Cell Biology Overview

Cell Biology

Basic Unit of Life: Cells are the fundamental building blocks of all living organisms.
Types of Cells:
- Prokaryotic: Simple, no nucleus (e.g., bacteria).
- Eukaryotic: Complex, contains a nucleus (e.g., plant and animal cells).
Cell Structure:
- Cell Membrane: Semi-permeable barrier; regulates entry and exit of substances.
- Nucleus: Contains DNA; controls cell activities.
- Organelles:
  - Mitochondria: Powerhouse; site of ATP (energy) production.
  - Ribosomes: Protein synthesis.
  - Endoplasmic Reticulum (ER):
    - Rough ER: Studded with ribosomes; processes proteins.
    - Smooth ER: Detoxifies; synthesizes lipids.
  - Golgi Apparatus: Modifies, sorts, and packages proteins.
  - Lysosomes: Contains digestive enzymes; breakdown of waste.
Cell Division:
- Mitosis: Process of cell division for growth and repair.
- Meiosis: Specialized cell division that produces gametes (sex cells).

Biological Molecules

Carbohydrates:
- Composed of sugars (monosaccharides, disaccharides, polysaccharides).
- Functions: Energy source, structural component (e.g., cellulose in plants).
Proteins:
- Made up of amino acids linked by peptide bonds.
- Functions: Catalysts (enzymes), structural support, transport, signaling.
Lipids:
- Hydrophobic molecules; includes fats, oils, and sterols.
- Functions: Energy storage, cellular membranes (phospholipids), signaling (hormones).
Nucleic Acids:
- Composed of nucleotides (DNA and RNA).
- Functions: Genetic information storage (DNA), protein synthesis (RNA).

Enzymes

Definition: Biological catalysts that accelerate chemical reactions.
Structure: Proteins with a specific active site for substrate binding.
Mechanism:
- Substrate Specificity: Enzymes only catalyze specific reactions.
- Enzyme-Substrate Complex: Formation of a temporary complex during the reaction.
Factors Affecting Enzyme Activity:
- Temperature: Optimal range enhances activity; extreme heat denatures enzymes.
- pH: Each enzyme has an optimal pH; deviations can reduce activity.
- Substrate Concentration: Increasing concentration raises activity until saturation point is reached.
Inhibition:
- Competitive Inhibition: Inhibitor competes with substrate for binding.
- Non-competitive Inhibition: Inhibitor binds to a different site, altering enzyme function.
Cofactors and Coenzymes: Non-protein molecules that assist enzymes (e.g., metal ions, vitamins).

Cell Biology

Basic Unit of Life: Cells are the fundamental building blocks that form all living organisms.
Types of Cells:
- Prokaryotic: These cells are simple in structure and lack a nucleus, for example, bacteria.
- Eukaryotic: These cells are complex and contain a nucleus, for example, plant cells and animal cells.
Cell Structure:
- Cell Membrane: This membrane acts as a barrier that regulates what enters and exits the cell. It's semi-permeable, meaning that only certain substances can pass through.
- Nucleus: This is the control center of the cell, housing the DNA that directs all cellular activities.
- Organelles: These specialized compartments within the cell perform specific functions.
  - Mitochondria: Responsible for generating energy in the form of ATP, the cell's main energy currency.
  - Ribosomes: These are responsible for protein synthesis, building the proteins the cell needs.
  - Endoplasmic Reticulum (ER): This network of membranes plays a crucial role in various cellular processes:
    - Rough ER: This ER is studded with ribosomes and is involved in the processing of proteins.
    - Smooth ER: This particular type of ER is responsible for detoxification and lipid synthesis.
  - Golgi Apparatus: This organelle modifies, sorts, and packages proteins before they are transported to their final destinations.
  - Lysosomes: These contain digestive enzymes and are responsible for the breakdown of waste products.
Cell Division:
- Mitosis: This process involves the division of a single cell into two identical daughter cells. Mitosis is crucial for growth and repair in organisms.
- Meiosis: This is specialized cell division that produces gametes (sperm and egg cells) for sexual reproduction.

Biological Molecules

Carbohydrates: These are organic compounds composed of sugars. They can be classified into three main categories:
- Monosaccharides: Simple sugars (e.g., glucose, fructose).
- Disaccharides: Two monosaccharides linked together (e.g., sucrose, lactose).
- Polysaccharides: Long chains of monosaccharides (e.g., starch, glycogen, cellulose)
Functions of Carbohydrates:
- They are a crucial energy source for cells.
- They provide structural support, like the cellulose found in plant cell walls.
Proteins: Made up of amino acids linked together by peptide bonds, proteins are essential for a wide range of cellular functions.
Functions of Proteins:
- Catalysts (enzymes): Enzyme proteins speed up chemical reactions within the cell.
- Structural Support: Proteins provide structural support and framework for cells and tissues.
- Transport: Proteins carry molecules across cell membranes and in the bloodstream.
- Signaling: Proteins act as messengers, transmitting signals between cells.
Lipids: These are hydrophobic (water-repelling) molecules and include fats, oils, and steroids.
Functions of Lipids:
- Energy Storage: Lipids store energy efficiently for later use.
- Cellular Membranes: Phospholipids are the major components of cell membranes.
- Signaling: Steroid hormones are lipids that act as signaling molecules.
Nucleic Acids: Nucleic acids are composed of nucleotides and are crucial for storing and transmitting genetic information.
- DNA (deoxyribonucleic acid): Stores genetic information in the form of genes.
- RNA (ribonucleic acid): Plays a vital role in protein synthesis, translating genetic information from DNA into proteins.

Enzymes

Definition: These are biological catalysts that accelerate chemical reactions within cells without being consumed in the process.
Structure: Enzymes are proteins with a specific three-dimensional shape, featuring an active site where the substrate (the molecule being acted upon) binds.
Mechanism:
- Substrate Specificity: Enzymes are highly specific, meaning they only catalyze specific reactions involving particular substrates.
- Enzyme-Substrate Complex: An enzyme temporarily binds to its substrate, forming an enzyme-substrate complex that facilitates the reaction.
Factors Affecting Enzyme Activity:
- Temperature: Each enzyme has an optimal temperature range where it operates at its highest efficiency. Extreme temperatures can denature (destroy) the enzyme's structure.
- pH: Enzymes work best at a specific pH, deviations from which can affect their activity.
- Substrate Concentration: Increasing substrate concentration generally increases enzyme activity until the enzyme becomes saturated with substrate.
Inhibition:
- Competitive Inhibition: Another molecule competes with the substrate for the active site on the enzyme, slowing down the reaction.
- Non-competitive Inhibition: The inhibitor binds to a different site on the enzyme, altering its shape and function.
Cofactors and Coenzymes: Non-protein molecules that assist enzymes in their reactions. These can be metal ions (e.g., zinc, magnesium) or organic molecules (e.g., vitamins). They participate in the catalytic process by providing additional binding sites or carrying electrons or atoms for the reaction.