Numbered carbons from milk galactose travel through the Leloir pathway, glycolysis, pyruvate dehydrogenase and the citric acid cycle to exhaled carbon dioxide in this SC335 Unit 7 pathway map. Searches like "sc 335 unit 7 assignment example", "sc335 unit 7 sample" and "sc335 unit 7 example" land here.
What a finished SC335 Unit 7 pathway map looks like
A two-page map with a one-page key. The map begins at lactose, split by lactase at the intestinal brush border, and follows galactose through galactokinase, galactose-1-phosphate uridylyltransferase, the epimerase that regenerates UDP-glucose and phosphoglucomutase, arriving as glucose-6-phosphate. Glycolysis runs down the page in the cytosol to pyruvate, with phosphofructokinase-1 boxed as a control point. A dashed line marks the mitochondrial membrane; pyruvate dehydrogenase sits just below it, labeled with its five cofactors. The citric acid cycle is drawn as a wheel with its three regulated steps boxed. Colored dots track the numbered carbons: carbons 3 and 4 leave at pyruvate dehydrogenase, carbons 2 and 5 leave in the cycle's second turn, and carbons 1 and 6 linger, half of what remains leaving in each turn from the third onward.
How a SC335 Unit 7 example is structured
Compartments give the map its layout, cytosol above the dashed membrane line and matrix below, so a reader sees where pyruvate must be carried across before its carbon can be released. The carbon labels are the map's argument, and the key justifies each assignment in a sentence, including the symmetry of succinate that scrambles which end of the molecule a label occupies. Cofactors appear at every step that needs them, with the vitamin behind each named once in the key, since a map missing them is marked as incomplete. Control points are boxed and annotated with their main effectors, and the key keeps regulation separate from carbon tracking so the two stories stay readable. A final note corrects a common assumption: the oxygen atoms in exhaled carbon dioxide come from water and the fuel's own atoms, not from inhaled oxygen, which ends up in water.
A membrane drawn as a line
Cytosolic steps sit above a dashed line and matrix steps below it, so the transport of pyruvate appears as a crossing rather than an unmarked arrow.
Six carbons, six colors
Each numbered carbon keeps one color from galactose onward, which lets a reader follow carbons 3 and 4 to their early release without consulting the key.
A symmetric molecule scrambles the labels
Succinate's two identical ends explain why a tracked carbon's position becomes uncertain after that step, and why the methyl-derived carbons leave only gradually.
Cofactors named with their vitamins
Thiamine pyrophosphate, lipoamide, coenzyme A, FAD and NAD appear where they act, with the key tying each to the vitamin that supplies it.
Where the oxygen really goes
A closing note states that inhaled oxygen becomes water at the end of the electron transport chain, while exhaled carbon dioxide takes its oxygen from fuel and water.
Where marks go in SC335 Unit 7
Every intermediate listed and no carbon located is the pattern that misses the prompt's actual question, since tracing carbon is the whole assignment, and graders look for the labels before anything else. Claiming the acetyl carbons leave in the first turn of the cycle is the most common tracing error; the two carbons released in that turn come from oxaloacetate. Galactose shown entering glycolysis directly, without the uridylyltransferase and epimerase steps, skips the pathway that makes it usable. A missing membrane boundary hides the transport step. Cofactors omitted at pyruvate dehydrogenase or at the cycle's dehydrogenases are marked as content errors. Regulatory arrows mixed into the carbon tracking make both unreadable. Arrows without enzymes named, and a key that cites nothing, cost smaller amounts.
Get a SC335 Unit 7 example written to your instructions
Which sugar and which endpoint does your SC335 Unit 7 prompt specify? Add the rubric and whatever drawing format is required. Drawn to that prompt and free of charge, a first custom map returns inside 24-48h with enzymes, cofactors and compartments at every step and each tracked carbon labeled to its release.
SC335 Unit 7 questions, answered
Why do the acetyl carbons not leave in the first turn of the cycle?
The two carbon dioxide molecules released in a turn come from the oxaloacetate portion of citrate, not from the acetyl group that just entered. The acetyl carbons become part of the regenerated oxaloacetate and leave in later turns. This is one of the most frequently tested points in carbon tracking, so labeling it clearly on your map is worth the effort.
Does a pathway map need cofactors?
In most SC335 sections, yes. Cofactors are part of the chemistry: pyruvate dehydrogenase cannot work without thiamine pyrophosphate, lipoamide, coenzyme A, FAD and NAD, and several of these come from vitamins. A map that omits them leaves out what made each step possible, and many rubrics treat that as a content error rather than a presentation issue.
Can I trace glucose instead of galactose?
Usually, where the prompt leaves the sugar open. Glucose skips the galactose-specific steps and enters glycolysis at hexokinase, but the carbon assignments from there onward are the same. Fructose is another option with its own entry route in the liver. Use the sugar your assignment names, and keep the numbered labels consistent from the first step to the last.