Sample Answer to an Open Response Question

To help you better understand my expectations for what your open response question should include, see the samples below. Since the question being answered is the first one from your review sheet, don't expect this question to be on the test.

Membranes are important structural features of cells. (a)Describe how membrane structure is related to the transport of materials across a membrane. (b) Describe the role of membranes in the synthesis of ATP in cellular respiration

HH Response:

At its very core, a membrane defines a cell with in its surroundings. Membranes are composed of a phospholipid bilayer. The heads of the phospholipids are hydrophilic, meaning they are attracted to water and the tails of the phospholipids are hydrophobic, meaning they "fear" water. A natural consquence of these attactions is that the phospholipids form a bilayer. Embedded within the bilayer are various proteins. These protiens are responsible for active and passive transport of molecules in and out of the cell, cell to cell recognition, working with enzymes and cytoskeletal attachment. Proteins that permeate the lipid bilayer are referred to as integral membrane proteins and these proteins can move fluidly throughout the lipid bilayer (hence the name "fluid mosaic model.") One protein in particular is called ATP synthase (shown below) which also happens to be an enzyme.


ATP synthase is located on the inner membrane of mitochondria and on the thylakoid membrane in chloroplasts. For our purposes we will focus only on mitochodria as this is where cellular respiration takes place. Throughout cellular respiration, a proton gradient is created which results in an increase of protons in the inter membrane space and less protons (H+) in the matrix. This difference creates an electrochemical gradient. As a result of the basic principle of diffusion (molecules moving from an area of high concentration to low concentration), protons are pumped through the ATP synthase. As the protons are pumped through ATP synthase, the molecular machinery turns and joins together ADP and Pi (inorganic phosphate) to form ATP. This mechanism of producing ATP is referred to as oxidative phosphorylation.

This is an HH response because not only does it include detailed information that demonstrates a clear understanding of the question, it is also well written and uses diagrams to supplement the information.

H Response:

Membranes are composed of a phospholipid bilayer. There are proteins in the membrane. There are difference types of membrane proteins like transport proteins and channel proteins. These proteins are responsible for moving things in and out of the cell. One protein in particular is called ATP synthase which also happens to be an enzyme. ATP synthase is located on the inner membrane of mitochondria. Throughout cellular respiration , a proton gradient is created which results in an increase of protons in the on one side of the membrane and less protons on the otherside. This difference creates an gradient. As a result of the basic principle of diffusion (, protons are pumped through the ATP synthase. As the protons are pumped through ATP synthase, the molecular machinery turns and joins together ADP and Pi (inorganic phosphate) to form ATP.

This is an H response because the author demonstrates a basic understanding of the structure of the cell membrane and the role of ATP synthase. Details which would highlight a greater understanding of the process are omitted as is the figure of ATP synthase.

HP Response:

Membranes have two layers called bilayer. There are proteins in the membrane. These proteins are responsible for moving things in and out of the cell. One protein in particular is called ATP synthase. ATP synthase is located on the membrane of mitochondria. Throughout cellular respiration , a gradient is created which results in an increase of stuff on one side of the membrane and less stuff on the otherside. This difference creates an gradient. As a result of the basic principle of diffusion (, protons are pumped through the ATP synthase. As the protons are pumped through ATP synthase, the molecular machinery turns and joins together ADP and Pi (inorganic phosphate) to form ATP.

This is an HP response because the author demonstrates little understanding of the information needed to answer the question. Details which would highlight a greater understanding of the process are omitted as are any figures which would help convince the reader that the author knows what he/she is talking about.

P Response:

Serriously, there should be no P responses.
You have the questions ahead of time.