Cells

Cells: the basic units of life

A cell is the smallest living unit. Plants and animals are both made of cells, but the cells are not the same.

CAPS

Grade 10 · Life Sciences · Cells

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

  • Where it is examined

    Grade 10 is the chemistry of life, cells, tissues, organs, support and transport, and the biosphere, biodiversity and the history of life.

  • 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 put chloroplasts in an animal cell, or to say the cell wall is the same thing as the cell membrane.

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

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Diagram

Worked theory

Worked theory. A leaf cell and a cheek cell. The leaf cell stays box-shaped because the wall holds it, and it is green because chloroplasts catch light. The cheek cell is soft-edged, has no green chloroplasts, and cannot make food from light. Both still have a nucleus and mitochondria, so both are alive and both need energy. Killing the nucleus does not leave a working cell. The membrane is the gate, not a decoration.

More worked examples

  • Potato cell and muscle cell

    A cell from a potato has a wall and stores starch, but it has no chloroplasts, because a potato grows underground and does not catch light. A cell from thigh muscle has no wall and is packed with mitochondria, because the muscle needs ATP to contract. Both have a nucleus and a membrane. The potato cell cannot contract. The muscle cell cannot hold a square shape.

  • A waterweed cell and a red blood cell

    A cell from a pondweed leaf has a wall, a large vacuole and green chloroplasts, so it can photosynthesise. A mature human red blood cell has no nucleus and no chloroplasts. It carries oxygen and it cannot divide or make food. Both are cells. They are not the same kind of cell. A diagram that puts chloroplasts in the red cell, or a nucleus in the mature red cell, has mixed the two.

In ordinary words

The nucleus holds the DNA and controls the cell. The cell membrane decides what enters and leaves. Mitochondria release energy by cellular respiration. Ribosomes build proteins. A plant cell also has a cellulose cell wall, chloroplasts for photosynthesis, and one large vacuole that stores water and keeps the cell firm. An animal cell has no wall, no chloroplasts, and only small vacuoles.

In South Africa

Onion epidermis and a cheek scrape are the usual Grade 10 slides in a South African lab.

Part 1 / 4

What it is

A cell is the smallest living unit. Plants and animals are both made of cells, but the cells are not the same.

Diagram
Diagram
Diagram

More worked examples

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

Example 1 / 20

Under a microscope a cell has a cell wall, a large central vacuole and chloroplasts. Is it a plant or animal cell? Give two reasons.

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: Under a microscope a cell has a cell wall, a large central vacuole and chloroplasts. Is it a plant or animal cell? Give two reasons.

Before any working — hunt first

Given

Numbers and units already in the sentence: no numbers yet — only a name, a diagram, or a worded unknown. Copy each one into a column. A name without a number is not given.

Missing

After you copy the given, the letter that still has no number is missing. The paper is pointing at: two reasons. Circle that word — that is the missing variable.

Find

We are required to find: two reasons. Write that as a symbol on the left, with a question mark, before you touch a formula.

Calculate

What we need to calculate: Only plant cells have a cellulose cell wall and chloroplasts. Then substitute the given, one line at a time, to get two reasons.

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

If you have never seen this before: Only plant cells have a cellulose cell wall and chloroplasts. 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?

Cell wall, large vacuole, chloroplasts.

3. Which method — and why this one?

Only plant cells have a cellulose cell wall and chloroplasts.

4. Step-by-step working

  1. 01 / 08

    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 / 08

    Step A2 — Hunt: Given, Missing, Find, Calculate

    Given: Numbers and units already in the sentence: no numbers yet — only a name, a diagram, or a worded unknown. Copy each one into a column. A name without a number is not given. Missing: After you copy the given, the letter that still has no number is missing. The paper is pointing at: two reasons. Circle that word — that is the missing variable. Find: We are required to find: two reasons. Write that as a symbol on the left, with a question mark, before you touch a formula. Calculate: What we need to calculate: Only plant cells have a cellulose cell wall and chloroplasts. Then substitute the given, one line at a time, to get two reasons.

    Why this step: Do not name the letters yet. First hunt: what already has a number (Given), what has no number (Missing), the word the paper wants (Find), and which formula still contains the missing letter (Calculate).

  3. 03 / 08

    Step B — Write the given in a column

    Cell wall, large vacuole, chloroplasts.

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

  4. 04 / 08

    Step C — Name the method in words

    Only plant cells have a cellulose cell wall and chloroplasts.

    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.

  5. 05 / 08

    Identify the given

    Cell wall (cellulose) — plants only. Chloroplasts — plants only. Large central vacuole — typical of plants.

    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.

  6. 06 / 08

    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.

  7. 07 / 08

    Step F — Box the answer with its unit

    Plant cell: it has a cell wall and chloroplasts (and a large central vacuole).

    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.

  8. 08 / 08

    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

Plant cell: it has a cell wall and chloroplasts (and a large central vacuole).

Copy onto your answer sheet — in this order

Answer: Plant cell: it has a cell wall and chloroplasts (and a large central vacuole).

6. Check it like a marker

Animal cells have small or no vacuoles and no cell wall.

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…”

Ntsako · fx-991ZA PLUS. Tap to calculate.