Slide set 2 Flashcards
Function of proteins
Form enzymes: control synthesis and
breakdown
- Form transport proteins and pores in the PM
and in organelle membranes: regulate
movement
- Form the structural skeleton of cells and
tissues
What keeps genes inactive
Genes are tightly coiled with histones
Two stages of of protein synthesis
DNA->RNA - transcription
RNA->protein-translation
Rosalind Franklin discovered helix structure in
1953
Nucleosome is
A block of DNA coiled around histones . Nucelosome is repeated to make chromatin
Name of 4 histones in nucleosome
H2A
H2B
H3
H4
What is an enzyme that copies DNA
RNA polymerase
DNA is unwound by ___ during transcription
DNA helicase
What initiates transcription
RNAa polymerase and TFs that bind to the promoter sequence
Two types of TFs
-if they can activate specific genes they are called
gene-specific transcription factors ex estrogen
receptor =estrogen target gene specific
• Transcription factors that are required to activate all
genes are called general transcription factors.
What mice are infertile
CREM null
Exons vs introns
Exons-expressed (exit the nucleus)
Introns- non-coding regions
epigenetic mechanisms are affected by
Developement (childhood, in utro) Environemntal chemicals Drugs/Pharmaceuticals Aging Diet
DNA methylation result in
Inactivating the gene
What are housekeeping genes
That are always expressed
Two types of channels that create a water-filled pore
Open channels
Gated channels
Types of proteins that never form an open channel between the two sides of the membrane
Uniport
Cotransporter (symport or antiport)
What do cell pumps do
Mmebrane transporters that move a substance against its concentration gradient-the opposite of diffusion
What does transport by vesicles allow
Allows substances to enter or leave the interior of a cell without actually moving through its plasma membrane
What is osmotic equilibrium
the fluid concentrations are equal on the two sides of the
cell membrane.
What is electrical disquilibrium
the inside of cells is slightly negative relative
to the extracellular fluid.
What ions are more present in extracellular than in intracellular
HCO3-, Na,Cl,Ca -extracellular fluid
K-more present inside the cell
Difference between primary and secondary active transport
Primary active transport directly uses a source of chemical energy (e.g., ATP) to move molecules across a membrane against their gradient.
The electrochemical gradients set up by primary active transport store energy, which can be released as the ions move back down their gradients. (Sodium-glucose co-transporter)
Three properties that exhibit carrier-mediated transport
Specificity
Competition
Saturation
What happens to the many macromolecules that are too large to enter or leave cells through protein channels
Vesicle transport
What is phagocytosis
is the actin-mediated process by which a cell
engulfs a bacterium or other particle into a large membranebound
vesicle called a phagosome, later phagosome fuses with lysosome, requires ATP
Happens in certain types of WBSc
Difference between endocytosis and phagocytosis
First, in endocytosis the membrane surface indents rather
than pushes out. Second, the vesicles formed from endocytosis
are much smaller. In addition, some endocytosis is constitutive;
that is, it is an essential function that is always taking place. In
contrast, phagocytosis must be triggered by the presence of a substance
to be ingested.
Pinocytosis is ___ type of transport
nonselective
Receptor-mediated endocytosis takes place in
Regions of cell membrane called coated pits
The most common protein found in coated pits is
Clathrin
Some endocytosis uses small flask-shaped indentations called ____
Caveolae , membrane regions with lipid rafts, membrane receptor proteins and specialized membrane proteins -caveolins and cavins
Ensocytosis is used for
Export of proteins synthesized inside the cell and to get rid of waste
How endocytosis occur
enclosed in membranous vesicles, pulled by the
cytoskeleton to the plasma membrane, where
the contents are released
4 classes of membrane proteins
membrane transporters
Structural proteins
Membrane enzymes
Membrane receptors
3 types of gated channels
Mechanically gated
Voltage-gated
Chemically gated
What is apical membrane
The surface of the epithelial cell that
faces the lumen of an organ, also called mucosal membrane
What is basolateral membrane
the three
surfaces of the cell that face the extracellular fluid, also called serosal
Transporting epithelial is said to be ____ because of different properties
Polarized
Na-K-ATPase is usually only found on __ and Na-gluvose symporter SGLT are restricted to ___
Apical membrane
The basolateral membrane
What is absorption
Transport of material from the lumen of an organ to the extracellular
fluid
two types of movement across an epithelium and its characteristics
paracellular transport
through the junctions between adjacent cells or as transcellular
transport through the epithelial cells themselves
Epethilia can be either ___ (like capillaries) or ___ (like in kidney)
Leaky
Tight
Transporting epithelium __ (whata does it do)
Selectively regulates exchange of ions and nutrients
Characteristic of transporting epithelia
Thicker, membrane modification (microvili), cell junctions, mitochondria
What is transcytosis
a combination of endocytosis,
vesicular
transport across the cell, and exocytosis
Explain transcytosis
the molecule is brought into the epithelial cell via
receptor-mediated endocytosis. The resulting vesicle attaches to
microtubules in the cell’s cytoskeleton and is moved across the
cell by a process known as vesicular transport. At the opposite
side of the epithelium, the contents of the vesicle are expelled
into the interstitial fluid by exocytosis.
What is absorbed by means of transcytosis
infants absorb maternal antibodies in breast milk
