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.