Download all living things are composed of cells

Cells
CELL STRUCTURE AND
FUNCTION
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Pretest – take a test on the cell, organelles and functions!!
? WHAT IS A CELL?
LAB – Have different cells underneath several
microscopes, (plant, leaf, nerve cells, bacteria,
paramecium) draw at least 3 of the cells, record a
description of their features – shape and internal
parts. Use your observations to write a definition of a
“cell”, try to classify the cells they draw into 2 or more
groups. Put each cell in a particular group.
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Grade Pretest
Watch video “Secrets of a Cell” 26 min. Worksheet
Plant cell
A. CELL THEORY
• 1. CELL – Collection of living matter
enclosed by a barrier that separates the
cell from its surroundings
• 2. 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
B. BASIC CELL STRUCTURE
• 1. CELL MEMBRANE/PLASMA MEMBRANE –
a thin, flexible barrier around the cell
• 2. CELL WALL – a strong layer around the cell
membrane
• Cell Membrane and Cell Wall – support and
protect cells while allowing them to interact with
their surroundings
• 3. NUCLEUS – a large structure that contains
the cells genetic material and controls the cells
activities
• 4. CYTOPLASM – material inside the cell
membrane, but not including the nucleus
C. PROKARYOTES AND
EUKARYOTES
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BIOLOGISTS DIVIDE CELLS INTO 2 CATEGORIES:
EUKARYOTES AND PROKARYOTES. THE CELLS
OF EUKARYOTES HAVE A NUCLEUS, BUT THE
CELLS OR PROKARYOTES DO NOT.
PROKARYOTES – have cell membranes and
cytoplasm but do not contain nuclei.
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Example – bacteria, escherichia coli – live in intestines
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They grow, reproduce and respond to stimuli
EUKARYOTES – do contain nuclei, cell membrane,
cytoplasm and organelles
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ORGANELLES - “little organs” specialized structures that
perform important cellular functions
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Example – some singular, most multicellular, all plants, animals
and fungi
Prokaryotic cell
PLANT CELL
Questions
– WHAT IS THE MAIN DIFFERENCE BETWEEN
PROKARYOTIC CELLS AND EUKARYOTIC
CELLS
» EUKARYOTIC CELS CONTAIN A NUCLEUS
WHILE PROKARYOTIC CELLS DON’G
– DO BACTERIAL CELLS CONTAIN A NUCLEUS?
» NO. ALL BACTERIA ARE PROKARYOTES
– WHAT ELSE DO EUKARYOTIC CELLS CONTAIN
THAT PROKARYOTIC CELLS DON’T?
» EUKARYOTIC CELLS CONTAIN
ORGANELLES, WHICH ARE SPECIALIZED
STRUCTURES THAT PERFORM IMPORTANT
CELLULAR FUNCTIONS
ASSESMENT #1
• What three statements describe the 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
• What is the main characteristic that distinguishes
eukaryotes from prokaryotes?
– The cells of eukaryotes have a nucleus, but the cells
or prokaryotes do not.
• Name two structures that all cells have.
– All cells have a cell membrane and cytoplasm
Cell Structures
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Cell wall
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The main function of the cell wall is to provide support and
protection for the cell
It allows water, oxygen, carbon dioxide, and other substances to
pass through the cell wall
Nucleus
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The nucleus controls most cell processes and contains the
hereditary information of DNA
– Chromatin and Chromosomes
» Chromatin – the granular material visible within the
nucleus
» Chromosomes – chromatin condenses into chromosomes
when the cell divides – threadlike structures containing
genetic information that is passed from one generation of
cell to the next
Nucleus cont.
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Nucleolus
– A small dense region within most nuclei
in which the assembly of ribosomes
begins
• Nuclear Envelope
– A double membrane layer, which
surrounds the nucleus. It is dotted with
thousands of nuclear pores which
allows material to move into and out of
the nucleus.
Cytoskeleton
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The cytoskeleton is a network of protein
filaments that helps the cell to maintain its
shape. The cytoskeleton is also involved in
many forms of cell movement.
– microtubules – hollow tubes of protein about
25 nanometers in diameter. They maintain
cell shape and can also serve as “tracks”
along which organelles are moved
– microfilaments – long, thin fibers that function
in the movement and support of the cell.
(tough flexible framework that supports the
cell)
Organelles in the cytoplasm
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Ribosomes – small particle in the cell in
which proteins are assembled: made of
RNA and protein
– Endoplasmic Reticulum – (ER) found
in eukaryotic cells, which components
of the cell membrane, and some
proteins are assembled
– rough ER – synthesis of proteins
ribosomes stud the surface
– smooth ER – contains a collection of
enzymes that perform specialized tasks
– synthesizing lipids
ENDOPLASMIC RETICULUM
The endoplasmic reticulum is the organelle in which
components of the cell membrane are assembled and
some proteins are modified. The endoplasmic reticulum
illustrated is called rough endoplasmic reticulum because
of the ribosomes on its surface.
• What are ribosomes composed of?
– RNA and Proteins
• Where are ribosomes produced?
– In the nucleolus
• What do ribosomes produce
– Proteins
• What happens to these proteins after they are composed
by ribosomes?
– They move directly into the ER, where they are chemically
modified
• How is the smooth ER different from the rough ER?
– Smooth surface
• What is the function of the smooth ER?
– Collection of enzymes that perform specialized tasks, such as
synthesis of lipids.
ORGANELLES CONT.
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Golgi apparatus – enzymes in the Golgi apparatus attach
carbohydrates and lipids to proteins – go to outside of cell
Lysosome – small organelles filled with enzymes. Break down lipids,
carbohydrates and proteins from foods into particles used by rest of
cell
Vacuoles – sac like structures that store materials such as water, salt,
proteins and carbohydrates
Chloroplast – only found in plants and some other organisms (not in
animals) use the energy from sunlight to make energy food molecules
in a process known as photosynthesis.
Mitochondria – release energy from stored food molecules. Convert
food into high energy compounds that the cell can use to power
growth, development and movement.
GOLGI APPARATUS
Enzymes in the Golgi apparatus
attach carbohydrates and lipids to
proteins. Notice the stacklike membranes
that make up the Golgi apparatus.
Assesment #2
• Describe the functions of the endoplasmic reticulum
Golgi apparatus, chloroplast and mitochondrion.
– Cell membrane components and some proteins are assembled
in the ER. Enzymes in the Golgi apparatus attach carbohydrates
and liplids to proteins. Chloroplasts use sunlight to make food
molecules. Mitochondria convert food molecules into highenergy compounds.
• What does the cell wall provide for a cell?
– The main function of the cell wall is to provide support and
protection for the cell.
• Describe the role of the nucleus in the cell.
– The nucleus controls most cell processes and contains DNA
• What are two functions of the cytoskeleton?
– The cytoskeleton is a network of protein filaments that helps the
cell maintain its shape. The cytoskeleton is also involvedin
many forms of cell movement.
Movement through the membrane
Cell membrane
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The cell membrane regulates what enters and leaves
the cell and also provides protection and support
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Lipid bilayer – double layered sheet that forms the core
of nearly all cell membranes
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intakes food and water, eliminates waste
cell membranes contain protein molecules, carbohydrates are
attached to proteins
» figure 7-15
Diffusion – molecules move from an area of high
concentration to low concentration
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Diffusion causes many substances to move across a
cell membrane without the cells using energy
Concentration – the mass of solute in a given volume
of solution, or mass/volume (video from website)
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Osmosis – allows water molecules to pass
easily through most biological membranes
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Osmosis is diffusion of water through a
selectively permeable membrane
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does not require energy
Selective Premeable – some substances can
pass across them and others can not.
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isotonic – same strength
hypertonic – above strength
hypotonic – below strength
figure 7-18 chart (short video, osmosis,from website)
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Osmotic pressure – osmosis exerts a pressure
known as osmotic pressure on the hypertonic
side of a selectively permeable membrane.
– example – osmotic pressure should produce
a net movement of water into a typical cell
that is surrounded by fresh water. If this
happens, the volume of a cell will increase
until the cell becomes swollen, and bursts.
– ? How do cell walls protect cells from osmotic
pressure?
» Cell walls prevent the cells from
expanding even under tremendous
osmotic pressure
Faciliated Diffusion – movement of specific molecules
across cell membranes through protein channels
Example – some only allow glucose to pass through the channel
does not require energy
– Active transport – material moves from an
area of lower concentration to an area of
greater concentration (video on website)
• Requires input of energy
– Endocytosis – process by which a cell moves large
amounts of material across the cell membrane by turning
part of the cell membrane inside out.
» Phagocytosis – large particles taken into the cell
» Exocytosis – large particles taken out of the cell
» Video on exo and endo on website
• Passive transport – video
Assesment #3
• What processes are made possible by the cell
membrane?
– The cell membrane regulates what enters and leaves the cell
• How does diffusion affect cells?
– Diffusion causes many substances to move across a cell
membrane without the cell using energy
• Describe how water moves during osmosis.
– Water tends to diffuse from a region where it is highly
concentrated to one where it is less concentrated. Water will
move across a membrane until equilibrium is reached.
• What is the basic structure of a cell membrane?
– The core of nearly all cell membranes is a double layered sheet
called a lipid bilayer. Most cell membranes contain protein
molecules that run through the lipid bilayer, and carbohydrate
molecules are attached to the membrane that scientists call the
membrane a mosaic of molecules
• How does active transport differ from diffusion?
– Active transport requires the input of energy , while diffusion
does not require energy