A&P Cell Key terms
Concentration ([ ])
Number of molecules in a given volume
Peripheral proteins
Peripheral proteins in membrane are loosely bound to the surface of the membrane (inside or outside)
Nucleolus
Small, dense body in nucleus, No surrounding membrane where ribosomes are made out of proteins and rRNA
Transcription Elongation
RNA polymerase makes mRNA longer Nucleotides are attached to 3'end of growing mRNA mRNA is complementary to DNA template
rRNA
Ribosomal RNA Important part of the ribosome (structural function)
Genetic code
--Instructions for making proteins --Correspondence of gene and protein sequence --Each of the 20 amino acids is represented in DNA by a particular sequence of 3 nucleotides = codon --Other nucleotide sequences encode instructions for beginning and ending the synthesis of protein• Start codon• Stop codon
Translation
--Making of a specific protein using the mRNA sequence as a templatem --RNA must leave nucleus and associate with a ribosome in cytoplasm --Making proteins is a multi-step process mediated by enzymes --Sequence of bases in mRNA specifies sequence of amino acids of protein --Transfer RNA (tRNA): brings and aligns amino acids anticodon in tRNA connects with codon in mRNA and the right amino acid is placed next to growing polypeptide chain --Amino acids are linked through peptide bonds to form polypeptide
Centrosome
--Organelle composed of two centrioles During the prophase of mitosis, the centrosomes migrate to opposite poles of the cell --The mitotic spindle then forms between the two centrosomes --Upon division, each daughter cell receives one centrosome
Cell cycle
--life of a cell from formation to its own division --Series of changes that it undergoes from the time it forms until it divides --Controlled by checkpoints: Highly regulated --Disruption affects health (delayed wound healing, cancer)
Cleavage furrow
--membrane pinches inward separating newly formed cells --Cleavage furrow is formed from contracting ring of microfilaments and deepens to separate contents into two cells
RNA
-3 types that have different functions (mRNA, tRNA, rRNA) -Nucleotides contain: ribose, phosphate and bases (A,G,U,C) -single chain
Isotonic
-A solution having the same solute concentration as another solution -If cell is in isotonic solution, no net water movement
Interphase
-Before the cell divides, cell must grow and duplicate its contents -great synthetic activity -Cell uses nutrients/fuels to duplicate membranes, organelles and genetic material
Endocytosis
-Bulk transport -Requires energy = active transport -Import (engulfment) of substances useful to the cell from the outside cell takes in molecules and particulate matter by forming new vesicles from the plasma membrane -types: Phagocytosis, Pinocytosis, Receptor-mediated endocytosis
DNA
-Genetic information - instructions to make all possible proteins -Located in the nucleus -Nucleotides contain: deoxyribose, phosphate and bases (A,G,T,C) -Double chain
Integral proteins
-Integral proteins in membrane penetrate the hydrophobic interior of the lipid bilayer = transmembrane proteins -Protein in membrane spans across the bilayerHas hydrophilic and hydrophobic parts *Example: transport molecules, receptors, enzymes, adhesion proteins (e.g. protein that allows attachment to the cytoskeleton and extra-cellular matrix)
Nucleus
-Large, spherical structure, contains genetic material, contains nucleoplasm -contains genetic material controls cellular activities: directs protein synthesis, inheritance (DNA is copied prior to cell division)nuclear envelope = Double-layered, inner and outer lipid bilayer membranes -nuclear pores = protein-lined channels (let molecules in/out of nucleus)
Protein synthesis
-Making of proteins using instructions encoded in the DNA -Happens in cytoplasm (in ribosomes: free or attached to endoplasmic reticulum) -Requires correct amino acids available
mRNA
-Messenger RNA -Carries DNA info to cytoplasm and acts as template for protein -mRNA must leave nucleus and associate with a ribosome in cytoplasm -Has series of codons: each codon is made of 3 bases that code for a specific amino acid
Ion Pumps
-Transport protein that moves ions against their concentration gradient -Needs energy (ATP) -Active transport
Osmosis
-diffusion of water across a selectively permeable membrane, with no expenditure of energy -Membrane must be impermeable to solute -Water diffuses across a membrane from the region of lower solute concentration to the region of higher solute concentration until the solute concentration is equal on both sides -Aquaporin: channel protein in the plasma membrane that specifically facilitates osmosis
Tight junctions
-especially common in epithelial tissue -Specialized proteins form a barrier that is impermeable to the majority of soluble molecules between the two sides of the epithelium
Desmosomes
-especially common in epithelial tissue -specialized adhesive protein complexes that localize to -intercellular junctions and are responsible for maintaining the mechanical integrity of tissues
Centrosome
-microtubules grow out from a centrosome to create the mitotic spindle during cell division = "microtubule-organizing center" -made out of a pair of centrioles microtubules connect with chromosomes and "pull them apart" during cell division
Facilitated diffusion
-passage of a substance across a membrane down its concentration gradient, aided by specific transport proteins, with no expenditure of energy -Usually polar or charged molecules -Without the transport protein (carrier or channel) the membrane is not permeable to substance
Vesicles
-small cellular containers made of membrane -variety of functions: move molecules, secrete substances, digest materials, or regulate pressure in cell
Simple diffusion
-spontaneous movement of particles from where they are more concentrated to where they are less concentrated down the [ ] gradient -Membrane (phospholipid bilayer) is permeable to small non-polar molecules
Phases of Cell Cycle
1. Interphase:• G1 phase: normal cell growth • S phase: copying of chromosomes (DNA replication)• G2 phase: growth in preparation for cell division 2. Mitotic (M) phase: mitosis and cytokinesis
Translation process
1. Ribosome binds mRNA (initiation) 2. 1st tRNA with complementary anticodon holds amino acid in place 3. 2nd tRNA binds to next codon 4. Peptide bond forms between amino acids (making chain) 5. 1st tRNA is released + returns to cytoplasm to be recycled 6. Process repeated as ribosome moves along mRNA (elongation) 7. Amino acids added one at a time to growing protein 8. As the protein molecule forms it folds 9. When the last codon is reached the polypeptide is then released (termination)Process needs energy (GTP)
Codon
3 contiguous bases in mRNA sequence that correspond to a specific anticodon in tRNA and a specific amino acid
Gene expression
A gene that is transcribed and translated is said to be expressed Proteins in a cell determine its function and this can vary with changing conditions - gene expression increases or decreases Gene expression is the basis for cell differentiation (different cells turn on/off different genes and produce different sets of proteins)
Organ system
A group of organs with a common goal (example: digestive system made up of stomach, intestines, pancreas and liver)
Equilibrium
A state of balance. The point at which molecules on one side of a membrane equal molecules on the other side of a membrane
M (mitotic) phase
Actual cell division 2 separate processes• Mitosis: division of nucleus (DNA)• Cytokinesis: division of cytoplasm
Replicated DNA
After S phase Each duplicated chromosome has two identical sister chromatids Sister chromatids are joined Chromatids will separate during cell division
RNA processing
Before mRNA leaves the nucleus addition of a 5' cap and a 3'poly-A tail (RNA splicing
Transcription Initiation
Beginning of transcription transcription factors bind to a specific DNA sequence at the beginning of a gene triggers transcription by RNA polymerase
Somatic cells
Body cells Each cell has 2 copies of each chromosome (one from dad, one from mom)
Exocytosis
Bulk transport Requires energy = active transport Export (secretion) of substances from the inside to the outside of the cell
Mitosis
Cell division in somatic cells Two identical cells arise from one cell
Prophase
Chromatin condenses (gets more compact) Chromosomes made of identical sister chromatids are visible Nuclear envelope and nucleolus break up (disappear) in cytoplasm microtubules assemble from centrosomes to form spindle centrosomes move towards opposite ends (poles) of cell spindle fibers attach to each chromatid
Cilia
Cover free surface of epithelia Many tiny, hair-like structure Move coordinated, beat in succession producing wave of motion that sweeps (move fluids)
Concentration gradient ( [ ])
Difference of the concentration of a solute on both sides of a membrane
Tissues
Different types of cells arranged in a specific way to create specific aggregates that form the structural materials of multi-cellular organism
Plasma membrane
Encloses the cell Phospholipid bilayer (except in archaea: membrane is monolayer with branched hydrocarbon tails) bilayer = stable boundary between two aqueous compartments Components: phospholipids, cholesterol, proteins Fluid-mosaic model: constant sideways movement of molecules; Most lipids and some proteins can shift about laterally; lateral movement of phospholipids is rapid; proteins move more slowly; Some proteins move in a directed manner; others seem to be anchored in place Phospholipids (most abundant lipid in membranes) - molecules with hydrophobic and hydrophilic regions Factors that affect membrane fluidity - As temperatures cool, membranes switch from a fluid state and become more stiff A membrane remains fluid to a lower temperature if it is rich in phospholipids with unsaturated hydrocarbon tails Membranes must be fluid to work properly At warm temperatures (such as 37oC), cholesterol restrains movement of phospholipids; at cool temperatures, it maintains fluidity by preventing tight packing (cholesterol reduces membrane fluidity at moderate temperatures, but at low temperatures hinders solidification)
Intercellular junctions
Extracellular components and connections between cells help coordinate cellular activities Neighboring cells often adhere, interact, communicate by direct physical contact types of intercellular junctions: Tight junctions, Desmosomes, Gap junctions
Cytoplasm
Fills out the cell, contains organelles, space where cell activities occur Liquid part = cytosol = colloid Networks of membranes and organelles suspended in fluid
G1 period (of interphase)
Gap or growth period
G2 period (of interphase)
Gap or growth period, Structures are duplicated
Cytokinesis
Happens during the M (mitotic) phase of cell cycle Continuous process right after mitosis Ring of microfilaments assembles and attaches to inner surface of cell membrane, pinches inward separating newly formed nuclei and distributing about half the organelles into each new cell New cells may differ slightly in size and number of organelles, but contain identical genetic information New cells are ready to enter next interphase
Telophase
Separating chromosomes reach poles Cell continues to elongate Nuclear envelope and nucleoli re-form Chromatin becomes diffuse Spindle disappears
gametes
Sex cells Egg and sperm have only half of the genetic material (one copy of each chromosome)
Hypertonic
In comparing two solutions, the one with the greater concentration of solutesIf cell is in hypertonic solution, water movement OUT OF cell cell gets shriveled
Hypotonic
In comparing two solutions, the one with the lower concentration of solutes If cell is in hypotonic solution, water movement INTO cell cell gets lyzed ("explodes")
Chromosome
Individual molecule of DNA Human cell has 46 chromosomes linear shape (molecule has 2 edges) Visible when they are in condensed (tight) form during cell division
Stages of transcription
Initiation, Elongation, Termination
RNA splicing
Introns (non-coding sequence in mRNA) are cut out Exons (coding sequences in mRNA) are joined together Forms mature mRNA ready to leave the nucleus
Microtubules
Long, slender tubes composed of tubulin, arranged in spiral Thicker than microfilaments Function: cell shape, motility (cilia and flagella), chromosome movement (spindle fibers), organelle movements
Flagella
Longer than ciliaUsually just one (flagellum) Undulating wavelike motion (propeller), example: tail of sperm cell
Chromatin
Loosely coiled fibers of DNA (chromosomes) + proteins (histones) Can have different levels of condensation (loosely tightly packed)
Mitochondria
Major sites of energy production - aerobic cellular respiration (Process to convert chemical energy in lipids and CHOs into ATP) Elongated, fluid-filled sacs that vary in size and shape Move slowly through cytoplasm and reproduce by dividing Contain small amounts of DNA and ribosomes Inner membrane folds extensively (cristae) and contains enzymes for cellular respiration Inner fluid = matrixATP: adenosine triphosphate, energy in a form that can be used during chemical reactions
Transcription
Making a transcript (copy of RNA) of a specific gene Happens in the nucleus Messenger RNA (mRNA) is made by RNA polymerase following rules of complementary base pairing
Membranes
Membranes have distinct inside and outside faces asymmetrical distribution of proteins, lipids, and associated carbohydrates in plasma membrane
Spindle
Microtubules that emerge from the centrosomes and bind to each sister chromatid during prophase The spindle helps the chromosomes meet in the middle during metaphase As the spindle shortens it pulls chromatids apart during anaphase Spindle not attached to chromosomes helps elongate the cell during anaphase Spindle disappears during telophase
Solute
Molecules dissolved in a solvent (liquid) Solvent: Liquid in which molecules are dissolved
Cilia and flagella
Motile extensions from surface of certain cells share a common structure: core of microtubules sheathed by the plasma membrane, basal body that anchors the cilium or flagellum + motor protein called dynein, which drives the bending movements of a cilium or flagellum Differ mainly in length, abundance and motion characteristics
To move down a gradient
Movement from high concentration to low concentration
To move against a gradient
Movement from low concentration to high concentration
Active transport
Movement of particles from where they are less concentrated to where they are more concentrated, against the [ ] gradient with expenditure of energy in the form of ATP Requires a pump *Example: Sodium-potassium pump
Organelles
Structures inside the cell that have a specific cellular function Nucleus, cell membrane, Endoplasmic Reticulum (rough and smooth), Ribosomes, Golgi Apparatus, Mitochondria, Lysosomes and Peroxisomes, Cytoskeleton, Centriole
S phase (of interphase)
Synthesis period with DNA replication
Smooth ER
Synthesizes lipids, metabolizes carbohydrates, Detoxifies drugs and poisons, Stores calcium ions
Tonicity
The ability of a solution to cause a cell within it to gain or lose water
Passive transport
The diffusion of a substance without any input of energy
Microfilaments
Tiny rods of actin that form meshwork or bundles important in movement of the cell and movement of molecules inside the cell Function: cell shape, motility (muscle contraction and cell motion), cytokinesis
Organs
Tissues working together with a common purpose -A part of the body that has a particular function (example: heart, kidney, lung, stomach)
tRNA
Transfer RNA Translates the instructions in mRNA to create a protein Carries specific amino acids to the ribosome Has an anti-codon (region at one end that consists of a particular sequence of 3 bases) that is complementary to a specific codon each tRNA is specific for one type of codon and deliver the corresponding amino acid to the ribosome
Protein channel
Transport protein that allows a specific polar or charged molecules to move across a membrane following its concentration gradient
Carrier protein
Transport protein that changes shape to facilitate the diffusion of a specific molecule(s) across a membrane When it functions against the concentration gradient it is called a pump
Transcription Termination
When RNA polymerase reaches the end of the gene it releases the newly formed mRNA
composite cell
a "universal" cell or a "model" cell, includes all known cell structures (organelles); in reality, a cell has most but not all of these structures (specialized cells differ in number and type of organelles)
Cell division
a way to do exponential growth in cells Cell divides Results in daughter cell IDENTICAL to parent cell Needed for growth of organs/tissues and repair & replacement of cells in an adult organism
cell theory
all living things are composed of cells and all cells come from other cells
Cytoskeleton
cell's internal skeleton framework of thin, threadlike strands in cytoplasm, made of microfilaments, intermediate filaments and microtubules function: Support (cell shape) and motility
Extracellular matrix (ECM)
cells are covered by an elaborate ECM made up of glycoproteins such as collagen, proteoglycans, and fibronectin
Chromosome
chromatin that is packaged into thread-like structures (very compact) before S period of interphase each chromosome has one chromatid after S period of interphase (DNA replication) each chromosome is made of 2 identical sister chromatids held together by the centromere
Lysosomes
digestive compartments within a cell, membranous sac containing digestive enzymes Lysosomal enzymes work best in the acidic environment inside the lysosome function: to digest food and to remove or recycle damaged parts of a cell, damaged organelles
Gap junctions
especially common in epithelial tissue specialized intercellular connection: allows various molecules, ions and electrical impulses to directly pass through a regulated gate between cells
Endoplasmic reticulum (ER)
flattened sacs, elongated canals and fluid-filled vesicles, interconnected with cell membrane and nuclear envelope
Golgi Apparatus
flattened sacs, elongated canals and fluid-filled vesicles; one side of Golgi functions as receiving dock for the product and the other as a shipping dock function: finishes, sorts, and ships cell products; functions in conjunction with the ER, modifies products of the ER
Endomembrane system
membranes within a cell, important to connect cell organelles, regulates protein traffic and performs metabolic functions in the cell Network of membranous organelles important for manufacturing products that mostly will end up in the plasma membrane or will be excreted involves the nucleus, nuclear envelope, ribosomes, endoplasmic reticulum, and Golgi
Ribosome
organelle synthesized in the nucleolus (in the nucleus): made of rRNA and 2 protein subunits function: protein synthesis free in cytoplasm vs bound to membrane (RER or nuclear envelope)
Rough ER
outer membrane studded with ribosomes, participates in synthesis of proteins that need further processing or that will be secreted from the cell
Anticodon
region at one end of tRNA that consists of a particular sequence of 3 bases and is complementary to a specific codon
Cell
simplest collection of matter that can live basic unit of life Though cells can differ substantially from one another, they share common features
Peroxisomes
small, membrane-enclosed organelles that contain enzymes involved in a variety of metabolic reactions, including several aspects of energy metabolism. functions: break down fatty acids to be used for forming membranes and as fuel for respiration; and transfer hydrogen from compounds to oxygen to create hydrogen peroxide and then convert hydrogen peroxide into water
Metaphase
spindle fibers attached to each chromatid move chromosomes chromosomes line up midway in the equatorial plate
Anaphase
spindle fibers shorten and pull attached chromatids towards centrosome sister chromatids are pulled apart chromatids separate and become individual chromosomes move in opposite direction guided by microtubules cell elongates
Phases of mitosis
• Prophase • Metaphase • Anaphase • Telophase