Introduction to Biology & Human
Body Systems Study Guide – Cells,
Biochemistry, Homeostasis, Nervous,
Endocrine, Circulatory & Respiratory
Systems (Complete Review 2026)
What is a molecule?
Two or more atoms bound to each other by chemical bonds.
What is a cell?
The smallest living unit, the basic unit of life, capable of carrying out processes needed
for life.
What is tissue?
A group of similar cells that work together to perform a specific function.
What are the levels of organization in biology?
Atom, Molecule, Organelle, Cell, Tissue, Organ, Organ system, Organism.
What are the major elements of the human body?
Oxygen (65%), Carbon (18%), Hydrogen (10%), Nitrogen (3%), Calcium (1.5%),
Phosphorus (1%).
How do humans obtain minerals?
By extracting them from soil through plants and passing them up food chains.
What is the difference between organic and inorganic molecules?
Organic molecules come from living sources and contain carbon; inorganic molecules
come from nonliving sources and contain no carbon.
What are the four major types of biomolecules?
Nucleic acids, carbohydrates, lipids, proteins.
What is a prokaryotic cell?
A simple single-celled organism with no nucleus or membrane-bound organelles.
What is a eukaryotic cell?
A cell with a nucleus; major types include plant and animal cells.
What is the function of the nucleus?
Controls cell growth, metabolism, and reproduction by regulating gene expression.
What are ribosomes and their function?
Ribosomes make proteins and synthesize proteins used in the cytosol.
What are mitochondria and their functions?
Double membrane-bound organelles that generate ATP and are involved in cellular
respiration.
What are chloroplasts and their function?
Double membrane organelles that produce glucose through photosynthesis.
What is homeostasis?
Maintaining internal consistency or a steady internal environment.
Body Systems Study Guide – Cells,
Biochemistry, Homeostasis, Nervous,
Endocrine, Circulatory & Respiratory
Systems (Complete Review 2026)
What is a molecule?
Two or more atoms bound to each other by chemical bonds.
What is a cell?
The smallest living unit, the basic unit of life, capable of carrying out processes needed
for life.
What is tissue?
A group of similar cells that work together to perform a specific function.
What are the levels of organization in biology?
Atom, Molecule, Organelle, Cell, Tissue, Organ, Organ system, Organism.
What are the major elements of the human body?
Oxygen (65%), Carbon (18%), Hydrogen (10%), Nitrogen (3%), Calcium (1.5%),
Phosphorus (1%).
How do humans obtain minerals?
By extracting them from soil through plants and passing them up food chains.
What is the difference between organic and inorganic molecules?
Organic molecules come from living sources and contain carbon; inorganic molecules
come from nonliving sources and contain no carbon.
What are the four major types of biomolecules?
Nucleic acids, carbohydrates, lipids, proteins.
What is a prokaryotic cell?
A simple single-celled organism with no nucleus or membrane-bound organelles.
What is a eukaryotic cell?
A cell with a nucleus; major types include plant and animal cells.
What is the function of the nucleus?
Controls cell growth, metabolism, and reproduction by regulating gene expression.
What are ribosomes and their function?
Ribosomes make proteins and synthesize proteins used in the cytosol.
What are mitochondria and their functions?
Double membrane-bound organelles that generate ATP and are involved in cellular
respiration.
What are chloroplasts and their function?
Double membrane organelles that produce glucose through photosynthesis.
What is homeostasis?
Maintaining internal consistency or a steady internal environment.
