Download Biology Notes: Membrane Structure and Function, Membrane Proteins, and Membrane Transport and more Quizzes Physiology in PDF only on Docsity!
plasma membrane
Bimolecular layer of lipids and proteins in a constantly changing fluid mosaic Plays a dynamic role in cellular activity Separates intracellular fluid (ICF) from extracellular fluid (ECF) Interstitial fluid (IF) = ECF that surrounds cells TERM 2
membrane lipids
DEFINITION 2 75% phospholipids (lipid bilayer) Phosphate heads: polar and hydrophilic Fatty acid tails: nonpolar and hydrophobic (Review Fig. 2.16b) 5% glycolipids Lipids with polar sugar groups on outer membrane surface 20% cholesterol Increases membrane stability and fluidity TERM 3
functions of membrane proteins
DEFINITION 3 1.Transport 2.Receptors for signal transduction 3.Attachment to cytoskeleton and extracellular matrix 4.Enzymatic activity 5.Intercellular joining 6.Cell-cell recognition TERM 4
3 types of membrane
junctions
DEFINITION 4 Tight junction Desmosome Gap junction TERM 5
tight
junctions
DEFINITION 5 Tight junctions: Impermeable junctions prevent molecules from passing through the intercellular space
desmosomes
Anchoring junctions bind adjacent cells togetherand help form an internal tension-reducing network of fibers TERM 7
gap
junctions
DEFINITION 7 Transmembrane proteins form pores that allow small molecules to pass from cell to cell For spread of ions between cardiac or smooth muscle cells TERM 8
types of membrane transports
DEFINITION 8 Passive processes No cellular energy (ATP) required Substance moves down its concentration gradient Active processes Energy (ATP) required Occurs only in living cell membranes TERM 9
What determines whether or not a substance
can passively permeate a membrane?
DEFINITION 9 1.Lipid solubility of substance 2.Channels of appropriate size 3.Carrier proteins TERM 10
passive processes
DEFINITION 10 Simple diffusion Carrier-mediated facilitated diffusion Channel-mediated facilitated diffusion Osmosis
tonicity
The ability of a solution to cause a cell to shrink or swell TERM 17
hypotonic
DEFINITION 17 A solution having lesser solute concentration than that of the cytosol TERM 18
hypertonic
DEFINITION 18 A solution having greater solute concentration than that of the cytosol TERM 19
isotonic
DEFINITION 19 A solution with the same solute concentration as that of the cytosol TERM 20
membrane transport active
DEFINITION 20 Two types of active processes: Active transport Vesicular transport Both use ATP to move solutes across a living plasma membrane
active transport
Requires carrier proteins (solute pumps) Moves solutes against a concentration gradient Types of active transport: Primary active transport Secondary active transport TERM 22
primary active transport
DEFINITION 22 Energy from hydrolysis of ATP causes shape change in transport protein so that bound solutes (ions) are pumped across the membrane ATP + water= ADP Hydrolysis of ADP= ATP ADP + protein = ATP Sodium-potassium pump (Na+-K+ ATPase) Located in all plasma membranes Involved in primary and secondary active transport of nutrients and ions Maintains electrochemical gradients essential for functions of muscle and nerve tissues TERM 23
secondary active transport
DEFINITION 23 Depends on an ion gradient created by primary active transport Energy stored in ionic gradients is used indirectly to drive transport of other solutes TERM 24
vesicular transport
DEFINITION 24 Transport of large particles, macromolecules, and fluids across plasma membranes Requires cellular energy (e.g., ATP) TERM 25
vesicular transport functions
DEFINITION 25 Functions: Exocytosistransport out of cell Endocytosistransport into cell Transcytosistransport into, across, and then out of cell Substance (vesicular) traffickingtransport from one area or organelle in cell to another
mitochondria
Double-membrane structure with shelflike cristae Provide most of cells ATP via aerobic cellular respiration Contain their own DNA and RNA TERM 32
ribosomes
DEFINITION 32 Granules containing protein and rRNA Site of protein synthesis Free ribosomes synthesize soluble proteins Membrane-bound ribosomes (on rough ER) synthesize proteins to be incorporated into membranes or exported from the cell TERM 33
endoplasmic reticulum
DEFINITION 33 Interconnected tubes and parallel membranes enclosing cisternae Continuous with nuclear membrane Two varieties: Rough ER Smooth ER TERM 34
rough ER
DEFINITION 34 External surface studded with ribosomes Manufactures all secreted proteins Synthesizes membrane integral proteins and phospholipids TERM 35
smooth ER
DEFINITION 35 Tubules arranged in a looping network Enzyme (integral protein) functions: In the liverlipid and cholesterol metabolism, breakdown of glycogen, and, along with kidneys, detoxification of drugs, pesticides, and carcinogens Synthesis of steroid-based hormones In intestinal cellsabsorption, synthesis, and transport of fats In skeletal and cardiac musclestorage and release of calcium
Golgi apparatus
Stacked and flattened membranous sacs Modifies, concentrates, and packages proteins and lipids Transport vessels from ER fuse with convex cis face of Golgi apparatus Proteins then pass through Golgi apparatus to trans face Secretory vesicles leave trans face of Golgi stack and move to designated parts of cell TERM 37
lysosomes
DEFINITION 37 Spherical membranous bags containing digestive enzymes (acid hydrolases) Digest ingested bacteria, viruses, and toxins Degrade nonfunctional organelles Break down and release glycogen Break down bone to release Ca2+ Destroy cells in injured or nonuseful tissue (autolysis) TERM 38
peroxisomes
DEFINITION 38 Membranous sacs containing powerful oxidases and catalases Detoxify harmful or toxic substances Neutralize dangerous free radicals (highly reactive chemicals with unpaired electrons) TERM 39
cytoskeleton
DEFINITION 39 Elaborate series of rods throughout cytosol Microtubules Microfilaments Intermediate filaments TERM 40
centrosome
DEFINITION 40 Cell center near nucleus Generates microtubules; organizes mitotic spindle Contains centrioles: Small tube formed by microtubules
chromatin
Threadlike strands of DNA (30%), histone proteins (60%), and RNA (10%) Arranged in fundamental units called nucleosomes Condense into barlike bodies called chromosomes when the cell starts to divide TERM 47
cell cycle
DEFINITION 47 Defines changes from formation of the cell until it reproduces Includes: Interphase Cell division (mitotic phase) TERM 48
interphase:
DEFINITION 48 Period from cell formation to cell division Nuclear material called chromatin Four subphases: G1 (gap 1)vigorous growth and metabolism G0gap phase in cells that permanently cease dividing S (synthetic)DNA replication G2 (gap 2)preparation for division TERM 49
messenger RNA
DEFINITION 49 Carries instructions for building a polypeptide, from gene in DNA to ribosomes in cytoplasm TERM 50
Ribosomal RNA
DEFINITION 50 A structural component of ribosomes that, along with tRNA, helps translate message from mRNA
transfer RNA
Bind to amino acids and pair with bases of codons of mRNA at ribosome to begin process of protein synthesis TERM 52
transcription
DEFINITION 52 Transfers DNA gene base sequence to a complementary base sequence of an mRNA Transcription factor Loosens histones from DNA in area to be transcribed Binds to promoter, a DNA sequence specifying start site of gene to be transcribed Mediates the binding of RNA polymerase to promoter RNA polymerase Enzyme that oversees synthesis of mRNA Unwinds DNA template Adds complementary RNA nucleotides on DNA template and joins them together (au, c g) Stops when it reaches termination signal mRNA pulls off the DNA template, is further processed by enzymes, and enters cytosol TERM 53
translation
DEFINITION 53 Converts base sequence of nucleic acids into the amino acid sequence of proteins Involves mRNAs, tRNAs, and rRNAs mRNA attaches to a small ribosomal subunit that moves along the mRNA to the start codon Large ribosomal unit attaches, forming a functional ribosome Anticodon of a tRNA binds to its complementary codon and adds its amino acid to the forming protein chain New amino acids are added by other tRNAs as ribosome moves along rRNA, until stop codon is reached TERM 54
role of rough ER in protein synthesis
DEFINITION 54 mRNAribosome complex is directed to rough ER by a signal- recognition particle (SRP) Forming protein enters the ER Sugar groups may be added to the protein, and its shape may be altered Protein is enclosed in a vesicle for transport to Golgi apparatus
