Semester One Free Responses

  1. Cells contain organelles that perform specific functions critical for survival. Describe the structure and function of the following organelles: the Golgi apparatus, lysosomes, and vacuoles. Explain how these organelles interact during the process of intracellular digestion and waste management.

Golgi apparatus, lysosomes, and vacuoles

The Golgi apparatus modifies, packages, and sorts enzymes into vesicles. The lysosomes than use these enzymes transported by the Golgi to break down waste alongside the vacuole, a sac that stores water, nutrients, and waste.

  1.  ATP (adenosine triphosphate) is a central molecule in cellular energy transfer. Explain how the structure of ATP makes it suitable for energy transfer within cells. Describe one specific cellular process that uses ATP and explain the role of ATP in that process.

ATP Structure and Role

ATP has three phosphate groups, with high-energy bonds between them. When one bond breaks (ATP → ADP + Pi), energy is released for cellular processes. For example, in muscle contraction, ATP provides energy for myosin heads to detach and reattach to actin filaments, enabling movement.

  1. Carbon, hydrogen, oxygen, and nitrogen are key elements in biological macromolecules. Describe the role of dehydration synthesis and hydrolysis in the formation and breakdown of biological macromolecules. Provide one specific example of how carbohydrates and proteins are assembled or broken down in cellular processes.

Dehydration Synthesis and Hydrolysis

Dehydration synthesis forms macromolecules by removing water to bond monomers, while hydrolysis breaks them down by adding water. For example, in proteins, amino acids join through dehydration to form peptide bonds, and in digestion, enzymes hydrolyze these bonds to release amino acids.

  1. What are the characteristics of materials that can cross the plasma membrane on their own?  Please address size and polarity.  What characteristics of the plasma membrane allow these molecules to cross the membrane?

Crossing the Plasma Membrane

Small, nonpolar molecules (like oxygen and CO₂) can cross the plasma membrane freely due to their size and lack of charge. The membrane’s phospholipid bilayer, with hydrophobic tails, allows these molecules to diffuse through because they are also nonpolar.

  1. How do animals modify their cell membranes to prepare for cold weather?  How do plants modify their membranes to overwinter?  How do these modifications change the physical and chemical characteristics of the cell membrane to allow the organism to survive?  (Think about polarity, presence or absence of cell wall, etc.)

Membrane Adaptations for Cold Weather

Animals increase unsaturated fatty acids in their membranes, making them more fluid in the cold. Plants add unsaturated lipids and reduce saturated ones to prevent rigidity. These changes prevent the membrane from freezing, maintaining transport and cellular function.

  1. Identify three properties of water that are important for life to be able to exist on Earth AND explain how each one specifically influences living organisms and provide an example of each.  

Properties of Water

  1. Cohesion: Water molecules stick together, enabling surface tension, which helps insects walk on water.

  2. High Specific Heat: Water resists temperature changes, stabilizing climates for organisms.

  3. Solvent Properties: Water dissolves polar molecules, enabling nutrient transport in blood and cells.