Biophysics Midterm Content Self PDF

# Self Biophysics ## Chapter 1: Units and Dimensions - To define a physical quantity, one must have a set of rules for calculating the quantity in terms of other well-defined quantities. - **Kinetic energy** is defined as half the product of mass and the square of the velocity, so if mass and veloc...

# Self Biophysics ## Chapter 1: Units and Dimensions - To define a physical quantity, one must have a set of rules for calculating the quantity in terms of other well-defined quantities. - **Kinetic energy** is defined as half the product of mass and the square of the velocity, so if mass and velocity can be measured accurately, then kinetic energy can be measured accurately. - **Physics** is the branch of science that studies non-living things and provides answers to questions related to their behavior. - The distance between the Earth and stars is measured in "light years". - The size of an atom nucleus is very small, while the age of the universe is very large. - **Physics** makes constant attempts to measure quantities, whether small or large, with the best possible accuracy. ### 2: System of Units - Three fundamental units are used in physics, which include **Length**, **Mass**, and **Time**. - The **International System of Units (SI):** is a coherent system consisting of six basic units: - **Kilogram** (mass) - **Meter** (length) - **Second** (time) - **Ampere** (current) - **Degree Kelvin** (temperature) - **Candela** (luminous) - **Supplementary SI units:** - **Radian** (plane angle) - **Steradian** (solid angle) - **Derived (SI) units:** - Many physical quantities are expressed in derived SI units, which have been named after renowned scientists. ### 4: Dimensions - **Dimensions** are the powers of fundamental units used to represent a physical quantity. For example, **area**: - **A = L x L** - **A = L²** - Different physical quantity dimensions are: - **Velocity:** **v = LT^-1** - **Acceleration:** **a = LT^-2** - **Force:** **F = MLT^-2** - **Work:** **W = ML²T^-2** - **Pressure:** **P = ML^-1T^-2** - **Power:** **power = ML²T^-3** - **Energy:** **energy = ML²T^-2** ### 5: Main Uses of Dimensional Theory - **Dimensional analysis** can be used to: - **Test the correctness of equations:** By substituting dimensional formulae on both sides of an equation and confirming that they are the same. - **Derive equations:** Using the principle of homogeneity of dimensions, where dimensions on both sides of an equation are equal. ### Chapter 3: Surface Tension - Surface Tension is a phenomenon where the surface of a liquid acts like a thin elastic sheet. - **Examples of surface tension:** - A floating needle on the surface of water - The strength of soap films - **Surface tension** is caused by the cohesive forces between liquid molecules and adhesive forces between liquid and solid molecules. - **Cohesive force** is the force of attraction between molecules of the same substance. - **Adhesive force** is the force of attraction between molecules of different substances. - **Explanation of surface tension:** Molecules on the surface experience a net downward force due to the cohesive forces and tend to minimize the surface area, creating a thin elastic sheet. - **Surface tension coefficient (y):** is the ratio of the surface force F to the length L along which the force acts or the work done per unit area: - **y = F/L = W/A** - The **surface tension coefficient (y)** depends on: - **Liquid Type:** Varies between different liquids. - **Temperature:** Increases with temperature. - **Excess of pressure inside a spherical bubble:** Due to surface tension, the pressure inside a spherical bubble is higher than the outside pressure. - **P = 2y/r** ### Chapter 4: Fluid Dynamics - **Fluid Dynamics** is the study of fluids in motion. - **Fluid flow** can be characterized as either **laminar** or **turbulent**. - **Ideal fluid flow** assumptions: - **Non-viscous:** No internal friction. - **Steady:** Velocity remains constant at each point. - **Incompressible:** Density is constant. #### 1. Equation of Continuity - The equation of continuity states that the mass flow rate of an ideal fluid remains constant through a pipe with varying cross-sectional areas. - **A₁v₁ = A₂v₂** #### 2. Bernoulli's Equation - **Bernoulli's principle:** states that in a streamline flow, the pressure is low when the fluid's velocity is high, and vice versa. - **P₁ + ½ρv₁² + ρgh₁ = P₂ + ½ρv₂² + ρgh₂** ### Chapter 5: Cells and Biological Molecules - **Cell membrane** is the basic part of the cell, which controls what enters and exits the cell and separates intracellular components from the extracellular environment. - **The cell membrane** is: - **Selectively permeable:** Allows specific substances to pass through - **Contains proteins:** For various functions like transport, signaling, and adhesion. - **The cell membrane consists of a lipid bilayer**: - **Phospholipids:** The majority, with hydrophobic tails and hydrophilic heads. - **Glycolipids:** Hydrophobic tails with carbohydrate attached to hydrophilic heads. - **Steroids:** Cholesterol, important for membrane fluidity and stability. - **Cell membrane proteins:** - **Integral Proteins:** Embedded in the membrane, spanning across the bilayer. - **Lipid-Anchored Proteins:** Attached to the membrane via lipids. - **Peripheral Proteins:** Associated with the membrane's surface. - **Membrane skeleton:** - **Cytoskeleton** provides structure and shape to the cell membrane. - **Cilia and microvilli:** Projections that extend from the cell.