Cell Boundaries
 Every cell has a cell membrane along
its boundary.
 The principal role of the cell
membrane is to separate and protect
the cell from its surroundings.
 The cell membrane is said to be
selectively permeable
Selectively Permeable
 Selectively Permeable means that the
cell membrane allows some
substances through but denies
passage to other substances
Lipid Bilayer
The cell membrane is
composed of a phospholipid
bilayer. A phospholipid has a
polar end called the head and a
nonpolar end called the tail.
The polar heads group together
on the outside of the lipid
bilayer. The nonpolar heads
group together on the inside of the bilayer because they avoid
water.
The lipid bilayer provides the cell membrane with a tough, flexible
barrier that protects the cell from substances.
Cell Membrane
Cell Wall
Found in plants, algae, and bacteria.
Located outside the cell membrane.
Helps to support and protect the cell.
Made up of carbohydrates and
protein. The principle carbohydrate is
cellulose.
 Cellulose provide the cell with rigidity
and strength.
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Cell Wall
Passive Transport
 Substances cross the cell membrane
without the cell expending energy
 Examples1. Diffusion
2. Facilitated Diffusion
3. Osmosis
Diffusion
 Diffusion is the process by which
substances spread throughout a liquid
or gas.
 In diffusion, substances move from
regions of high concentration to
regions of low concentration
Diffusion
Facilitated Diffusion
 Substances diffuse across the cell
membrane through special channels
in protein
 Example is glucose
Osmosis
 The diffusion of water through a
selectively permeable membrane
Hypertonic Solution
 Hypertonic Solution: Solute
concentration of solution higher than
cell
 More dissolved particles outside of cell
than inside of cell
 Hyper = more (think hyperactive); Tonic
= dissolved particles
 Water moves out of cell into solution
 Cell shrinks
Hypertonic Solution
Hyoptonic Solution
 Hypotonic Solution: Solute
concentration of solution lower than
cell
 Less dissolved particles outside of cell
than inside of cell
 Hypo = less, under (think hypodermic,
hypothermia); Tonic = dissolved
particles
 Water moves into cell from solution
 Cell expands (and may burst)
Hypotonic Solution
Isotonic Solution
 Isotonic Solution: Solute
concentration of solution equal to that
of cell
 No net water movement
Isotonic Solution
Active Transport
 Requires energy
 The movement of substances against
a concentration gradient
 Similar to a pump.
 Examples
1. Endocytosis
2. Phagocytosis
3. Exocytosis
3-3 Inside the Cell
 There are two categories of
organisms: prokaryotes and
eukaryotes
 Prokaryotes- organisms that do not
contain nuclei and membrane bound
organelles (ex.bacteria)
 Eukaryotes- organisms that contain a
nucleus and organelles
Nucleus
 Control center of the cell
 Large and dense
 Contains nearly all of the cell’s DNA
DNA
 Contains coded instructions for
making proteins
 DNA wrapped around special
proteins(histones) is known as
chromatin
 Chromatin condenses to form
chromosomes
Chromatin/Chromosomes
Structures in the Nucleus
 Nucleolus- small, dense region found
in the nucleus; ribosomes are
assembled here
 Nuclear envelope- two distinct
membranes that contain many holes
called nuclear pores
Structures of the Nucleus
Cytoplasm
 Portion of the cell outside of the
nucleus
 Fluid like material that contains
organelles
 Organelles-small structure that
performs a specialized function within
the cell
Organelles
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Ribosomes
Rough Endoplasmic Reticulum
Smooth Endoplasmic Reticulum
Golgi Apparatus
Lysosomes
Cytoskeleton
1. Microtubules
2. Microfilaments
Organelles- continued
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Cilia
Flagella
Vacuoles
Centrioles
Plastids
Mitochondria
Chloroplast
Ribosomes
 Ribosomes
Protein and RNA complex responsible
for protein synthesis
Rough Endoplasmic Reticulum
 Rough endoplasmic reticulum (RER)
A network of interconnected
membranes forming channels within
the cell. Covered with ribosomes
(causing the "rough" appearance)
which are in the process of
synthesizing proteins.
Smooth Endoplasmic Reticulum
 Smooth endoplasmic reticulum (SER)
A network of interconnected
membranes forming channels within
the cell. A site for synthesis and
metabolism of lipids.
Golgi Apparatus
 Golgi apparatus
A series of stacked membranes.
Vesicles (small membrane surrounded
bags) carry materials from the RER to
the Golgi apparatus. Vesicles move
between the stacks while the proteins
are "processed" to a mature form.
Lysosomes
 Lysosymes
A membrane bound organelle that is
responsible for degrading proteins
and membranes in the cell, and also
helps degrade materials ingested by
the cell.
Cytoskeleton
 The cytoskeleton extends through out
the cytoplasm. Composed of protein
fibers called intermediate filaments,
microtubules and microfilaments, the
cytoskeleton maintains cell shape,
allows the cell to move, and moves
structures within the cell.
Cilia and Flagella
 Plant cells do not have cilia and
flagella. Both are anchored in the
cytoplasm by centrioles and extend
from the outside surface of the
plasma membrane. Flagella are used
to propel the cell. Cilia can be used
to propel the cell, or move fluids past
the cell.
Cilia and Flagella
Vacuole
 Vacuoles
Membrane surrounded "bags" that
contain water and storage materials
in plants.
Centrioles
 A centriole is a short, barrel shaped
ring composed of nine microtubules
around an empty center. Centrioles
are found only in animal cells. They
are arranged in pairs that sit
perpendicular to one another.
Plastids
 Plastids are a storage organelle
unique to plant cells and some
photosynthetic protists. They are not
found in animal cells. Located in the
cytoplasm, the plastids are used to
store substances such as pigments
and starches.
Mitochrondria
 Mitochondria
Surrounded by a double membrane
with a series of folds called cristae.
Functions in energy production
through metabolism. Contains its own
DNA.
Chloroplast
 Chloroplasts (plastids)
Surrounded by a double membrane,
containing stacked thylacoid
membranes. Responsible for
photosynthesis, the trapping of light
energy for the synthesis of sugars.
Animal Cell
Plant Cell