Biochemistry 1 - Cell Membranes Quiz

BIOCHEMISTRY 1 - Midterm 1 Content

• Cell Membranes:

  • Cells without a nucleus are prokaryotes (bacteria, pathogens)
  • Cells with a nucleus are eukaryotes (animals, plants, fungi)
  • Plasma membrane separates the cell from its environment.
  • Internal membranes separate subcellular organelles within the cytoplasm.
  • Components: lipids (bilayer of cholesterol and simple/complex lipids), proteins, and carbohydrates.
  • Lipids (phospholipids): major components of the cell membrane, amphipathic (hydrophilic head, hydrophobic tails), glycerophospholipids form the backbone, sphingolipids include ceramides, sphingomyelins, cerebroside, and gangliosides.
  • Movement of lipids in the membrane (rotation, lateral diffusion, transversal diffusion via flippase, floppase, or scamblase).
  • Cholesterol provides rigidity and contributes to atherosclerosis.
  • Proteins (60% of the membrane): integral (embedded, hydrophobic/hydrophilic), peripheral (loosely bound).
  • Carbohydrates: branched oligosaccharides attached to lipids (glycolipids) or proteins (glycoproteins).
  • Membrane fluidity increases with temperature and unsaturated fatty acids.
  • Properties of membranes: selective barriers, metabolic compartments, dynamic and continuously renewed.
  • Cell membranes are asymmetric.

• Transport Across the Membrane:

  • Passive transport: follows the concentration gradient; no ATP needed.
    • Simple diffusion: through the membrane (uncharged/lipid-soluble).
    • Facilitated diffusion: with carrier molecules or pores (proteins, glucose transporters, carnitine, aquaporins).
  • Active transport: against the concentration gradient; requires ATP.
    • Primary active transport: carrier proteins (sodium-potassium pump).
    • Secondary active transport: coupled with the movement of another molecule (osmotic gradient).
  • ABC transporters
  • Proton pumps (in the respiratory chain)
  • SGLT-1 - SGLT2 (in epithelial and kidney cells)

• Amino Acids and Proteins:

  • Properties of amino acids (AA): chiral carbon, L-form common in proteins.
  • Protein structure: primary (sequence of AAs), secondary (alpha-helix/beta-sheet), tertiary (3D structure, interactions of side chains), and quaternary (multiple polypeptide chains).
  • Types of proteins (globular: spherical, water soluble, enzymes; fibrous: sheet-like, water insoluble, collagen, keratin, elastin).
  • Protein structure determination by techniques like electrophoresis, spectroscopy, x-ray crystallography.
  • Structure, function, and properties

• Enzymes: Proteins with Catalytic Power:

  • History of enzyme discovery; Enzymes are made to accelerate reactions.
  • Role of enzymes in intermediary metabolism and biological processes; Highly specialized (1000-4000 enzymes per cell).
  • Properties of enzymes; Active and catalytic sites.
    • Mechanisms by which enzyme function; Induced-fit model
    • Factors affecting enzyme activity (temperature, pH, concentration, inhibitors); Michaelis-Menten kinetics
    • Types of enzymes (serine proteases: chymotrypsin, trypsin, elastase).

• DNA and RNA Molecules:

  • Difference between DNA and RNA (deoxyribose vs. ribose, presence of T vs. U)
  • Nucleotides & nucleosides
  • Structure of DNA; Double helix, base pairing (A-T, G-C)
  • Types of DNA: A-DNA, B-DNA, Z-DNA.
  • Difference between prokaryotic and eukaryotic DNA structure.
  • Levels of DNA structure: DNA→ Nucleosome→ Chromatin→ Chromosome
  • DNA replication; semi-conservative
  • Enzymes involved in DNA replication (DNA polymerase, primase, ligase)

• Transcription:

  • DNA to RNA; RNA synthesis
  • Steps in transcription: initiation, elongation, termination
    • Promoters, RNA polymerase, coding region.
  • Transcription factors and types of RNA polymerases (prokaryotes vs. eukaryotes)
    • Prokaryotes-Polycistronic; Eukaryotes-monocistronic, Introns vs. Exons
  • Maturation of RNA (capping, tailing, splicing.)

• Translation:

  • Process of protein synthesis (mRNA, tRNA, ribosomes); Universal start codon(AUG, for Met)
  • Structure of mRNA, tRNA, Ribosomes
  • Types of Ribosomes: Prokaryotic vs Eukaryotic
  • Steps in translation: initiation, elongation, and termination

• Regulation of gene expression.

• Post-transcriptional & post-translational modification

• Structure Proteins:

  • Keratin; alpha-helix structure, S-S bonds, H-bonds, and ionic interactions, found in wool, feathers, hair
  • Collagen; Triple helix structure, Gly, Pro, hydroxyproline, hydroxylysine, found in skin, bones, tendons
  • Elastin; cross-linked protein, found in lungs, aorta, flexible connective tissue.

• Fibronectin, laminin, proteoglycans: extracellular matrix proteins: cell adhesion, regulate molecule movement.

Test your knowledge on the essential components and functions of cell membranes in eukaryotic and prokaryotic cells. This quiz covers lipid structures, membrane proteins, and the role of cholesterol in membrane dynamics. Prepare for your Midterm 1 in Biochemistry!