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Basic Structure of a Cell

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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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ORGANS ORGAN SYSTEMS

ORGANISM

Different tissues working together

Different organs working together

More Living Levels

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CELL THEORY

1.Cells are the basic unit of structure and function in an organism (basic unit of life)

2. Plants and animals are made of cells

3. Cells come from the reproduction of existing cells (cell division)

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History of Cells & the Cell Theory

Cell Specialization

Scanning Electron Microscope

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Scanning Electron Microscope-scans the surface detail or organisms

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Transmission Electron Microscope

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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, etc.

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Cell Size and Types

• Cells, 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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CELL SIZE

Typical cells range from 5 – 50 micrometers (microns) in diameter

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Which Cell Type is Larger?

_________ > _____________ > ___________ Plant cell Animal cell Bacteria

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Multicellular Organisms

• Cells in multicellular organisms often specialize (take on different shapes & functions)

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Cell Specialization

• Cells in a multi-cellular organisms 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

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Specialized Plant cells

Xylem cells Pollen

Guard Cells

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Prokaryotes – The first Cells • Cells that lack a nucleus or membrane-

bound organelles

• DNA in a region of the cell (nucleoid region)

• Plasmid – circular chromosome found in some bacteria

• Surrounded by cell memb, cell wall, and sometimes a capsule

• Include bacteria…super simple cells

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Prokaryotes

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Eukaryotes • Cells that HAVE

-a nucleus

-membrane-bound organelles

- larger in size

• Includes protists, fungi, plants, and animals

• More complex type of cells

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Two Main Types of Eukaryotic Cells

Plant Cell Animal Cell

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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 (surrounded by a membrane)

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Animal Cell Organelles

Nucleolus

Nucleus

Nuclear envelope

Ribosome (attached)

Ribosome (free)

Cell Membrane

Rough

endoplasmic

reticulum

Golgi apparatus

Mitochondrion

Smooth

endoplasmic

reticulum

Centrioles

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Plant Cell Organelles

Bacterial Cell

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Plant vs. Animal vs. Bacteria Cells Plant Animal Bacteria

Eukaryotic (nucleus) Has a cell wall made of cellulose Have chloroplasts No centrioles Contain large central vacuole

Eukaryotic(nucleus) No cell wall No chloroplasts Has centrioles for cell division No major vacuole

Prokaryotic (no nucleus) – nucleoid region Has a cell wall made of peptidoglycan No chloroplasts No centrioles No membrane bound organelles No vacuoles

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• Nonliving layer • Found in plants, fungi, &

bacteria • Made of cellulose in

plants • Made of peptidoglycan

in bacteria • Made of chitin in fungi

Cell wall Cell Wall

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Cell or Plasma Membrane

Outside of cell

Inside of cell (cytoplasm)

Cell membrane

Proteins

Protein channel Lipid bilayer

Carbohydrate chains

• Composed of double layer of phospholipids and proteins

• Surrounds outside of ALL cells

• Controls what enters or leaves the cell

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• Lies immediately against the cell wall in plant cells

• Pushes out against the cell wall to maintain cell shape

Cell Membrane in Plants Cell membrane

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• Jelly-like substance enclosed by cell membrane

• Provides a medium for chemical reactions to take place

• Contains organelles to carry out specific jobs

• Found in ALL cells

Cytoplasm of a Cell

cytoplasm

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• Controls the normal activities of the cell b/c…

It contains DNA in the form of chromosomes

The Nucleus

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AND…genes control what proteins are made in the cell

Nucleus

More on the Nucleus

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Nuclear Envelope • Double membrane surrounding

nucleus

• Also called nuclear membrane

• Contains nuclear pores for materials to enter & leave nucleus

• Connected to the rough ER

Nuclear pores

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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 CHROMOSOMES in dividing cells

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What Does DNA do?

DNA is the hereditary material of the cell

• DNA made of many genes • Each gene “codes” for a

specific protein

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Nucleolus • Inside nucleus

• Makes ribosomes

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Ribosomes

• Made of PROTEINS and ribosomal RNA (rRNA)

• Where protein synthesis occurs (the making of proteins)

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Ribosomes

Can be attached to Rough ER

OR

Be free (unattached)

in the cytoplasm

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Cytoskeleton

• Helps cell maintain cell shape

• Also help move organelles around

• Made of proteins (microtubules & microfilaments)

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Cytoskeleton

MICROTUBULES

MICROFILAMENTS

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Centrioles

• Found only in animal cells

• Paired structures near nucleus

• Made of bundle of microtubules

• Appear during cell division

• Help to pull chromosome pairs apart to opposite ends of the cell during cell division

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Centrioles & the Mitotic Spindle

Made of MICROTUBULES (Tubulin)

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Mitochondrion (plural = mitochondria)

• “Powerhouse” of the cell

• Where cellular respiration occurs (where sugar is broken down to make ATP)

• More active cells like muscle cells have MORE mitochondria

• Both plants & animal cells have mitochondria

• Mitochondria have their own DNA

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MITOCHONDRIA

Surrounded by a DOUBLE membrane

Folded inner membrane called CRISTAE (increases surface area for more chemical reactions) Interior called MATRIX

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Endoplasmic Reticulum - ER

Two kinds of ER ---ROUGH & SMOOTH

• Network of hollow membrane tubules

• Helps with the production of proteins and transports materials through the cell.

• Connects to nuclear envelope & cell membrane

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Rough Endoplasmic Reticulum (Rough ER)

• Has ribosomes on its surface

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Rough Endoplasmic Reticulum (Rough ER)

• Proteins are made by ribosomes on ER surface

• They are then threaded into the interior of the Rough ER to be modified and transported

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Smooth Endoplasmic Reticulum

• Smooth ER lacks ribosomes on its surface

• Is attached to the ends of rough ER

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Functions of the Smooth ER

• Carbohydrate metabolism

• Makes membrane lipids (steroids)

• Regulates calcium (muscle cells)

• Destroys toxic substances (Liver)

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Endomembrane System

Includes nuclear membrane connected to ER connected to cell membrane (transport)

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Golgi Bodies • Stacks of flattened sacs

• Have a shipping side and receiving side

• Receive proteins made by ER

• Modify, sort, & package

molecules from ER

for storage within the cell OR

for transport out of cell

Transport vesicle

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Golgi Bodies

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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-digesting machines • Contain digestive enzymes.

• Break down food, bacteria, and worn out cell parts for cells

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Lysosome Digestion

• Cells take in food by phagocytosis

• Lysosomes digest the food & get rid of wastes

http://learn.genetics.utah.edu/content/begin/cell

s/insideacell/

Peroxisomes • Similar to lysosomes

• Membrane bound and have enzymes that break down toxic materials in the cell

• By-product of their breakdown is Hydrogen peroxide (H2O2) which they then break down into water and oxygen.

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Cilia & Flagella • Function in moving

cells, in moving fluids, or small particles across the cell surface

• Cilia are shorter and more

numerous on cells

• Flagella are longer and fewer (usually 1-3) on cells

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Cell Movement with Cilia & Flagella

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Cilia Moving Away Dust Particles from the Lungs

Respiratory System

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Vacuoles

• Plant cells have a large central vacuole

• Includes storage of sugars, proteins, minerals, lipids, wastes, salts, water, and enzymes

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Contractile Vacuole

• Found in unicellular protists like paramecia

• Regulate water intake by pumping out excess (homeostasis)

• Keeps the cell from lysing (bursting)

Contractile vacuole animation

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Chloroplasts • Use energy from sunlight to

make own food (glucose) - photosynthesis

• Inner membrane modified into sacs calledThylakoids

• Thylakoids in stacks are called Grana …which are connected

• Stroma – gel like material surrounding thylakoids

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Chloroplasts

• Never in animal or bacterial cells

• Chloroplasts contain their own DNA

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Cell to Cell Interactions • Gap Junctions

• Tight Junctions

• Desmosomes

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Gap Junctions

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• Gap junctions (yellow) are clusters of channels that form tunnels of aqueous connectivity between cells.

• These permit the free passage of ions and small molecules between cells (ex: nerve impulse through heart muscle cells)

Tight Junctions • Tight junctions (blue dots)

between cells are connected areas of the plasma membrane that stitch cells together.

• They prevent the passage of molecules and ions through the space between cells. So materials must actually enter the cells (by diffusion or active transport) in order to pass through the tissue.

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Desmosomes • Desmosomes are even stronger connections that join the

intermediate filaments of neighboring cells.

• Desmosomes are localized patches that hold two cells tightly together. They are common in epithelia (e.g., the skin)

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Bacterial Cell • Know this diagram and what each thing is!

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Bacterial Cells • Bacteria cells have 3 major shapes: coccus (round), bacillus

(rods), and spirilla (coils).

• Bacterial cells can be arranged in different patterns including: strepto (chains), staphylo (clusters), palisades (hinged together), diplo (groups of 2), tetrads (groups of 4), or sarcina (groups of 8, 16 or more).

• Bacteria are classified and named based upon their genetic structure, physical structure, and metabolism

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Bacterial Growth Curve • There are 4 phases in the bacterial growth cycle: lag,

log, stationary, and death.

• Factors that impact microbial growth and survival include: nutrient availability, temperature, pH, moisture, oxygen requirements and light.

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Bacterial Phases • Lag Phase – getting accustomed and starting to eat

food/haven’t started to reproduce

• Log/Exponential phase – taking in nutrients and reproducing

• Stationary phase- no change in number of bacteria - # birth=#death. Bacteria are running out of resources

• Decline/Death phase - accumulation of waste products and depletion of nutrients so bacteria start dying.

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Gram Staining Bacteria • Procedure used to identify different types of bacteria

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Gram Staining

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Bacteria that retain the color of the dye are called Gram positive; bacteria that don't are Gram negative. The diagram to the right shows Gram-positive Staph aureus at the top and Gram-negative

Pseudomonas aeruginosa at the bottom