biology cellular components

prokaryotic

cells that lack a nucleus and membrane-bound organelles, typically unicellular.

eukaryotic

cells that have a nucleus, larger more complex, multicellular/single-celled

plasmids

small circular piece of DNA which can move between different cells

Pili

hair-like appendages on the surface of prokaryotic cells which play a role in bacterial sexual reproduction and facilitate DNA transfer

Capsule

slime-like layer that covers the outer layer of bacterial cell wall providing protection and aiding in adhesion to surfaces.

plasma membrane

separates cell’s interior from surrounding environmentand regulates the movement of substances in and out of the cell.

phospholipids

key membrane component w/ hydrophilic heads and hydrophobic tails

Receptors

transmembrane protein molecules that are embedded in plasma membrane and facilitate communication between the cell and its extracellular environment

channels

transmembrane proteins that allow substances to pass through the cell membrane when activates (voltage-sensitive, ligand-sensitive, etc)

cholesterol

fat-like and waxy substance which makes up to 30% of cell membranes

enzyme proteins

catalyze chemical reactions

cytoplasm

jelly-like substance containing cell organelles

proteins

building blocks of cells

glucose & polysaccharides

resource of energy for cell metabolism

fatty acids

conduct signaling cascades and influence cell and tissue responsiveness to hormonal signals

ions

maintain membrane potentials & regulate neurotransmitter release

nucleic acids

building blocks that form circular DNA in mitochondria and RNA

cytoskeleton

network of protein filaments in the cytoplasm of all cells that helps them maintain their shape and internal organization

nuclear receptors

proteins on nuclear membrane responsible for sensing steroids, thyroid hormones, vitamins, etc to regulate the expression of specific genes. They directly communicate with DNA

chromatin

complex of DNA and protein (histones) found in eukaryotic cells

Endomembrane System

produces and modifies molecules to be exported to other parts of the organism + breaks down toxic chemicals (comprised of rough/smooth endoplasmic reticulum, golgi apparatus)

Rough endoplasmic reticulum

covered in ribosomes! modifies proteins that will be shipped to other locations in the endomembrane system, the cell surface, or outside the cell

Smooth endoplasmic reticulum

no ribosomes on surface! synthesizes lipids and detoxifies molecules

golgi apparatus

processes and packages proteins, lipids, & other molecules for export to other locations or outside the cell

ribosomes

where proteins are made (translation). found in both eukaryotes and prokaryotes

Mitochondria

Cell’s energy factory found in the cytoplasm of most eukaryotic cells. Can number up to 1000 per cell and have their own DNA. They regulate process of cell death!

Lysosomes

garbage disposals

Peroxisomes

detoxify poisons like alcohol, abundant in liver. breaks down fatty and amino acids. single membrane organelle

centrioles

made of protein tubulin and plays important role in cell division by forming spindle fibers. They organize microtubes in cell’s skeletal system. also form sperm tail

chloroplasts

where photosynthesis happens

vacuole

enclosed compartments filled with water. stores nutrients, waste products, and toxins.

cell wall

surrounds the plasma membrane of plant cells. plays a role for growth

extracellular matrix

complex network of proteins, made up of materials secreted by the cells. It provides architectural support to cells and tissues

Tight junctions

water-tight & anchors cells in place (small intestine, skin, etc)

Desmosomes

similar to velcro, holds cells together but not water-tight (e.x tissue lining)

gap junctions

formed by two hemi-channels and permits bi-directional exchanges with no delay (heart muscle cells, neurons)

plasmodesmata

dynamic structures that open and close to control the movement of molecules between cells

Passive transport

energy-free → facilitated diffusion and osmosis

Active transport

requires energy → across the membrane, endocytosis, exocytosis. Involves moving a substance against its chemical concentration or electrical gradient

co-transport

requires energy → symporters, antiporters

Osmosis

diffusion of water through a semi-permeable membrane

endocytosis

allows cells to bring specific amount of substances into themselves

exocytosis

contents of the cell in the vesicle are released to the exterior

symporters

transport 2+ molecules across a cell membrane in the same direction

antiporters

transport 2+ molecules across a cell membrane in different directions

Simple diffusion

molecules pass directly through the plasma membrane without the assistance of another molecule

facilitated diffusion

molecules move across the plasma membrane with the help of a carrier molecule

Electro-chemical gradient

membrane voltage differs inside and outside the cell. Sodium and chlorine concentrations higher outside the cell. Potassium concentrations are high inside the cell