Cell Membrane and Transport Quiz

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Questions and Answers

What is the main role of the glycocalyx in cellular function?

Cell recognition and attachment to other cells (correct)

Insulation of the cell membrane

Storage of genetic material

Facilitation of nutrient absorption

Which of the following processes is considered a nonselective form of endocytosis?

Pinocytosis

Active transport

Receptor-mediated endocytosis

Phagocytosis (correct)

What differentiates exocytosis from endocytosis at the molecular level?

The energy requirements of the processes

The protein molecules utilized (correct)

The membrane potential changes

The type of molecules transported

Which type of transport includes both active and passive mechanisms?

Bulk movement Signup and view all the answers

What structural components contribute to the formation of the glycocalyx?

Carbohydrate chains linked to proteins and lipids Signup and view all the answers

What is the primary structural feature that distinguishes phospholipids from triglycerides?

Presence of a phosphate group on the glycerol backbone Signup and view all the answers

How do phospholipids achieve their amphipathic nature?

By containing a hydrophobic phosphate group Signup and view all the answers

What characteristic does the fluid mosaic model attribute to the cell membrane?

Dynamic flexibility allowing movement of components Signup and view all the answers

Which type of bond connects fatty acids to the glycerol backbone in glycerophospholipids?

Ester linkages Signup and view all the answers

What key functional feature differentiates sphingophospholipids from glycerophospholipids?

The presence of a sphingosine backbone Signup and view all the answers

What role do coated pits play in the process of endocytosis?

They are sites for the formation of clathrin-coated vesicles. Signup and view all the answers

What happens to the clathrin coat after the coated vesicle fuses with early endosomes?

It is recycled back to the cell membrane. Signup and view all the answers

Which of the following statements accurately describes the fate of ligands in early endosomes?

Ligands are transported to late endosomes for degradation. Signup and view all the answers

How do ATP-linked H+ pumps affect the endosomal environment?

They acidify the interior of the endosome by pumping H+ ions inside. Signup and view all the answers

What occurs when both the receptor and ligand are transported to the late endosome?

They are sent to lysosomes for degradation. Signup and view all the answers

What causes respiratory distress syndrome in premature infants?

Absence of lecithin in the lungs Signup and view all the answers

Which component is primarily responsible for the formation of sphingomyelin?

Sphingosine backbone Signup and view all the answers

Which phospholipid serves as a major blood clotting factor?

Cephalin Signup and view all the answers

What is the role of the hydrophilic head of phospholipids in membranes?

To interact with the aqueous environment Signup and view all the answers

What substance is produced when lecithin is split by lecithinase enzyme?

Lysolecithin Signup and view all the answers

Study Notes

Cell Membrane and Vesicular Transport

Cell membranes have diverse functions, relating to molecular structure of membrane lipids and integral/peripheral molecules.
The fluid mosaic model describes membrane structure.
Endocytosis and exocytosis are vital processes for transport across the cell membrane.
Different types of endocytosis exist under normal and pathological conditions.

Cell Components

Cells are composed of cytoplasm and nucleus.
Cytoplasmic components are typically not easily distinguished in standard staining.
The nucleus stains dark blue/black.
Plasma membrane (plasmalemma) separates cytoplasm from external environment.
Cytoplasm contains cytosol, organelles, cytoskeleton, and deposits of carbohydrates, lipids, and pigments.
Cells organize into tissues, organs, and systems.

Plasma Membrane Structure

Composed of phospholipids, cholesterol, proteins, and oligosaccharides.
Functions as a selective barrier.
Membranes are thin (7.5-10nm) and only visible under electron microscopes.

Membrane Phospholipids

Two nonpolar hydrocarbon tails linked to a hydrophilic head group.
Tails are hydrophobic; heads are hydrophilic.
Cholesterol is also a constituent.

Membrane Proteins

Integral proteins are embedded within the lipid bilayer.
Peripheral proteins are loosely associated with membrane surfaces.
Organelle-specific proteins confer unique functions to organelles.

Carbohydrates (Glycocalyx)

Carbohydrate-rich layer lining the cell exterior (glycocalyx).
Linked to membrane proteins and lipids, and cell-secreted components.
Involved in cell recognition and attachments.

Membrane Transport

Passive transport (simple and facilitated diffusion).
Active transport (pump and cotransport carrier).
Bulk transport (endocytosis and exocytosis).

Endocytosis

Nonselective processes: phagocytosis (cell eating) and pinocytosis (cell drinking).
Receptor-mediated endocytosis is a selectively endocytotic process.
Involves receptors binding with cargo molecules.
Cargo receptors are transmembrane proteins and molecules such as LDLs or protein hormones bind to these receptors.

Endosome Fate

Early endosomes may recycle receptors to the cell surface or transfer them to late endosomes for degradation.
Late endosomes fuse with lysosomes.
Contents of endosomes are broken down; this includes cargo molecules, receptors, and sometimes the whole vesicle.
Receptor-ligand complexes are also returned to cell membrane for reuse.

Lipid Structure & Functions in Bio-Membranes

Membranes are "fluid mosaic model", meaning they are flexible to allow cell motion of components.

Phospholipids

Ionic compounds with hydrophilic heads and hydrophobic tails.
Two main classes: glycerophospholipids (phosphoglycerides) and sphingophospholipids.
Glycerophospholipids have a glycerol backbone attached to two fatty acids and a phosphate group.

Cholesterol

A steroid with four interconnected rings.
Amphipathic.
Controls membrane fluidity; increases fluidity at low temperatures and decreases fluidity at high temperatures.
Helps secure proteins.

Lipid Rafts

Specialized microdomains in the plasma membrane enriched in cholesterol and sphingolipids.
Involved in signal transduction and other cellular processes.
Example of microdomains include caveolae

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Description

Test your knowledge on cell membranes and vesicular transport with this quiz. Explore the complex structures and functions of cell membranes, the fluid mosaic model, and the processes of endocytosis and exocytosis. Understand how cells organize into larger systems.