Bioman Biology Flashcards

Plasma Membrane and Homeostasis

• Without the plasma membrane, cells cannot maintain homeostasis, leading to cell death.

Phospholipid Structure

• Phospholipids consist of a hydrophilic phosphate head and two hydrophobic fatty acid tails.

Hydrophilic and Hydrophobic Properties

• Heads of phospholipids are hydrophilic (water-loving) and orient themselves towards water.
• Tails are hydrophobic (water-fearing) and face each other, creating a bilayer.

Role of Cholesterol

• Cholesterol is crucial for stabilizing the plasma membrane's structure.

Selective Permeability

• The plasma membrane is selectively (or semi-) permeable, allowing specific molecules to pass through while blocking others.

Molecules Passing Through Membrane

• Small, nonpolar molecules like oxygen and carbon dioxide pass through the membrane easily due to their size and charge characteristics.

Molecules That Cannot Pass Easily

• Charged ions (positive and negative) and large polar molecules such as sugars cannot easily pass through the phospholipid bilayer.

Characteristics of Polar Molecules

• Polar molecules have partial charges due to uneven electron sharing, resulting in some atoms being slightly negative and others slightly positive.

Facilitated Diffusion

• Facilitated diffusion occurs through channel proteins, allowing substances to move across the membrane from high to low concentration without energy until equilibrium is reached.

Active Transport Mechanism

• Active transport moves substances from low to high concentration, requiring energy (ATP) and use of carrier proteins.

ATP as Energy Carrier

• ATP is the primary energy currency in cells, used to fuel various cellular processes.

Role of Carbohydrates in Identification

• Membrane carbohydrates function as identification markers. Different carbohydrates indicate different cell roles, helping the immune system recognize self versus foreign cells.

Immune Response to Foreign Cells

• The immune system, primarily through white blood cells, targets and eliminates foreign invaders.

Channel vs. Carrier Proteins

• Channel proteins facilitate the diffusion of substances like sugar down their concentration gradient without energy.
• Carrier proteins are used in active transport to pump substances against their concentration gradient, utilizing energy from ATP.

Osmosis Defined

• Osmosis is the diffusion of water across a membrane, moving from areas of high to low water concentration, opposite of general diffusion.

Aquaporins Function

• Aquaporins are specialized proteins that facilitate the passive movement of water through the membrane.

Test your knowledge on cellular structures and functions with these flashcards focused on plasma membranes and phospholipids. Each card highlights essential terms and their definitions to help you understand cell homeostasis and membrane dynamics.