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General Features of Cells, Life on Earth emerged likely in four stages:
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- Life on Earth emerged likely in four stages:
- The first stage involves the synthesis of organic molecules to form a soup called prebiotic soup.
- Second is the polymer formation when simple molecules combine to form polymers.
- Third, polymers aggregate with a boundary separating them from the environment called protobionts.
- In the fourth stage, polymers enclosed in membranes acquired properties of cells, such as self-replication and catalytic functions.
- Cell structure is determined by 4 factors: matter, energy, organization, and information.
- Life forms can be classified into two categories based on cell structure: prokaryotes and eukaryotes.
- Bacteria and archaea have prokaryotic cells with a relatively simple structure that lacks a membrane-enclosed nucleus. Structures in prokaryotic cells include the plasma membrane, cytoplasm, nucleoids, and ribosomes.
- Eukaryotic cells are compartmentalized into organelles and contain a nucleus that houses most of the DNA.
- The proteome of a cell determines its structure and function.
- The cytosol is central to many metabolic activities in eukaryotic cells.
- It is the site of polypeptide ( protein ) synthesis.
- The cytosol houses the cytoskeleton, a network of protein filaments that provide structural support and enable movement within the cell.
- The cytoskeleton consists of three types of filaments:
- Microtubules: involved in cell shape, organization, and movement.
- Intermediate filaments: contribute to cell shape, rigidity, and strength.
- Actin filaments: support the plasma membrane and play a role in cell strength, shape, and movement.
- The nucleus is where the cell's DNA is stored and where genes are expressed to make proteins.
- The nucleolus within the nucleus is responsible for creating ribosomes, the protein synthesis machinery of the cell.
- The endomembrane system includes the nuclear envelope, endoplasmic reticulum (ER), rough ER the initial sorting of proteins, smooth ER the metabolic processes like detoxification, carbohydrate metabolism, etc., Golgi apparatus for processing, lysosomes to degrade macromolecules, Vacuoles: central, contractile, food, phagocytic, Peroxisomes for breakdown of toxic molecules.
- Plasma membrane proteins: involved in membrane transport, cell signaling, and cell adhesion.
- Mitochondria and chloroplasts can grow and divide independently, but still rely on other parts of the cell for their internal components.
- Mitochondria produces most of the cell's ATP, It's involved in various metabolic processes like synthesis, modification, and breakdown of cellular molecules and lastly generate heat in specialized fats cells.
- Chloroplasts are found in lants and algae, it can carry out photosynthesis, converting sunlight into energy.
- Both mitochondria and chloroplasts have their own DNA and divide by binary fission.
- Endosymbiotic theory suggests that mitochondria and chloroplasts originated from bacteria that were engulfed by early eukaryotic cells and formed a symbiotic relationship.
- Proteins synthesized in eukaryotic cells are sorted to their correct cellular destinations.
- Co-translational sorting directs proteins to the ER, Golgi, Lysosomes, vacuoles, plasma membrane, and secretory vesicles.
- Post-translational sorting directs proteins to the nucleus, mitochondria, chloroplasts, and peroxisomes.
- Systems biology studies how complex interactions between components give rise to new properties of life.
- In eukaryotic cells, the nucleus, cytosol, endomembrane system, and semiautonomous organelles work together to produce dynamic organization.
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