L4 - L6 Exam Review

The plasma membrane is built mainly from

Phospholipids and proteins 

Describe the ABO blood groups and their associated sugars

Type O = ?

Type A = ?

Type B = ?

Type AB = ?

O = core fucose

A = N-acetyl (GalNac)

B = Gal

AB = GalNac + gal

Which disease from L2 is caused by a broken membrane channel?

Cystic fibrosis 

Which organelle keeps its lumen acidic with a proton pump?

Lysosome

Would the following be able to cross the phospholipid bilayer?

Oxygen (O₂)

Crosses

Would the following be able to cross the phospholipid bilayer?

Ethanol

Crosses

Would the following be able to cross the phospholipid bilayer?

Glucose

Blocked

Would the following be able to cross the phospholipid bilayer?

Na+ ion

blocked

Would the following be able to cross the phospholipid bilayer?

A steriod hormone

Crosses

Would the following be able to cross the phospholipid bilayer?

ATP

Blocked

Which molecule diffuses easily across a pure lipid bilayer

a) Glucose

b) O₂

c) Na⁺

b) O₂

The most abundant class of membrane lipid

Phosphoglycerides

___________ = Glycerol backbone, two fatty acyl chains and a polar head

Phosphoglycerides

_______ = Sphingosine backbone with one fatty acid

Sphingolipids

_______ = Rigid four-ring sterol, mostly hydrophobic

Cholesterol

_______ = the most abundant membrane lipid

_______ = thicker; more stable membrane lipid

_______ = the fluidity buffer

Phosphglycerides

Spingolipids

Cholesterol

Phosphatidylcholine (PC), would be an example of?

A phosphoglyceride (the most abundant type of membrane lipid )

sphingomyelin and gangliosides would be an example of?

Sphingolipids (the thicker, more stable membrane lipid)

50 - 90% of all _______ sits in the plasma membrane

cholesterol

Gangliosides — stored in Tay-Sachs — are a type of…

Sphingolipid

Whch of the membranes would be the most fluid? (Rank the three from most fluid to least fluid)

Which change makes a membrane MORE fluid?

a) Longer fatty acid chains

b) More unsaturated chains 

c) More saturated chains

b) More unsaturated chains 

Lipid rafts are enriched in…

Cholesterol and sphingol

Annexin V marks apoptotic cells because it binds…

Phosphatidylserine on the outer leaflet 

Name the lipid…

Glycerol backbone; the most abundant membrane lipid

PHOSPHOGLYCERIDE

Name the lipid…

Ether-linked chain; made in peroxisomes

PLASMALOGEN

Name the lipid…

Phosphocholine head on a sphingosine backbone

SPHINGOMYELIN

Name the lipid…

Sugar-headed sphingolipid stored in Tay-Sachs

GANGLIOSIDE

Name the lipid…

Four rigid rings; buffers fluidity

CHOLESTEROL

Name the lipid…

Flips outward when a cell starts to die

PHOSPHATIDYLSERINE

Which change makes a membrane less fluid?

a) shorter fatty acid chains

b) more cholesterol

c) more unsaturated chains

b) more cholesterol (it decreases fluidty and increases saturation)

Phosphatidylserine normally sits on the?

inner (cytosolic) leaflet

Lipids and proteins move between leaflets…

a) freely and quickly

b) only in lipid rafts

c) rarely - they need specific proteins and energy

c) rarely - they need specific proteins and energy

A protein that crosses the bilayer 7 times with α-helices is a…

GPCR (has a lot of interaction with the plasma membrane)

Ras attaches to the membrane through…

A lipid anchor (prenylation)

(Ras is prenylated on the cytosolic face.)

Phospholipase A2 is an example of a…

Peripheral membrane protein 

Pump, channel or transporter?

Na⁺/K⁺-ATPase keeps Na⁺ out and K⁺ in

Pump

Pump, channel or transporter?

Acetylcholine opens a pore for Na⁺ on muscle

Channel

Pump, channel or transporter?

Glucose enters a red cell, downhill, one molecule type

Transporter (GLUT1 uniporter)

Pump, channel or transporter?

CFTR lets Cl⁻ flow out of airway cells

Channel

Pump, channel or transporter?

Lysosome acidifies its lumen using ATP

Pump

Pump, channel or transporter?

Na⁺ flowing in drags glucose in with it

Transporter (Na⁺/glucose symporter)

Which moves solute against its gradient?

a) An open ion channel

b) An ATP-powered pump

c) simple diffusion

b) An ATP-powered pump

Glucocorticoids reduce inflammation mainly by blocking

Phospholipase A2 

In glaucoma, excess TGFβ2 raises eye pressure by…

Adding ECM to the outflow pathway 

Name the protein

Cystic fibrosis

CFTR CHANNEL

Name the protein

Retinitis pigmentosa

RHODOPSIN (GPCR)

Name the protein

Familial hypercholesterolemia

LDL RECEPTOR

Name the protein

Duchenne muscular dystrophy

DYSTROPHIN COMPLEX

Name the protein

The target of glucocorticoids

PHOSPHOLIPASE A2

Name the protein

The target of aspirin

CYCLOOXYGENASE

In L1, one stem cell in the bone marrow gave rise to all

BLood cell types

Asymmetric division means one daughter cell

Self-renews, the other specializes 

x1 clone x1 stem

TGFβ receptors, from L5, are

Integral membrane signaling receptors 

Which germ layer?

Neurons and the retina

ECTODERM

Which germ layer?

Heart muscle

MESODERM

Which germ layer?

Liver and pancreas

ENDODERM

Which germ layer?

Blood cells

MESODERM

Which germ layer?

Epidermis and hair

ECTODERM

Which germ layer?

Lining of the lungs

ENDODERM

ES (embryonic stem) cells come from the

Inner cell mass of the blastocyst 

Methylation of a promoter CpG island usually…

Silences the gene 

A cell that can make an entire organism, including the placenta, is…

Totipotent

Intestinal stem cells are told to proliferate by…

Wnt

In many colon cancers, SFRP1 is silenced by…

Promoter DNA methylation 

A key advantage of iPSCs over ES cells is that they…

C   Can come from the patient's own cells 

Name the stem cell

Can make a whole organism, placenta included

TOTIPOTENT

Name the stem cell

From the blastocyst's inner cell mass

EMBRYONIC SC

Name the stem cell

Skin cell reprogrammed with transcription factors

iPSC

Name the stem cell

Lives in the hair follicle bulge

EPITHELIAL SC

Name the stem cell

Lives in the subventricular zone

NEURAL SC

Name the stem cell

About 1 in 10⁴ marrow cells

HEMATOPOIETIC SC

Describe the fluid mosiac model

Lipid bilayer + many proteins that move sideways; each organelle’s membrane differs

what are the two faces of plasma membrane

Every membrane has a cytosolic face and an exoplasmic face

describe the amphipathic nature of phospholipids

Hydrophilic heads face water; hydrophobic tails face each other

describe the permeability of the plasma membrane

Gases and small uncharged molecules (ethanol) cross; ions, glucose, amino acids, peptides cannot

describe phosphoglyerides

Glycerol backbone, two fatty acyl chains; most abundant (e.g., PC, PE, PS)

Describe sphingolipids. Gangliosides?

Sphingosine backbone; sphingomyelin, gangliosides; thicker, more stable

Dsscribe cholesterol

Rigid sterol; buffers fluidity; mostly in the plasma membrane

describe the fluidity of the plasma membrane

More fluid: unsaturated, shorter chains, warmer; lateral movement fast, flip-flop rare

What are lipid rafts?

Cholesterol- and sphingolipid-rich, less fluid microdomains

DEsrcibe the asymmetry of the plasma membrane.

What happens during apoptosis

PS on the cytosolic leaflet; flips outward in apoptosis → annexin V binds it

Describe intergral porteins

Embedded in the bilayer: single-pass, multipass (GPCRs), β-barrels (porins)

Describe lipid-anchored proteins

GPI anchor = outside face; prenylation and fatty acylation = cytosolic face

Describe peripheral proteins

What is an example of this?

Bind head groups or other proteins on the surface (e.g., phospholipase A2)

What are integrins

Anchor the cell to the extracellular matrix

Describe GPCRs. What is an important one

Seven transmembrane helices; couple to heterotrimeric G proteins (switches);

Rhosopsin

Describe glycolyx and what arrises from them

Glycoproteins, glycolipids, proteoglycans; protects, aids contact; ABO groups (codominance)

Describe the transport of the biomembrane

Facilitated diffusion (downhill, no energy) vs. active transport (uphill, ATP or a gradient

Describe the 3 important ways of transporting proteins

Pumps (slowest, ATP), channels (fastest, gated), transporters (uni-, sym-, antiporters)

What is arachidonic acid and COX

PLA2 releases it from phospholipids; COX (blocked by aspirin) is the enzyme that converts arachidonic acid and makes prostaglandins

Describe the importance of TGFβ

Excess → fibrosis; TGFβ2 raises eye pressure in glaucoma

What are the major membrane diseases and their associated diseases

CF (CFTR), Duchenne (dystrophin), retinitis pigmentosa (rhodopsin), FH (LDL receptor)

What is differentiation?

Progressive restriction of developmental potential to form specialized cells

What is a stem cell?

Unspecialized cell; can self-renew and form several different cell types

What is a progenitor cell?

Partly differentiated intermediate that forms more specialized cells

What is terminal differentiation

Irreversible; highly specialized cells that usually stop dividing