Cellular Processes: Photosynthesis, Respiration, Transport
Photosynthesis and Cellular Respiration
Photosynthesis is a process used by plants, algae, and some bacteria that harnesses energy from sunlight. Cellular respiration is a process that takes place in all parts of the body of living beings, in all their cells. Through respiration, living beings obtain the energy required for their development and daily activities by decomposing organic substances in the presence of oxygen.
Cellular Transport
- Active transport: Occurs within the cell with energy expenditure.
- Passive transport: The movement of substances across different concentration gradients without the need to expend energy.
- Turgor: A physical phenomenon where cells swell and can absorb liquids.
- Plasmolysis: A physical phenomenon in which cells lose fluid and shrivel.
- Phagocytosis: The cell engulfs food particles to digest them.
- Diffusion: The passage of a substance through a semi-permeable membrane from an area of lower concentration to one of greater concentration.
- Osmosis: The passage of a substance from an area of greater concentration to one of lower concentration.
- Mobile transport: The movement of substances into and out of the cell.
Types of Cellular Respiration
- Aerobic respiration: The process responsible for most living things, so-called aerobes, requiring oxygen. Aerobic respiration is characteristic of eukaryotic organisms in general and certain types of bacteria.
- Anaerobic respiration: A biological process of oxidation-reduction of sugars and other compounds where the terminal electron acceptor is a molecule, usually inorganic, other than oxygen. This process is carried out solely by certain groups of bacteria.
- Fermentation: A catabolic process of incomplete oxidation, completely anaerobic, with the end product being an organic compound.
Respiration: A Physiological Process
Respiration is the physiological process by which living organisms take oxygen from the surrounding environment and give off carbon dioxide. The term “respiration” is also used for the process of releasing energy by the cells from the combustion of molecules such as carbohydrates and fats. Carbon dioxide and water are the products that result from this process, called cellular respiration, as distinct from the global physiological process of breathing. Cellular respiration is similar in most organisms, from unicellular ones, such as amoeba and paramecium, to higher organisms.
The Nucleus: Control Center of the Cell
- The nucleus directs the core functions of cellular activity, as it contains the genetic program that directs the development and functioning of the cell.
- It is the headquarters of replication (duplication of DNA) and transcription (RNA synthesis), whereas translation occurs in the cytoplasm. In prokaryotes, these processes coincide in the same cell compartment.
Mitochondria: The Powerhouse of the Cell
The main function of mitochondria is to generate energy to sustain cellular activity through processes of aerobic respiration. Nutrients are cleaved in the cell cytoplasm to form pyruvic acid that enters the mitochondrion. In a series of reactions, some of which are the so-called Krebs cycle or citric acid cycle, pyruvic acid reacts with water to produce carbon dioxide and ten hydrogen atoms. These hydrogen atoms are transported to the crest of the inner membrane along a chain of special molecules called coenzymes. Once there, the coenzymes donate the hydrogen to a series of membrane-bound proteins that form what is called an electron transport chain.
Plasma Membrane Functions
Plasma membrane functions
- Reception of information: Proteins can have the intrinsic ability to attract certain specific substances and transmit information from them to the cell. Intrinsic proteins with such qualities are known as receptors.