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Questions and Answers
What type of transport uses specialized proteins to help molecules move across a cell membrane?
What type of transport uses specialized proteins to help molecules move across a cell membrane?
Active transport requires energy input from the cell.
Active transport requires energy input from the cell.
True
Name one example of primary active transport in animal cells.
Name one example of primary active transport in animal cells.
Sodium-potassium pump
Osmosis is the movement of solvent molecules from high ______ concentration to low ______ concentration.
Osmosis is the movement of solvent molecules from high ______ concentration to low ______ concentration.
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In secondary active transport, what does the movement of sodium ions enable?
In secondary active transport, what does the movement of sodium ions enable?
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Match the following transport mechanisms with their descriptions:
Match the following transport mechanisms with their descriptions:
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A symporter moves substances in opposite directions.
A symporter moves substances in opposite directions.
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What do you call protein channels that allow coordinated movement of two different molecules?
What do you call protein channels that allow coordinated movement of two different molecules?
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What structure primarily forms the cellular membrane?
What structure primarily forms the cellular membrane?
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Integral proteins are loosely associated with the surface of the membrane.
Integral proteins are loosely associated with the surface of the membrane.
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Name one type of active transport.
Name one type of active transport.
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In passive transport, substances move from an area of _____ concentration to an area of _____ concentration.
In passive transport, substances move from an area of _____ concentration to an area of _____ concentration.
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Match the following terms with their descriptions:
Match the following terms with their descriptions:
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Which of the following is NOT a type of passive transport?
Which of the following is NOT a type of passive transport?
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Peripheral proteins are removed by detergents and organic solvents.
Peripheral proteins are removed by detergents and organic solvents.
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What is the minimum raw exam points required to pass the make-up exam?
What is the minimum raw exam points required to pass the make-up exam?
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What is the role of the glycoproteins in the membrane?
What is the role of the glycoproteins in the membrane?
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Biological membranes are impermeable to all substances.
Biological membranes are impermeable to all substances.
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What are the two main functions of biological membranes?
What are the two main functions of biological membranes?
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Biological membranes are _______ and can change shape.
Biological membranes are _______ and can change shape.
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Match the property of biological membranes with its function:
Match the property of biological membranes with its function:
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What is a key role of membranes in cellular processes?
What is a key role of membranes in cellular processes?
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Energy transduction occurs in all cellular membranes.
Energy transduction occurs in all cellular membranes.
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What score is needed from the final exam to obtain the corresponding credit points?
What score is needed from the final exam to obtain the corresponding credit points?
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Which of the following molecules can pass through cell membranes directly?
Which of the following molecules can pass through cell membranes directly?
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Larger molecules such as glucose can easily enter the cell through the membrane.
Larger molecules such as glucose can easily enter the cell through the membrane.
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What is the term used for the pressure that results from the movement of water through a semi-permeable membrane?
What is the term used for the pressure that results from the movement of water through a semi-permeable membrane?
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A solution with a lower concentration of solute compared to the inside of a cell is called a ______ solution.
A solution with a lower concentration of solute compared to the inside of a cell is called a ______ solution.
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In which type of solution does a red blood cell retain its normal shape?
In which type of solution does a red blood cell retain its normal shape?
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Match the term with its definition:
Match the term with its definition:
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In a hypertonic solution, a red blood cell appears to swell.
In a hypertonic solution, a red blood cell appears to swell.
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What happens to the volume of the solution that contains sugar when water moves across a semi-permeable membrane?
What happens to the volume of the solution that contains sugar when water moves across a semi-permeable membrane?
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Study Notes
Subatomic Particles in Atoms
- Protons, neutrons, and electrons are the three main subatomic particles in an atom.
Net Force on a Moving Object
- If an object moves with constant velocity, the net force acting on it is zero.
Acceleration
- Acceleration is a vector quantity.
- It is the rate of change of speed.
- Acceleration can occur even if the speed is not constant.
- Acceleration can be positive or negative.
Center of Mass (CM)
- The center of mass (CM) of an object is the average position of its mass distribution.
Class 2 Lever Components
- The components of a Class 2 lever, from one end to the other, are:
- Fulcrum
- Load
- Applied force
Study of Friction, Lubrication, and Wear in Biological Systems
- Bio-tribology is the study of friction, lubrication, and wear in biological systems.
Laminar or Turbulent Fluid Flow
- Fluid flow is classified as laminar or turbulent based on the velocity of flow.
- Density of fluid is another factor.
Snell's Law
- Snell's Law relates the angles of incidence and refraction to the refractive indices.
- It determines the relationship between pressure and volume of gases.
Exam (Biophysics)
- Penalty session exam (September 2025) is worth 100 raw exam points and 100 credit points.
- The minimum condition is 51 raw exam points.
- No activity points are needed.
Biological Membranes and Molecular Transport
- Topics covered include:
- Introduction to membrane structure and function
- Understanding molecular transport mechanisms
Membrane Properties and Functions
- Membranes form the boundaries of cells and control molecular traffic.
- Membranes are flexible, self-sealing, and selectively permeable to polar solutes.
- Membrane flexibility allows for changes in cell shape during growth and movement.
- Membranes organize cellular functions, including the synthesis of lipids and proteins.
- Membranes facilitate energy transfer within mitochondria and chloroplasts.
Fluid Mosaic Model of Membranes
- The fluid mosaic model describes the structure of biological membranes.
- The model proposes that membranes consist of a fluid phospholipid bilayer with proteins embedded in or associated with it.
- Phospholipids are in a fluid state, allowing them to move laterally within the membrane.
- Integral proteins span the bilayer, while peripheral proteins are associated with the surface.
- Cholesterol is also a component and helps modulate membrane fluidity and stability.
Biological Membrane Functions
- Membranes divide cells and organelles from their environments.
- Membranes control what enters and exits cells.
- They facilitate the transport of substances.
- Membranes host receptors for signaling. Also, they are involved in energy conversion processes.
Major Components of Plasma Membranes
- The composition of plasma membranes varies among different organisms.
- Human myelin sheath has higher protein content while bacteria have a higher proportion of phospholipids.
Membrane Evidence and Fluid Mosaic Model
- Combined evidence from electron microscopy and studies of chemical composition led to the development of the fluid mosaic model to describe membrane structure.
- This provides a description of the trilaminar appearance of cell membranes.
Phospholipid Distribution and Membrane Structure
- Phospholipids are asymmetrically distributed between the inner and outer layers of a membrane, contributing to membrane structure and function.
Structure of Biological Membranes
- Phospholipid bilayer: Hydrophilic heads outward, hydrophobic tails inwards
- Proteins: Integral (embedded) and peripheral (surface-associated)
- Cholesterol: Modulates membrane fluidity and stability
- Glycocalyx: Carbohydrate-rich layer on outer surface involved in cell recognition.
Peripheral Membrane Proteins
- Integral proteins are firmly embedded in the membrane, requiring agents to remove them like detergents.
- Peripheral proteins are associated with the membrane through electrostatic interactions and hydrogen bonding.
Types of Membrane Transport
- Passive transport: no energy needed
- Simple diffusion (small, nonpolar molecules)
- Facilitated diffusion (requires membrane proteins)
- Osmosis (water across a semipermeable membrane)
- Active transport: needs energy
- Primary active transport (direct energy use, e.g., Na+/K+ pump)
- Secondary active transport (uses electrochemical gradients created by primary transport)
- Bulk transport: Involves larger molecules or particles
- Endocytosis (cells engulf materials)
- Exocytosis (vesicles expel materials)
Passive Transport
- Substances move from an area of higher concentration to one of lower concentration.
- Passive transport does not require the cell to expend any energy.
Facilitated Diffusion
- Specialized proteins, like channel and carrier proteins, aid the movement of substances across the cell membrane.
- Molecules can travel down their concentration gradient in this type of passive transport.
Active Transport
- Active transport involves the movement of substances against their concentration gradient, requiring energy (typically ATP).
- Primary active transport describes the direct use of energy for this purpose.
- Secondary active transport uses electrochemical gradients generated by primary active transport.
Primary Active Transport - Sodium-Potassium Pump
- The sodium-potassium pump is a primary active transport that uses ATP to move sodium out of cells and potassium into them.
Secondary Active Transport
- Secondary active transport uses the energy stored in electrochemical gradients to move other substances against their own gradients.
Symporters and Antiporters
- Symporters move substances in the same direction.
- Antiporters move substances in opposite directions.
Osmosis
- Osmosis is the diffusion of water through a selectively permeable membrane from an area of high water potential to an area of low water potential.
- It equalizes solute concentrations across the membrane
- It involves the movement of water, not solutes, to equalize the concentration of solutes on both sides of the membrane.
Semi-Permeable Membranes
- Semi-permeable membranes allow certain substances to pass through while blocking others based on size, charge, or polarity.
Osmotic Pressure
- Osmosis creates osmotic pressure, the tendency of water to flow across a membrane.
- Adding solutes like sugar to the water decreases the water concentration.
- The water flows from the section with higher water concentration to the section with lower concentration.
- The osmosis process continues until the water concentration on both sides is equal across the membrane, resulting in a change in volume of those fluid-containing sections.
Solutions
- Water mixed with other substances form solutions.
- The substance that dissolves is the solute; the substance doing the dissolving is the solvent.
- For example, water mixed with sugar forms a sugar solution.
Isotonic Solution
- An isotonic solution has an equal concentration of solute as the cells.
- The rate of water entering the cell equals the rate leaving the cell
Hypertonic Solution
- A hypertonic solution has a higher concentration of solute than the cells.
- Water flows out of the cells, causing them to shrink.
Hypotonic Solution
- A hypotonic solution has a lower concentration of solute than the cells.
- Water flows into the cells, causing them to swell and potentially rupture.
Membrane Dynamics
- Biological membranes have flexibility, and do not break while changing shape; maintained by noncovalent interactions between lipids (not covalent bonds)
- Lipid bilayer structure is stable, but lipids have freedom to move.
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Description
Test your knowledge on essential physics concepts, including subatomic particles, net forces, acceleration, and fluid dynamics. The quiz covers fundamentals such as levers and bio-tribology. Challenge yourself with questions from various aspects of physics.
