Importants Quiz 1 Flashcards
levels of organization
cell, tissue, organ, organ system
4 primary tissue types
epithelial, connective, muscular, nervous
epithelial
inside of mouth, skin
connective
tendon, blood, lymph
muscular
skeletal, smooth, cardiac
nervous
neurons and spinal cord
3 basic germ layers
ectoderm, endoderm, mesoderm
ectoderm
forms skin including mammary glands and neural tissue
mesoderm
muscle, connective, plural tissues
endoderm
lungs, organs, gut and liver
larger organisms have
smaller surface area/volume ratios
advantage and disadvantage of smaller surface are/ volume ratio
advantage: better retention of heat
disadvantage: reduced ability to obtain enough nutrients
endocrine vs exocrine
exocrine - secretes out of body
endocrine - degrades and absorbs
3 epithelial cells
squamous, columnar, cubodial
homeostatically regulated factors of internal environment
pH, temperature, volume and pressure, concentration of O2 and CO2
whole body control systems
nervous and endocrine
nervous system
travels fast (neurons and nerve cells)
endocrine system
hormones (inner protein or fat)
categories of organic molecules
carbohydrates, pipids, proteins, nucleic acids
carbohydrates
monosaccharides, polysaccharides
lipids
fatty acids, triglycerides, phospholipids, cholesterol
proteins
composed of amino acids, highly complex 3D structures, peptides are smaller chains of amino acids
nucleic acids
composed of nucleotides, DNA and RNA
plasma membrane
separates the cells content from the surrounding environment, selectively controls movement of molecules between intracellular fluid and extracellular fluid
nucleus
-contains materials for genetic instructions and inheritance
-packaged with histones to form chromosomes
-control center of cell
cytoplasm
contains organelles and cytoskeleton dispersed within the cytosol
functions of DNA
provides a code of information for RNA and protein synthesis
-serves as a genetic blueprint during cell replication
DNA contains codes for making RNAs and proteins through
transcription and translation
transcription
gene copied into pre-messenger RNA by RNA polymerase, pre messenger RNA is processed into messenger RNA by removing noncoding sequences and adding signal sequences
translation
mRNA leaves the nucleus and delivers a coded message to a ribosomes, ribosomal RNA (rRNA) translates the mRNA code into amino acid sequences, transfer RNA transfers the appropriate amino acids from cytoplasm to ribosome to be added to the protein under construction
all cells in a multicellular eukaryote have
the same DNA sequence
different genes are expressed in
different tissues or at different times
endoplasmic reticulum
elaborate, fluid filled membranous system distributed throughout the cytoplasm
rough ER
ribosomes bound to outer surface gives rough ER its granular appearance, new proteins synthesized by ribosomes are released into lumen of rough ER
smooth ER
no ribosomes, synthesis of lipids, detoxify toxic compounds in liver cells, sarcoplasmic reticulum stores calcium in muscle cells
important minerals
calcium, sodium, potassium
ribosomes
ribosomal RNA protein complexes, synthesize proteins under direction of nuclear DNA
free ribosomes
dispersed throughout the cytosol, synthesize proteins that remain in the cell
bound ribosomes
found on membranes of the rough endoplasmic reticulum, synthesize proteins that are exported out
golgi complex
consists of stacks of flattened, slightly curved sacs (cisternae)
main function of golgi complex
modifies proteins and sorts
lysosomes
small organelles that vary in size and shape, break down organic molecules, contain hydrolases, enzymes that catalyze hydrolysis reactions, remove worn out organelles
process of endocytosis
pinocytosis, receptor mediated endocytosis, phagocytosis
proteosomes
large tunnel like strucutures made of proteins, break down internal proteins into amino acids, unwanted proteins are tagged with ubiquitin in order to be recognized by proteosomes
peroxisomes
membrane enclosed sacs smaller than lysosomes, contain oxidative enzymes, strip hydrogen from organic molecules, major product is hydrogen peroxide, catalase in peroxisomes decomposes H2O2 into H2O and O2
mitochondria
oval shaped organelles enclosed by double membrane, smooth outer membrane, inner membrane has infolding shelves called cristae, inner gel like matrix contains enzymes
how is the mitochondria the power plant of the cell
makes 90% of energy that cells need to survive and function
aerobic metabolism in mitochondria relies on
O2 to convert energy in food to ATP
aerobic vs anaerobic
aerobic requires comsumption of O2, anaerobic pathways can proceed in absense of O2
major steps in generation of ATP
glycolysis, citric acid cycle, electron transport chain associated with oxidative phosphorylation
glycolysis
chemical process that breaks down glucose into 2 pyruvate molecules, involves 10 sequential reactions, each catalyzed by a separate enzyme, all glycolytic enzymes are found in the cytoplasm, can proceed in anaerobic conditions, releases 2 electrons to form NADH, not very efficient
citric acid cycle
8 reactions catalyzed by enzymes, pyruvate produced by glycolysis then converted to acetyl CoA by removinga carbon and forming CO2. acetyl CoA then combines with oxaloacetic acid to form citric acid, 2 carbons released as CO2, 1 atp produced
key purpose of citric acid cycle
produce hydrogens for entry into electron transport chain
electron transport chain
electron carrier molecules located in inner mitochondrial membrane, electrons transferred through a chain of reactions with electrons faling to lower energy levels at each step, O2 is final electron acceptor, O2 combines with elecrtons and hydrogen to form H2O
some energy released during transfer is used to synthesize ATP, total ATP yield 30-32 ATPs per molecule of glucose
metabolism under anaerobic conditions
O2 deficiency forces cells to rely on glycolysis, pyruvate is converted to lactate, lactate accumulates in the tissues and reduces pH, can be converted back to pyruvate
tolerance of O2 deficiency varies
obligate aerobes, facultative anaerobes, obligate anaerobes
vaults
hollow, octagonal organelles capable of docking with nuclear pores, transport molecules from (eg mRNA) nucleus to cytoplasm
cytosol
highly organized, gelatinous mass surrounding the organelles in the cytoplasm
functions of cytosol
enzymatic regulation of intermediary metabolism, ribosomal protein synthesis, storage of fat and carbohydrates, temporary storage of vesicles
centrosome
cell’s microtubule organizing center, composed of microtubules radiating outward from two centrioles, microtubles are highways for transport of chromosomes and vesicles, form mitotic spindle during cell division, cilia and flagella in some cells
cytoskeleton
provides an intracellular scaffolding to support and organize cell’s components and control their movements
microtubules
maintain cell shape and are important in cell movements
microfilaments
part of the cellular contractile systems and as mechanical stiffeners
intermediate filaments
maintain cell structure and resist mechanical stress
cells held together by
cell adhesion molecules, extracellular matrix secreted mostly by fibroblasts that hold cells together, specialized cell junctions
specialized cell junctions
desmosomes, tight junctions, gap junctions
desmosomes (adhering junctions)
anchor together two closely adjacent cells through cell adhesion molecule (cadherins), abundant in tissues subject to stretching
tight junctions
join sheets of epithelial tissue, membranes of 2 cells join together, prevent materials from pass between cells, IMPERMEABLE
gap junctions
adjacent cells are linked by small connecting tunnels (connexons), movement on ions through gap junctions transmit electrical activity, enable synchronized contraction of muscle, COMMUNICATION JUNCTIONS
plasma membrane
encloses the intracellular contents, selectively permits specific substances to enter or leave the cell, responds to changes in cell’s environment
plasma membrane is a
fluid lipid bilayer embedded with proteins
phospholipids
most abundant membrane component, head contains charged phosphate group (hydrophilic), 2 nonpolar fatty acid tails (hydrophobic), assemble into lipid bilyaer with hydrophobic tails in center and hydrophilic heads in contact with water, fluid structure not held together by chemical bonds
cholesterol
placed between phospholipids to prevent crystallization of fatty acid chains, helps stabilize phospholipids position, provides rigidity especially in cold temps, cold induced rigidity is countered in poikilotherms by enriching membrane lipids with polyunsaturated fatty acids
membrane proteins
integral proteins are embedded in lipid bilayer, have hydrophilic and hydrophobic regions, transmembrane proteins extend through the entire thickness of the membrane, peripheral proteins found on inner or outer surface of membrane, polar molecules and anchored by weak chemical bonds to polar parts of integral proteins or phospholipids
2 models of membrane structure
fluid mosaic model (membrane proteins float freely in a sea of lipids) and membrane skeleton fence model (mobility of membrane proteins is restricted by the cytoskeleton)
specialized functions of membrane proteins
- channels
- carriers
- receptors
- docking marker acceptors
- enzymes
- cell adhesion molecules
- self identify markers
membrane carbohydrates
located only on outer surface of membrane, short chain carbohydrates bound to membrane proteins (glycoproteins) or lipids (glycolipids), important roles in self recognition and cell to cell interactions
plasma membrane is _____ permeable
selectively
permeability depends on
high lipid solubility and small size
force is needed to produce the movement of particles across the membrane
passive - doesnt require cell to expend energy
active - require cellular energy (ATP)
diffusion
passive, higher concentration to lower, equilibrium reached when no concentration gradient and no net diffusion
Fick’s law of diffusion
rate of which diffusion occurs depends on
1. concentration gradient
2. permeability
3. surface area
4. molecular weight
5. distance
6. temperature
unassisted membrane transport
movement of ions across the membrane is affected by electrical charge. difference in charge produces an electrical gradient, electrical gradient passively induces ion movement (conduction), only ions that can permeate plasma membrane can conduct down this gradient
electrochemical gradient
existence of electrical gradient and concentration gradient
osmosis
water moves across a membrane from lower solute to higher solute concentration, driving force = concentration gradient, hydrostatic pressure opposes osmosis , osmotic pressure is pressure required to stop osmotic flow, stops when theres a balance of tendency of osmosis and hydrostatic pressure, osmotic pressure proportional to concentration of nonpenetrating solute
isotonic
same concentration of nonpenetrating solutes as in normal cells, cell volume constant
hypotonic
lower solute concentration, cell volume increases, maybe lysis
hypertonic
higher solute concentration, cell volume decreases, causes crenation
phospholipid bilayer impermeable to
large poorly lipid soluble molecules and small charged molecules
3 assisted membrane transport
channel, carrier mediated, vesicular
channel transport
transmembrane proteins form narrow channels, highly selective, permit passages or ions or water, gated channels can be open or closed, leak channels always open, faster than carrier mediated
carrier mediated transport
transmembrane proteins that can undergo reversible changes in shape, binding sites can be exposed to either side of membrane, transport small water soluble substances, facilitated diffusion or active transport are carrier mediated
facilitated diffusion
passive carrier mediated transport from high to low, doesnt need energy, molecule attaches on binding site of protein carrier, carrier protein changes conformation, exposing bond molecule to other side of the membrane, bound molecule detaches from carrier, carrier returns to OG state
active transport
moves a substance against its concentration gradient, requires energy, primary active transport - energy directly required, ATP split to power transport, secondary active transport - ATP not directly used, carrier uses energy stored in form of ion concentration gradient build by primary active transport
Na+ - K+ ATPase pump
pumps 3 Na+ out of cell for every 2 K+ in, splits ATP for energy, phosphorylation induces change in shape of transport protein, maintains Na+ and K+ concentration gradients across plasma membrane, helps regulate cell volume
secondary active transport
simultaneous transport of nutrient molecule and ion across plasma membrane by cotransport protein, nutrient molecule transported against concentration gradient, driven by simultaneous transport of an ion along its concentration graident
characteristics of carrier mediated transport systems
specificity, saturation, competition
specificity
each carrier protein specialized to transport specific substances
saturation
limit to the amount of a substance that a carrier can transport in a GIVEN TIME
competition
closely related compounds may compete for same carrier
vesicular transport
transport between icf and ecf wrapped in membrane bound vesicles, rate of endocytosis and exocytosis must be balanced, caveolae may help transport substances and cell signaling
endocytosis
incorporates outside substances into cell,
exocytosis
releases substances into ECF
direct intercellular communication
gap junctions, transient direct linkup of surface markers, nanotubes
indirect intercelllular communication
intercellular chemical messengers, synthesized by specialized cells to serve a designated purpose, bind with specific receptors on target cells
categories of chemical messengers
paracrines, neurotransmitters, hormones, neurohormones, pheromones, cytokines
paracrines
local chemical messengers whose effect is exerted only on neighboring cells
neurotransmitters
used by neurons which communicate directly with the cells they innervate
hormones
long range chemical messengers that are secreted into the circulation by endocrine glands
neurohormones
hormones released into the circulation by neurosecretory neurons
pheromones
chemical signals released into the environment to reach sensory cells of other animals
cytokines
regulatory peptides made by almost any cell, generally involved in development and immunity
signal transduction
extracellular chemical messengers bind with receptors to trigger a biochemical chain of events inside the target cell, process by which incoming signals are conveyed to target cell’s interior for execution, lipophilic and lipophobic
lipophilic
extracellular messengers, pass through the target cell’s plasma membrane to bind to intracellular receptors
1. produce second messenger or 2. alter gene transcription
lipophobic
extracellular messengers, cannot pass through the target cell’s plasma membrane, bind with surface membrane receptors,
1. open or close specific membrane channels to regulate ion movement or 2. activate an enzyme that phosphorylates a cell protein or 3. transfer the signal to an intracellular second messenger
opening and closing of membrane receptor channels
chemically gated, voltage gated, mechnically gated
chemically gated
respond to binding of an extracellular chemical messenger to a specific membrane receptor
voltage gated
respond to changes in electrical current in plasma membrane
mechnically gated
respond to stretching and other mechanical deformation
phosphorylating enzymes
protein kinase phosphorylates a target cell protein, phosphorylated protein changes shape and function, activated protein kinase sites phosphorylate cytoplasmic proteins to lead to the cellular response tyrosine kinase phosphorylates its own tyrosine residues (autophosphorylation)
G protein coupled membrane receptors
inactive G protein on inner surface of plasma membrane contains a,b,c subunits with a GDP bound to the a subunit, hormone binds with its receptor, receptor attaches to G protein releasing GDP and attaching GTP to the a subunit, activated a subunits links with an effector protein in the membrane and alters its activity
cyclic AMP second messenger GPCR pathway
binding of hormone to its receptor activates a G protein, activated a subunit links with adenylyl cyclase in the membrane, activated adenylyl cyclase converts intracellular ATP to cyclic AMP, cyclic AMP activates protein kinase A, protein kinase A phosphorylates intracellular proteins, leading to the cellular reponse
why do multiple steps exist in signal transduction pathway
trying to correct and amplify signal
second messenger system
shared by many cell types, multiple steps lead to AMPLIFICATION of initial signal, receptors are subject to regulation (downregulation or upregulation of receptor number), drugs and toxins alter communication pathways (antagonists and agonists_
antagonists vs agonists
antagonists - block a step, agonists activate a step
resting membrane potential
due to differences in distribution and permeability of key ions, NA is greater in ECF, K is greater in ICF, concentration differences maintained by Na-K_ATPase pump, differnt solubilities in cell water and affinity for cell proteins, large negatively charged proteins (A-) are concentrated in ICF, Na - K pump transports 3 Na out for every 2 K in, membrane has more K lead channels than Na leak channels
equilibrium potential
membrane potential at which there is no net movement of the ion across the membrane, concentration gradient balanced by opposing electrical gradient, greater the permeability of the plasma membrane for a given ion, greater the tendency for that ion to drive the membrane potential toward the ions own equilibrium potential, membrane more permeable to K than to Na, so membrane potential is closer to K equilbirium potential
membrane potential maintained at
steady state, passive leaks of K out of cell and Na into cell balanced by N K pump
Na/ K pump main functions
maintain resting membrane potential, control cell volume, provide concentration gradient for glucose and protein transport
