basic structure of a cell...basic structure of a cell adapted from work of cmassengale 1. main...
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Basic Structure of a Cell
1Adapted from work of CMASSENGALE
Main Characteristics of Living Things
1. Made of CELLS
2. Maintain HOMEOSTASIS
3. METABOLISM (produce and/or use energy)
4. RESPOND to stimulus
5. REPRODUCTION at species level
6. HEREDITY (DNA)
7. GROW and DEVELOP
8. EVOLVE as a species over generations
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LEVELS OF ORGANIZATIONNonliving Levels:
1. ATOM (element)
2. MOLECULE (compounds like carbohydrates &
proteins)
3. ORGANELLES (nucleus, ER, Golgi …)
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LEVELS OF ORGANIZATIONLiving Levels:
1. CELL (makes up ALL organisms)
2. TISSUE (cells working together
3. ORGAN (heart, brain, stomach …)
4. ORGAN SYSTEMS (respiratory, circulatory …)
5. ORGANISM
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LEVELS OF ORGANIZATIONLiving Levels continued:
1. POPULATION (one species in an area)
2. COMMUNITY (several populations in an area
3. ECOSYSTEM (forest, prairie …)
4. BIOME (Tundra, Tropical Rain forest…)
5. BIOSPHERE (all living and nonliving things on Earth)
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History of Cells & the Cell Theory
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Cell Specialization
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First to View Cells•In 1665, Robert Hooke used a microscope to examine a thin slice of cork.
•Cork consists of dead plant cell walls.
•What he saw looked like small boxes.
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First to View Cells
•Hooke is responsible for naming cells.
•Hooke called them “CELLS” because they looked like the small rooms that monks lived in called cells.
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Anton van Leeuwenhoek•In 1673, Leeuwenhoek(a Dutch microscope maker), was first to view organism (living things)
•Leeuwenhoek used a simple, handheld microscope to view pond water & scrapings from his teeth
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Beginning of the Cell Theory
• In 1838, a German botanist named Matthias Schleidenconcluded that all plants were made of cells
• Schleiden is a cofounder of the cell theory
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Beginning of the Cell Theory• In 1839, a German zoologist named Theodore Schwannconcluded that all animals were made of cells
• Schwann also cofounded the cell theory
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Beginning of the Cell Theory
• In 1855, a German medical doctor named Rudolph Virchow observed, under the microscope, cells dividing.
• He reasoned that all cells come from other pre-existing cells by cell division.
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CELL THEORY
• All living things are made of cells.
• Cells are the basic unit of structure and function in an organism (basic unit of life.)
• Cells come from the reproduction of existing cells (cell division.)
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Cell Size and TypesCells, the basic units of organisms, can only be observed under microscope.
Three basic types of cells include:
Animal Cell Plant Cell Bacterial Cell
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Number of Cells
Although ALL living things are made of cells, organisms may be:
Unicellular – composed of one cell
Multicellular- composed of many cells that may organize into tissues, organs, and so on.
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CELL SIZE
Typical cells range from 5 – 50 micrometers (microns) in diameter
Which Cell Type is Larger?
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> > Plant cell Animal cell Bacteria
What Cells Look Like
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Multicellular Organisms
Cells in multicellular organisms often specialize (take on different shapes and functions.)
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Cell Specialization
• Cells in a multi-cellular organism become specialized by turning different genes on and off
• This is known as DIFFERENTIATION
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Specialized Animal Cells
Muscle cells Red blood cells
Cheek cells
Organization Levels of Life
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Atoms to Organisms
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ATOMS ���� MOLECULES ���� ORGANELLES
Nonliving Levels
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CELLS –
life starts here
TISSUES –
Similar cells working together
Living Levels
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ORGANSORGAN
SYSTEMSORGANISM
Different tissues
working together Different organs
working together
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More Living Levels
Different organ systems
working together
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Simple or Complex Cells
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Prokaryotes – the first cells
• Cells that lack a nucleus or membrane-bound organelles
• Includes bacteria
• Simplest type of cell
• Single, circular chromosome
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Eukaryotes
• Cells that HAVE a nucleus and membrane-bound organelles
• Includes protists, fungi, plants, and animals
• More complex type of cells
Two Main Types of Eukaryotic Cells
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Plant Cell Animal Cell
Organelles
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Organelles
• Very small (microscopic)
• Perform various functions for a cell
• Found in the cytoplasm
• May or may not be membrane-bound
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Animal Cell Organelles
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Nucleolus
Nucleus
Nuclear envelope
Ribosome (attached)
Ribosome (free)
Cell Membrane
Rough
endoplasmic
reticulum
Golgi apparatus
Mitochondrion
Smooth endoplasmic
reticulum
Centrioles
Plant Cell Organelles
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• Composed of double layer of phospholipids interspersed with proteins (phospholipid bilayer)
• Surrounds cytoplasm of ALL cells
• Controls what enters and leaves the cell
Cell or Plasma Membrane
Outsideof cell
Insideof cell(cytoplasm)
Cellmembrane
Proteins
Proteinchannel Lipid bilayer
Carbohydratechains
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The Cell Membrane is Fluid
Molecules in cell membranes are constantly moving and changing.
COPYRIGHT CMASSENGALE 36
Cell Membrane Proteins
• Proteins help move large moleculesor aid in cell recognition
• Peripheral proteins are attached on the surface (inner or outer)
• Integral proteins are embedded completely through the membrane
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Cell Membrane in Plants
• Surrounds the
cytoplasm
• Pushes out against
the cell wall to
maintain cell shape
Cell membrane
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Cell Wall
• Supports and protects cell
• Found outside of the cell membrane
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Permeability Permeable: allowing substances to pass through
• Cell walls are semi-permeable based on molecule size.
• Cell membranes are selectively permeable based on
molecule recognition.
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Cytoplasm of a Cell
• Jelly-like substance
enclosed by cell
membrane
• Provides a medium
for chemical reactions
to take place
cytoplasm
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More on Cytoplasm
• Contains organelles to
carry out specific jobs
• Found in ALL cells
cytoplasm
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The Control Organelle - Nucleus
• Controls the normal
activities of the cell
• Contains the DNA in
chromosomes
• Bounded by a
nuclear envelope
(membrane) with pores
• Usually the largest
organelle
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More on the Nucleus
• Each cell has fixed
number of
chromosomes that
carry genes
• Genes control cell
characteristics
Nucleus
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Nuclear EnvelopeDouble membranesurrounding nucleus
Also called nuclear membrane
Contains nuclear poresfor materials to enter & leave nucleus
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Inside the Nucleus -
The genetic material (DNA) is found
DNA is spread out
And appears as
CHROMATIN
in non-dividing cells
DNA is condensed &
wrapped around proteins
forming
as CHROMOSOMES
in dividing cells
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What Does DNA do?DNA is the hereditary material of the cell
Genes that make up the DNA
molecule code for different
proteins (which means you)
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Nucleolus
Inside nucleus
Cell may have 1 to 3nucleoli
Disappears when cell divides
Makes ribosomes that make proteins
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CytoskeletonHelps cell maintain cell shape
Also help move organellesaround
Made of proteins
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Centriole
Found only in animal cells
Found near the nucleus
Centrioles:
Made of bundle of microtubules
Found in pairs
Form the mitotic spindle during cell division
Help to pull chromosome pairs apart
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Centrioles and the Mitotic Spindle
Made of MICROTUBULES (Tubulin)
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Mitochondrion(plural = mitochondria)
“Powerhouse” of the cell
Generate cellular energy (ATP)
More active cells like muscle cells have more mitochondria
Both plants and animal cells have mitochondria
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Mitochondria
Surrounded by a double outer
membrane
Has folded inner membrane
Rod shape
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Fact… Mitochondria come from cytoplasm in the egg cell during fertilization
Therefore …
You inherit your mitochondria (and mitochondrial DNA) from your mother
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Endoplasmic Reticulum - ERNetwork of hollow membranes
Connects to nuclear envelope and cell membrane
Functions in synthesis and transport of cell products
Two kinds of ER ---ROUGH & SMOOTH
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Rough ER
Has ribosomes on its surface
Makes, stores, and transports proteins
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Rough ER
Proteins are made by ribosomes on ER surface.
They are then threaded into the interior of the rough ER to be transported.
Examples:
•digestive enzymes stored in sacs until transported out of the cell
•proteins created and placed into cell’s membrane
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Smooth ER
Smooth ER lacks ribosomes on its surface.
Attached to the ends of rough ER.
Most cells have very little smooth ER.
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Functions of the Smooth ER
Functions:
•Makes lipids (fats)
•Makes steroids (in ovaries and testes makes estrogen and testosterone)
•Regulates calcium (heart and skeletal muscle, controls contractions)
•Detoxifies drugs and poisons (liver and kidney; contributes to drug tolerance)
COPYRIGHT CMASSENGALE 60
RibosomesMade of PROTEINS and rRNA
“Protein factories” for cell
Join amino acids to make proteins
Process called protein synthesis
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Ribosomes
Can be attached to Rough ER
(eukaryotic)
OR
Be free (unattached) in the cytoplasm
eukaryotic and prokaryotic
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Golgi Bodies
Stacks of flattened sacs
Receive proteins made by ER
Transport vesicles received by side nearest the nucleus and/or ER, passed through membranes, and exit the opposite side.
Transport
vesicles
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Golgi Bodies
Look like a stack of pancakes
Modify, sort, package, and label
molecules from ER for storage OR transport out of cell
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Golgi Animation
Materials are transported from Rough ER to Golgi
to the cell membrane by VESICLES
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Lysosomes
Bud from the golgi body
Membrane bound sacs
Contain digestive enzymes
Break down large molecules:• liver: break down glycogen for release of glucose into bloodstream
• white blood cells: break down bacteria
• digest worn out cell parts
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Lysosomes
Suicide SacsWhen it is time for a cell to die, lysosomes lyse (break open) themselves.
This results in the breakdown and digestion of the entire cell.
This “programmed cell death” is called autolysis and is critical to
maintaining and organism's health.
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Vacuoles
Fluid filled sacs for storage
Plant cells have a large Central Vacuole
Small or absent in animal cells
No vacuoles in bacterial cells
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Central Vacuole
Central vacuole stores mostly water and can take up 90% of the interior of a plant cell
In addition to water, they can also contain enzymes and wastes
Examples: ◦ Acacia trees store poisons◦ Tobacco plants store nicotine
Presence means it is
a plant cell
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Chloroplasts
Found only in plants
Use light energy to combine CO2 and water to make glucose (sugar)
Each chloroplast:
System of flattened membranous sacs called thylakoids
Thylakoids contain chlorophyll
Chlorophyll is the molecule that absorbs light energy
Chloroplasts can only arise by dividing existing chloroplasts
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Cilia and Flagella
Function in moving cells, in moving fluids, or detection of vibration.
Composed of microtubules
• Cilia are short and numerous
• Flagella are longer and fewer in number
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Cilia and Flagella
Bacteria
Sperm
Inner ear
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Cilia move like oars
Flagella move like a whip
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Cell Size
Cell size varies, but only within
a relatively small margin… the
size of an elephant cell is
approximately the same size of
a mouse cell.
Two important factors affecting cell size:
1. Type
2. Surface area to volume ratio
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Surface Area to Volume Ratio
Surface area (cell membrane surface) of a cell is important to allow nutrients in and to remove wastes
Volume of a cell is where all the life processes happen
Math dictates that volume increases FASTER than surface area
When the volume of the cell exceeds the membrane’s ability to regulate nutrients and wastes, the cell is too big and must divide
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Surface Area to Volume Ratio
The cell type can affect the surface area to volume ratio
The cell type is related to cell shape
Different shapes allow for different sizes, but the RATIO REMAINS WITHIN NARROW LIMITS