Flashcards in Cell Biology Deck (72):
Selectively permeable plasma membrane
Composed of a phospholipid bilayer
Function to provide a continuous barrier to separate the cell and its internal components from the external environment.
What is the lipid bilayer selectively permeable for/against?
Permeable to: nonpolar, hydrophobic and uncharged substances (ex: steroids, O2, CO2, N2)
Impermeable to: polar, hydrophilic and charged substances (ex. ions and large proteins)
Exception: permeable to H2O, even though it is polar/hydrophillic
Fluid Mosaic Model
The model usually used to describe cell membrane action.
Membrane is highly fluctuating due to the high rate of fluctuation and movement of the phospholipids.
The chemical difference between the inside and outside of the cell.
If the difference involves ions with charges, the result is a Membrane Potential
Ampipathic properties of phospholipids
Polar, hydrophilic phosphate head, and non polar, hydrophobic, lipid tail.
What is the lipid bilayer composed of?
1. phospholipids (75%)
2. cholesterol (20%). Carries an OH- (thus polar) and attaches to phosphate head
3. glycolipids (5%). Contains polar carbohydrate and found only on extracellular side of membrane.
1. integral (many are glycoproteins)
What are the roles of the cell membrane glycolipids believed to be?
Signal transduction, cell to cell adhesion, binding
Sugary coat created by the carbohydrate ends of the glycoproteins that marks the cell's uniqueness
What are the 6 functions of proteins in the cell membrane?
2. ion channel
Transports polar (hydrophilic) uncharged substances.
Selectively transports ions through the membrane. Very important in nerve impulses. Specific to certain ions.
Cellular regulation sites
A specific molecule that bonds to a receptor
Integral proteins that catalyze specific reactions at the inside or outside of the cell's surface
Attach to other cells. Example: clotting with linkers attach to surrounding platelets
Glycoproteins (and glycolipids) that help cells recognize each other, and identify foreign cells
Ex. ABO blood markers
Doesn't require ATP.
Uses kinetic energy, via electrical or concentration gradients
What are the two main types of passive transport?
Diffusion (can be simple or facilitated)
Why are integral proteins required to help diffuse some ions through the membrane?
Because ions are polar, and thus hydrophilic, they have difficulty moving through the fatty acid tail lipid bilayer.
What are the two ways that diffusion can be facilitated?
Channel or carrier mediation
A special type of diffusion in which a solvent goes from higher to lower concentration through a selectively permeable membrane
Membrane channel specific to H2O
Pressure exerted by the solvent on the solute side of the membrane. Directly proportional to the concentration of the solute.
Pressure exerted by the presence of colloids (large solutes) in a closed tube. Pulls solves to the side with the higher solute concentration.
Pressure exerted by the solvent on its surroundings, usually on the side of the solute.
Measure of a solution's ability to change the volume of cells by altering the water content.
Any solution in which a cell maintains its normal shape and volume, because the concentration of solutes is the same inside and outside of the cell.
Higher concentration of solutes in the surrounding solution. Water tends to leave the cell --> Crenation
Lower concentration of solutes outside of the cell, so water will enter the cell via osmosis. May lead to lysis
Primary active transport
Uses ATP to move substance across membrane, against the concentration gradient (ex. sodium-potassium pump)
Secondary active transport
Indirectly utilizes the energy from primary transport pumps. Uses the kinetic energy of molecules travelling down their concentration gradient to fuel movement up their own gradient.
Symporters move two substances in the same direction; antiporters move them in opposite directions
A substance is released out of the cell.
If it's useful: secretion
If it's waste: excretion
The process of taking a substance into the cell for metabolism
A form of endocytosis in which the cell engulfs large solid particles. Two of the few cells large enough to engage in phagocytosis are neutrophils and macrophages
Pseudopods may be used to engulf target microbes
AKA bulk phase endocytosis
The taking in of fluids (and floating solutes) into the cell by pinching off bits of the plasma membrane
Combination endo and exocytosis. Just passing through
Includes everything that is in between the cell membrane and the nucleus. Composed of 1) cytosol and 2) organelles
The fluid portion of cytoplasm (approx 50% cell volume).
Site of many of the cell's biochemical reactions.
Components that make up the shape and structure of the cell. Three types:
2) intermediate filaments
Smallest of the cytoskeleton structures.
Composed of actin protein.
Involved in movement, muscle contraction, cell division, locomotion, and structure
Helps anchor cytoskeleton to integral proteins of the cell membrane
Helps form microvilli
Medium sized cytoskeleton
Composed mostly of keratin protein.
Aids in internal stability and keeps organelles in specific postions
Helps forming connections between cells
Largest of the cytoskeletons
Composed mostly of tubulin protein
Long and hollow. Formed in centrosome
Helps determine cell's shape and internal organelle movement
Forms cilia and flagella
Contributes to chromosome mobility during mitosis and meiosis
Involved in meiosis and mitosis
Always found near nucleus and has two components:
1) centriole (pair)
2) pericentriolar material
One component of the centrosome
Found in pairs
Cylindrical structure composed of 9 clusters of 3 microtubules
One component of the centrosome
Contains tubulin protein to help build microtubules
Starting point for mitotic spindles during mitosis
Cilia & Flagella
Composed mostly of microtubules.
Found on external surface of cells
Assist in locomotion
Cilia: hair-like projections the move in a coordinated wave to provide mobility
Flagella: long, tubular talilish structure
Free floating: make proteins for use in the cytosol
Attached (to endoplasmic reticulum): make proteins for other organelles, exocytosis or the cell membrane.
Made of two separate subunits in nucleus, which are assembled in the cytosol
Also found in mitochondria, which it synthesizes enzymes
Network of flattened tubes/sacs that extend from the nuclear membrane, throughout the cytoplasm.
Rough endoplasmic reticulum
Continuous with nuclear membrane. Studded with ribosomes.
Produce lipoproteins and glycoproteins for internal cell use or secretion via exocytosis.
Secretory proteins, membrane proteins, organellar proteins.
Smooth endoplasmic reticulum
Extends from rough ER. No ribosomes
Doesn't synthesize proteins, but does synthesize fatty acids and steroids.
Involved in catabolism of glycogen --> glucose
In the liver, release glucose in bloodstream and inactivate or detoxify lipid-soluble drugs etc.
In muscle cells, equivalent called sarcoplasmic reticulum, and stores and releases Ca+ for muscle contractions.
Transports, receives, modifies and packages amino acids arriving from the rough ER.
The FedEx of the cell
Action of the golgi body
1. Entry/Cis Face: convex, receives amino acid/protein from rough ER.
2. Medial cisternae: modifies polypeptide chains with enzymes to form either glycoproteins or lipoproteins.
3. Exit/Trans Face: concave side. Releases finished product in vesicles.
Three forms of enzyme vesicles
Contains digestive and hydrolytic enzymes that digest absorbed substances into cytoplasmic vesicles
Created by golgi body
Autophagy: destroys organelle (usually to recycle)
Autolyse: destroys entire cell.
Similar to lysosomes. Contain oxidase enzyme that removes H+ from organic molecules, and catalase, which decomposes hydrogen peroxide (H2O2) into safer substances
Cleans up used proteins in cytoplasm
Generates ATP through aerobic metabolism
Composed of : Cristae, and the matrix (space between cristae).
Contains ribosomes and its own set of mDNA. Can self replicate proteins for normal functioning.
Spherical bodies within the nucleus, made up of clusters of RNA, DNA and protein.
Produce rRNA and ribosomal subunits
The scattered RNA, DNA and proteins, prior to cell division. Will cluster for division
Segments of DNA that encode for specific traits and characteristics.
Structure of nucleic acids, pentose sugars and phosphate groups
The arrangement of genes into chromatin fibres during cell division. Exists only during meiosis/mitosis (otherwise in chromatin state).
Humans have 23 pairs
Total genetic information of an organism
Protein balls that DNA double helix coils around for stability
Combination of histones and clusters of DNA
Section of the double helix that likes nucleosomes togther
Section of many nucleosomes and linker DNAs in a row
1/2 of a chromosome. 2 chromatids = 1 chromosomes
The central portion of a chromosome that holds the sister chromatids together
The terminal portions of the chromosomes
Base pairing in DNA