Cell Membrane Structure and Functions

Cell Membrane

Structure

• Phospholipid bilayer: a double layer of lipids with phosphate heads and fatty acid tails
• Hydrophilic (water-loving) heads face outward, interacting with water
• Hydrophobic (water-fearing) tails face inward, away from water

Functions

• Regulation of what enters and leaves the cell: selectively permeable, allowing certain substances to pass through while keeping others out
• Protection: provides a barrier against external environment, maintaining cellular integrity
• Cell signaling: involved in cell-to-cell communication and signaling pathways

Components

• Phospholipids: main structural components, providing a flexible and semi-permeable membrane
• Proteins: embedded in the membrane, performing various functions such as transport, signaling, and cell adhesion
• Cholesterol: helps maintain membrane fluidity and stability

Types of Cell Membrane Transport

• Passive transport: movement of molecules from high to low concentration without energy expenditure
  • Diffusion: random movement of molecules across the membrane
  • Osmosis: movement of water molecules across the membrane
• Active transport: movement of molecules from low to high concentration using energy
  • Carrier proteins: transport molecules across the membrane using ATP energy

Cell Membrane

Structure

• A phospholipid bilayer consisting of a double layer of lipids with phosphate heads and fatty acid tails forms the cell membrane
• Phosphate heads are hydrophilic (water-loving) and face outward, interacting with water
• Fatty acid tails are hydrophobic (water-fearing) and face inward, away from water

Functions

• The cell membrane regulates what enters and leaves the cell, being selectively permeable to allow certain substances to pass through while keeping others out
• It provides a barrier against the external environment, maintaining cellular integrity
• The cell membrane is involved in cell-to-cell communication and signaling pathways

Components

• Phospholipids are the main structural components of the cell membrane, providing a flexible and semi-permeable membrane
• Proteins are embedded in the membrane, performing various functions such as transport, signaling, and cell adhesion
• Cholesterol helps maintain membrane fluidity and stability

Types of Cell Membrane Transport

• Passive transport is the movement of molecules from high to low concentration without energy expenditure
• Diffusion is the random movement of molecules across the membrane
• Osmosis is the movement of water molecules across the membrane
• Active transport is the movement of molecules from low to high concentration using energy
• Carrier proteins transport molecules across the membrane using ATP energy

Gravity

• Gravity is a fundamental force of nature that causes objects with mass to attract each other.
• It is a universal force that affects everything with mass or energy.

Gravity and Motion

• Gravity affects the motion of objects on or near the surface of the Earth, pulling them towards the center of the Earth.
• Gravity gives objects weight, dependent on their mass and gravitational acceleration.
• Gravity also affects the motion of celestial bodies, such as planets and stars.

Key Concepts

• Gravitational force is the force that attracts two objects with mass towards each other.
• Gravitational acceleration is the acceleration of an object due to gravity, typically 9.8 m/s² on Earth.
• Weight is the force exerted on an object by gravity, dependent on its mass and gravitational acceleration.

Effects of Gravity on Motion

• Free fall is an object falling under the sole influence of gravity, accelerating towards the ground.
• Projectile motion is the motion of an object under the influence of gravity, following a curved path.
• Orbital motion is the motion of an object in a curved path around a celestial body, such as a planet or moon.