Cell Theory and Structure

Discoveries

What are Cells?

Cell Theory

Cell Structures

Organelles

Discoveries

What he saw reminded him of the rooms in a monastery, so he called what he saw under the microscope a “cell” (Latin for ‘room’)

In 1665 Robert Hooke observed a thin slice of cork from an oak tree

Discoveries

He saw living creatures that we now call single celled organisms

In 1670 Anton van Leeuwenhoek used the first “real” microscope to view pond water

What are cells?

• Cells are the smallest unit of life that can carry out all the functions of a living organism

• Cells were not discovered until the invention of the microscope

What are cells?

• Some living organisms are unicellular (only made of only 1 cell)

• They are the smallest of all living organisms

−Examples: some bacteria, many protists

−These are what Leeuwenhoek noticed under the microscope in 1670

What are cells?

Some living organisms are multicellular (made of many cells)

Examples: Plants, Animals, Fungi

What are cells?

Shape is related to Function

Blood Cell-hemocyte; round to move through vessels

Nerve-neuron; long to carry message to spinal cord

Cell Theory

• M. Schleiden 1838, botanist, “all plants are made of cells”

• T. Schwann 1839, zoologist, “all animals/organisms are made of cells”

• R. Virchow 1855, physician, “all new cells come from existing cells” (biogenesis)

Cell Theory

1. Cells are the basic units of all life

2. All organisms are made of one or more cells

3. All new cells come from existing cells

Cell Structure

• Many components make up a cell and carry out specific activities

• Each component works together with the others to keep the cell functioning

• These components are called organelles

Just as many organs work together to make your body function, organelles work together to make a cell function

• All cells have cell membranes

• All cells have genetic material:

DNA and ribosomes

• All cells have cytoplasm:

the interior portion of the cell

Common features in cells

Types of cells: Prokaryotic

• have genetic material but no nucleus.

• NO membrane bound organelles except

ribosomes

Simplest cellular organisms. Example: bacteria

Types of cells: Eukaryotic

• More complex, organized cells

• Has a true nucleus and other

organelles

• About 10X bigger than prokaryotic

cells

–Ex. - plant and animal cells

• The cells in your body are eukaryotic!

Types of Cells: Plant

Types of Cells: Animal

Organelles: Cell Membrane

Structure: Made of phospholipids and proteins

• Phospholipid bi-layer

• Semipermeable (selectively permeable)

• Hydrophilic (H2O loving) head

• Hydrophobic

(H2O fearing) tail

Organelles: Cell Membrane

Function: maintain homeostasis

• Controls what enters and leaves

• Boundary separating the cell from its environment

Organelles: Cell Wall

Structure:

• Found only in plant cells

• composed of proteins and cellulose

Function:

• Provides support and protection

• Helps maintain square shape

Organelles: Cell Wall

Organelles: Cytoplasm

Structure:

• Jelly like base throughout the cell

• consists of mainly water and cytosol (an organic compound)

• contains the cytoskeleton

Function:

• Contains or “suspends” organelles inside the cell

Organelles: Cytoskeleton

Structure

• composed of protein fibers

– Actin fibers: contract and expand to give the cell flexibility

– Microtubules: transport information from nucleus to other parts of the cell (like neurons)

– Intermediate fibers: framework of metabolic pathways for ribosomes/enzymes

Organelles: Cytoskeleton

Function

•provides support and a place to anchor other structures

Organelles: Nucleus

Structure:

• Found in the cytoplasm

• Contains the genetic material (chromosomes made of DNA & proteins)

• Surrounded by a nuclear envelope (double membrane)

• Contains the nucleolus that makes ribosomes

Function:

• Control headquarters for the cell (brain)

Organelles: Nucleolus

• Located inside the nucleus

Structure

• Knot of chromatin

Function

• Produces ribosomes

Organelles: Ribosomes

Structure • spheres composed of RNA and protein Function • site of protein synthesis

– Free ribosomes make proteins that remain inside the cell

– Attached ribosomes make proteins that become part of the cell or are exported from the cell (usually attached to the ER)

Free Floating

Attached to the ER

Organelles: Endoplasmic Reticulum

• Rough ER: has ribosomes attached

• Smooth ER: does NOT have ribosomes

Organelles: Rough ER

Structure:

• Network of folded membranes near nucleus

• Contains ribosomes on surface

Function:

• Transports proteins that were made by the attached ribosomes through the cell to the golgi

Rough Endoplasmic

Reticulum (ER)

Ribosomes-

make proteins

Organelles: Smooth ER

Structure:

• Network of folded membranes throughout cell

• Contains NO ribosomes on surface

Function:

• Makes lipids and breaks down toxic substances

Organelles: Golgi

Structure

• Closely stacked, flattened membrane sacs

• Found in the cytoplasm near nucleus

Function

• Stores, packages, and transports products inside for use outside

• Releases vesicles (a bit of the golgi pinched off) for transport of stored materials.

Golgi Apparatus-packaging

and distribution center of the

cell.

Organelles: Vesicles

Structure

• bits of membrane from the plasma membrane or from the golgi

• found inside or outside of the plasma/cell membrane

Organelles: Vesicles

Function

• Vesicles fuse with the cell membrane

• may be used to release or transport chemicals in or out of the cells:

– Exocytosis out of the cell

– Endocytosis into the cell

• Transports chemicals to lysosomes or vacuole

http://www.stanford.edu/group/Urchin/GIFS/exocyt.gif

Organelles: Lysosomes

Structure

• found only in animal cells

• sac-like

• contain digestive enzymes

Function

• digests food particles and old organelles

Organelles: Vacuole

Structure

• Located in cytoplasm

• Sac of fluid surrounded by a membrane

• Plant cells have one large central vacuole

• Animal cells have many small vacuoles

Plants have one large central vacuole

Organelles: Vacuole

Function

• Stores water, ions and some nutrients

• Help plant cells maintain turgor pressure

Organelles: Mitochondria

• Found in plant and animal cells

Structure

• A complex matrix of folded membranes to increase surface area

– Chemical processes in organisms occur across membrane surfaces

Function

• Powerhouse of the cell

• Converts stored energy (glucose) into useable energy (ATP)

– Glucose is a product of photosynthesis

– ATP is a product of cellular respiration

Organelles: Mitochondria

Organelles: Chloroplast

Structure

• Found only in plant cells (and some

protists)

• Double phospholipid bilayer

– Stacks = grana

– Non stacked area = stroma

http://www.google.com/url?sa=i&rct=j&q=&esrc=s&frm=1&source=images&cd=&cad=rja&docid=ZZgba0yvE0IgHM&tbnid=uqPto5v3Xf-QCM:&ved=0CAUQjRw&url=http%3A%2F%2Fmicro.magnet.fsu.edu%2Fcells%2Fchloroplasts%2Fchloroplasts.html&ei=3o1IUrj-KcGo2wXkv4F4&bvm=bv.53217764,d.b2I&psig=AFQjCNFUB64hAz-bTRb0TLa0gfSiWiyBrQ&ust=1380573007337604

Organelles: Chloroplast

Function

• Capturing radiant energy and converting it to chemical energy during photosynthesis

• Chlorophyll is the green pigment that traps the energy from the sun

Organelles: Flagella

Structure

• long whip-like tail

Function

• Locomotion (movement)

• one big wave motion will cause a large movement

Organelles: Cilia

Structure

• Surrounds outside of the cell

• short hair-like

Function

• locomotion (movement)

• tiny flutters of movement

Organelles: Centrioles

Structure

• Found only in animal cells

• Made of protein fibers

Function

• Aid in the division of chromosomes during mitosis