Cell Biology Lecture Week 3

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40 Questions

What is the main function of transport proteins present in the plasma membrane?

Actively bringing things in or sending things out

Which macromolecule is NOT mentioned as a component of membranes in the text?

Nucleic Acids

Where are carbohydrates typically found in relation to membranes?

Attached to either lipids or proteins

A phospholipid has three fatty acid tails.

False

Phospholipids contain a phosphate group (which is negatively charged).

True

Phospholipids have a variable head group, which is polar in nature and will interact with aqueous environments.

True

Phospholipids are amphipathic.

True

What is the term used for the constant spinning of a phospholipid on its axis?

Rotation

How does unsaturated fatty acids impact membrane fluidity?

Increase fluidity

What is the role of cholesterol in membrane fluidity at warm temperatures?

Increase rigidity

Which type of motion involves two phospholipids swapping places within the same leaflet?

Lateral diffusion

How do longer hydrocarbon chains in fatty acids affect membrane fluidity?

Make membranes less fluid

What is the main characteristic of phospholipids that allows them to spontaneously form a bilayer in an aqueous environment?

Amphipathic nature

Which type of phosphoglyceride has a head group of choline?

Phosphotidylcholine

What is the major structural difference between phosphoglycerides and phosphosphingolipids?

Type of backbone

How many fatty acid chains do phosphosphingolipids typically have?

One

Who made the discovery that phospholipids form a bilayer in 1925?

Gorter and Grendel

Phosphoglycerides and sphingolipids are examples of phospholipids.

True

Which feature is true for sphingolipids?

Single fatty acid chain that is longer than those found in phosphoglyceride

A membrane will be more rigid if it has many unsaturated fatty acids.

False

What is the defining characteristic of integral membrane proteins?

They penetrate into the hydrophobic region of the bilayer

Which type of protein is usually attached to glycolipids called GPI?

Lipid-anchored proteins

What is the key characteristic of lipid rafts within the membrane?

Sequester signaling proteins due to unique lipid composition

Oligosaccharides are only ever found attached to proteins or lipids.

True

What type of bond is found between monomers in a polysaccharide?

Glycosidic

In membrane biology, what is the term used when sugar is attached to an asparagine amino acid residue?

N-linked glycosylation

What determines blood type in red blood cell membranes?

Glycolipids

Which of the following is NOT a reason why proteins may not move freely in the cell membrane according to the text?

Protein linked to ribosomes

What type of glycosylation occurs when sugar is attached to a serine or threonine amino acid residue?

O-linked glycosylation

What was demonstrated by Larry Frye and Michael Edidin in the 1970s regarding membrane protein movement?

Some membrane proteins move

What is the main characteristic of epithelial cells mentioned in the text?

They are very organized with two clear ends.

Which proteins are primarily responsible for attaching cells together in adherens junctions?

Cadherins, catenins, and actin cytoskeleton

What is the role of cadherins in cell junctions?

Mediate attachment between cells

Which type of junction is specifically mentioned as being highly prominent in epithelial cells?

Adherens junctions

What is the function of plasmodesmata in plant cells?

Transporting water and nutrients between cells

What is the main function of desmosomes in tissues?

Provide structural integrity

Which type of proteins make up tight junctions?

Claudins

What is the main role of elastin in tissues?

Confer elasticity/flexibility

Which of the following is NOT a component of the extracellular matrix?

Integrins

What is the primary role of cell walls in plant cells?

Provide a permeability barrier for large molecules

Explore the various functions and composition of the plasma membrane, including its role as a boundary, sites for specific proteins, signaling, and cell-to-cell adhesion. Understand the significance of transport proteins and membrane composition in cellular activities.

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