Cell biology is a branch of biology that studies the different structures and functions of the cell and focuses mainly on the idea of the cell as the basic unit of life. Cell biology explains the structure, organization of the organelles they contain, their physiological properties, metabolic processes, signaling pathways, life cycle, and interactions with their environment. This is done both on a microscopic and molecular level as it encompasses prokaryotic cells and eukaryotic cells. Knowing the components of cells and how cells work is fundamental to all biological sciences it is also essential for research in bio-medical fields such as cancer, and other diseases. Research in cell biology is closely related to genetics, biochemistry, molecular biology, immunology, and developmental biology.
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 carry out 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 microbiolgy. 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 sub-cellular membrane-bounded compartments called organelles.
Organelles
| ORGANELLE | LOCATION | DESCRIPTION | FUNCTION |
| cell wall |
plant, not animal | *outer layer *rigid, strong, stiff *made of cellulose |
*support (grow tall) *protection *allows H2O, O2, CO2 to pass into and out of cell |
| cell membrane |
both plant/animal | *plant - inside cell wall *animal - outer layer; cholesterol *selectively permeable |
*support *protection *controls movement of materials in/out of cell *barrier between cell and its environment *maintains homeostasis |
| nucleus |
both plant/animal | *large, oval | *controls cell activities |
| nuclear membrane | both plant/animal | *surrounds nucleus *selectively permeable |
*Controls movement of materials in/out of nucleus |
| cytoplasm |
both plant/animal | *clear, thick, jellylike material and organelles found inside cell membrane | *supports /protects cell organelles |
| endoplasmic reticulum (E.R.) |
both plant/animal | *network of tubes or membranes | *carries materials through cell |
| ribosome | both plant/animal | *small bodies free or attached to E.R. | *produces proteins |
| mitochondrion |
both plant/animal | *bean-shaped with inner membranes | *breaks down sugar molecules into energy |
| vacuole |
plant - few/large animal - small |
*fluid-filled sacs | *store food, water, waste (plants need to store large amounts of food) |
| lysosome |
plant - uncommon animal - common |
*small, round, with a membrane | *breaks down larger food molecules into smaller molecules *digests old cell parts |
| chloroplast |
plant, not animal | *green, oval usually containing chlorophyll (green pigment) | *uses energy from sun to make food for the plant (photosynthesis) |
No comments:
Post a Comment