Slide set 2 Flashcards by Valeriya Boyarkina

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

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What keeps genes inactive

Genes are tightly coiled with histones

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Two stages of of protein synthesis

DNA->RNA - transcription

RNA->protein-translation

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Rosalind Franklin discovered helix structure in

1953

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Nucleosome is

A block of DNA coiled around histones . Nucelosome is repeated to make chromatin

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Name of 4 histones in nucleosome

H2A
H2B
H3
H4

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What is an enzyme that copies DNA

RNA polymerase

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DNA is unwound by ___ during transcription

DNA helicase

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What initiates transcription

RNAa polymerase and TFs that bind to the promoter sequence

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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.

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What mice are infertile

CREM null

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Exons vs introns

Exons-expressed (exit the nucleus)

Introns- non-coding regions

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epigenetic mechanisms are affected by

Developement (childhood, in utro)
Environemntal chemicals
Drugs/Pharmaceuticals
Aging
Diet

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DNA methylation result in

Inactivating the gene

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What are housekeeping genes

That are always expressed

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Two types of channels that create a water-filled pore

Open channels

Gated channels

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Types of proteins that never form an open channel between the two sides of the membrane

Uniport

Cotransporter (symport or antiport)

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What do cell pumps do

Mmebrane transporters that move a substance against its concentration gradient-the opposite of diffusion

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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