3.1 Cell Shapes / Basic Components of Cells & 3.2 Plasma Membrane

Squamous Cells

Thin, flat, scaly

Bulge where nucleus is at

Kind of like a fried egg sunny side up

Found in: esophagus and form surface layer (epidermis) of skin

Cuboidal Cells

Squarish front section

Equal in height and width

Found in: liver

Columnar Cells

Taller than wide

Found in: inner lining of stomach and instestines

Plasma cell Membrane

Made of proteins and lipids

Is selectively permeable through either active or passive mechanisms

Cytosol / Intracellular fluid (ICF)

Clear gel containing cytoskelteon organelles and more

Extracellular fluid (ECF)

All body fluids not contained in cells

ECF amid cells are called tissue interstitial fluid

Also include blood plasma, lymph, and cerebrospinal fluid

Cytoplasm

Fluid between nucleus and surface membrane

Plasma membrane

Defines boundaries of the cell, governs interactions with other cells, and controls passage in and out of cell

Membrane proteins

Functions include

• receptors: chemical signals bind to them for cell communication, chemical cannot enter directly, so bind instead

• Second-messenger systems: messengers bind to surface receptors it can trigger second messenger in cytoplasm

• Enzymes: Carry out final stages of starch and protein digestion in small intestine, produce second messengers, break down hormones, and other signaling molecules

• Channel proteins: passages that allow water and hydrophillic solutes to move through membrane - more info below

• Carriers: transmembrane proteins that bind to glucose, electrolytes, and other solutes, transfering them to the other side of the membrane. Some can be called pump - they consume ATP

• Cell identity markers: glycoproteins contribute to glycocalyx which id’s cells that belong to us and those that do not

Channel Proteins

• leak channels: always open, allow materials to pass though continually

• gates (gated channels): open and close under specific circumstances, allow solutes through sometimes and not others

• ligand-gated channels: respond to chemical messengers

• voltage-gated channels: respond to changes in electrical potential (voltage) across plasma membrane

• mechanically gated channels: respond to physical stress on a cell such as stress or pressure

Second messengers / G proteins

Second messengers are very important for transmitting chemicals

G proteins are vitals for drugs, up to 60% require G proteins to work

Glycocalyx

A fuzzy coat that all animals cells external to plasma membrane

It’s chemically unique to all animals except for identical twins

Acts as a ID tag so that the body can distinguish it’s own healthy cells and invading cells

Protects the plasma membrane from physical or chemical injury

Enables immune system to recognize and attack foreign organisms

Changes in glycocalx of cancerous cells enables the body to recognize and destroy

How compatibility is determined for blood transfusions, tissue graft, and organ transplants

Binds cells together so tissue doesn’t fall apart

Enables sperm to recognize and bind to eggs

Guides embryonic cells to destination in the body

Microvilli

Extension of plasma membrane

Increase cells surface area

Best developed in cells that specialize in absorption (epithelial cells of intestines and kidneys)

15 - 40 times as much absorption surface

On some cells they are dense and appear as fringe called brush boarder

Little internal structure except for bundles of stiff filaments called actin, they extend in and out of the cell and they are able to pull things through so that absorption can happen

Can also be sensory as seen on the taste buds and inner ear

Cilia

Hairlike processes on nearly every cell that is singular and doesn’t move

Sometimes it is sensory, other times its unknown why it is there

Some are motile, they beat in waves in the same direction and help to move materials such as mucus onward

Flagellum

Only instance is whip like tail of sperm

Longer than cilium

Pseduopods

Cytoplasm filled extensions of their cell varying shape

Change continually