To
1. choose the correct order of events in the kreb's cycle:

the correct order of krebs cycle is

Explanation:In the first step of the citric acid cycle, acetyl CoA}CoA, C, o, A, end text joins with a four-carbon molecule, oxaloacetate, releasing the {CoA}CoAC, o, A, end text group and forming a six-carbon molecule called citrate.

Step 2. In the second step, citrate is converted into its isomer, isocitrate. This is actually a two-step process, involving first the removal and then the addition of a water molecule, which is why the citric acid cycle is sometimes described as having nine steps—rather than the eight listed here

Step 3. In the third step, isocitrate is oxidized and releases a molecule of carbon dioxide, leaving behind a five-carbon molecule—α-ketoglutarate. During this step,

s, N, A, D, is reduced to form N, A, D, H, end text. The enzyme catalyzing this step, isocitrate dehydrogenase, is important in regulating the speed of the citric acid cycle.

Step 4. The fourth step is similar to the third. In this case, it’s α-ketoglutarate that’s oxidized, reducing {NADH} NADH and releasing a molecule of carbon dioxide in the process. The remaining four-carbon molecule picks up Coenzyme A, forming the unstable compound succinyl , C, o, A, end text. The enzyme catalyzing this step, α-ketoglutarate dehydrogenase, is also important in regulation of the citric acid cycle.

dit: modified from "Oxidation of pyruvate and citric acid cycle

Step 5. In step five, the C, o, A, is replaced by a phosphate group, which is then transferred to. In some cells, —guanosine diphosphate—is used instead of —guanosine triphosphate—as a product. The four-carbon molecule produced in this step is called succinate.

Step 6. In step six, succinate is oxidized, forming another four-carbon molecule called fumarate. In this reaction, two hydrogen atoms—with their transferredThe enzyme that carries out this step is embedded in the inner membrane of the mitochondrion, so it can transfer its electrons directly into the electron transport chain.

Step 7. In step seven, water is added to the four-carbon molecule fumarate, converting it into another four-carbon molecule called malate.

Step 8. In the last step of the citric acid cycle, oxaloacetate—the starting four-carbon compound—is regenerated by oxidation of malate. Another molecule of NADPH

the correct answer, according to e2020, is the second choice there is an occluded front in region a and a cold front in region b.

many other transport proteins, often called pumps, move materials against a concentration gradient. active transport drives molecules across a membrane from a region of lower concentration to a region of higher concentration. this process, shown in figure 5.1, uses transport proteins powered by chemi- cal energy.