2) A phosphate group (head= polar or hydrophilic = H2O- loving)
What makes up 50% of the membrane mass?
Why is the description of the membrane as a fluid mosaic?
"Fluid": Molecules can move freely within the membrane
"Mosaic": A diversity of proteins exists within the membrane
what are integral membrane proteins and peripheral membrane proteins?
Integral membrane proteins are transmembrane; they span entire width of membrane and contain both hydrophilic and hydrophobic regions
Periphreal Membrane Proteins do not span the entire membrane; are loosely associated with other proteins or lipid molecules
What are the functions of membrane proteins?
1) attachment to cytoskeleton and extracellular matrix
2) cell signaling
3) enzymatic activity
5) Intercellular joining
6) cell-cell recognition
What does it mean that membranes of the cells have selectivepermeability?
-they allow some substances to cross more easily than others (i.e size or charge)
-they block passage of some substances altogether
What are some common processes of movement across membranes?
Diffusion and osimosis
What is diffusion?
Movement of molecules from High to Low; as well as a passive transport; no energy is needed
What is facilitated diffusion?
The transport of some substances by specific transport proteins that act as selective corridors
What is osmosis?
The passive transport of WATER across a selectively permeable membrane
High [H2O] to Low [H2O]
What are the 3 types of solutions, concerning "water balance"?
Isotonic solution (equal concentration of ions in solution and cell)
Hypertonic solution (higher concentration of ions in solution than in cell)
Hypotonic solution (lower concentration of ions in solution than in cell)
what is osmoregulation?
The control of water balance in animals
What is endocytosis and what are the forms?
Mechanism by which particles enter cells
3) receptor-mediated endocytosis
What is phagocytosis?
A cell engulfs a particle and packages it within a food vacuole (ex. most WBCs)
What is pinocytosis?
"cellular drinking" Absorption of extracellular fluids
What is receptor-mediated endocytosis?
the binding of external molecules to membrane proteins. Upon membrane proteins binding to certain molecules, the membrane invaginates and forms a coated pit which then pinch off to become a coated vesicle
What is exocytosis?
mechanism that moves substances out of the cell; vesicles migrates to the plasma membrane; proteins from the vesicles (v-SNAREs) bind with membrane proteins (t-SNAREs); lipid layers from both membranes fuse, and the vesicle releases its contents to the outside of the cell
What is cytoplasm and what are the 3 main parts?
Part of the cell that lies internal to the plasma membrane and external to the nucleus
What is the cytosol?
jelly-like, fluid-containing substance within the cell
-consists of water, ions, and enzymes
-Makes up half of the volume of the cytoplasm
-Fluid in which other cytoplasmic elements are suspended
What 9 main organelles does the cytoplasm contain?
mitchondria, ribosomes, ROugh ER and smooth er, golgi appartus, cytoskeleton, lysosomes, cytoskeleton, centrioles, peroxisomes
What are ribosomes, what are they made of, and what the types?
THey are constructed of proteins and ribosomal RNA; they are the site of protein synthesis
-composed of two subunits (60S and 40S) that fit together to form a functional ribosome
1) Free ribosomes = float in cytosol; make soluble proteins (function in cytosol)
2) Attached ribosomes = attached to rough ER and make membrane proteins or exported proteins
What process do ribosomes build all the cell's proteins?
What do antibiotics target?
The process of ribsomes
What is endoplasmic reticulum (ER)?
"network within the cytoplasm", an extensive system of membrane-walled envelopes and tubes.
What is Rough ER, and what does it make?
Ribosomes stud the external surfaces; makes all membrane proteins and membrane
What is smooth ER, and does it make?
Consists of tubules in a branching network; no ribosomes are attached ; NO PROTEINS ARE MADE
but it does store Ca2+ and makes enzymes for lipid metabolism, as well as makes steroids and lipids
What is the Golgi appartus, and what does it do?
Its basically the "packing& shipping center".
-Works in partnership with the ER; sorts products of rough ER at the cis end and sends them to proper destination from the trans end
What is the mitochondria?
It is the "power plant" of the cell
-Generates most of the cell's energy (ATP) via cellular respiration
Enclosed by a double membrane; the inner membrane folds in forming shelf-like cristae
-contains own DNA (maternal DNA)
What are lysosomes?
Spherical membranous bags containing digestive enzymes, "demolition crew" that break down macromolecules
NOTE: secretory lysosomes are found in white blood cells, immune cells, and melanocytes
Go into more detail what lysosomes do.
They digest ingested bacteria, viruses, and toxins; degrage nonfunctional organelles; breakdown glycogen and release thyroid hormone; breakdown non-useful tissue (webbing fingers and toes during fetal development); breakdown bone to release calcium
What are peroxisomes? And what main function do they have?
They are ubiquitous organelles in eukaryotes that participate in the metabolism of fatty acids and other metabolites.
-Detoxify harmful or toxic substances; Break down long chains of fatty acids (numerous in the liver and kidneys); neutralize dangerous free radicals and break down posions.
What do peroxisomes contain?
oxidases and catalases
What are free radicals?
highly reactive chemicals with unpaired electrons
What is the cytoskeleton, and is its main function?
An infrastructure of the cell consisting of a network of RODS/FIBERS that run throughout the cytosol.
-Provides mechanical support to the cell and maintain its shape and provides machinery for various cellular movements
What types of protein rods does the cytoskeleton contain?
What are the protein rods made up from, and what do they do?
Microtubules are cylindrical strucutres made of proteins called TUBULIN, and the THICKEST
-radiate from CENTROSOME = cell center, which are organelles that attach to and move along microtubules, which constantly assemble and dissemble.
Intermediate filaments - protein fibers; most stable and permanent; help cells resist pulling forces = prodvie tensile strength; play a role in linking cells together
microfilaments (actin filaments)- filaments of contractile protein actin that interact with myosin to create cell division, perfrom endo- and exocytosis, and play a role on pseudopod extension and retraction; organelles also attach to and move along actin filaments, which constantly assemble and dissemble; thinnest