The basic unit of life that can be found in every living thing, including humans, animals, plants and bacteria
Cells
Small in structure, 0.1 to 5.0 μm in diameter for prokaryotic cells, 10 to 100 μm in diameter for eukaryotic cells
Have general structures that allow them to be self-regulating, such as producing energy, movement, removing wastes etc.
Unicellular organism
Living things that are made of a single cell, such as bacteria
Multicellular organism
More complex organisms like humans, animals and plants
All known living things are made up of one or more cells
All living cells arise from pre-existing cells by division
The cell is the building block of structure and function in all living organisms
The activity of an organism depends on the total activity of independent cells
Cells are the site of all chemical reaction of life (metabolism and energy flow)
Cells contain hereditary material (DNA), the blueprint for their cell growth, development and behavior
All cells are basically the same in chemical composition in organisms of similar species
Prokaryotes
Earliest organisms on earth, mostly unicellular, lack well-defined nuclei and membrane-bound organelles, have a single circular chromosome, classified into Bacteria and Archaea
Eukaryotes
More complex and evolved organisms, can be unicellular (algae, protozoa) or multicellular (animals, plants, fungi), have a nucleus wrapped in a nuclear membrane and membrane-bound organelles
Similarities between prokaryotes and eukaryotes
Ribosome
DNA
RNA
Cytoplasm
Differences between prokaryotes and eukaryotes
Circular DNA (prokaryotes) vs Complex and extensive DNA (eukaryotes)
No nucleus (prokaryotes) vs Have nucleus (eukaryotes)
Mostly unicellular (prokaryotes) vs Can be uni- or multicellular (eukaryotes)
All have cell wall (prokaryotes) vs Some do contain cell wall (eukaryotes)
Few organelles (prokaryotes) vs Have membrane bound organelles (eukaryotes)
Small in size (prokaryotes) vs Larger in size (eukaryotes)
Similarities between plant and animal cells
Mitochondrion
Golgi apparatus
Rough and smooth endoplasmic reticulum
Nucleus
Cytoplasm
Ribosomes
Differences between plant and animal cells
Cell wall (plants) vs No cell wall (animals)
Large vacuole (plants) vs Small or no vacuole (animals)
Chloroplasts (plants) vs No chloroplasts (animals)
Flagella only in gametes (plants) vs Flagella (animals)
Theoretically it is possible to build a living organism from cells
Applications of prokaryotic cells
Cleaning up oil spills
Decompose organic matter into sludge
Produce vitamins, antibiotics, hormones (e.g. insulin)
Amplify DNA, cloning and genetic manipulation
Applications of eukaryotic cells
Mammalian cell biology - DNA replication, gene expression, cell division etc.
Drug discovery and screening
Transgenic crop plants - make corn resistant to specific insect pest
Transgenic animals - production of pharmaceutically important protein
The seven characteristics of life are: cells and organisation, metabolism, responsiveness and movement, growth and development, reproduction, homeostasis, and evolution
Levels of organisation in the human body
Atoms and molecules
Cells
Tissues
Organs
Organ systems
Organism
Types of stem cells
Totipotent stem cells
Pluripotent stem cells
Multipotent stem cells
Examples of cells adapted to their function
Muscle cells with myofilaments to contract and relax
Nerve cells with axons and dendrites to produce and move nerve impulses
Red blood cells with biconcave shape and haemoglobin to carry oxygen
Intestinal epithelial cells with microvilli to increase surface area for nutrient absorption
My Healthy Plate
Recommended diet for average Singaporean to maintain a balanced diet
Tim adjusted his diet in order to lose weight
Alan, Marilyn and her friends are aspiring athletes wanting to achieve their goals in weightlifting and marathon running respectively
Adhesion
The attraction between unlike molecules or surfaces
Cohesion
The attraction between like molecules or surfaces
Density
The mass per unit volume of a substance
Hydrophobic
Having a tendency to avoid or repel water
Hydrophilic
Having a tendency to attract or be attracted to water
Inter-molecular
Occurring between molecules
High specific heat capacity
The amount of heat required to raise the temperature of a substance by one degree
Intra-molecular
Occurring within a molecule
Non-polar
Having no permanent electric dipole moment
Polar
Having a permanent electric dipole moment
Solvent
A liquid that dissolves a solute, forming a solution
Solutes
A substance dissolved in a solvent to form a solution
Surface tension
The cohesive force between the surface molecules of a liquid that causes the surface to behave like an elastic sheet