Introduction to Biochemistry, Page 2

Cells: Universal Building Blocks

•Living organisms are made of cells

•Simplest living organisms are singe-celled

•Larger organisms consists many cells with 

different functions

•Not all the cells are the same

Three Domains of Life

•Differences in cellular and molecular level define three 

distinct domains of life

Bacterial, Plant, and Animal Cells are Different

•The internal structure and 

properties of cells from 

organisms in different 

kingdoms are rather different 

but fundamental

macromolecules are highly

conserved

Components of Bacterial Cell

Structure            Composition           Function

Cell wall               Peptidoglycan          Mechanical support

Cell membrane    Lipid + protein          Permeability barrier

Nucleoid              DNA + protein          Genetic information

Ribosomes          RNA + protein          Protein synthesis

Pili                       Protein                     Adhesion, conjugation

Flagella               Protein                     Motility 

Cytoplasm          Aqueous solution     Site of metabolism 

Eukaryote Cells: More Complexity

•Have nucleus by definition

–protection for DNA; site of DNA metabolism

–selective import and export via nuclear membrane pores

–some cells become anuclear (red blood cells)

•Have membrane-enclosed organelles

–Mitochondria for energy in animals, plants and fungi

–Chloroplasts for energy in plant

–Lysosome for digestion of un-needed molecules

•Spatial separation of energy-yielding and energy consuming reactions helps cells to maintain homeostasis and stay away from equilibrium

Components of Animal Cells

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