AP Mid-Term FRQ REVIEW Scoring Guidelines
1. 1993:
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 either
respiration or photosynthesis.
Membranes serve diverse functions in eukaryotic and prokaryotic cells. One
important role is to regulate the movement of materials into and out of cells.
The phospholipid bilayer structure (fluid mosaic model) with specific membrane
proteins accounts for the selective permeability of the membrane and passive
and active transport mechanisms. In addition, membranes in prokaryotes and in
the mitochondria and chloroplasts of eukaryotes facilitate the synthesis of ATP
through chemiosmosis.
PART A. (6 Maximum)
Membrane Structure (3 Internal Maximum)
__ Phospholipid structure - hydrophilic, hydrophobic, amphipathic
__ Phospholipid bilayer / fluid mosaic description
__ Proteins embedded in the membrane
__ Sterols embedded in the membrane
__ Well-labeled diagram may replace one of the above
Membrane Transport (3 Internal Maximum)
__ Use of the term "selectively permeable" or a good definition of
selective permeability or an explanation of the role of phospholipids
or proteins including nuclear pore proteins in determining selective
permeability
__ Description of the effect of size, charge, polarity, lipid solubility on
membrane permeability
Mechanisms + description related to structure:
__ Passive transport: diffusion / osmosis + reference to membrane gradient
__ Ion channel: transport as a mechanism for a change in permeability
__ Facilitated diffusion: description (symport, antiport, uniport)
__ Active transport: description
__ Exocytosis, endocytosis, phagocytosis, pinocytosis: description
(1 pt additional) A good example of one of the above mechanisms
PART B. Role of the Membrane in the Production of ATP in Photosynthesis or Respiration (6
Maximum)
Chemiosmosis:
__ Involved molecules are embedded in the membrane
__ Electron carriers are sequentially organized
__ The energy comes from the flow of electrons
__ H+ / Proton / pH gradient established
__ Movement through the membrane generates ATP
__ A specific protein makes ATP
RESPIRATION
or
__ Site is the mitochondrion
__ Inner mitochondrial membrane
(cristae) are involved in eukaryotes
__ Folded membrane present
__ Cell membrane is involved in
PHOTOSYNTHESIS
__ Site is the chloroplast
__ Thylakoid / grana membranes
are involved in ejkaryotes
__ Folded membrane present
__ Thylakoid / grana membranes
prokaryotes
__ Correct direction of H+ flow
involved in prokaryotes
__ Correct direction of H+ flow
2. 1994
Enzymes are biological catalysts.
a. Relate the chemical structure of an enzyme to its specificity and catalytic activity.
b. Design a quantitative experiment to investigate the influence of pH or temperature
on the activity of an enzyme.
c. Describe what information concerning the structure of an enzyme could be inferred
from your experiment.
Since the question asked students to respond with both specific facts about enzymes and broad
conceptual statements about the design of an experiment, these standards reflect both
approaches. In understanding how an enzyme could be affected by a quantitative experiment with
temperature or pH, students not only had to state specific features such as the three dimensional
shape of an enzyme, but they also had to describe how to control variables in an experiment.
Finally, students were expected to apply the results of their experiment to changes in the structure
of the enzyme.
Structure and catalytic activity of enzyme (maximum of 4 points)
__
protein or amino acids (and/or others, such as ribozyme)
__
3-D shape/levels of structure (primary, secondary, teritary, etc.)
__
bonding explanation of structure (alpha helix, hydrophobic interactions,
van der Waals forces, etc.)
__ active site ("groove", "pocket") / special shape for substrate / "lock and key"
__ modifiers of enzyme shape (cofactors, activators, inhibitors)
__ induced fit theory (function of enzyme substrate fit)
__ activation energy lowered
__ substrate altered
Experimental design (maximum of 5 points)
Experiment based on enzymatic activity / inital choice of temperature or pH is binding
__ eliminate other variables (conc., amounts, time, pH, temp in alternate experiment)
__ negative control (setup without enzyme or without substrate)
__ describe experimental variable (temperature or pH) values or range
__ uses correct enzyme-substrate pair
__ measure disappearance of substrate, appearance of product, heat production, etc.
__ report data
(predicted results, such as loss of activity, reduced activity or no change in activity)
__ elaboration of experiment (exemplary set-up; indep, dep variables identified;
rate calculation or explanation; replication of experiment, etc.)
Inference from experimental design (maximum of 2 points)
__ correct link of predicted results to changes in enzyme structure
a. range of activity implies slight change in shape OR
b. loss of activity implies denaturation OR
c. no loss in activity implies no change in structure
__ elaboration on changes in enzyme structure (conformation explanation,
bonding shifts or an explanation of why no change in activity is predicted)
3. 1995:
Energy transfer occurs in all cellular activities. For 3 of the following 5 processes
involving energy transfer, explain how each functions in the cell and give an example.
Explain how ATP is involved in each example you choose.
Cellular movement
Active transport
Synthesis of molecules
Chemiosmosis
Fermentation
1 pt function of process
1 pt example
1 pt ATP involvement
4 pts = MAX/process
1 pt additional for detail
ATP <====> ADP + Pi + Energy 1 pt
Cellular Movement
Function Locomotion, Mitosis, Cytoplasmic Streaming,
Muscle Contraction (sliding filaments)
Examples Cilia, Flagella, Pseudopodia, Exocytosis, Endocytosis,
Microfilaments, Spindle Fibers
Details 9 + 2 Microtubules, Dynein, Actin-Myosin (Myosin heads),
Kinesins
ATP Involvement ATP used
Motor molecules powered by ATP hydrolysis
(Conformational change with ATP use)
Active Transport
Function Concentration gradient low to high / Protein carrier w/use of ATP
Examples Sodium/Potassium Pump, Other Transports Specified
Details Protein carrier related to example
ATP Involvement ATP used
Conformational change with ATP use
Synthesis of Molecules
Function Small to Large / Monomer to Polymer
Examples
Intermediates to Monosaccharides to Polysaccharides
Intermediates to Fatty Acids (Glycerol) to Lipids
Intermediates to Amino Acids to Proteins
Intermediates to Nucleotides to Nucleic Acids
Intermediates to Vitamins
Details Charging tRNA
Reactions catalyzed by enzymes
ATP Involvment ATP used
ATP's energy stored in chemical bonds
Chemiosmosis
Function Form electrochemical proton (H+) gradient
Examples Mitochondria, Chloroplasts, Bacterial Cell Membrane
Details Cristae, Thylakoids, Direction/ H+ vs eATP Involvement ATP formed
Proton pump/gradient with ATP synthase yields ATP
Fermentation
Start with glucose
Start with pyruvate
Function breakdown of organic
recycling NADH
compounds
Examples Ethanol / Lactic Acid
Ethanol / Lactic Acid
Details Anaerobic
Anaerobic
Less energy produced
Regenerate oxidized NAD
Cytosolic process
Cytosolic process
Yeast, Muscle
Yeast, Muscle
ATP Involvement
ATP used and formed
Substrate-level
Phosphorylation
(No direct involvement)
Makes ATP production
possible in glycolysis
Overall Commentary on Question:
This question was a cell biology energetics question that required both breadth and depth
of knowledge to answer the question successfully. Full credit could only be obtained by
responding to three of the process examples listed in the question. Also, if more than three
processes were discussed, readers were directed to grade the first three unless specifi indications
directed one to be omitted. Each process had a four point maximum score. One point was
available for description of the function of the process, which might also be a definition or
description of a mechanism. One point came from an example in context with the process. One
point was available for showing how ATP was involved in the process. For each of these points, it
was possible to get an additional point for detail (elaboration). In addition, it was possible to obtain
a point frordescription of the ATP <==> ADP cycle.