Cell Organelles and Their Functions

Organelle Cell Type Function
Lysosomes All eukaryotes A membrane-enclosed bag of digestive juices. Break down large molecules and old cell parts into their components that can be recycled to build new cell parts.
Rough Endoplasmic Reticulum All eukaryotes Large folded membrane system studded with ribosomes. Builds proteins and helps fold or modify them. Products are shipped to the Golgi.
Smooth Endoplasmic Reticulum All eukaryotes Large folded membrane system. Puts together lipids and is important in making new membranes.
Microtubules and Microfilaments All eukaryotes Long tubes or cord-like structures that provide the cell's internal structure and allow cell movement. Other organelles are anchored to this network called the cytoskeleton. Work together in muscle contractions, and the motion of cilia and flagella.

Structural differences between cell wall and cell membrane

Cell Wall Cell Membrane
Rigidity Rigid Flexible
Composition Made of cellulose Made of protein and lipid or phospholipids
Permeability Permeable Semi-permeable
Thickness Thick Thin
Cell Separation Cells separated by middle lamella Continuous layer

Comparison between plant cell and animal cell

Differences
Plant cells Animal cells
Cell wall Presence of cellulose cell wall Absence of cellulose cell wall
Vacuole Contain large and permanent vacuole Contain small and temporary vacuole
Chloroplast Chloroplast is present Chloroplast is absent
Protoplasm Protoplasm is less dense Protoplasm is more dense
Shape Has definite shape Shape is indefinite
Size Comparatively larger in size Comparatively smaller in size
Carbohydrate storage Carbohydrate is stored as starch granules Store carbohydrates as glycogen granules
Plant cells Animal cells
Cytoplasm Less dense More dense
Centriole/Centrosome Does not have Has
Similarities
  • Cytoplasm
  • Nucleus
  • Vacuole
  • Mitochondrion
  • Golgi body (smooth and rough)
  • Endoplasmic reticulum
  • Cell membrane or plasma membrane
  • Ribosomes

Differences between prokaryotic and eukaryotic cells

Prokaryotic cells Eukaryotic cells
Nucleus Lack nucleus/non-nucleated Have nucleus/nucleated/presence of nuclear material
Genetic material Genetic material or DNA is present in the cytoplasm Genetic material or DNA is found in the nucleus
Organelles Lack membrane bound organelle Have membrane bound organelle
Size and complexity Simpler and smaller Complex and larger
Number of organelles Few organelles Many organelles
DNA structure Circular DNA is present Linear DNA is present

Structures found in plant cells only Structures found in animal cells only
  • Cellulose cell wall

  • Chloroplast (or leucoplast or plastids)

  • Starch granules

  • Large permanent central vacuole
  • Centrioles

  • Cilia

  • Lysosomes

  • Glycogen granules

  • Small temporary vacuole

  • Fat droplets

NB:
Plastids are usually doubled membraned sac-like organelles, involved in either the manufacture or storage of food. e.g. chloroplast
A specialized cell is a type of cell structurally adapted to perform a specific function in multicellular organisms.

The word "Eukaryotic" means "true nucleus" and eukaryotic cells have. Eukaryotic cells only contain organelles that are distinctly membrane-bound such as nuclei, mitochondria and chloroplasts. Animals, Plants, Fungi and Protoctista are all eukaryotes.


Examples of specialized animal cells and their function
Cell type Structural specialization Function
Sperm cell The head contains genetic information and an enzyme to help penetrate the egg cell membrane. The middle section is packed with mitochondria for energy. The tail moves the sperm to the egg. Fertilizes an egg cell - female gamete
Red blood cells The biconcave disc shape or absence of nucleus provides large surface area for oxygen to enter or leave. Contain haemoglobin to carry oxygen to the cells.
White blood cell Can change shape To attack invading microorganisms

Examples of specialized animal cells and their function
Cell type Structural specialization Function
Nerve cell Long thin fibre To conduct nerve impulses
Muscle cell Spindle-shaped or cylindrical and can contract or relax Cause movement

Specialized plant cells and their function
Cell type Structural specialization Function
Palisade mesophylls Contain many chloroplasts closely packed Make food by photosynthesis (trapping energy of the sunlight)
Spongy mesophylls Cells are irregular in shape which creates a lot of intercellular spaces between them To allow carbon dioxide circulation in the leaf since carbon dioxide is a raw material for photosynthesis

Specialized plant cells and their function
Cell type Structural specialization Function
Xylem Have no end walls leaving hollow lumen and thick cell walls to withstand pressure Transport water
Phloem This consists of elongated sieve elements, phloem parenchyma, and companion cells Translocate products of photosynthesis
Root hair cell Long 'finger-like' process with very thin wall, which gives a large surface area Absorbs water and mineral ions from the soil
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