Cell Structures

By: Amber Tharpe

• Invention of the microscope was important for the discovery and study of cells

Cell Theory1.All living things are

made of cells2.Cells are the smallest

unit of life3.Cells come from other

living cells

All Cells have 3 Things

1.DNA2.Cytoplasm3.Cell membrane

Two Main Types of Cells

Prokaryotic• No nucleus

– DNA floats in cytoplasm

• No membrane-bound organelles

• All single-celled• Bacteria and

Archaea

Eukaryotic• Has a “true nucleus”

– DNA is housed there• Has membrane-

bound organelles• Single or multicellular• Plants, animals, fungi,

and protists

Cytoplasm

•Jelly-like substance containing organelles that cushions and protects the cell

Cytosol

•The fluid portion of cytoplasm minus the organelles

Cell membrane

•Double-layered membrane that surrounds cells

•Controls what goes in and out of the cell

Organelles•Structures that perform specific jobs in the cell

•Surrounded by membranes

Nucleus

• Round organelle in the center of cell

• Houses the DNA• Controls the activities of the cell• Surrounded by the nuclear

envelope–Contains pores that allow certain

materials in and out

Nucleolus

•Found inside the nucleus

•Makes ribosomes

Cytoskeleton

•Made of protein fibers•Provide structure and allow for movement

Types of Cytoskeleton

• Microtubules– Long hollow tubes– Shape, “tracks” for organelle movement, and

make fibers for cell division• Intermediate filaments

– Smaller and give cell strength• Microfilaments

– Smallest allow cells to move and divide and contact as in muscle cells

Endoplasmic Reticulum• Network of folded membranes with spaces

between• Extension of the nuclear envelope• Delivers proteins to the Golgi• Two types

– Smooth- without ribosomes• makes lipids and detoxifies the cell

– Rough- studded with ribosomes• modifies proteins

Ribosomes

• A combination of RNA and protein (no membrane)

• Site of protein synthesis• Proteins are made here• Found on rough ER and

free floating in cytoplasm

Golgi Apparatus

• Aka Golgi body or Golgi complex• Close network of membranes and

vesicles pinch off of it• Processes, sorts, and delivers

proteins • Like UPS

Vesicle

•Small membrane-bound sacs that transport substances in the cell

Endomembrane System• Connection between ER, vesicles, Golgi,

then cell membrane• Parts of the membranes of these

organelles pinch off and fuse to other parts to allow for transport in the cell

Mitochondria• Make energy for the cell in the

form of ATP• Where the process of cellular

respiration occurs• Known as the “powerhouse” of

the cell

Mitochondria

• Bean-shaped with folded inner membrane called cristae

• Also have their own ribosomes and DNA inside

• Cells like muscle cells will have more of these because they need more energy

Vacuole

• Fluid-filled sac used for storing materials

• Plant cells–Central vacuole for water storage

Lysosomes• Contain enzymes used for

digestion• Enzymes are activated in the

Golgi• Break down and recycle old cell

parts• Defends the body from bacteria

and viruses• http://www.cleanvideosearch.com/media/action/yt/watch?videoId=ekdIEpSf-1I

Centrioles

• Cylinder-shaped• Microtubules arranged in a

circle• Involved in cell division• Only found in animal cells

Cilia- in some cells

• Small hairlike projections• Allow for movement• Not found in all cells• Found in paramecium and

in respiratory tract

Flagella- in some cells

•Tail-like projections •Allow for movement•Found in sperm

Flagellum

Cell Wall

• Found in –Plants- made of cellulose–Fungi- made of chitin–Bacteria- made of peptidoglycan

• Found outside the cell membrane• Thick and inflexible (rigid)• Provides protection and shape to the

cell

Chloroplast

• Only found in plant cells• Where photosynthesis occurs• Have sacs called thylakoid

membranes containing chlorophyll

• Own ribosomes and DNA

Cell Membrane

By: Amber Tharpe

Cell Membrane

•AKA–Plasma membrane

Cell membrane

• 2 layers of phospholipids• Outer flexible boundary of cell• Controls what goes in and out

of the cell–Selectively permeable

•Allows some things to cross, while not allowing others

Phospholipids• 2 main parts

– Head• Phosphate and Glycerol• Polar (slightly charged)• Hydrophilic- loves water

– Tail• 2 fatty acid chains• Nonpolar (not charged)• Hydrophobic- hates water

Additional Parts of Cell Membrane

• Cholesterol- strengthens the membrane

• Proteins- give support and extend through one or more of the phospholipid layers to help materials cross

• Carbohydrates- serve as ID tags to enable cells to distinguish between different types of cells

Transport through cell membrane

• Depends on molecule’s:– Size – Polarity– Concentration in vs. out of the cell

• Generally– Small, nonpolar molecules pass easily– Small polar transport through proteins– Large molecules are moved in vesicles

Receptor

–Protein that detects a signal molecule (ligand) and performs an action in response

• The ligand bonding causes a change in the 3-D shape of the receptor allowing it to do its job

• http://www.cleanvideosearch.com/media/action/yt/watch?v=LwI0fz18LK0• http://www.cleanvideosearch.com/media/action/yt/watch?v=Du-BwT0Ul2M

Receptor Protein

Passive Transport

By: Amber Tharpe

Passive Transport

• Movement of molecules across a membrane, without using energy

• Usually small molecules• Types

–Diffusion–Osmosis–Facilitated diffusion

Concentration

• Amount of dissolved particles (solutes) in a solution

• Concentration gradient–Difference in concentration from 1 area to the next

Diffusion

• Movement of molecules from an area of high to low concentration

• Moves down the concentration gradient–From high to low concentration

Equilibrium

•No net reaction•Reaction occurs at the same rate forwards and backwards

Equilibrium = homeostasis

exists when the concentration of a substance is equal through out a space

Molecules continue to move

· · · · · · · ·

· · · ·

before

after

· · · ·

Osmosis

•Diffusion of water•Movement of water through a selectively permeable membrane from a high to a lower concentration

Osmosis

Types of Solutions• Isotonic

–Equal concentrations of solute in and out of the cell

–At equilibrium–Water moves in and out at an

equal rate–Cell looks normal–Ex: Grape in grape juice

Types of Solutions

•Hypertonic–More solute outside than inside the cell

–Water leaves cell–Cell shrivels and dies

Types of Solutions

• Hypotonic–Less solutes outside the cell than inside

–Water moves into the cell–Cells swell and lyse–Ex: distilled water (pure)

Turgor Pressure

• Pressure that water in the central vacuole exerts on the cell membrane of a plant which keeps it against the cell wall

• Keeps a plant from wilting

Facilitated Diffusion

• When a protein embedded in the membrane transports a substance by diffusion

If the fluid outside the cell

has…

Then outside fluid is…

Water diffuses…

Effect on cell

…more solute than inside the cell

…hypertonic. …out of cell. Cell shrinks.

…less solute than inside the cell

…hypotonic. …into cell. Cell swells.

…the same amount of solute as the cell

…isotonic. …into and out of cell at equal rates.

Cell stays the same size.

Animal Cell

Plant Cell

Active Transport

By: Amber Tharpe

Active Transport• Moves molecules from low to

high concentration• Uses energy from cell in the

form of ATP• Goes against the

concentration gradient• Moves large particles

Active Transport Examples

•Protein pumps•Endocytosis•Exocytosis

Pump

• uses energy to move molecules across the cell membrane (usually ions)

• Sodium-Potassium pump– How neurons communicate– Uses energy to pump 3 Na+ out and 2 K+ in

• Proton pump– Used in cellular respiration in the

mitochondria– Uses energy to move H+ out of the cell

Vesicles•Pinched off portions of membrane containing substances

•Used as a transport vehicle

Endocytosis

•Taking in substances by engulfing them in cell membrane

Endocytosis

Phagocytosis

• Type of endocytosis when cell membrane engulfs large particles like bacteria

• Means “cell eating”• Used by white blood cells to fight

infections

Exocytosis•Releasing substances through fusion of a vesicle with the cell membrane

Exocytosis

Animations for Transport

• http://www.northland.cc.mn.us/biology/Biology1111/animations/transport1.html