Energy

Animal nutrition

Animal nutrition is how a human takes food in, breaks it down, absorbs the useful molecules, and egests what cannot be used.

CAPS

Grade 11 · Life Sciences · Energy

Life Sciences is two papers. Use the strand to know which one.

  • Where it is examined

    Grade 11 works through energy transformations, gas exchange, excretion, population ecology and human impact. The same two-paper pattern is used.

  • How to write it

    Name the structure, then say what it does. A labelled diagram only scores if the labels are the biological names. “It helps the body” is not a function.

  • How a marker reads it

    A common mix-up is to say bile digests fat the way lipase does, or that the stomach absorbs most of the food.

A 2-mark “explain” wants two facts, or one fact and its reason. Extra sentences that contradict the first one can cancel a mark.

RL

Diagram

Worked theory

Worked theory. A cheese sandwich. Starch in the bread meets amylase in the mouth. Protein in the cheese is attacked in the stomach and finished in the small intestine. Fat in the cheese is emulsified by bile, then lipase splits it. Glucose and amino acids cross the villi into the blood. Fatty products enter the lymph. Fibre continues and is egested. If the villi were flattened, as in untreated coeliac disease, the food could be digested and still not absorbed. Digestion and absorption are two different events.

More worked examples

  • Pap and grilled chicken

    The pap is starch. Amylase in the mouth starts it. The chicken is protein. Acid and protease in the stomach start it, and the small intestine finishes it. Fat on the chicken is not touched by the stomach acid. Bile from the liver breaks it into droplets, then lipase splits the droplets. Glucose and amino acids enter the blood at the villi. A classmate who says the stomach absorbs the meal has skipped the villi, which is where the food actually enters the body.

  • A blocked bile duct

    Bile, made in the liver and stored in the gall bladder, breaks fats into droplets. If the duct is blocked, fat in the meal is not emulsified. The stool becomes pale and fatty, and the fat-soluble vitamins are poorly absorbed. The stomach acid still worked. The protease still worked. The missing step was bile. A learner who treats every digestive problem as “the stomach” has skipped the organ that actually failed.

In ordinary words

The path is mouth, oesophagus, stomach, small intestine, large intestine, anus. Teeth and saliva start starch digestion. The stomach’s acid and protease start protein. The liver makes bile, which emulsifies fats. The pancreas adds enzymes for starch, protein and fat. The small intestine’s villi give a huge surface for absorption into the blood. The large intestine takes back water. Egestion is not excretion. Excretion removes metabolic waste such as urea.

In South Africa

A school lunch is enough of a worked meal: starch, protein and fat on one plate.

Part 1 / 4

What it is

Animal nutrition is how a human takes food in, breaks it down, absorbs the useful molecules, and egests what cannot be used.

Diagram
Diagram

More worked examples

Board walkthroughs on this topic. Open one, copy the working, then try the next.

Example 1 / 20

Name the enzyme, substrate and product for digestion in the mouth.

How we got there

Read this like a teacher at the board. We go slowly, name every number, and say why we take each step.

Explain in another language · 11

1. What is the question asking?

Read the question twice. Circle the unknown. Underline every number and unit. The paper is asking: Name the enzyme, substrate and product for digestion in the mouth.

In other words — as if you have never seen this before

If you have never seen this before: Salivary amylase. We will name a method in words, write the formula with no numbers, then substitute one line at a time.

2. What do we already know?

Mouth digestion.

3. Which method — and why this one?

Salivary amylase.

4. Step-by-step working

  1. 01 / 07

    Step A — Read the question twice

    Slow down. Circle the word that names the unknown. Underline every number and its unit. Do not grab a formula yet — first decide what the paper is actually asking.

    Why this step: If you can say the method in a sentence, you will pick the right formula. First-timers skip this and grab the first equation they remember.

  2. 02 / 07

    Step B — Write the given in a column

    Mouth digestion.

    Why this step: A column with units stops you mixing cm with m, or minutes with seconds. Markers can also see you started correctly.

  3. 03 / 07

    Step C — Name the method in words

    Salivary amylase.

    Why this step: If you can say the method in a sentence, you will pick the right formula. First-timers skip this and grab the first equation they remember.

  4. 04 / 07

    Identify the given

    Salivary amylase breaks down starch into maltose at about pH 7.

    Why this step: We only do one job per line so a marker can follow the marks — and so you can find a slip without starting over.

  5. 05 / 07

    Step G — Sense-check the size

    Ask: is this the kind of number a Grade 10–12 paper would want? A speed of 3 000 ms for a learner walking, or a probability bigger than 1, means a unit or algebra slip. Estimate first: round the numbers and do the sum in your head.

    Why this step: Markers write ‘unrealistic’ in the margin when the method is right but the size is wild. A 10-second head check often finds a missing 10² or a unit that never changed.

  6. 06 / 07

    Step F — Box the answer with its unit

    Amylase: starch → maltose.

    Why this step: A number without a unit is half a mark on a Physics paper, and a marker can miss a Maths answer that is buried in working.

  7. 07 / 07

    Step H — What the marker is looking for

    On an NSC memo you usually earn: (1) a method mark for naming the right formula or idea in words, (2) an accuracy mark for substituting the given numbers with units, (3) an accuracy mark for the boxed answer with its unit. Write those three lines even if you are unsure of the arithmetic — blank pages score zero.

    Why this step: First-timers chase the final number and leave the method blank. The memo still pays out for the idea and the substitution even when the last line is wrong.

5. The answer

Amylase: starch → maltose.

Copy onto your answer sheet — in this order

Answer: Amylase: starch → maltose.

6. Check it like a marker

Protein digestion starts in the stomach (pepsin).

7. A trap first-timers fall into

First-timers often grab the first formula they remember, mix units (cm with m, minutes with seconds), or drop a minus sign. Write the formula in words first: “this equals that, because…”

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