Cell Membrane Structure and Function

• The cell membrane supports the cell and separates the cytoplasm from the extracellular fluid.

Integral Proteins

• Interact with both the internal and external environments of the cell.

• Channel proteins create pores for molecules to pass through the membrane.

• Carrier proteins transport specific molecules across the membrane by changing shape.

• Cholesterol maintains membrane stability by preventing it from becoming too rigid or fluid and helps regulate permeability.

• Glycoproteins are involved in cell recognition, communication, and immune responses.

• The cytoskeleton is an internal scaffolding of protein fibers within the cytoplasm.

• The endoplasmic reticulum (ER) is a pair of parallel membranes that form a network of channels.

• The ER modifies proteins and packages them for secretion and produces transport vesicles.

• The nucleus controls cellular activity.

• Nuclear pores allow molecules like RNA to move in and out of the nucleus.

• Connective tissue binds and supports other tissues in the body.

• Muscular tissue cells are long and thin, known as muscle fibers.

• Epithelial tissue lines and covers body cavities and ducts.

Glandular Epithelial Tissue

• Exocrine glands release hormones directly into the bloodstream.
• Endocrine glands release substances through ducts onto surfaces or into cavities.

Facilitated Transport

• Molecules move across the cell membrane via special proteins.
• Carrier-mediated transport uses specific carrier proteins that bind to molecules and help them move across the membrane.

Vesicular Transport

• Transports large molecules that can't pass through other forms of transport.
• Endocytosis brings substances into the cell.
• Exocytosis moves substances out of the cell.
• Pinocytosis, a type of exocytosis, is used by cells to take in nutrients or other substances from the surrounding environment.

Metabolism

• Chemical processes occur within a living organism to maintain life.
• Catabolism is the breakdown of organic molecules into smaller molecules, releasing energy (e.g., digestion).
• Anabolism involves smaller organic molecules combining to form larger organic molecules, requiring energy (e.g., amino acids joining to make dipeptides).

Nutrients

• Carbohydrates (e.g., glucose) are the primary source of quick energy in cells.
• Glucose undergoes glycolysis and aerobic respiration to produce ATP.
• Proteins provide amino acids for protein synthesis, tissue repair, and enzyme function.
• Some amino acids can be used in gluconeogenesis for energy production.
• Lipids (fats) are a key source of long-term energy storage.
• Fatty acids are broken down into acetyl-CoA and enter the Krebs cycle to produce ATP.
• Vitamins and minerals act as coenzymes and co-factors in various metabolic reactions.
• Vitamin B (like B6 and B12) is crucial in energy metabolism.
• Minerals like iron are involved in oxygen transport and ATP production.
• Enzymes are biological catalysts that change the rate of reaction and lower activation energy in cells.

Factors Affecting Enzyme Function

• pH: Enzymes have an optimal pH range; deviations can denature the enzyme.
• Temperature: High temperatures speed up reactions but can denature enzymes; low temperatures slow enzyme activity.
• Inhibitors: Competitive inhibitors block the active site, slowing reactions; non-competitive inhibitors change the enzyme's shape, preventing substrate binding.
• Coenzymes and cofactors assist enzymes by helping bind substrates or participate in reactions.
• Coenzymes are organic (e.g., NAD+), while cofactors are often metal ions (e.g., zinc, iron).
• Reactant/Product Concentrations: High reactant concentration speeds up the reaction; high product concentration can slow or reverse the reaction.

Aerobic vs. Anaerobic

• Both are processes of breaking down glucose to produce ATP, with aerobic respiration using oxygen.

Anaerobic Process

• After glycolysis, pyruvate is converted into lactic acid (in animals) or ethanol and carbon dioxide (in yeast and some bacteria) through fermentation.
• This regenerates NAD+, necessary for glycolysis to continue, producing a small amount of ATP without oxygen.