Writing Prompts Q2 Benchmark Exam

#1 Describe how the basic structure of a cell membrane enables it to maintain homeostasis within the cell by naming at least two different components of the membrane and describing the function of each part that you name.

#1 The cell membrane helps maintains homeostasis is by controlling the movement of substances in/out of the cell. Gases such as oxygen can diffuse in & carbon dioxide can diffuse out through the phospholipid bilayer. (Flow from high to low concentration = passive transport = no energy) Water can diffuse in or out of a cell through membrane proteins called aquaporins. (Flow from high to low concentration = passive transport = no energy) Monosaccharides and amino acids can enter or leave through membrane proteins by facilitated diffusion. (Flow from high to low concentration = passive transport = no energy) Ion channels are proteins the allow various ions into or out of the cell. (Flow from high to low concentration = passive transport = no energy) Three sodium ions are pumped out & two potassium ions are pumped in via the sodium- potassium pump. (Flow from low to high concentration = active transport = requires energy) Large molecules, such as polysaccharides or proteins, can enter the cell through pouches formed by the cell membrane in a process called endocytosis. (Active transport = requires energy) Large molecules, such as polysaccharides or proteins, can leave the cell through vessicles formed in a process called exocytosis. (Active transport = requires energy)

#2 Draw and label a phospholipid. Explain why phospholipid molecules form a bilayer within the watery environment of a cell.

#2 When phospholipids are mixed with water, the hydrophobic regions find ways to remove themselves from water, while the hydrophilic regions interact with water. The resulting structure is called a lipid bilayer.

#3 One job of the plasma membrane is to control the passage of substances into and out of the cell. Identify a specific type of passive transport used by cell membranes to move molecules into or out of the cell. Identify the specific type of passive transport that you are describing. Name the type of molecule(s) transported by this process and explain how the molecules enter or leave the cell through the membrane by identifying the specific part of the membrane through which the substance(s) move.

#3 Gases such as oxygen can diffuse in & carbon dioxide can diffuse out through the phospholipid bilayer. (Flow from high to low concentration = passive transport = no energy) Water can diffuse in or out of a cell through membrane proteins called aquaporins. (Flow from high to low concentration = passive transport = no energy) Monosaccharides and amino acids can enter or leave through membrane proteins by facilitated diffusion. (Flow from high to low concentration = passive transport = no energy) Ion channels are proteins the allow various ions into or out of the cell. (Flow from high to low concentration = passive transport = no energy)

#4 Write the balanced equations for photosynthesis and cellular respiration. Identify which equation is which. Explain how the processes of photosynthesis and cellular respiration transform energy.

#4 The products of photosynthesis become the reactants of cellular respiration. Photosynthesis = Cellular respiration =

#5 Why is ATP important in biochemical reactions? Give two examples of biochemical reactions and explain how an organism uses ATP in those reactions.

#5 ATP is a form of energy “currency” within cells that powers metabolism. In photosynthesis, ATP is used to convert inorganic carbon into sugar. In glycolysis, 2 ATP molecules are used to break down 1 glucose molecule into 2 pyruvate molecules. In the process, 4 ATP molecules are generated, for a net gain of 2 ATP molecules.