Cellular Structure and Function

Cellular Structure and Function

• Cells are the basic units of life, exhibiting a wide array of shapes and sizes.
• All cells share fundamental features including a plasma membrane, cytoplasm, and DNA.
• Prokaryotic cells (bacteria) lack a nucleus and membrane-bound organelles.
• Eukaryotic cells (plants and animals) possess a nucleus and various organelles.
• The nucleus houses the cell's genetic material, DNA.
• Ribosomes synthesize proteins.
• The endoplasmic reticulum (ER) facilitates protein and lipid synthesis.
• The Golgi apparatus processes and packages proteins.
• Mitochondria are responsible for cellular respiration, producing ATP.
• Chloroplasts, found in plant cells, perform photosynthesis.
• Vacuoles store water, nutrients, and waste products.
• Lysosomes contain enzymes for intracellular digestion.
• The cytoskeleton provides structural support and facilitates cell movement.
• Cell membranes regulate the passage of substances into and out of the cell.
• The cell membrane is composed of a phospholipid bilayer with embedded proteins and cholesterol.
• Cell membranes exhibit selective permeability.

Biological Molecules

• Four major classes of biological molecules—carbohydrates, lipids, proteins, and nucleic acids—are crucial for life.
• Carbohydrates provide energy and structural support.
• Simple sugars (monosaccharides) are the fundamental units.
• Complex carbohydrates (polysaccharides) store energy (starch, glycogen) or provide structural support (cellulose).
• Lipids are diverse hydrophobic molecules including fats, phospholipids, and steroids.
• Fats store energy and insulate.
• Phospholipids form the cell membrane.
• Steroids regulate various metabolic processes.
• Proteins have diverse functions including structural support, catalysis, and transport.
• Proteins are constructed from amino acids linked by peptide bonds.
• Nucleic acids (DNA and RNA) store and transmit genetic information.
• DNA carries the genetic code.
• RNA plays a role in protein synthesis.

Metabolism

• Metabolism encompasses all chemical reactions within a living organism.
• Catabolism breaks down complex molecules, releasing energy.
• Anabolism builds complex molecules, requiring energy.
• Cellular respiration converts glucose to ATP.
• Photosynthesis converts light energy into chemical energy (glucose).
• Enzymes are biological catalysts speeding up reactions without being consumed.
• Enzymes exhibit specificity towards their substrates.
• Factors like temperature and pH influence enzyme activity.

Cell Communication

• Cells communicate through various mechanisms, coordinating responses to internal and external stimuli.
• Signal transduction pathways relay signals from the cell surface to the nucleus.
• Signaling molecules (hormones, neurotransmitters) bind to receptors.
• Receptors on the cell surface or inside the cell initiate responses.
• Responses involve changes in gene expression, enzyme activity, or cellular movement.

Genetics

• Genetics studies heredity and variation in organisms.
• DNA is the carrier of genetic information.
• Genes are segments of DNA coding for proteins.
• Genetic material determines an organism's traits, passed through reproduction.
• Genotype refers to the genetic makeup; phenotype describes observable traits.
• Mendelian genetics predicts inheritance likelihood.
• Chromosomes are structures containing DNA.

Evolution

• Evolution is the change in heritable characteristics of biological populations over successive generations.
• Natural selection favours traits enhancing survival and reproduction.
• Adaptation enhances survival and reproduction in specific environments.
• Common ancestry links all organisms.
• The diversity of life on Earth results from evolutionary processes.

Ecology

• Ecology studies the relationship between organisms and their environment.
• Ecosystems are complex systems of biotic and abiotic components.
• Interactions between organisms (competition, predation, symbiosis) are crucial.
• Energy flow and nutrient cycling are key aspects of ecosystem dynamics.