Cell Components Quiz

Cell Components

• Cytoplasmic Matrix: Provides structural support and a framework for cell organelles.
• Cytoskeleton:
  • Composed of Microtubules, Intermediate Filaments, and Microfilaments.
  • Facilitates intercellular communication.
• Mitochondrion:
  • Contains two membranes:
    • Outer membrane: Porous
    • Inner membrane: Selectively permeable, and site of the electron transport chain.
• Nucleus:
  • Largest organelle.
  • Surrounded by the nuclear envelope.
  • Contains DNA, forming the cell genome (entire set of genetic information).
• Nucleolus:
  • Site of RNA transcription and ribosome assembly/synthesis, starting in the nucleus and completing in the cytoplasm.
• Nucleic Acids:
  • DNA and RNA.
  • Composed of adenine, guanine, and cytosine, with uracil only found in RNA and thymine only found in DNA.
  • DNA is double stranded with complementary base pairing.
  • RNA is single stranded, capable of folding to create complex secondary structures.

Protein Synthesis

• Ribosomes link amino acids together to form proteins.

Biological Energy

• ATP: Major energy storage form in cells.
• ATP synthase:
  • Protein that catalyzes ATP formation using ADP and inorganic phosphate.
  • Generates two molecules of ATP and two molecules of NADH.

Glucose Metabolism

• Complete glucose oxidation:
  • Formula: Glucose + 6O2 = 6 CO2 + H2O
  • Releases -2840 kJ/mol of free energy.
• Glycolysis:
  • Takes place in the cytosol.
  • Formula: Glucose + 2NAD+ = 2Pyruvate + 2NADH + 2H+
  • Releases -146 kJ/mol of free energy (5.2% of total energy from glucose oxidation).
  • Essential for tissues like the brain and cells with limited oxygen access.
  • Generates lactate and ATP under anaerobic conditions.

Stages of Glycolysis

• Stage 1 (Reactions 1-5):
  • Preparatory phase involving phosphorylation of glucose, conversion to fructose, re-phosphorylation, and cleavage into two glyceraldehyde-3-phosphate molecules.
  • Requires an investment of 2 ATP molecules.
• Stage 2 (Reactions 6-10):
  • Conversion of two glyceraldehyde-3-phosphate molecules to pyruvate, generating four ATP molecules and two NADH molecules.
  • Results in a net gain of two ATP molecules per glucose molecule.

Membrane Transporters of Glucose

• GLUT1:
  • Most ubiquitously expressed transporter.
  • Responsible for glucose transport across the blood-brain barrier and supply to the developing central nervous system.
  • Essential for erythrocytes, brain endothelial cells, and fetal tissue.
  • Deficiency leads to GLUT1 deficiency syndrome, characterized by seizures due to insufficient brain glucose.
• GLUT2:
  • Low-affinity, high-capacity transporter.
  • Predominant expression in pancreatic β-cells, liver, small intestine, and kidneys.
  • Transports monosaccharides from enterocytes into the portal blood.
  • Involved in insulin release from β-cells in response to blood glucose levels.
• GLUT3:
  • High-affinity transporter.
  • Primarily expressed in glucose-dependent tissues, such as the brain and neurons as well as spermatozoa, placenta, and preimplantation embryos.
  • Potential dysregulation could lead to glucose deficits in the brain and associated with dyslexia.
• GLUT4:
  • Primary transporter for insulin-regulated glucose uptake in muscle and adipose tissue.
  • Absence in other tissues renders them independent of insulin for glucose uptake.
  • Insulin promotes translocation of GLUT4 from intracellular storage to the plasma membrane.
• GLUT5:
  • Highly specific for fructose.
  • Expressed in the small intestine, kidneys, brain, muscles, and adipose tissue.
  • Primarily responsible for fructose transport across enterocyte brush border membranes.

Glycemic Index

• Measures the rate at which a particular food raises blood glucose levels.
• Calculated by comparing the area under the blood glucose curve after consuming the food with the area under the curve for a reference food (either glucose or white bread).
• Foods with a high glycemic index cause rapid and significant spikes in blood glucose, while foods with a low glycemic index cause slower and more gradual rises.
• Factors influencing Glycemic Index:
  • Type of carbohydrate: Simple sugars have a higher GI than complex carbohydrates.
  • Processing of food: Processed foods have a higher GI than unprocessed or minimally processed foods.
  • Cooking methods: Boiling or steaming vegetables lowers GI compared with frying.
  • Fat content: Adding fat can lower the GI.
  • Fiber content: Foods high in fiber have a lower GI.
  • Amount of food: Consuming a larger amount of food will increase the GI.
  • Individual factors: Factors like age, fitness levels, and genetics can affect GI.

Test your knowledge on the essential components of a cell! This quiz covers various organelles such as the cytoplasmic matrix, mitochondria, nucleus, and nucleic acids. Understand the structures and functions that make up cellular biology.