Cell structure and function Flashcards
Large quantities of ATP are stored in all cells. T/F
False: ATP must be continuously synthesized to meet energy needs.
glycolysis occurs where
in the cytosol and is an anaerobic process
lipid bilayer is highly permeable to?
lipid soluble and non-charged molecules.
channel proteins allow
passive transport of ions
intercellular communication is accomplished by 3 principal means:
Gap junctions
Direct cell-to-cell
Chemical mediators.
List functions of the plasma membrane (8)
endocytosis– highly selective shield
exocytosis– recognition
active transport– communication
membrane potentials– growth regulation
3 types of membrane lipids are
cholesterol
phospholipids
glycolipids
define amphipathic
lipids have a hydrophillic charged end and a hydrophobic non-polar end.
Proteins filaments that comprise the cellular skeleton
actin filaments
microtubules
intermediate filaments
Largest cytoplasmic organelle
controls production of cellular enzymes. membrane receptors and structural proteins.
Nucleus
converts energy to forms needed to drive cellular reactions. Oxidative phosphorylation occurs here, generating most of the cell’s ATP
Mitochondria
membrane bound bags of degradative enzymes.
Peroxisomes
many found in liver and kidneys.
coated with ribosome and their primary role is the synthesis of proteins for membrane components, and synthesis of products to be excreted from the cell.
Rough ER
gathers simple molecules and combines them to make complex molecules which are then packaged and transported out of the cell.
Golgi Apparatus
involved in lipid metabolism and are found in large quantities in cells specializing in the production of steroid hormones or lipoproteins
Smooth ER
organelles containing acid hydrolases capable of digesting organic molecules.
lysosomes
small, lipid insoluble molecules are transported across plasma membrane by
transporter proteins
calcium against its concentration gradient is transported across plasma membrane by
membrane calcium transporter
large, lipid insoluble molecules are transported across plasma membrane by
endocytosis
ions moving down concentration gradient are transported across plasma membrane by
membrane channel proteins
glucose is transported across the plasma membrane by
passive transport carrier
tissue with synchronized function use this type of cell signaling
gap junctions
ligand signaling
target cells respond to ligands signaling through specific protein receptors.
synaptic signaling
nerve cell releases neurotransmitter into gap junction where it binds to target cell to cause an effect.
paracrine
affect localized cells.
endocrine
hormone released through bloodstream.
autocrine
cell responds to its own signals.
Active transport
transports substances against concentration gradient
sodium-potassium pump
transports 3 sodium ions out of the cell in exchange for 2 potassium ions.
major determinant of resting potential is
potassium ion concentration across the membrane
Binding of a ligand to a G-Protein receptor stimulates
adenylyl cyclase to produce a second messenger within the target cell
saturated lipids
straight tails that pack together and tent to stiffen membrane
unsaturated lipids
bent tails tend to increase fluidity
glycolipids and glycoproteins
found in outer half of lipid bilayer, with the sugar groups exposed at the cell surface.
Glycolipids involved in cell recognition and cell to cell interations
tight junctions
connect neighboring cells like a fence to confine proteins to a certain area.
actin filament
movement, information transfer
microtubules
organization, orderly transport within cell, equal distribution of chromosomes during division.
intermediate filament
strong, ropelike
nucleus inner membrane
unbroken sphere around DNA and contains protein binding sites that help organize chromosomes.
nucleus outer membrane
continuous with endoplasmic reticulum and closely resembles it in structure and function
nuclear pores
holes in membrane allowing proteins into the nucleus.
- mediate export like RNA and ribosomes
nucleolus
manufactures ribosomes
Endoplasmic reticulum
central role in the synthesis of membrane components, proteins, and lipids for the plasma membrane, organelles, and synthesis of products to be secreted.
ribosomes
synthesis of proteins, can free float or ind to the ER.
-signal recognition particles bind to leading sequence of the protein
translocon
pore in the ER that protein chain pushed through.
cisternae
stack of smooth membrane bound compartments
3 processing compartments of golgi
cis face
middle compartment
final compartment
cis face of golgi cisternae
next to ER, receives newly synthesized proteins and lipids from transport vesicles which bind and become part of golgi
middle compartment of golgi cisternae
modify proteins and lipids
final comartment of golgi cisternae
depart for final destination
lysosomes obtain materials to digest in 3 ways
endocytosis
autophagy
phagocytic cells
autophagy
damaged/obsolete parts of cell destroyed
phagocytic cells
WBC engulf particles then fuse with lysosome
peroxosomes
use oxidative enzymes to perform degradative functions
oxidative enzymes
use molecular oxygen to breakdown organic substances- byproduct is hydrogen peroxide which is then used to degrade other molecules by catalase enzyme.
Mitochondria inner membrane
forms enclosed space called matrix, contains a concentrated mix of enzymes
cristea
highly convoluted structure with multiple folds of inner membrane of mitochondria, provides large surface area for membrane bound enzymes of respiratory chain; production of ATP.
mitochondria outer membrane
numerous porin transport proteins forming large aqueous channels making membrane porous
- large proteins can pass through freely
- specific protein transporters need to shuttle across inner mitochondrial membrane.
anabolism
energy using metabolic processes that results in synthesis of complex molecules; fats
catabolism
energy releasing breakdown of. nutrients such as glucose to produce ATP.
glycolysis
10 enzymatic steps to break the six-carbon glucose molecule into a pair of three-carbon pyruvate molecules
- requires 2 ATP in early stage
- produces 4 ATP in later stage; net gain of 2 ATP and 2 NADH
- anaerobic process
lactic acidosis
may result after prolonged anaerobic conditions; leading to glycolysis.
pyruvate
product of glycolysis; converted to lactate and excreted in blood stream.
NADH
Product of glycolysis; contain high-energy electrons that are transferred to electron transport chain in mitochondria
citric acid cycle
results in complete oxidation of glucose to final products; CO2 and H2O.
- pyruvate and fatty acid enter mitochondrial matrix and are converted to acetyl CoA
- acetyl CoA (2 carbon) transferred to oxaloacetate molecule (4 carbon) creating citrate (6 carbon)
- 2 carbons cleaved to create 2 CO2 molecules for each turn of the cycle.
- produces one ATP molecule per cycle but captures a great deal of energy in form of H-
- H- combines with NAD+ and FAD to create NADH and FADH2 which got into oxidative phosphorylation
oxidative phosphoylation
results in ATP by reaction of ADP + inorganic phosphate (Pi) ADP + Pi = ATP
oxidative phosphorylation steps
- hydrogen transported to electron transport chain by carrier molecules NADH and FADH2.
- enzymes of transport chain harness energy from the transported protons (H+) gradient.
- proton gradient used to power synthesis of ATP
- ATP synthase: enzyme in the inner mitochondrial membrane allows protons to flow back into mitochondria down their gradient
- About 30 ATP are form ed from complete oxidation of glucose into CO2 and H2O.
- – 2 from glycolysis
- – 2 from citric acid cycle
- — remainder from oxidative phosphorylation
transporter proteins
highly specific to transport specific molecules
Active transport pumps
move solutes across the membrane against the concentration gradient
Membrane transport carriers
bind molecules then move across membrane
Na+ driven carrier
Na+ gradient produced by Na+-K+ pump is used to power a variety of transporters by secondary active transport.
passive transport carrier
move substances across membrane passively
membrane channel proteins
water filled pores in membrane.
- transport ions passively
- highly selective
- open and close according to membrane signals.
voltage gated membrane channel
respond to change in membrane potential
mechanically gated membrane channel
respond to mechanical deformation
ligand gated membrane channel
responds to binding of a signaling molecule
resting potential
electrical charge present in side cell when there is no ion movement across the membrane
K+ remains inside cell due to
active transport
attraction of negatively charged ions inside cell
action potential
cells are electrically excitable
- react to changes in voltage across membrane
- influx of positive ions causes shift in membrane potential to a less negative value: depolarization
- threshold: reached when membrane patch becomes approx. -65mV
- activate volate-gated Na+ channels allowing rapid influx of Na+.
- – influx in one patch causes membrane depolarization of next patch, opening more Na+ channels
- repolarization: Na+ inflow is stopped by closing channels and K+ outfow is increased: passive and channels open.
gap junction
connecting channels between adjacent cells, allows passage of small molecules.
direct cell to cell contact
cell membrane receptors with signaling molecules present on another molecule.
- important for development of immune response.
chemical mediators
synaptic
paracrine
endocrine
autocrine
cell surface receptor-mediated responses
ion channel linked receptor
enzyme linked receptors
G-Protein-coupled receptors (GPCR’s)
ion channel linked receptor
bind neurotransmitter causing ion channels in membrane to open or close
enzyme linking receptors
catalyze enzyme reaction when activated.
- function as protein kinases: mediate transfer of phosphate groups from ATP or GTP to proteins and thus affect activity of target protein
G-Protein-coupled receptors (GPCR’s)
controls production of 2nd messenger
- most hormones and drugs have effects here
- activated subunits influence activity of target enzymes.
- 3 types: G- proteins, Gq and Gi
G-proteins (GPCR’s)
subunit stimulates production of cAMP
Gq (GPCR’s)
subunit stimulates enzyme phospholipase C.
- cleaves a membrane phospholipid to form 2 secondary messengers
- inositol 1,4,5-triphosphate (IP3)
- diacylglycerol (DAG)
Gi (GPCR’s)
inhibitory to the production of cAMP
secondary messengers (5)
cAMP IP3 DAG Ca2+ cGMP
intracellular receptor mediated response
specific for particular ligand, must be lipid soluble and able to pass directly through cell membrane.
Proliferation
G1
S phase- synthesis
G2
M phase- mitosis and cell division
pRb
Rb protein important in preventing a cell form proceeding through cell cycle.
- bind to E2F and gene transcription factor, rendering it unable to bind to DNA and begin replication.
