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Cell biology (formerly cytology, from the Greek κυτος, kytos, which means "vessel"), and otherwise known as molecular or cellular biology, is a branch of biology that studies the different structures and functions of the cell, and focuses mainly on the idea that the cell is the basic unit of life. Cell biology explains the the structure, organization of organelles, physiological properties, metabolic processes, signaling pathways, life cycle, and interaction of the cell with the environment. This done both on the microscopic and molecular level as it encompasses prokaryotes and eukaryotes. Knowing the components of cells and how cells work is fundamental to all biological sciences. Therefore, research in cell biology is closely related to genetics, biochemistry, molecular biology, immunology, and developmental biology.

Content

Internal Cellular Structures

·       Chemical and Molecular Environment

·       Organelles

Processes

·       Growth and Development

·       Signalling Pathways

Techniques Used to Study Cells

Careers and Related Fields

Internal Cellular Structure

Chemical and Molecular Environment

The study of the cell is done on a molecular level; however, most of the processes within the cell is made up of a mixture of small organic molecules, inorganic ions, hormones, and water. Approximately 75-85% of the cell’s volume is due to water making it an indispensable solvent as a result of its polarity and structure. These molecules within the cell, which operate as substrates, provide a suitable environment for the cell to carryout metabolic reactions and signalling. The cell shape varies among the different types of organisms, and are thus then classified into two categories: eukaryotes and prokaryotes. In the case of eukaryotic cells - which are made up of animal, plant, fungi, and protozoa cells - the shapes are generally round and spherical, while for prokaryotic cells – which are composed of bacteria and archaea - the shapes are: spherical (cocci), rods (bacillus), curved (vibrio), and spirals (spirochetes). Cell biology focuses more on the study of eukaryotic cells, and their signalling pathways, rather than on prokaryotes which is covered under microbiology. The main constituents of the general molecular composition of the cell includes: proteins and lipids which are either free flowing or membrane bound, along with different internal compartments known as organelles. This environment of the cell is made up of hydrophilic and hydrophobic regions which allows for the exchange of the above mentioned molecules and ions. The hydrophilic regions of the cell are mainly on the inside and outside of the cell, while the hydrophobic regions are within the phospholipid bilayer of the cell membrane. The cell membrane consists of lipids and proteins which accounts for its hydrophobicity as a result of being non-polar substances. Therefore in order for these molecules to participate in reactions, within the cell, they need to be able to cross this membrane layer to get into the cell. They accomplish this process of gaining access to the cell via: osmotic pressure, diffusion, concentration gradients, and membrane channels. Crossing the phospholipid bilayer to the inside of the cell there are extensive internal subcellular membrane-bounded compartments called organelles.

Organelles

•           Cell membrane (plasma membrane) - the part of the cell which separates the cells from the outside environment and protects the cell, as well as regulating what goes in and out of the cell

•           Cell wall - extra layer of protection and gives the cell its structure (only found in plant cells)

•           Chloroplast - key organelle for photosynthesis (only found in plant cells)

•           Cilium - motile structure of eukaryotes having a cytoskeleton, the axoneme.

•           Cytoplasm - contents of the main fluid-filled space inside cells. Chemical reactions also happen in this jelly-like substance.

•           Cytoskeleton - protein filaments inside cells (microfilaments, microtubules, and intermediate filaments)

•           Endoplasmic Reticulum (rough) - major site of membrane protein synthesis

•           Endoplasmic Reticulum (smooth) - major site of lipid synthesis

•           Endosomes - vesicles that traffic membrane and intra and extra cellular contents for recycling or degradation by lysosomes

•           Flagellum - motile structure of bacteria, archaea and eukaryotes

•           Golgi apparatus - site of protein glycosylation in the endomembrane system

•           Lipid bilayer - fundamental organizational structure of cell membranes

•           Lysosome – acidic organelle that breaks down cellular waste products and debris into simple compounds (only found in animal cells)

•           Microvilli – increases surface area for absorption of nutrients from surrounding medium

•           Mitochondrion - major energy-producing organelle by releasing it in the form of ATP

•           Nucleus – contains chromosomes composed of DNA

•           Organelle - term used for major subcellular structures

•           Peroxisomes -   A very small organelle that uses oxygen to breakdown and detoxify long fatty acids and other molecules

•           Pili - also called fimbria is used for conjugation and sometimes movement

•           Ribosome - RNA and protein complex required for protein synthesis in cells

•           Secretory vesicles – stores secreted proteins and fuses with the cell membrane

•           Starch grain - found in the cytoplasm of a typical plant cell, it stores chemical energy of the plant.

•           Vacuole - contain cell sap (only found in plant cells)

•           Vesicle - small membrane-bounded spheres inside cells

Processes

Growth and Development

Signalling Pathway

'''Techniques Used to Study Cells'''

Chemical and Molecular Makeup

Careers

Research

'''Related Fields'''

Genetics, biochemistry