The Cell Flashcards
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The cell
the basic functional unit of all living things
Plasma membrane (function)
separates the internal metabolic events from the external environment and controls the movement of materials into and out of the cell.
cytoplasm
consists of specialized organelles suspended in the cytosol
cytosol
fluid matrix within the cytoplasm which consists of water and dissolved substances such as proteins and nutrients
Plasma membrane (constituents)
a double phospholipid membrane (lipid bilayer) with polar hydrophilic heads forming the two outer faces and non polar hydrophobic tails facing inside the membrane.
Peripheral proteins
proteins that may attach loosely to the inner and outer surface of the membrane
Integral proteins
proteins that may extend into the membrane or across the membrane appearing at both surfaces. They are also amphipathic like the phospholipids.
fluid mosaic model
described by the mosaic nature of scattered proteins within a flexible matrix of phospholipid molecules
What does it mean for the phospholipid layer to be selectively permeable?
Only small uncharged polar molecules (like H2O and CO2) and hyrdrophobic molecules (non polar O2 and lipid soluble hydrocarbons) freely pass the membrane.
Channel proteins
allow the passage of certain hydrophillic substances such as polar and charged molecules to pass through the membrane
ion channels
allow the passage of ions across the membrane.
gated channels
ion channels in nerves and muscle cells that open and close in response to specific chemical or electrical stimuli to allow specific ions (Na+ or K+)
Porins
proteins that allow the passage of certain ions and small polar molecules through membranes.
AquAporins
found in the plasma membrane of certain cells dramatically increasing the passage rate of H2O
Carrier proteins
bind to specific molecules which are then transferred across the membrane after the carrier protein changes shape. such as glucose
Transport proteins
use energy (ATP) to transport materials across the membrane. When energy is used for this purpose, the materials are said to be actively transported.
Active transport
when energy is used to carry materials across the membrane.
Na+K+ pump
uses active transport to maintain high concentrations of Na+ and K+ on opposite sides of the plasma membrane
recognition proteins
give each cell type a unique identification. this helps with the id of self and foreign cells and normal and infected. It is a glycoprotein because they have a short oligosaccharide attached that extends from the surface
adhesion proteins
attach cells to neighboring cells or provide anchors for the internal filaments and tubules that give stability to the cell.
receptor proteins
provide binding sites for hormones or other trigger molecules. In response to the hormone or trigger molecule a specific cell response is activated.
what is the function of cholesterol in the phosopholipid bilayer
they are distributed throughout to provide some rigidity to the plasma membrane of animal cells. in plant cells sterol provides a similar functions.
glycolax
a carbohydrate coat that covers the outer face of the cell wall of some bacteria and the outer face of plasma membrane of some animal cells. It consists of various oligosaccs that are attached to the glycolipids and glycoproteins
organelles
bodies within the cytoplasm that serve to physically separate the various metabolic reactions that occur within the cells.
Nucleus
bounded by a nuclear envelope, contains DNA also where DNA is replicated, components of ribosomes are manufactured and serves as the site for separation of chromosomes during cell division.
nuclear envelope
encases the nucleus consisting of two phospholipid bilayers each similar to the plasma membrane.
Deoxyribonucleic Acid
DNA the hereditary information of the cell. Normally spread out within the nucleus as a threadlike matrix called chromatin.
chromosomes
rod shaped bodies formed from chromatin during the beginning of cell division (all within the nucleus). Made up of two long DNA molecules and various histone molecules
Histones
serve to organize the lengthy DNA, coiling it into bundles called nucleosomes.
Nucleoli
concentrations of DNA in the process of manufacturing ribosomes.
ribosomes
subunits made in the nucleus and consist of RNA molecules and proteins. The subunits are 40S and 60S they move across the nuclear envelope and into the cytoplasm where they are assembled into a single 80S ribosome.
in the cytoplasm ribosomes assist in the assembly of amino acids into proteins.
Svedburg Unit
S unit on ribosomes expresses how readily a product forms a sediment in a centrifuge, with larger values representing larger and heavier products.
The endoplasmic reticulum
ER, consists of stacks of flattened sacs involved in the production of various materials. closely associated with the nucleus.
Rough ER
ribosomes that present on the ER, it creates glycoproteins by attaching polysacchride groups to polypeptides as they are assembled by ribosomes.
Smooth ER
responsible for the synthesis of lipids and hormones, especially in cells that produce these substances for export from the cell.
in liver cells it is involve in the breakdown of toxins, drugs and toxic byproducts
Golgi apparatus
Golgi complex, golgi bodies, a group of flattened sacs arranged like a stack of bowls. They modify and package proteins and lipids into vesicles.
Vesicles
modified and packaged small spherical shaped sacs that bud from the outside surface of the golgi appatratus. that migrate and merge with the plasma membrane, releasing their content to the outside of the cell.
Lysosomes
vesicles from a golgi body that contain digestive enzymes. they break down food, cellular debris and foreign invaders like bacteria. They maintain the the low pH (acidic) inside. So any enzyme that escapes the lysosomes is inactive in the neutral cytosol.
None in plants
Peroxisomes in animals
break down various substances including hydrogen peroxide (forming water and oxygen), fatty acids and amino acids. Common in liver and kidney cells where they break down toxic substances.
peroxixomes in plants
modify by-products of photorespiration. in germinating seeds, they are called glyoxysomes breaking down stored fatty acids to help generate energy for growth.
Photorespiration
a process by which CO2 is diverted from its use in photosynthesis.
Mitochondria
carry out aerobic respiration, a process in which energy (ATP) is obtained from carbohydrates.
Chloroplasts
carry out photosynthesis, the plant process of incorporating energy form son light into carbohydrates.
Cytoskeleton
the internal structure of the cytoplasm made up of microtubules, intermediate filaments, and microfilaments. Involved in the shape and movement.
Microtubules
made up of protein tubulin and provide support and motility for the cellular activities. They are found in spindle apparatus and in flagella and cilla
Intermediate filaments
provide support for maintaining the shape of a cell
Microfilaments
are made up of protein actin and are involved in cell motility. They are found in muscle cells and cells that move by changing shape such as phagocytes
phagocytes
white blood cells that wander throughout the body attacking bacteria and other foreign invaders.
Flagella and cilla
structures that protrude from the cell membrane and make wave like movements. They are classified by their length, numbers per cell and movement.
Flagella
long, few and move in a snake like motion. a single flagellum propels sperm. it consists of microtublues arranged in 9+2 array
Cilla
short, many, move back and forth, found numerous , an example that lines a respiratory tract to sweep away debris. consists of microtubules in a 9+2 array.
Centrioles
act as mictrotuble organizing centers. a pair of centrioles located outside the nuclear envelope gives rise to the microtubules that make up the spindle apparatus used in cellular division. not in plants
Transport vesicles
move materails between organelles or between organelles and the plasma membrane
food vacuoles
ate temporary receptacles of nutrients. often merge with lysosomes so that it can break down the food
storage vacuoles
in plants store starch, pigments and toxic substances
central vacuoles
large bodies occupying most of the interior of certain plant cells. When fully filled they exert turgor, pressure, on the cell walls thus maintianing the rigidity in the cell. also act as lysosomes
contractile vacuoles
are specialized organelles in single cell organisms that collect and pump excess water out of the cell.
Extracellular region
area outside of the plasma membrane
Cell wall
found in plants, fungi, protists and bacteria. tehy develop outside of the plasma membrane and provide support for the cell.
Cell wall of plants
consists mainly of cellulose, a polysacc made of beta glucose
cell wall of fungi
usually made of cellulose or chitin.
chitin
a modified polysacc differing from cellulose in that one of the hydroxyl groups is replaced by a group containing nitrogen.
extracellular matrix
is found in animals, in the area between adjacent cells. the area is occupied by fibrous structural proteins, adhesion proteins and polysaccs secreted by the cells.
provides mechanical support and helps bind adjacent cells together, most common substance is the protein collagen.
Cell junctions
serve to anchor cells to another or to provide a passageway for cellular exchange.
anchoring junctions
are protein attachments between animal cells. example is the desmosome
desmosome
consists of proteins that bind adjacent cells together, providing mechanical stability to tissues. also associated with protein filaments that hold cellular structures together.
tight junctions
tightly attached seams between animal cells. the junction completely encircles each cell, producing a seal that prevents the passage of materials between the cells.
communicating junctions
passageways between cells that allow the transfer of chemical or electrical signals. two kinds are gap junctions and plasmodesmata.
gap junctions
narrow tunnels between animal cells that consist of proteins called connexins. the proteins prevent the cytoplasms of each cell from mixing but allow the passage of ions and small molecules.
Channels for two adjacent cells that are closely aligned.
Plasmodesmata
are narrow channels between plant cells. a narrow tube of endoplasmic reticulum called desmotubule, surrounded by cytoplasm and the plasma membrane passes through the channel. the exchange occurs through the cytoplasm
Eukaryotes
include all organisms except for bacteria, cyanobacteria and archeabacteria. and have multi organelles.
prokaryotes
consist of bacteria, cyanobacteria and archeabacteria and lack all teh organelles. they generally only consist of a plasma membrane, DNA molecule, robosomes, cytoplasm and maybe a cell wall.
prokaryotes and DNA
the hereditary material in a prokaryote exists as a single naked DNA molecule with out proteins
Prokaryotic ribosomes
are smaller (70S, with 50S and 30S subunits)
Cell walls of bacteria and cyanobacteria
when present are constructed from peptidoglycans a polysacc protein molecule
cell walls of archeabacteria
contain various polysaccs but not peptidoglycan, cellulose or chitin
flagella in prokaryotes
not constructed of microtubles
selectively permeable membrane
allows only specific substances to pass
solvent
water (liquid)
solute
substance being dissolved in the water (liquid)
down the concentration gradient
movement of substances occurring from higher to lower concentrations
against the concentration gradient
substances moving from lower to higher concentrations.
Hypertonic
(shrink or crenate) a solute may be at a higher concentration relative to another region
Hypotonic
(pop or lyse) a lower concentration of solutes relative to another region
Isotonic
an equal concentration of of solutes relative to another region
Passive transport
processes describe the movement of substances from regions of higher to lower concentration and do not require expenditure of energy.
Bulk flow
the collective movement of substances in the same direction in response to to a force or pressure. Blood moving through a vessel is a bulk flow
Simple diffusion
the net movement of substances from an area of higher concentration to an area of lower concentration. this movement occurs as a result of the random and constant motion characteristic of all molecules
osmosis
the diffusion of water molecules across a selectively permeable membrane. When water moves into a body by osmosis, a hydrostatic pressure (osmotic pressure) may build up inside the body. Turgor pressure is the osmotic pressure that develops when water enters the cells of plants and microorganisms.
Dialysis
is the diffusion of solutes across a selectively permeable membrane. The term dialysis is usually used when different solutes are separated by a selectively permeable membrane
plasmolysis
the movement of water out of a cell that results in a calapse of cell especially plant cells.
Facilitated diffusion
the diffusion of solutes or water through channel proteins in the plasma membrane. Note water can move through without help but aquaporins assist in making it move faster which is facilitated diffusion.
countercurrent exchange
the diffusion of substances between two regions in which the substances are moving by bulk flow in opposite directions. Example water coming in by fish gills and blood flow within the vessels of the fish. they are maximized due to the correlation
vesicular transport
uses vesicles or other bodies in the cytoplasm to move macromolecules or large particles across the plasma membrane.
exocytosis
describes the process of vesicles fusing with the plasma membrane and releasing their contents to the outside of the cell. this is common when a cell produces substances for export
endocytosis
describes the capture of a substance outside the cell when the plasma membrane merges to engulf it. the substance subsequently enters the cytoplasm enclosed in a vesicle.
phagocytosis
cellular eating- occurs when undissolved material enters the cell. the plasma membrane wraps around the solid material and engulfs it forming a phagocytic vesicle
pinocytosis
cellular drinking- occurs when dissolved substances enter the cell. the plasma membrane folds inward to form a channel allowing the liquid to enter.
receptor mediated endocytosis
a form on pinocytosis, occurs when specific molecules in the fluid surrounding the cell bind to specialized receptors that concentrate coated pits in the plasma membrane. proteins that transport cholesterol in the blood (LDLs) and certain hormones target specific cells by receptor mediated endocytosis.
