Dunn M&C - Cell Structure (prokaryotes, eukaryotes, etc.)

plasma membrane

present in all cells, which separates the cell from its environment

DNA

present in all cells, represented by DNA genomes (the entire chromosomal DNA sequences of a cell)

cytosol

found in all cells. the aqueous fluid contained by the plasma membrane. densely packed with proteins that are jelly-like

cytoplasm

found in all cells. containing the jelly-like substance and fills it with organelles and other substances

ribosomes

molecular machines found in all cells that synthesize proteins by translating messenger RNA sequences.

cytoskeleton

cables present in all cells, that run through the cell to give structural support

nucleus

found in eukaryotes; the genome-enclosing structure surrounded by a double membrane with nuclear pores

organelles

membrane-enclosed subcompartments for carrying out specialized functions (increasingly discovered in prokaryotes & archaea,, but not too many in prokaryotes) in cytoplasm

cell wall

protective outer layer rich in carbohydrates; not found i animal cells but present in plant cells and prokaryotes

flagellum/cilium

a membrane covered projection that is used to create movement; found in humans like sperm cells as an example

prokaryotic cells

do not have a nucleus or internal membrane system; consisting of nucleoids, possible plasmids and ribosomes, and some of these are motile due to the present of flagella

motility

the ability of an organism to move independently using metabolic energy

plasmid

small, circular piece of extra-chromosomal DNA (often carry genes that provide advantageous traits to the bacteria, like antibiotic resistance)

nucleoid

circular chromosome is supercoiled and located in cytoplasm

peptidoglycan

mixture of proteins & carbohydrates that forms a semi-rigid but permeable cell wall in bacteria, providing structural support and protection

cell wall

a rigid outer layer found in plant cells and bacteria that provides structure and protection. prevents osmotic lysis

osmotic lysis

the rupture of a cell due to excessive internal pressure from water influx, often occurring when the cell is in a hypotonic environment.

prokaryotes v. eukaryotes

• all cells have a plasma membrane which acts as a selective barrier against the extracellular environment

• one is 10 to 100 times bigger than the other

• one has a nucleus while the other does not

endosymbiotic theory

the theory that explains the origin of eukaryotic cells from prokaryotic organisms, suggesting that certain organelles, such as mitochondria and chloroplasts, originated as free-living bacteria that were engulfed by ancestral eukaryotic cells, giving an advantage to the host eukaryotic cell

endomembrane system

evolved from inner folds of the plasma membrane that pinched off and enclosed DNA, thus creating eukaryotes

chloroplast

an organelle found in plant cells and some protists, responsible for photosynthesis by converting sunlight into chemical energy (synthesizes carbohydrates like glucose from CO2). only found in cytoplasm

eukaryotic cells

divided into two major cellular compartments, the nucleus and cytoplasm

nuclear envelope

a double membrane structure that surrounds the nucleus, separating it from the cytoplasm and regulating the passage of molecules in and out.

nuclear pore complex

gates the nucleus for most proteins; gate between nucleus and cytoplasm but regulated

nuclear lamina

provides cytoskeletal support, underneath nuclear envelope; provides the structure

nucleolus

ribosome subunit factory and processes rRNAs

chromatin

“native” DNA

mitochondria

harnesses energy from chemical compounds and produces most of the ATP that serves as the energy currency of the cell; present in both animal and plant cells (but plant cells also have chloroplasts) and only in the cytoplasm

nucleus

the storehouse for the cell’s genetic information and the site for RNA synthesis

endoplasmic reticulum

involved in both protein and lipid synthesis

lysosomes

membrane-bound organelles containing enzymes that digest cellular waste, debris, and foreign substances; degrade macromolecules

golgi apparatus

modifies and sorts proteins and lipids as they move to their final destinations in or out of the cell

vacuoles

water-filled organelles that contribute to the structural rigidity of plants by maintaining turgor pressure against cell walls

turgor pressure

the outward pressure of the aqueous cell against the cell wall; caused by the vacuole and cell wall; providies stability and rigidity to plant cells

plant cell wall

protein poor; get their structural from carbohydrates

cellulose

contains carbohydrate sugar (glucose); primary structural component of plant cell walls

thylakoid

membrane-bound compartments in chloroplasts that are responsible for the light-dependent reactions of photosynthesis; contain chlorophyll (which absorbs light)

glucose vs cellulose

cellulose

• provides zero energy for us humans

• different glycosidic linkages despite being polymers of glucose

zip code hypothesis

proteins are directed to the correct cellular location by signals within their amino acid sequence (usually encoded by primary a.a. sequence); most prevalent in eukaryotes

• in the absence of a specific signal, the default location for a protein is the cytoplasm

amino acid in zip code hypothesis

sequence recognized as a signal to transport the protein

lipid bilayer

the structural basis for virtually all cellular membranes; a membrane made of two layers of lipids that surrounds cells and organelles

lipids

hydrophilic head, hydrophobic tails; present in lipid bilayer

fluid-mosaic model

within the “sea” of membrane lipids, the integral membrane proteins are floating around; ALL cellular membranes have LOTS of proteins in them

carbohydrate chains in fluid-mosaic models

modify proteins and lipid of the plasma membrane on the extracellular side