Biology Hidden Gems Eukaryotes and Human Systems Flashcards
Eukaryotes
Have a nucleus and membrane bound organelles
Nucleus
Wrapped in a double phospholipid bilayer called the nuclear envelope or membrane
Nuclear Pores
Nuclear envelope is perforated with large holes that allows RNA to exit but not DNA
Nucleolus
Area where rRNA is transcribed and subunits of the ribosome are assembled; not separated by a membrane
Endocytosis
Three types. Phagocytosis Pinocytosis Receptor mediated endocytosis
Phagocytosis
The cell membrane protrudes outward to envelope and engulf matter -Only a few cells are capable of this and the impetus is the binding of proteins on the particulate matter to protein receptors on the phagocytotic cell -Ex. Antibodies or complement proteins
Pinocytosis
-extracellular fluid is engulfed by small invaginations-Performed in random fashion by most cells; nonselective
Receptor mediated endocytosis
Refers to specific uptake of macromolecules such as hormones, nutrients; ligand binds to a receptor protein on the cell membrane and then moves to a clathrin coated pit that invaginates to form a coated vesicle -Purpose is to absorb the ligands and that’s how it differs from phagocytosis
Phospholipid bilayer of eukaryotic membrane
-Similar to prokaryotic plasma membrane except in eukaryotes the membrane invaginates and separates to form individual, membrane bound compartments and organelles.
Endoplasmic Reticulum
-A thick maze of membranous walls separating the cytosol from the ER lumen (cisternal space) -Contiguous with the cell membrane and nuclear membrane -Contiguous in places with the space between the double bilayer of the nuclear envelope
Rough/ Granular ER
ER near the nucleus has many ribosomes attached to it on the cytosolic side -Translation of the Rough ER propels proteins into the ER lumen as they are created -These proteins are tagged with a signal sequence of amino acids and sometimes glycosylated (carbohydrate chains attached) -Proteins move through the lumen towards the Golgi apparatus
Golgi Apparatus
Series of flattened, membrane bound sacs -Organizes and concentrates the proteins -Proteins without signal sequences are put in secretory vesicles and sent out of the cell -Can modify proteins by removing amino acids or glycosylating them -Some polysaccharide formation takes place in the golgi apparatus -End product is a vesicle filled with proteins that can be released from the Golgi to mature into lysosome transported to other parts of the cell such as the mitochondria or even the ER.
Secretory Vesicles
-Supply the membrane with its proteins and also act in membrane expansion -Endocytotic vesicles from the membrane are transferred to the Golgi for recycling of the cell membrane
Lysosomes
-contain acid hydrolases (hydrolytic enzymes that function best in an acid environment) such as proteases, lipases, nucleases, and glycosidases -These enzymes are capable of breaking down everything -pH 5 interior -Fuse with endocytotic vesicles and digest their contents; anything not digested is ejected from the cell -Sometimes they autolyse to kill the cell
Smooth ER
-Hydrolyzes G6P to glucose ; an important step in making glucose from glycogen -Shares in role of cholesterol formation and subsequent change into steroids with cytosol -Most of the phospholipids in the cell membrane are synthesized in the smooth ER -Oxidizes foreign substances, detoxifying drugs, pesticides, toxins, and pollutants
Adipocytes
-Contain mainly fat droplets -Important in storage and body temp regulation
Peroxisomes
-Vesicles in the cytosol -Growth by incorporating lipids and proteins from the cytosol. -Rather than budding off membranes like lysosomes, peroxisomes self replicate -Involved in production and breakdown of hydrogen peroxide -Inactivate toxic substances such as alcohol, regulate oxygen concentration, play a role in the synthesis and breakdown of lipids and in the metabolism of nitrogenous bases and carbohydrates.
Cell can be divided into
cytosol and ER lumen
Stuff can reach the ER lumen by
endocytosis without ever transporting across a membrane
Rough ER has ribosomes attached to its
cytosol
Cytoskeleton
-Structure and motility of a cell is determined by a network of filaments -Anchors some membrane proteins and other cellular components, moves components within the cell, and moves the cell itself.
Microtubules
-Larger than microfilaments and are involved in flagella and cilia construction, and the spindle apparatus -Rigid hollow tubes made from a protein called tubulin -Makes up the mitotic spindle
Tubulin
Globular protein that polymerizes into long straight filaments under certain conditions
Axoneme
Major portion of the flagellum and cilium contains 9 pairs of microtubules to its neighbor -Have a + and - end, -end attaches to microtubule-organizing center -Microtubules grow away from the MTOC at its +end -Major MTOC is the centrosome; centrioles function in production of flagella and cilia
