Cell Biology & Molecular Biology Flashcards
cell membrane
- encloses the cell, exhibits selective permeability to regulate the passage of materials in and out of the cell
- PM permeable to small NP molecules (O2) and and small polar molecules (H20)
fluid mosaic model
- cell membrane consists of a phospholipid bilayer w/ proteins embedded throughout
- lipids/proteins can move freely within the membrane
nucleus
- controls activities of the cell (cell division)
- contains DNA (composed of structural proteins called histones)
- nucleolus: dense structure in the nucleus where ribosomal RNA synthesis occurs
ribosome
- sites of protein production
- synthesized by nucleolus
- free ribosomes found in cytoplasm, bound ribosomes line ER
endoplasmic reticulum
- involved in transport of materials throughout the cell, particularly those secreted by th cell
- smooth ER: does not contain ribosomes, involved in metabolism and lipid production
- rough ER: contains ribosomes and involved in protein synthesis
golgi apparatus
-receives vesicles from smooth ER and modifies them (glycosylation), repackages, and distributes to cell surface by exocytosis
mitochondria
- site of aerobic respiration
- supplier of energy (ATP)
cytoplasm
- most of cell metabolic activity occurs here
- cytosol: fluid contained within the cell membrane
- cyclosis: transport within the cytoplasm
vacuoles/vesicles
- membrane bound sacs involved in transport and storage of materials
- vacuoles are larger and more common in plants
centrioles
- involved in spindle organization during cell division
- animal cells have a pair of centrioles that lie in a region called the centrosome
lysosomes
- membrane bound vesicles that contain hydrolytic enzymes involved in digestion
- break down ingested material
- autolysis: injured or dying tissue ruptures the lysosome and releasing its enzymes
cytoskeleton
- support, shape, and motility
- composed of intermediate filaments, microtubules, and microfilaments
- microtubules: hollow rods made up of tubulin, support and movement (cilia and flagella)
- microfilaments: solid rods of actin (muscle contraction)
simple diffusion
- movement of particles down their conc gradient (high conc to low conc)
- passive process, requires no energy
osmosis
- simple diffusion of water from low conc to high conc
- hypertonic: conc is higher outside cell, shrink (plasmolysis)
- hypotonic: conc higher inside cell, swell and lyse
facilitated diffusion
- movement of particles down their conc gradient through channels or carrier proteins
- passive process, no energy required
active transport
- movement of particles against conc gradient
- requires energy
carrier molecules
- energy-independent carriers: facilitate movement along a conc gradient
- symporters: move 2 ions in same direction
- antiporter: move in opposite directions
- pumps: energy-dependent carriers, require ATP
endocytosis
-cell membrane invaginates, forming a vesicle that contains extracellular medium bringing it into the cell
pinocytosis
-ingestion of fluids of small particles
phagocytosis
-engulfing of large particles
exocytosis
-vesicle within the cell fuses with the cell membrane and releases contents to the outside
intracellular circulation
materials move within a cell by:
- Brownian movement: KE spreads small particles throughout the cytoplasm
- cyclosis or streaming: circular motion of cytoplasm
- ER: network of channels for a passageway from PM to nuclear membrane
extracellular circulation
- diffusion: if in close contact, can serve as a means of transport for food and oxygen from environment; if larger animals, transport b/w cells and interstitial fluid
- circulatory system: complex animals whose cells are too far from the external environment require this to transport materials
cell division
-process by which a cell doubles its organelles and cytoplasm, replicates it DNA, and then divides into 2
interphase
- precedes cell division
- growth and chromosome replication
- after replication, chromosomes consist of 2 sister chromatids held together at the centromere
- consists of 3 parts: G1, S, G2
G1
- initiates interphase
- active growth phase
- cells increase in size and synthesizes proteins
- length of G1 determines length of cell cycle
S
period of DNA synthesis
G2
- cell prepares to divide
- grows and synthesizes proteins
Mitosis
- division and distribution of the cell’s DNA to its 2 daughter cells
- takes place in somatic cells
prophase
- chromosomes condense
- centriole pair moves to opposite poles, spindle apparatus forms b/w them
- nuclear membrane dissolves
metaphase
- fibers of the spindle apparatus attach to each chromatid at its kinetochore (location of centromere)
- chromosomes align at center of the cell forming a metaphase plate
anaphase
- centromeres split and sister chromatids separate
- spindle fibers shorten and pull sister chromatids to opposite poles
telophase
- spindle apparatus disappears
- nuclear membrane forms around chromosomes
- each nucleus contains a diploid number of chromosomes (same as parent)
- chromosomes uncoil
cytokinesis
- cytoplasm divides into 2 daughter cells
- in animals, cleavage furrow forms and pinches cell into 2 separate nuclei
- in plants, a cell plate forms
meiosis
- process by which sex cells are produced
- results in 4 haploid cells called gametes
interphase (meiosis)
chromosomes are replicated resulting in 2n number of sister chromatids
first meiotic division
produces 2 intermediate daughter cells with N chromosomes and sister chromatids
prophase 1
- chromatin condenses into chromosomes, spindle apparatus forms, and the nucleoli and nuclear membrane disappear
- synapsis: homologous chromosomes come together and intertwine
- tetrad: 2 sister chromatids, 4 chromatids
- crossing over occurs between homologous chromosomes (at chiasmata)
metaphase 1
tetrads align at the equatorial plate and each pair attaches to a separate spindle fiber at the kinetochore
anaphase 1
- homologous pairs separate and are pulled to opposite poles, called disjunction
- paternal origin separates from the maternal origin and either can end up in the daughter cell (random)
nondisjunction
occurs when cells do not separate appropriately, results in incorrect number of chromosomes
telophase 1
nuclear membrane forms around each nucleus, 2 sister chromatids still joined at a centromere
second meiotic division
- chromosomes align at the equator, separate, and move to opposite poles
- surrounded b a re-formed nuclear membrane with a haploid number of chromosomes
- 4 gametes produced
metabolism
- sum of all chemical reactions that occur in the body
- catabolic (break down chemicals) and anabolic (build up chemicals) reactions
absorption
passage of nutrient molecules thru the lining of the digestive tract into the body by diffusion or active transport
assimilation
building up of new tissues from digested food
regulation
- control of physiological activities
- body’s metabolism maintains its internal environment known as homeostasis and includes regulation of hormones
- irritability: ability to respond to a stimulus
respiration
- conversion of the chemical energy in molecular bonds into usable energy
- uses oxygen to convert glucose into ATP
external respiration
entrance of air into the lungs and gas exchange b/w alveoli and blood
internal respiration
exchange of gas b/w blood and the cells
fuel molecules
carbs and fats (C-H bond is energy rich)
dehydrogenation
- high energy hydrogen atoms are removed from organic molecules
- oxidation reaction
- reduction part is the acceptance of H by a H acceptor (ETC)
glycolysis
- oxidative breakdown of glucose into 2 molecules of pyruvate
- production of ATP
- reduction of NAD+ to NADH
- occurs in cytoplasm
fermentation
- NAD+ must be regenerated in order to continue in the absence of O2
- 2 ATP produced/glucose
alcohol fermentation
- occurs in yeast and bacteria
- pyruvate is converted to ethanol, which regenerates NAD+
lactic acid fermentation
- occurs in fungi and bacteria, human muscles during strenuous activity
- pyruvate reduced to lactic acid, NAD+ regenerated
cell respiration
- occurs in mitochondria
- 3 steps: pyruvate decarboxylation, CAC, ETC
pyruvate decarboxylation
- pyruvate from glycolysis is transported into the mitochondrial matrix and loses a CO2
- transferred to coenzyme A to form acetyl-CoA
- NAD+ reduced to NADH
citric acid cycle (Krebs cycle)
- 2 C acetyl group from acetyl-CoA combines with oxaloacetate to form a 6 C citrate
- 2 CO2 released, 2 ATP produced
- 6 NADH and 2 FADH2 produced and transport e- to ETC
electron transport chain
- located in the inner mitochondrial membrane
- series of carrier molecules (cytochromes) transfer e- to O2
- each carrier is reduced as it accepts e- and oxidized when it passes them
- free energy is released which is used to form ATP
- O2 picks up a pair of H ions to form water
substrate level phosphorylation
- forming ATP from the addition of a phosphate to ADP
- 4 ATP (2 form glycolysis and 2 for CAC)
oxidative phosphorylation
- transfer of e- fromNADH/FADH2 to O2, 32 ATP
- 2 NADH of glycolysis yield 4 ATP
- 8 NADH yield 24 ATP
- 2 FADH2 yield 4 ATP
alternative energy sources where glucose runs low
carbs, fats, then proteins
carbs
disaccharides converted into monosaccharides, which can be converted into glucose
fats
- stored in adipose tissue in form of triglycerides
- hydrolyzed by lipase into fatty acids and glycerol, can be converted into PGAL (a glycolytic intermediate)
- must be activated in the cytoplasm (requires 2 ATP), transported into mitochondria and converted to acetyl CoA
- yield greatest number of ATP per gram
proteins
- AA undergo transamination reaction in which they lose an amino group, then converted to acetyl CoA, pyruvate, or intermediates
- oxidative deamination: removes ammonia from AA, fish excrete it, birds/insects convert to uric acid, mammals convert to urea
enzymes
- organic catalysts
- regulate metabolism by speeding up certain chemical reactions, decrease activation energy
- many are conjugated proteins with a nonprotein coenzyme
- very selective
characteristics of enzymes
- do not alter the equilibrium constant
- not consumed in the reaction
- pH and temp sensitive
lock and key theory
-spatial structure of an enzymes active site is exactly complementary to its substrate (discounted theory)
induced fit theory
-active site has flexibility of shape
enzyme specificity
- as temp increases, rate increases until an optimum temp is reached
- optimal pH, above and below that enzymatic activity decreases
- conc low, rate is low; increasing conc increases the reaction rate until all active sites are occupied (then inc in conc doesn’t inc rate, reached Vmax)
competitive inhibition
- molecules that are similar to the substrate bind to the active site
- if sufficient quantities of the substrate are introduced, the substrate can outcompete the competitor
noncompetitive inhibition
- substance forms strong covalent bonds with an enzyme and it is unable to bind the substrate
- cannot be displaced by excess substrate
- never reach its Vmax
allosteric inhibition
inhibition takes place at a site other than the active site, changes the structure of the enzyme so the active site is also changed
enzymatic activity
- hydrolysis: digest large molecules into smaller ones
- lactase: hydrolyzes lactase to the monosaccharides glucose and galactose
- proteases: degrade proteins to AA
- lipase: break down lipids to fatty acids and glycerol
cofactors
-nonprotein molecule that is incorporated into an enzyme, can be metal cations (Zn2+ or Fe2+)
prosthetic groups
cofactors that bind to the enzyme by strong covalent bonds
