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Functions of cell organelles — KCSE Biology

KCSE Biology · 91 practice questions · 3 syllabus objectives · 3 revision lessons

30 easy31 medium30 hard

Last updated · Aligned to the KNEC KCSE syllabus

What You'll Learn

Key learning outcomes for this topic, aligned to the KNEC KCSE syllabus.

State the functions of the nucleus, mitochondria, and ribosomes

Relate the structure of organelles to their functions

Functions of cell organelles

Revision Notes

Concise lesson notes for Functions of cell organelles, written to the KCSE Biology marking standard. Read the first lesson free below.

Functions of Key Cell Organelles

The nucleus, mitochondria, and ribosomes are essential organelles in eukaryotic cells, each serving unique functions:

  • Nucleus: This organelle acts as the control center of the cell. It contains the cell's genetic material (DNA) and is responsible for regulating gene expression and cell division.
  • Mitochondria: Known as the powerhouse of the cell, mitochondria generate adenosine triphosphate (ATP) through cellular respiration, providing energy for various cellular processes.
  • Ribosomes: These small structures are crucial for protein synthesis. They translate messenger RNA (mRNA) into polypeptide chains, which then fold into functional proteins.

Understanding these functions is vital for grasping how cells operate and maintain life processes.

Key points to remember

  • Nucleus controls cell activities and stores genetic information.
  • Mitochondria produce ATP, supplying energy for the cell.
  • Ribosomes synthesize proteins from amino acids.
  • All organelles work together for cellular function and survival.
  • Their roles are fundamental to growth and metabolism.

Worked example

Question: State the functions of the nucleus, mitochondria, and ribosomes.

  • The nucleus controls cell activities and contains DNA.
  • Mitochondria produce ATP through cellular respiration.
  • Ribosomes synthesize proteins from mRNA.

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Lesson 2: Cell Organelles and Their Functions

Objective: Relate the structure of organelles to their functions

Cell organelles are specialized structures within cells, each designed for specific functions. Understanding their structure helps explain how they perform their roles effectively. Here are key organelles:

  • Nucleus: Contains genetic material (DNA) and controls cellular activities. Its double membrane structure protects DNA and regulates molecule entry.
  • Mitochondria: Known as the powerhouse of the cell, they have a double membrane with inner folds (cristae) that increase surface area for ATP production through respiration.
  • Ribosomes: Composed of RNA and protein, they can be free-floating or attached to the endoplasmic reticulum (ER). Their structure allows them to synthesize proteins from amino acids.
  • Chloroplasts: Found in plant cells, they contain chlorophyll and have a double membrane. Their structure enables them to capture sunlight for photosynthesis effectively.
  • Endoplasmic Reticulum (ER): The rough ER has ribosomes for protein synthesis, while the smooth ER is involved in lipid synthesis and detoxification. Their extensive network facilitates transport within the cell.

By relating the structure of these organelles to their functions, we can appreciate how cells operate efficiently.

  • Nucleus controls cell activities and stores DNA.
  • Mitochondria produce ATP through respiration.
  • Ribosomes synthesize proteins from amino acids.
  • Chloroplasts capture sunlight for photosynthesis.
  • ER assists in protein and lipid synthesis.

Explain how the structure of the mitochondria relates to its function.

  • Mitochondria have a double membrane, increasing surface area.
  • Inner folds (cristae) enhance ATP production efficiency.
Lesson 3: Functions of Key Cell Organelles

Objective: Functions of cell organelles

Cell organelles perform specific functions essential for cellular activities. Here are some key organelles and their roles:

  • Nucleus: Acts as the control center, housing genetic material (DNA) and regulating cell activities.
  • Mitochondria: Known as the powerhouse of the cell, they generate ATP through respiration, providing energy.
  • Ribosomes: Sites of protein synthesis, translating mRNA into amino acids to form proteins.
  • Endoplasmic Reticulum (ER): Divided into rough (with ribosomes) and smooth (without ribosomes), it synthesizes proteins and lipids.
  • Golgi Apparatus: Modifies, sorts, and packages proteins and lipids for secretion or delivery to other organelles.
  • Lysosomes: Contain digestive enzymes for breaking down waste materials and cellular debris.

Understanding these functions helps in grasping how cells maintain homeostasis and perform vital processes.

  • Nucleus controls cell activities and stores DNA.
  • Mitochondria produce energy (ATP) for the cell.
  • Ribosomes synthesize proteins from amino acids.
  • ER synthesizes proteins (rough) and lipids (smooth).
  • Golgi apparatus modifies and packages cellular products.

Describe the function of the mitochondria in a cell.

  • Mitochondria are known as the powerhouse of the cell.
  • They generate ATP through cellular respiration, which provides energy for cellular processes.

Sample Questions

Read 3 questions and answers free. Sign up to access all 91 questions with full KNEC-style marking schemes and a personalised study plan.

1
easySHORT ANSWER3 marks

Name the cell organelle associated with each of the following functions: (a) Controls all cell activities and contains the genetic material (DNA) (b) Stores cell sap and maintains turgor in plant cells (c) Provides structural support and gives plant cells their shape

Answer & marking scheme

Part (a) — 3 marks
Correct organelle for function (a) (1 mk)
Correct organelle for function (b) (1 mk)
Correct organelle for function (c) (1 mk)
2
easySHORT ANSWER3 marks

List the functions of the following cell organelles: (a) nucleus (b) mitochondria (c) ribosomes. (3 marks)

Answer & marking scheme

Part (a) — 3 marks
Controls cellular activities and stores genetic information (nucleus) (1 mk)
Produces ATP through aerobic respiration (mitochondria) (1 mk)
Synthesize proteins by translating mRNA (ribosomes) (1 mk)
3
easySHORT ANSWER3 marks

State the metabolic process(es) that occur in each of the following organelles: (a) Chloroplast (b) Mitochondrion (c) Vacuole

Answer & marking scheme

Part (a) — 3 marks
Correct metabolic process for organelle (a) (1 mk)
Correct metabolic process for organelle (b) (1 mk)
Correct metabolic process for organelle (c) (1 mk)
4

Name the cell organelle associated with each of the following functions: (a) Packages proteins for export from the cell (b) Site of aerobic respiration and ATP production (c) Site of protein synthesis

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Frequently asked questions

What does the KCSE Biology topic "Functions of cell organelles" cover?

Functions of cell organelles covers State the functions of the nucleus, mitochondria, and ribosomes; Relate the structure of organelles to their functions; Functions of cell organelles, all aligned to the official KNEC KCSE Biology syllabus.

How many practice questions are available for Functions of cell organelles?

HighMarks has 91 Functions of cell organelles practice questions for KCSE Biology, each with a full marking scheme. The first 3 are free; sign up to access the rest, plus all KCSE mock exams and past papers.

Are these aligned with the KNEC KCSE syllabus?

Yes. Every objective on this page is taken directly from the official KNEC KCSE Biology syllabus. Practice questions match the KCSE exam format and are graded against the standard KNEC marking scheme.

How should I revise Functions of cell organelles for the KCSE exam?

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