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Which of the following is NOT a primary function of the plasma membrane?
Which of the following is NOT a primary function of the plasma membrane?
What is the term used to describe a property of the plasma membrane that allows only certain molecules to pass through it?
What is the term used to describe a property of the plasma membrane that allows only certain molecules to pass through it?
Which cellular component is primarily responsible for protein synthesis?
Which cellular component is primarily responsible for protein synthesis?
What is the main role of the mitochondria within the cell?
What is the main role of the mitochondria within the cell?
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Which of the following best describes the role of the Golgi apparatus?
Which of the following best describes the role of the Golgi apparatus?
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What is the primary function of peptidoglycan in bacterial cells?
What is the primary function of peptidoglycan in bacterial cells?
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Which of these best describes the molecular structure of peptidoglycan?
Which of these best describes the molecular structure of peptidoglycan?
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How do β-lactams (like penicillin) interfere with the functionality of bacterial cells?
How do β-lactams (like penicillin) interfere with the functionality of bacterial cells?
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Which of the following is correct regarding the DNA of a prokaryotic cell, such as bacteria?
Which of the following is correct regarding the DNA of a prokaryotic cell, such as bacteria?
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What are the structural components in multicellular organisms?
What are the structural components in multicellular organisms?
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What is the primary function of flippases within the phospholipid bilayer?
What is the primary function of flippases within the phospholipid bilayer?
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Which of the following lipid components is primarily responsible for making the plasma membrane more rigid and less permeable?
Which of the following lipid components is primarily responsible for making the plasma membrane more rigid and less permeable?
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Which of the following accurately describes the structure of a phospholipid?
Which of the following accurately describes the structure of a phospholipid?
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Which of the following best describes the arrangement of membrane proteins in a plasma membrane?
Which of the following best describes the arrangement of membrane proteins in a plasma membrane?
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Which type of membrane protein spans both layers of the plasma membrane?
Which type of membrane protein spans both layers of the plasma membrane?
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What is the primary role of glycolipids found on the outer leaflet of the plasma membrane?
What is the primary role of glycolipids found on the outer leaflet of the plasma membrane?
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Which of the following is NOT a major function of the plasma membrane?
Which of the following is NOT a major function of the plasma membrane?
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Why is the phospholipid bilayer described as 'asymmetrical'?
Why is the phospholipid bilayer described as 'asymmetrical'?
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Which of the following best describes lateral diffusion within the plasma membrane?
Which of the following best describes lateral diffusion within the plasma membrane?
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Which of the following distinguishes a peripheral membrane protein from an integral membrane protein?
Which of the following distinguishes a peripheral membrane protein from an integral membrane protein?
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How do cells maintain membrane fluidity?
How do cells maintain membrane fluidity?
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Which of the following is a function of transmembrane proteins?
Which of the following is a function of transmembrane proteins?
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If a cell has a high concentration of saturated fatty acids, what characteristic of the plasma membrane would be affected?
If a cell has a high concentration of saturated fatty acids, what characteristic of the plasma membrane would be affected?
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What is a distinct difference between a eukaryotic cell and a prokaryotic cell regarding their genetic material?
What is a distinct difference between a eukaryotic cell and a prokaryotic cell regarding their genetic material?
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A cell has a high concentration of sphingomyelin. What type of molecule is this?
A cell has a high concentration of sphingomyelin. What type of molecule is this?
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Study Notes
Cell Structure and Function
- Reading Assignments: Essential Cell Biology, Chapter 1; Essential Cell Biology, Chapter 11; Marks' Basic Medical Biochemistry, Chapter 10
- Lecture Objectives: Identify lipid, protein, and carbohydrate components of the plasma membrane
- Describe plasma membrane's functions, incl. selective permeability, cellular communication, and physical barriers.
- Identify major ions inside and outside cells, explaining ion concentration variations.
- Identify six major membrane-bound organelles in human cells.
- Describe the structure and primary function of each organelle.
- Identify genetic diseases connected with dysfunction in nuclear lamina, mitochondria, lysosomes, peroxisomes, and Golgi apparatus.
- Explain related molecular processes affected by this dysfunction.
- Apply knowledge to relevant clinical concepts.
Cells
- Cells are membrane-enclosed units filled with concentrated aqueous solutions of chemicals.
- Cells have the unique ability to self-replicate by growing and dividing into two.
- Cells are the smallest functional unit of life.
Prokaryotes vs. Eukaryotes
- All living organisms are categorized into two basic groups:
- Prokaryotes
- Eukaryotes
Components of Prokaryotic Cells (Bacteria)
- Typically possess a flagellum for movement.
- Lack membrane-bound organelles.
- DNA is in the cytoplasm and attached to the cell membrane.
- Cell contains a nucleoid.
- Cell membrane is covered by a cell wall.
Bacterial Cell Wall
- Composed of a large molecule called peptidoglycan (murein).
- Mesh-like layer with carbohydrate backbones cross-linked by peptide bridges.
- Some antibiotics inhibit bacterial cell wall formation, preventing peptidoglycan synthesis.
- Beta-lactams, penicillin, glycopeptide antibiotics (e.g. Vancomycin) commonly work against bacterial cell walls.
Hierarchy of Multicellular Organisms
- Organs are composed of tissues.
- Tissues are groups of highly specialized cells.
- These cells perform functions specific to the organ.
- Although specialized, different cell types share fundamental components.
Components of Eukaryotic Cells (Animal Cells)
- Plasma Membrane
- Membrane-enclosed organelles
- Nucleus
- Mitochondria
- Lysosomes
- Peroxisomes
- Endoplasmic Reticulum
- Golgi Apparatus
- Cytoskeleton
Comparison of Prokaryotic and Eukaryotic Cells
- Prokaryotes are unicellular organisms with cell walls protecting cell membranes.
- Prokaryotes lack organelles and a nucleus.
- Prokaryotic DNA is organized into a single circular chromosome.
- Prokaryotes are typically smaller (2-3 µm).
- Eukaryotes are multicellular organisms, cell membranes are exposed to the outside environment.
- Eukaryotes contain many membrane-bound organelles and a nucleus.
- Eukaryotic DNA is organized into many linear chromosomes.
- Eukaryotes generally are larger (~10 µm)
Plasma Membrane
- Sometimes called plasmalemma.
- Separates cell contents from the external environment.
- Composed of a phospholipid bilayer.
- Phospholipids have hydrophobic tails & hydrophilic heads
- Selectively permeable to ions and organic molecules.
- Integral and peripheral proteins are associated with the membrane.
- integral proteins: transmembrane; monolayer associated; lipid anchored
- peripheral proteins: associated with integral membrane proteins
Plasma Membrane—Components
-
Lipids:
- Phospholipids (75%)
- Cholesterol (20%)
- Glycolipids (5%)
-
Proteins:
- Makes up ~50% of membrane volume.
Lipids
- Three families found in plasma membranes:
- Phospholipids─polar head, linked to a glycerol molecule and two long nonpolar hydrocarbon tails
- Glycolipids─attached to a sugar molecule
- Cholesterol─steroid ring structure
Phospholipids
- Amphipathic (both hydrophilic and hydrophobic regions)
- Five parts: hydrophilic head, glycerol, phosphate group, and two hydrocarbon tails.
- Four major phospholipids:
- Phosphatidylethanolamine
- Phosphatidylserine
- Phosphatidylcholine
- Sphingomyelin
Fluid Mosaic Model
- Phospholipids form a bilayer in aqueous solution.
- Bilayer is asymmetrical, with distinct outer and inner layers.
- The lipid bilayer is a two-dimensional fluid structure, allowing individual phospholipids to exchange positions within the monolayer or between layers.
- Enzymes called flippases can mediate exchange between the inner and outer leaflets.
Glycolipids
- Backbone is a sphingosine molecules.
- Contains a short carbohydrate molecule.
- Found in outer leaflet of plasma membranes.
- Important in cell recognition.
- Examples include cerebrosides and gangliosides
Membrane Proteins
- Four ways proteins associate with the plasma membrane:
- Transmembrane proteins
- Monolayer-associated proteins
- Lipid-linked proteins
- Protein-attached proteins
- Transmembrane proteins span the membrane, with parts exposed to both the interior and exterior environments.
Transmembrane Proteins
-
Span both layers of plasma membrane.
-
Exposed to the extracellular and intracellular sides.
-
Four functional classes:
- Transporters (Membrane transport)
- Anchors (Cell adhesion & Membrane junctions)
- Receptors (Signal transduction)
- Enzymes (Signal transduction)
Fluidity of Membrane Proteins
- Plasma membrane is fluid.
- Proteins embedded within the membrane can move laterally.
Functions of Plasma Membranes
- Communication: Receptors recognize and respond to molecular signals.
- Physical barrier: Separates the intracellular contents from the outside environment.
- Intercellular connection: Forms connections, supports, and provides structure.
- Selective permeability: Regulates entry & exit of ions, nutrients, and waste.
Cholesterol
- Constitutes ~20% of plasma membrane lipids.
- Fills spaces between phospholipids.
- Makes the membrane more rigid and less permeable.
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Description
Test your knowledge on the essential concepts of cell structure and function as covered in chapters from Essential Cell Biology and Marks' Basic Medical Biochemistry. This quiz will challenge you to identify plasma membrane components, organelles, and the implications of genetic diseases related to cellular dysfunction. Apply your understanding to relevant clinical scenarios.
