CELL STRUCTURE AND
FUNCTION
Life Science Chapter 2
Chemistry of Life
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All matter is made up of atoms
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Matter is anything that has mass and takes up space
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Gas, liquid, solids
Atoms have a nucleus
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Center of atom
Contains protons (+) and neutrons (0)
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Around the nucleus are electrons (-)
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The number of protons in the atom determines what element it is
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The number of electrons determines its chemical properties
Organization is a characteristic of living
things
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Atoms  molecules
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Molecules  organelles
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Organelles  cells
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Cells  tissues
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Tissues  organs
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Organs  organ systems
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Organ systems  organisms
Elements
• Periodic Table
• An element is an atom with a certain number of protons
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All atoms in the universe with 1 proton are called Hydrogen
• The number of protons an atom has is called its atomic number
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Hydrogen is then atomic number 1
• If the number of protons changes, the element changes
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It is no longer the same element
• Electron and neutron numbers can change in an element
• A neutral atom has equal numbers of protons and neutrons
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If an atom loses or gains electrons, it gains a charge
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If it gains an electron, it becomes more negative (more of a negative charge)
If it loses electrons, it becomes positive (less negative charges)
Example
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Sodium (Na) is atomic number 11 because it has 11 protons
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When neutrally charged, it will have 11 electrons
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However, Sodium really wants to lose an electron
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When it loses that electron, it will have 11 protons and 10 electrons
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It will be positively charged
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Chlorine (Cl) is atomic number 17 because it has 17 protons
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Has 17 electrons when neutral
However, it really wants one more electron (again, not discussed here)
When it gains an electron, it will have 17 protons and 18 electrons
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Charged atoms are called ions
It is negatively charged
Like magnets, charged atoms attract
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Sodium and chlorine attract and form sodium chloride (NaCl)
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Also called table salt
Elements in Organisms
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Oxygen~61%
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Carbon~23%
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Hydrogen~10%
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Nitrogen~2.6%
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Calcium~1.5%
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Phosphorus~1.1%
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Other-Less than 1%
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Called Trace elements
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Still important, but found in lower amounts
How to remember: Our Cooks Have No Cakes or Pies
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1st letters are the chemical symbol of the element
Atoms to molecules
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Salt is an example of a molecule
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Water is the most important molecule to organisms
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Molecules are made up of atoms bonded together
Water is required for many of the chemical reactions that take place in organisms
Cells are mostly water.
Large molecules are called macromolecules
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4 important ones for life
Lipids
• Proteins
• Carbohydrates
• Nucleic Acids
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Properties of Water
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Water is a polar molecule
• It has areas of positive charge (the hydrogen atoms) and areas of
negative charge (the oxygen atom)
• This charge attracts ions
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Sodium and chloride break apart easily in water
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Salt water
As do sugar molecules
Water molecules also like to bond to other water molecules (called
cohesion)
• Causes surface tension
Structure of Macromolecules
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The 4 main macromolecules are large molecules
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Made up of chains of smaller molecules
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Think train made up of carts
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The large molecules are called polymers (poly=many)-The train
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The smaller molecules are called monomers (mono=one)-The carts
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The monomers are held together by bonds
Lipids
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Fats, oils, steroids
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Do not dissolve in water
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Make up the cell membrane
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Energy storage
Proteins
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Important for many cell processes
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Also help build cell structures
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Monomers are amino acids
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Proteins have a unique 3-D structure that determines their role
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Enzymes are important proteins that assist with chemical reactions
Carbohydrates
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Provide energy
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Sugars, starches
Nucleic Acids
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The most important macromolecules
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Monomers are nucleotides
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DNA, RNA, and ATP are all nucleic acids
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DNA is the material passed from parents to children and contains the instructions for
the organism’s features
RNA is used to manufacture proteins
ATP provides the cell with energy to do nearly everything
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Much, much more to come on these 3 molecules, so learn them now!
The Cell Theory
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Recall: Theory in science=explanation
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Explains what cells are, what they do, and where they come from
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4 scientists contributed: Robert Hooke, Matthias Schleiden, Theodor Schwann,
and Rudolf Virchow (Guaranteed Matching question on Test)
Robert Hooke
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1635-1703 (You will not need to know
dates)
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English philosopher and scientist
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Looked in a microscope at cork and
discovered small spaces
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Called them cells
Laid the foundation for cell theory
more than 100 years before others
Matthias Schleiden
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1804-1881
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German botanist (studied plants)
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Discovered that plants are all made
up of cells
Theodor Schwann
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1810-1882
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German physiologist (studied how
the body works)
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Discovered that all animals are made
up of cells
Rudolf Virchow
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1821-1902
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German doctor
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Discovered that all cells come from
other cells
Recap
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Hooke-Named cells
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Schleiden-Plants are made of cells
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Schwann-Animals are made up of cells
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Virchow-Cells come from cells
How do we see cells?
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Microscopes
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The ones we use are called Light
Microscopes
Pass light through the image
• The light is then collected by 2 different
lenses and becomes magnified
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Antonine van Leeuwenhoek
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Improved the microscope so that it
could be used in biology
First to observe microorganisms that
can not be seen without one
1. Ocular Lens (Eyepiece)
• This is what you look through to see the image.
• It contains a lens (usually 10x magnification)
2. Arm
• Structural piece
• Holds the parts of the microscope in the proper places.
• THE ARM IS NOT A HANDLE
• Never carry the microscope by the arm alone.
• One hand around the arm, the other hand underneath the
base to support it.
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Microscopes are very expensive. Use the utmost care when
transporting it.
3. Stage
• This is the flat portion where you put the slide.
• A hole in the stage allows light to pass through the
slide
4. Course Focus
• Moves the stage up and down.
• Doing so brings the object into focus.
• Move it until the image becomes visible. It will still be a bit
blurry.
• Note about the Course Focus: Using the course focus to
try to get a better image could result in the stage
moving the slide up into the objective. This could crack
the slide and/or objective lens, and could be a VERY
expensive mistake.
5. Fine Focus
• Makes tiny adjustments to the stage.
• Once you have found the image, use the fine focus to
make it clear.
6. Base
• Bottom of the microscope.
• Structural and support.
• Remember, one hand underneath the base and the
other holding the arm.
7. Light Source
• A light bulb
• Sends light through the slide.
8. Diaphragm
• Allows you to adjust the amount of light that comes
through.
9. Slide Clips
• Little metal pieces that hold the slide in place.
• Make sure that the slide is under the clips.
• You do not want the slide moving after you have just found
the image
10. Objectives
• Each is a different lens that magnifies the image.
• Most microscopes have several of these ranging from 4x to
200x
• Begin on the lowest objective to find the image, then increase
to zoom it in.
11. Rotating Nosepiece
• Holds the objectives
• Twist to change magnification.
12. Body Tube
• Holds eyepiece
Magnification
• Magnification is the product of the magnifications of the
eyepiece and the objective lenses
• Eyepiece x Objective= Total Magnification
• Example: Eyepiece 10x and objective 20x
• 20x10=200x magnification
Cell Types
• 2 major categories of cells
• Prokaryotic Cells
Bacteria and Archaea
• No organelles, including nucleus
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• Eukaryotic Cells
Protists, Plants, Fungi, and Animals
• Contains organelles, including nucleus
• Much more complicated
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• Organelles (small organs)
• Like organs to our body
• Each does a job for the cell
• All work together
Protection and Support
• All cells have a cell membrane
• Flexible boundary between cell and its environment
• Made up of proteins and lipids
• Protects the cell, gives it shape, and allows materials to enter
and exit the cell
• Plant cells, and some fungi, protists, and bacteria, also have a
cell wall
• Outside of the cell membrane
• Very rigid
• More protection
Cell Appendages
• Some cells have things attached to them that do a job
• Flagella are whip-like structures that work as a motor for the cell
• Spins and allows the cell to move
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Not common in humans except on sperm, very common in unicellular
organisms
• Usually 1 or 2
• Cilia are numerous, hair-like structures
• Work like a row team and move cell
• Also work to remove foreign materials
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Found in respiratory tract. Removes dust, pollen, and other materials
before they reach the lungs
• Hundreds on cells that contain them
Cellular Structure
• Cells are filled with a jelly-like substance called cytoplasm
• Function: Contains materials for the cell and holds organelles in
place
• Found in: All cells
• Throughout the cytoplasm are proteins that act as “bones”
• Called the cytoskeleton
• Does similar job to our skeleton
Function: Protection, support, allows some cells to move
• Found in all eukaryotic cells
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• Centrioles
• Function: help cells divide
• Found in animal cells (very few plants, fungi, protists have them)
• Made of the same material as cytoskeleton
The Nucleus
• Function: The control center for the cell
• Function: Contains DNA
• The DNA is in the form of chromosomes (more to come later)
• Found in all eukaryotes
• Also contains another organelle called the nucleolus
• Function: forms ribosomes
• Found in all eukaryotes
Manufacturing Organelles
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Ribosomes
• Function: Make proteins
• Can be free-floating in the cytoplasm or attached to the rough
endoplasmic reticulum (RER)
• Made in the nucleolus
• Found in all cells, prokaryotic and eukaryotic
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Rough Endoplasmic Reticulum (RER)
• Studded with ribosomes
• Function: Site of chemical reactions
• Found in all eukaryotic cells
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Smooth Endoplasmic Reticulum (SER)
• Function: Makes lipids and helps remove toxins from the cell
• Found in all eukaryotes
Energy Organelles
• Mitochondria
• The powerhouse of the cell
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Function: Converts sugars to chemical energy, manufactures ATP for
use in other processes
• Found in all eukaryotic cells
• Chloroplasts
• Function: Convert sunlight to sugars
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These sugars are used in mitochondria to make ATP
• Found in Plants and some protists (also some bacteria), never
in animals
• GREEN
Processing, Transportation, Cleaning
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Golgi apparatus
• Post office of cell
• Function: Packages and ships proteins
• Found in all eukaryotes
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Vesicles
• The mail trucks
• Function: Transport of proteins and other materials
• Found in all cells
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Lysosomes
• The cell’s cleaners
• Function: capture and destroy particles in the cell, clean up wastes and broken
down cell parts
• Found in all eukaryotes
Storage and Cell division
• Vacuoles
• Function: Store materials such as water, food, wastes
• Found in all cells
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Plants usually have one large one
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Called central vacuole
Animals have many small ones