Cell Structure and Organisation: Chapter 1

• Chapter 1 focuses on Cell Structure and Organisation

What Are Cells?

• Cells are the basic building blocks of life, functioning like chemical factories that perform different tasks to keep organisms alive

Robert Hooke's Discovery

• Robert Hooke coined the term "cells" in 1667.
• He used one of the earliest microscopes to examine thin slices of tree bark.
• Hooke observed packed little boxes with thick walls, which reminded him of cells in a prison.

Microscopy

• Most cells are too small to be seen without assistance.
• Light microscopes (1000x magnification) and electron microscopes (200,000x magnification) can be used to view cells and their parts.
• Robert Hooke and Anton van Leeuwenhoek are key inventors in the field of microscopy.
• Cameras can be fitted to microscopes to capture images called micrographs.

Units of Measurement

• 1 meter (m) is equivalent to 1,000 millimeters.
• 1 millimeter (mm) is equivalent to 10⁻³ m or 1,000 micrometers.
• 1 micrometer (μm) is equivalent to 10⁻⁶ m or 1,000 nanometers.
• 1 nanometer (nm) is equivalent to 10⁻⁹ m or 1,000 pedometers.

Cell Components

• A cell consists of a mass of living matter called protoplasm.
• Protoplasm (Greek: protos = first, plasm = form) is composed of:
  • Cell membrane
  • Cytoplasm
  • Nucleus

Cell Membrane

• It surrounds the cytoplasm.
• The cell membrane is made of lipids (lipid bilayer) and proteins.
• It is partially permeable, allowing only small and soluble substances to pass through.

Cell Wall

• Plant cells also have a cell wall, made of cellulose, surrounding the cell membrane.
• The cell wall is fully permeable.
• It provides the cell with a fixed shape and protects it from injury.

Cytoplasm

• It is located between the cell membrane and the nucleus.
• Cytoplasm is the site of cellular activities.
• Cytoplasm contains specialized structures called organelles.

Nucleus

• Controls cellular activities and is essential for cell division.
• Cells, without a nucleus are unable to divide
• Individual parts of the nucleus can only be seen under an electron microscope.
• Chromosomes are long, thread-like structures within the nucleus.
• Chromosomes are made up of DNA, which carries hereditary information.
• Chromosomes condense into thick, rod-shaped structures when the cell is dividing.
• The nuclear membrane separates the contents of the nucleus from the cytoplasm.

Organelles in the Cytoplasm

• Endoplasmic Reticulum (ER):
  • Rough ER (RER): A network of flattened spaces lined with a membrane. The outer surface is continuous with the nuclear envelope and studded with Ribosomes which transports proteins made to the Golgi apparatus.
  • Smooth ER (SER) is more tubular than RER, lacks ribosomes, and synthesizes fats and steroids; involved in detoxification.
• Ribosomes: Small, round responsible for protein synthesis which are attached to the RER or lie freely in the cytoplasm.
• Golgi Body (Golgi Apparatus): Consists of flattened spaces surrounded by membranes that chemically modifies substances by the ER, and stores and packages them in vesicles for secretion.
• Mitochondria: Oval or sausage-shaped organelles that are the site of aerobic respiration and oxidise food to release energy for cellular activities.
• Chloroplasts: Oval structures found in plant cells that contain chlorophyll, which is required for photosynthesis.
• Vacuole: Fluid-filled space enclosed by a partially permeable membrane that stores substances within the cell. It is large and central in plant cells, and small and numerous in animal cells.

Plant vs Animal Cells

How Are Cells Adapted to Their Functions?

• Differentiation is the process by which a cell becomes specialized for a specific function.
• There are many specialized cells in the human body, including red blood cells and root hair cells.

Specialized Cells and Their Adaptations

Lab-Grown Meat

• Cultured or lab-grown meat has been sold in Singapore since December 2020.
• Lab-grown meat is produced via in vitro cell culture of animal cells, aiming to be cruelty-free, safe, healthy, and environmentally friendly.

Cellular Organization

• Cells: A group of similar cells working together to perform a specific function.
• Tissues: Different tissues working together to carry out a specific function.
• Organ: Several related organs working together to carry out a particular function.
• Organ System: Specialised for a particular function.
• Stem cells can develop into other specialised
• Scientists can grow cells of different organs in the laboratory and transplant them into humans
• Used for Potential to treat diseases that were once considered untreatable

How to improve lab-grown meat

• Organ production