Cell Structures

Cells are the fundamental units of life that make up all living organisms, from the simplest bacteria to complex organisms like humans.
Each cell consists of a semi-permeable cell membrane, nucleus, and cytoplasm with various organelles.
The cell membrane encloses the cell and controls what goes in and out of the cell via passive (diffusion and osmosis) and active transport methods.
The nucleus, often referred to as the control center, houses chromosomes that contain genetic information (DNA).
The cytoplasm is a jelly-like substance inside the cell where most cellular activities occur such as metabolic processes, including glycolysis.
Mitochondria in the cytoplasm are the ‘powerhouses’ of the cell. They generate energy, stored as ATP, by respiration.
Ribosomes - tiny structures found either free in the cytoplasm or attached to the endoplasmic reticulum - make proteins from amino acids in a process known as protein synthesis.
The endoplasmic reticulum is a network of membranes involved in protein and lipid synthesis. Rough ER has ribosomes attached, while smooth ER doesn’t.
The Golgi apparatus modifies and packages proteins and lipids into vesicles for transport inside and outside the cell.
Lysosomes contain enzymes for digesting waste materials and cellular debris within a cell.
Plant cells have additional components such as a cell wall for structural support, chloroplasts for photosynthesis, and a large central vacuole for storing water, nutrients, and waste products.
Animal cells do not have a cell wall, chloroplasts or a large central vacuole, instead, they have small vacuoles.
Specialized cells have unique structures and functions. For example, red blood cells carry oxygen, while nerve cells transmit electrical signals.
Unicellular organisms perform all life processes within a single cell, whereas multicellular organisms have specialized cells performing different functions.
Systems of cells working together form tissues, tissues form organs, and organs form organ systems, highlighting the hierarchy of structure and function in multicellular organisms.