Question

problem set 2: choose one of the problems below to complete. read it carefully before you begin. problem a: lactic acid is a waste molecule in cells that comes from using energy in the cell. if too much builds up in the cells it causes acids and eventually can lead to cell - death. this is especially true for muscle cells that use a lot of energy and release a lot of lactic acid. the lactic acid molecule is too big to leave the cell straight through the cell membrane. how can a cell with high concentrations of lactic acid inside them regain homeostasis? problem b: calcium (ca²⁺) is needed in our bones to rebuild them and keep them strong. calcium is used up by the bone cells and needs to be replaced. because calcium is an ion, meaning it has a charge (+), it will be rejected by the hydrophobic region of the cell membrane and cannot pass directly through. how can bone cells get enough calcium to maintain their strength? which did you choose? problem a or problem b (circle one) 1. type of cellular transport ____________ energy required? ____________ 2. concentration gradient explanation: 3. claim, evidence, reasoning (cer) claim: evidence: atp allows the calcium to charge and go back into the bone. reasoning (model with explanation): sketch of a bone problem 1 grading rubric approaching developing emerging score proficiency (3) (2) (1) identification (#1 & 2) ⅛ claim ⅛ evidence ⅛ reasoning visual ⅜ reasoning

Explanation:

Step1: Identify transport type

Since calcium ions cannot pass directly through the cell - membrane due to their charge and the hydrophobic region, and they need to be taken up by bone cells, the type of cellular transport is active transport. Active transport moves substances against their concentration gradient and requires energy.

Step2: Explain concentration gradient

Calcium ions are needed inside the bone cells to maintain bone strength. The concentration of calcium ions is likely lower inside the bone cells compared to the outside environment (or the extracellular fluid), so they need to be transported against this concentration gradient into the cells.

Step3: Formulate CER

Claim: Bone cells use active transport to get enough calcium to maintain their strength.
Evidence: Calcium is an ion with a charge and is rejected by the hydrophobic region of the cell - membrane, so it cannot pass directly through. ATP (energy) is required for the movement of calcium into the bone cells.
Reasoning: The cell - membrane has a hydrophobic region that repels charged calcium ions. To overcome this barrier and move calcium against its concentration gradient into the bone cells, energy in the form of ATP is used. This energy - dependent process is active transport. A visual model could show the bone cell with its cell - membrane, the hydrophobic region, and the calcium ions being pumped in by a protein carrier using ATP.

Answer:

1. Type of cellular transport: Active transport; Energy Required? Yes
2. Concentration Gradient Explanation: Calcium ions need to move from an area where they may be more abundant outside the bone cell (or extracellularly) to an area of lower concentration inside the bone cell against the concentration gradient.
3. Claim: Bone cells use active transport to get enough calcium to maintain their strength. Evidence: Calcium is an ion with a charge and is rejected by the hydrophobic region of the cell - membrane, and ATP is required for its movement into the bone cell. Reasoning: The cell - membrane's hydrophobic region repels charged calcium ions. Energy (ATP) is needed to move calcium against its concentration gradient into the bone cell through a protein - mediated process (active transport). A simple drawing of a bone cell, its membrane, the hydrophobic part, and calcium ions being transported in with the help of an ATP - powered protein can be used as a visual model.