Movement into & out of Cells
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Questions and Answers

What is the primary source of energy for diffusion?

  • Potential energy stored in chemical bonds
  • Heat energy from the environment
  • Electrical energy generated by ions
  • Kinetic energy from the random movement of molecules (correct)

The surface area to volume ratio increases as a cell becomes larger.

False (B)

What is Brownian motion?

The random movement of particles in a fluid.

Root hair cells in plants are adapted for diffusion by having an increased __________.

<p>surface area</p> Signup and view all the answers

Match the following factors with their impact on diffusion:

<p>Increased surface area = Speeds up diffusion Smaller surface area = Slows down diffusion Higher temperature = Speeds up diffusion Lower temperature = Slows down diffusion</p> Signup and view all the answers

What effect does a smaller distance have on the rate of transport?

<p>It increases the rate of transport. (D)</p> Signup and view all the answers

Higher temperatures result in slower movement of molecules.

<p>False (B)</p> Signup and view all the answers

What structural adaptation do blood capillaries and alveoli have to improve diffusion?

<p>They have walls that are one cell thick.</p> Signup and view all the answers

A greater difference in concentration on either side of the membrane leads to a __________ rate of movement across it.

<p>faster</p> Signup and view all the answers

Match the factors with their effects on the rate of diffusion:

<p>Distance = Smaller distances increase the rate Temperature = Higher temperatures increase molecular movement Concentration Gradient = Greater differences accelerate movement Surface Area = More surface area enhances absorption</p> Signup and view all the answers

What is diffusion in biology?

<p>The movement of molecules from higher to lower concentration (C)</p> Signup and view all the answers

Diffusion does not occur across the cell membrane.

<p>False (B)</p> Signup and view all the answers

What is a partially permeable membrane?

<p>A membrane that allows some molecules to cross easily while restricting others.</p> Signup and view all the answers

Diffusion helps living organisms obtain many of their requirements and get rid of their ______.

<p>waste products</p> Signup and view all the answers

Match the following gases with their roles in living organisms:

<p>Oxygen = Required for respiration Carbon Dioxide = Used in photosynthesis</p> Signup and view all the answers

Which factor influences diffusion the most?

<p>Temperature (B)</p> Signup and view all the answers

What happens to plant cells in a dilute solution?

<p>Cells become turgid. (A)</p> Signup and view all the answers

Plants only require carbon dioxide for photosynthesis.

<p>False (B)</p> Signup and view all the answers

Explain what is meant by 'concentration gradient'.

<p>A concentration gradient refers to the difference in concentration of a substance between two areas.</p> Signup and view all the answers

When plant cells are placed in a concentrated solution, they become turgid.

<p>False (B)</p> Signup and view all the answers

What term describes plant cells when the cell membrane pulls away from the cell wall?

<p>plasmolysed</p> Signup and view all the answers

Plant cells become flaccid when placed in a solution with a lower __________ potential than the cells.

<p>water</p> Signup and view all the answers

Match the following terms with their definitions:

<p>Turgid = Firm and swollen due to high water potential Flaccid = Limp and lacking firmness due to low water potential Plasmolysis = Separation of cell membrane from cell wall Osmosis = Movement of water across a semipermeable membrane</p> Signup and view all the answers

What is the primary role of water as a solvent in living organisms?

<p>It allows for the easy transport of dissolved substances. (A)</p> Signup and view all the answers

Osmosis occurs when water molecules move from a concentrated solution to a dilute solution.

<p>False (B)</p> Signup and view all the answers

What is the term for the movement of water molecules through a partially permeable membrane?

<p>Osmosis</p> Signup and view all the answers

Water plays a crucial role in the ______ reactions in cells.

<p>metabolic</p> Signup and view all the answers

Match the following functions with the corresponding substances related to water as a solvent:

<p>Dissolved food molecules = Transported in the blood Urea = Easily removed in urine Toxic substances = Dissolved for elimination Digested food molecules = Moved to body cells</p> Signup and view all the answers

Which of the following best describes osmosis?

<p>The diffusion of water from a high concentration of water to a low concentration across a membrane. (D)</p> Signup and view all the answers

Water is not essential for the transport of substances in organisms.

<p>False (B)</p> Signup and view all the answers

Cells are surrounded by a ______ membrane that is partially permeable.

<p>cell</p> Signup and view all the answers

What is the main reason energy is required for active transport?

<p>Particles move against the concentration gradient (D)</p> Signup and view all the answers

Active transport does not require energy.

<p>False (B)</p> Signup and view all the answers

Name one type of cell that utilizes active transport for glucose uptake.

<p>Epithelial cells in the villi of the small intestine</p> Signup and view all the answers

Active transport is vital for the uptake of _______ from soil water by root hair cells in plants.

<p>ions</p> Signup and view all the answers

Match the following steps of active transport with their description:

<ol> <li>Substance combines with carrier protein = A. The substance is released into the cell</li> <li>Carrier transports substances = B. The carrier protein changes shape using energy</li> <li>Substance released into cell = C. The substance attaches to the protein</li> </ol> Signup and view all the answers

Which of the following processes primarily uses carrier proteins?

<p>Active transport (A)</p> Signup and view all the answers

Carrier proteins require energy from respiration to function.

<p>True (A)</p> Signup and view all the answers

What is the role of kinetic energy in active transport?

<p>To change the shape of the carrier protein and move the substance through the membrane.</p> Signup and view all the answers

Flashcards

Diffusion

The movement of molecules from a region of high concentration to a region of low concentration.

Concentration gradient

The difference in concentration of a substance between two regions.

Partially permeable membrane

A membrane that allows some molecules to pass through but not others.

How does diffusion benefit living organisms?

Diffusion helps organisms obtain necessary substances like oxygen and nutrients, get rid of waste products like carbon dioxide, and carry out gas exchange for respiration.

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Examples of diffusion in living organisms

Examples include the uptake of oxygen by lungs, uptake of carbon dioxide by plants, and removal of waste products from cells.

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What influences the rate of diffusion?

Factors affecting diffusion rate include the size of the molecules, the temperature, the concentration gradient, and the surface area available for diffusion.

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Why is the cell membrane important for diffusion?

The cell membrane controls the movement of substances into and out of the cell, ensuring the proper balance of molecules.

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What determines what molecules can pass through the cell membrane?

The size of the molecules and their solubility in the membrane's lipid bilayer play a key role in determining permeability.

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Brownian motion

The random movement of particles in a fluid due to collisions with other particles.

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Energy source for diffusion

The kinetic energy of the random movement of molecules and ions.

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Surface area to volume ratio

The ratio of the surface area of an object to its volume. This influences the rate of diffusion.

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Cell adaptations for diffusion

Cells that need to diffuse substances quickly can increase their surface area (e.g. root hair cells or cells lining the ileum).

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Surface Area

The total area of a surface. In biological systems, a larger surface area allows for faster diffusion.

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Distance

The space between two points. A shorter distance allows molecules to move faster during diffusion.

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Temperature

The measure of heat energy. Higher temperature leads to faster diffusion, as molecules move faster.

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Turgid Plant Cell

A plant cell that is swollen with water due to osmosis, pushing the cell membrane against the cell wall.

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Flaccid Plant Cell

A plant cell that has lost water through osmosis, causing the cell membrane to shrink away from the cell wall.

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Plasmolysis

The process where the cell membrane shrinks away from the cell wall in a plant cell due to water loss by osmosis.

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Water Potential

The tendency of water to move from one area to another, measured by the concentration of free water molecules in a solution.

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Osmosis in Plants

Osmosis in plants accounts for the movement of water across the cell membrane, influencing the turgor pressure and shape of plant cells.

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Water as a Solvent

Water is a solvent because it dissolves many substances, making it essential for living organisms.

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Transport in Organisms

Dissolved substances can be easily transported throughout an organism using water. This is crucial for moving nutrients, oxygen, and removing waste products.

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What role does water play in digestion?

Water helps to dissolve digested food molecules, allowing them to be easily absorbed and transported to cells throughout the body.

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Water's role in waste removal

Water dissolves waste products like urea and excess salts, making it easier for the body to eliminate them.

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Osmosis

Osmosis is the movement of water molecules from a region of high water concentration to a region of low water concentration across a partially permeable membrane.

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What is the concentration gradient in osmosis?

Water moves down the concentration gradient, meaning it moves from a region with a higher concentration of water to a region with a lower concentration of water.

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Why is osmosis crucial for cells?

Osmosis helps maintain the balance of water and solutes inside and outside cells, which is crucial for their proper functioning.

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Active transport

Movement of molecules across a cell membrane against their concentration gradient, requiring energy from the cell.

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Why is active transport important?

Active transport allows cells to maintain specific concentrations of molecules inside and outside themselves, essential for various functions like nutrient uptake and waste removal.

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What are carrier proteins?

Proteins embedded in the cell membrane that bind to specific molecules and transport them across the membrane.

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How do carrier proteins work in active transport?

  1. Substance binds to the carrier protein. 2. Energy from respiration fuels shape change in the carrier protein, moving the substance across the membrane. 3. Substance is released on the other side.
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Example: Glucose uptake by epithelial cells

Active transport is used by epithelial cells in the small intestine to absorb glucose from the digested food, even when the concentration of glucose is higher inside the cell.

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Example: Ion uptake by root hair cells

Root hair cells in plants use active transport to absorb essential ions like potassium and nitrates from the soil, despite the lower concentration within the cell.

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Active transport vs. diffusion

Active transport moves molecules against the concentration gradient, requiring energy, while diffusion moves molecules down the concentration gradient, requiring no energy.

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What does active transport need to work?

Active transport requires carrier proteins and energy, usually obtained from cellular respiration.

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Study Notes

Diffusion in Biology

  • Diffusion is the movement of molecules from a region of high concentration to a region of low concentration
  • Molecules move down a concentration gradient due to random movement
  • The cell membrane is a partially permeable membrane, allowing some molecules to pass through easily while others have difficulty or can't pass through at all
  • Diffusion is essential for living organisms to obtain necessary materials and remove waste products
  • Examples include: digested food products being absorbed in the small intestine, gases being exchanged in the lungs and leaves, and the absorption of water and mineral ions in root hair cells

Factors influencing Diffusion

  • Surface area to volume ratio: smaller surface area to volume ratio means slower diffusion rates. Cells adapted for diffusion have increased surface areas (e.g., root hair cells and cells lining the ileum).
  • Distance: shorter distances lead to faster diffusion rates. For example, the thin walls of capillaries and alveoli facilitate rapid diffusion.
  • Temperature: higher temperatures increase the kinetic energy of molecules, speeding up diffusion.
  • Concentration gradient: the larger the difference in concentration across a membrane, the faster the rate of diffusion.

Water as a Solvent

  • Water is a solvent, meaning many substances dissolve in it
  • Dissolved substances are easily transported throughout organisms (e.g., xylem and phloem, blood).
  • Digested food molecules must dissolve to be transported to all parts of the body.
  • Toxins and waste products are dissolved in water for easier removal (e.g., urine).
  • Water is essential for metabolic reactions within cells.

Osmosis

  • Osmosis is the movement of water molecules from a dilute solution (high water potential) to a concentrated solution (low water potential) across a partially permeable membrane.
  • Cell membranes are partially permeable, allowing water molecules to pass through but not larger solute molecules
  • Water moves down the water potential gradient
  • Osmosis experiments involve immersing plant cells (e.g., potato cylinders) in solutions of different concentrations to observe changes in mass.
  • Plant cells placed in a dilute solution will gain water and become turgid.
  • Plant cells placed in a concentrated solution will lose water and become plasmolysed.
  • Animal cells placed in a dilute solution will swell and potentially burst (lyse)
  • Animal cells in a concentrated solution will shrink (crenate)
  • Osmosis is important for maintaining cell structure and function in both plant and animal cells

Active Transport

  • Active transport moves substances from a region of low concentration to a region of high concentration.
  • This process requires energy (from respiration).
  • Carrier proteins in the cell membrane are essential for active transport to take place.
  • Substances bind to specific carrier proteins, and energy is used to change the shape of the protein and transport the substances across the cell membrane
  • This helps living organisms to maintain appropriate concentrations of molecules within cells.
  • Examples include uptake of ions in root hair cells, absorption in the villi of the small intestine and removal of waste from the kidney.

Importance of Active Transport

  • Active transport is important for maintaining needed concentrations of molecules within the cells.
  • Active transport enables plants and animals to absorb nutrients.
  • Examples of functions of active transport include reabsorption of glucose and amino acids by kidney tubules, uptake of mineral ions by plants, and absorption of glucose by cells lining the villi in the small intestine

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Cambridge CIE IGCSE Biology PDF Past Paper - Diffusion, Osmosis & Active Transport

Description

Explore the concept of diffusion in biological systems. This quiz covers how molecules move across cell membranes, the factors influencing diffusion rates, and the importance of diffusion for living organisms. Test your understanding of these fundamental principles in biology.

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