Understanding Biological Macromolecules and Cellular Processes
Biological Macromolecules and Cellular Processes
Monosaccharides
Monosaccharides are the simplest carbohydrates, consisting of a single chain of polyols with an aldehyde or ketone group. They are sweet, water-soluble, and can form crystals. Their primary function is to provide energy. Monosaccharides typically have 3 to 12 carbon atoms and are classified based on the presence of an aldehyde group (aldoses) or a ketone group (ketoses). The number of carbon atoms further categorizes them as trioses, tetroses, pentoses, hexoses, and so on.
Disaccharides
Disaccharides are formed by the union of two monosaccharides through an O-glycosidic bond, with the loss of a water molecule. Hydrolysis of disaccharides, either in acidic conditions or with specific enzymes, breaks them down into their monosaccharide components.
Polysaccharides
Polysaccharides are complex carbohydrates formed by the union of more than 11 monosaccharides through O-glycosidic bonds. They serve as energy reserves or structural components in living organisms. Examples include starch (energy reserve in plants), cellulose (structural component of plant cell walls), glycogen (energy reserve in animals), and mucopolysaccharides (components of the basic tissue substance).
Interphase Nucleus
The interphase nucleus is the state of the nucleus between cell divisions. It consists of several distinct parts:
- Nuclear Envelope: A double membrane structure that separates the nucleus from the cytoplasm.
- Chromatin: The genetic material (DNA) in its uncondensed form, associated with proteins.
- Nucleoplasm: The fluid-filled interior of the nucleus.
- Nucleolus: A spherical structure involved in ribosome synthesis.
Chromosomes
Chromosomes are condensed structures of DNA that become visible during cell division. They are located in the equatorial plane of the spindle during metaphase, the stage where they are most condensed and visible.
Nucleus Functions
The nucleus, containing DNA and the nucleolus, plays crucial roles in cell function, including:
- DNA replication and segregation during cell division.
- Regulation of cell function through gene expression (transcription and translation).
- Ribosome formation in the nucleolus.
Chloroplasts
Chloroplasts are organelles found in plant cells responsible for photosynthesis. They are surrounded by two membranes and contain an internal membrane system called thylakoids, which enclose the thylakoid space. The aqueous region outside the thylakoids is called the stroma.
Light-Phase and Dark-Phase Reactions
Photosynthesis consists of two sets of reactions:
- Light-Phase Reactions: Occur in the thylakoid membrane, where light energy is captured and converted into chemical energy (ATP) and NADPH. Water is split, releasing oxygen.
- Dark-Phase Reactions (Calvin Cycle): Occur in the stroma, where ATP and NADPH from the light-phase reactions are used to convert atmospheric CO2 into carbohydrates.
Factors Affecting Photosynthesis
Several factors influence the rate of photosynthesis:
- Temperature: Affects enzyme activity in the Calvin cycle.
- Humidity: Affects the water content of the stroma.
- Light: Affects the efficiency of the light-phase reactions.
- CO2 and O2 Concentrations: Affect the activity of the enzyme Rubisco, which is involved in both carbon fixation and photorespiration.
Immune Response
The immune response is the body’s defense against pathogens and foreign substances. Key components include:
- Antigens: Substances that trigger an immune response.
- Antibodies: Proteins produced by plasma cells that bind to specific antigens.
- Innate Immunity: Non-specific defense mechanisms present from birth.
- Adaptive Immunity: Specific defense mechanisms that develop after exposure to an antigen.
Examples of Infectious Diseases
- Meningitis: Bacterial or viral infection of the meninges (membranes surrounding the brain and spinal cord).
- Tetanus: Bacterial infection causing muscle spasms.
- Syphilis: Bacterial infection transmitted through sexual contact.