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CELLS
The Basic Unit: Cells
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Cells – tiny living structures that make up all living
things
A human liver – which weighs about 3 lb, is made
up of over 300 billion cells!
Whole body estimate? 60 trillion
Not all cells are alike; some are specialized (they
perform functions that no other cells do
Blood cells, muscle cells, nerve cells, gland cells
The Cell Theory
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Robert Hooke (1665) – the first to use the word
“cell” to describe what he saw
Observed a piece of cork through a microscope
What he actually saw were the walls of dead plant
cells
Later scientists observed living things – they
observed protoplasm
One made observation of plants. Another of
animals
The Cell Theory
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All of these observations were combines to form the
modern cell theory:
 All
cells come from preexisting cells
 All living things are made of cells and of the products
of cells
 The functions of living things are performed by the cells
they are made of
Cellular Functions
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All cells use energy
All cells manufacture materials
All cells respond to their environment
All cells reproduce themselves
Answer the following questions:
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Who was the first English scientist to use the word
“cell”?
According to the cell theory, can anything not made
of cells be alive? Explain your answer.
What happens when a cell stops using energy?
Answer the following questions:
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Who was the first English scientist to use the word
“cell”?
According to the cell theory, can anything not made
of cells be alive? Explain your answer.
What happens when a cell stops using energy?
Molecules and Life
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The smallest unit that can be alive is the cell – but
there are smaller structures within a cell
The smaller structures are essential for organism
survival
Molecule – made up of atoms
Most molecules belong to 1 of 4 categories:
 Carbohydrates
 Proteins
 Nucleic
acids
 Lipids (fats)
Molecules and Life
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Molecules from these categories:
 Are
used to build cells
 Store energy
 Regulate cell activities
 Store genetic information
Carbohydrates
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Sugars and starches
They are made of only carbon, hydrogen, and
oxygen atoms
Simple sugar: glucose (C6H12O6)
Other examples: cellulose, starch, glycogen
Proteins
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They are very diverse and involved in almost
everything a living cell does!
They may:
 Store
food
 Fight disease (antibodies)
 Help your muscles move
 Enzymes
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Made up of amino acids
There are 20 common amino acids (the
arrangement is important, especially for enzymes)
Nucleic Acids
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How does a cell know which amino acids to line up
to build the proper protein? This information is
stored in the cell’s DNA
Nucleic acids contain all the instructions that living
cells need to make proteins and maintain life.
Made up of smaller molecules: nucleotides
Two major kinds of nucleic acids:
 DNA
 RNA
Nucleic Acids
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Three things you need to know about nucleic acids:
 The
arrangement of the nucleotides in DNA forms a
code
 The DNA code determines which amino acids will be in
a protein
 The RNA helps in protein synthesis by using the coded
instructions in DNA
Lipids
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Fats and lipids are the same things
Too much can be unhealthy…but they are important
to maintaining good health.
It serves as energy storage
Membranes contain lipids
Lipid molecules in a membrane:
 Structural
 Communicative
 Transportive
Warm-up
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What are cell membranes?
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Get out a sheet of paper and tell me what you know
about them. You may use your book!
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(Chapter 4)
Membranes
 Each
cell is surrounded by a cell membrane, a thin
covering that forms the outer boundary of the cell
 Membranes sense and respond to changes in the
surrounding environment
 Membrane structure:
Composed of molecules of lipids and proteins
 The most accurate model: Fluid mosaic model
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Lipid molecules form a flexible (fluid), two-layered film in which
proteins are embedded
Membrane Properties
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Selective Permeability:
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This means only certain molecules can go through the
cell membrane
Molecules of water, oxygen, and carbon dioxide are
small enough to pass, but others are too large (starch
and protein)
One of the main ways that substances can pass through
is by passive transport
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Movement of substances across a membrane without using
energy
Membrane Properties
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Diffusion
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Osmosis
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A movement of molecules from an area of high
concentration to low until it reaches equilibrium
The diffusion of water through a selectively permeable
membrane
Active transport
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Another way substances move across the membrane –
but REQUIRES ENERGY!
Movement from area of low concentration to high OR
when molecules are too big to pass
Leeuwenhoek
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Let’s read the Facet together…
The Father of Microscopy
He called the organisms he viewed “animalcules” (or
beasties)
COMPLETE SR P. 54 #1-5
COMPLETE IDEAS 4A & 4B
Answer the following ?’s
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The thin covering that cells have is the ___________
Name the membrane model that is considered to be
the most accurate.
What did Leeuwenhoek call the organisms he views
with his microscopes?
Does osmosis require a cell to expend energy?
What type of transport requires energy?
Typical Parts of Cells
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Cell are like tiny factories in many ways
Factories have: headquarters, power supplies,
manufacturing equipment, clean-up crews, and
shipping departments
All cells have three basic parts:
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Cellular boundaries
The cytoplasm
Genetic material
Typical Parts of Cells
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Cell boundaries
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Plants – cell walls
Animal cell – cell (plasma) membrane
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Cytoplasm
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Keep things in and out; controls what allows to go in and out
A thick fluid that contains many organelles
Organelles – the parts of the cell that perform many
functions needed to keep the cell alive
Genetic Material
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Nucleus – compact, roundish structure that functions as the
control center of the cell. This contains the genetic info
(DNA)
Typical Parts of Cells
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Organelles in the Cytoplasm:
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Mitochondria – the cell’s powerhouse; site of energy
production
Typical Parts of Cells
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Organelles in the Cytoplasm:
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Endoplasmic Reticulum – ER for short; a maze of
passageways; it connects the nucleus to the cell
membrane; functions as the cell’s delivery system.
Typical Parts of Cells
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Organelles in the Cytoplasm:
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Ribosomes – tiny organelles directing the assembling of
proteins; serve as major building materials of cells;
scattered throughout the cytoplasm or attached to the
ER; These make PROTEINS!
Typical Parts of Cells
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Organelles in the Cytoplasm:
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Golgi Apparatus – chemicals from the cytoplasm are
collected here; believed to be connected with the ER;
packages chemicals and distributes them throughout the
cell
Typical Parts of Cells
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Organelles in the Cytoplasm:
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Vacuoles – look like bubbles and serve as containers
inside the cytoplasm of some cells; may contain food,
water, wastes, fats, or chemicals being
Typical Parts of Cells
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Organelles in the Cytoplasm:
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Lysosomes – tiny-enzyme filled capsules; circulate in the
cytoplasm and us their enzymes as a demolition crew;
dissolve away cellular structures not needed; also help
keep foreign invaders out.
Typical Parts of Cells
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Organelles in the Cytoplasm:
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Chloroplasts – ONLY IN PLANT CELLS; contain
chlorophyll (which captures energy from sunlight and
the energy is then used to make sugar through a
process called photosynthesis)
Typical Parts of Cells
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Organelles in the Cytoplasm:
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Nucleus – compact, roundish structure; functions as the
control center; contains genetic information of the cell;
surrounded by a nuclear membrane; contains
chromosomes (composed of DNA)
Typical Parts of Cells
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Cilia and Flagella
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Cilia – short, hair like structures on the outer part of a
cell
Flagella – a single, whiplike tail
Both provide for movement
Cellular Organization
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Most cells need other cells to survive
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Exception: paramecium; unicellular; feeds itself
Larger organisms divide the functions they need to
survive among many cells.
Tissue: a group of cells working together to
perform a specific function
Organ: groups of different kinds of tissues that
work together to accomplish a particular function
There is a division of labor among the tissues and
organs or multicellular organisms
Cellular Respiration
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Cellular respiration – the breakdown of an energy
source (sugar) by cells to obtain useable energy.
This process requires many enzymes, which serve as
catalysts
Catalysts – substances that help change other
substances without being permanently changed
themselves
Cellular Respiration
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Sugar is the most common energy source in cellular
respiration
It takes place in the cytoplasm and mitochondria
Sugar + oxygen  carbon dioxide, water, and
energy.
Two types of cellular respiration:
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Aerobic respiration – requires oxygen; make more
useable energy
Anaerobic respiration – no oxygen
Cellular Respiration
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Two types of anaerobic respiration (fermentation):
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Alcoholic fermentation
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Bread dough rising; leaven; yeast
Lactic acid fermentation
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Yogurt, cottage cheese, buttermilk
Muscles – lactic acid build up can cause muscle soreness
Photosynthesis
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The process that most producer organisms use to
change light energy into chemical energy (producer
organisms make their own food)
Carbon dioxide + water + light energy  sugar +
oxygen
Light is changed to energy (sugar)
Occurs in the chloroplast, which contain chlorophyll
Chlorophyll, a green pigment, that absorbs light
energy and uses it to power photosynthesis.
Photosynthesis
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Chloroplasts:
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Have two membranes
Contains things that look like stacks of coins