Gas Exchange Surfaces and Fick's Law
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Questions and Answers

What feature of alveoli contributes to efficient gas exchange?

  • They are located deep within the lungs.
  • They are composed of dense connective tissue.
  • They contain multiple layers of epithelial cells.
  • They have a large surface area. (correct)

How do fish gills enhance the efficiency of gas exchange?

  • By maintaining a low concentration gradient.
  • By reducing the number of blood vessels.
  • By having lamellae that increase surface area. (correct)
  • By thickening the epithelial layer.

What characteristic of the diffusion pathway across an exchange surface aids in efficient transport?

  • It consists of multiple thick layers of cells.
  • It is made up of flattened epithelial cells. (correct)
  • It is significantly long to allow time for diffusion.
  • It requires active transport mechanisms.

What is the role of the circulatory system related to gas exchange in mammals?

<p>It removes oxygen and supplies carbon dioxide to maintain concentration gradients. (A)</p> Signup and view all the answers

What happens to the surface area : volume ratio as body size increases?

<p>It decreases. (D)</p> Signup and view all the answers

What characteristic of the fluid mosaic model allows phospholipids to move within the bilayer?

<p>The model itself is described as 'fluid' (C)</p> Signup and view all the answers

Which of the following statements accurately describes the movement of phospholipids in the membrane?

<p>They mainly move sideways within their own layer. (B)</p> Signup and view all the answers

What type of molecules can pass through the phospholipid bilayer without needing assistance?

<p>Small, non-polar molecules (D)</p> Signup and view all the answers

What was one major flaw in the Gorter and Grendel model of membrane structure?

<p>It did not describe how large molecules interacted with the membrane. (D)</p> Signup and view all the answers

What significant contribution did Singer and Nicolson make to cell membrane understanding?

<p>They introduced the fluid mosaic model. (B)</p> Signup and view all the answers

Why did the Davson and Danielli model of the membrane face criticism?

<p>It failed to explain the irregular distribution of proteins. (D)</p> Signup and view all the answers

What does the phrase 'partially permeable' imply about the cell membrane?

<p>Only specific substances can pass through. (D)</p> Signup and view all the answers

What do the terms 'peripheral' and 'integral' refer to in the context of membrane proteins?

<p>Their interaction with the lipid bilayer. (C)</p> Signup and view all the answers

What evidence supported the fluid mosaic model as the best representation of membrane structure?

<p>Proteins were shown to extend into the membrane and move laterally. (A)</p> Signup and view all the answers

The main role of channel and carrier proteins in the cell membrane is to:

<p>Facilitate the transport of large, polar molecules. (C)</p> Signup and view all the answers

What is the primary method by which gas exchange occurs?

<p>Diffusion (C)</p> Signup and view all the answers

As an organism increases in size, what happens to its surface area to volume ratio?

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

Why do single-celled organisms effectively exchange gases?

<p>They have a high surface area to volume ratio (C)</p> Signup and view all the answers

What is the consequence of having a lower surface area to volume ratio in larger organisms?

<p>Less effective gas exchange (D)</p> Signup and view all the answers

Which adaptation helps large multicellular organisms facilitate gas exchange?

<p>Specialized organs with increased surface area (D)</p> Signup and view all the answers

What is the relationship between diffusion distance and cell size in larger organisms?

<p>Diffusion distance increases as cell size increases (A)</p> Signup and view all the answers

How does aerobic respiration affect gas exchange requirements?

<p>Increases both oxygen consumption and carbon dioxide production (B)</p> Signup and view all the answers

What defines an organism's surface area to volume ratio?

<p>The total surface area of the organism relative to its internal volume (D)</p> Signup and view all the answers

What component forms the hydrophilic part of a phospholipid?

<p>Phosphate group (D)</p> Signup and view all the answers

What is the primary role of cholesterol in cell membranes?

<p>Stabilize phospholipid tails and regulate fluidity (B)</p> Signup and view all the answers

Which type of protein is embedded within the phospholipid bilayer?

<p>Intrinsic protein (C)</p> Signup and view all the answers

What characterizes the tails of a phospholipid?

<p>They are non-polar and hydrophobic (B)</p> Signup and view all the answers

What is the term for the double-layered structure formed by phospholipids?

<p>Phospholipid bilayer (D)</p> Signup and view all the answers

What function do glycolipids and glycoproteins serve on the cell surface?

<p>Aid in cell-to-cell communication (B)</p> Signup and view all the answers

How do intrinsic proteins differ from extrinsic proteins?

<p>Intrinsic proteins penetrate the membrane while extrinsic do not (A)</p> Signup and view all the answers

Why are membranes without cholesterol likely to break down?

<p>Because cholesterol provides mechanical strength and stability (A)</p> Signup and view all the answers

What happens to the rate of diffusion if the thickness of the membrane is halved?

<p>The rate of diffusion increases. (C)</p> Signup and view all the answers

Which component of Fick's Law represents the difference in concentration between two areas?

<p>C1 - C2 (D)</p> Signup and view all the answers

What is the primary role of the lungs in gas exchange?

<p>To maximize gas exchange while minimizing water loss. (A)</p> Signup and view all the answers

Which feature of the trachea helps prevent airflow obstruction?

<p>C-shaped cartilage rings (D)</p> Signup and view all the answers

What type of epithelium forms the walls of the alveoli?

<p>Simple squamous epithelium (A)</p> Signup and view all the answers

The bronchi have a structural difference compared to the trachea, what is it?

<p>Bronchi cartilage rings are full circles (B)</p> Signup and view all the answers

What is the purpose of the layer of moisture lining the alveoli?

<p>To facilitate the dissolution of gases for diffusion (A)</p> Signup and view all the answers

Which of the following statements about bronchioles is false?

<p>All bronchioles contain cartilage rings. (D)</p> Signup and view all the answers

How do alveoli contribute to the efficiency of gas exchange?

<p>Through extensive capillary networks while being highly permeable (B)</p> Signup and view all the answers

Flashcards

Concentration gradient

The difference in concentration of a substance between two points.

Diffusion pathway

The distance a substance travels across an exchange surface.

Surface area

The total area of an exchange surface available for diffusion.

Surface Area : Volume Ratio

The ratio of an organism's surface area to its volume.

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What is the role of lamellae in fish gills and spongy mesophyll in leaves?

The process of moving substances across an exchange surface using specialized structures.

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Volume

Measures how much space is inside an organism.

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Surface area to volume ratio (SA:V ratio)

The ratio of an organism's surface area to its volume.

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High SA:V ratio

Organisms with a high SA:V ratio have more surface area relative to their volume.

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Low SA:V ratio

Organisms with a low SA:V ratio have less surface area relative to their volume.

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Diffusion

The process of gas exchange happens by the movement of molecules from an area of high concentration to an area of low concentration.

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Exchange surface

The surface where gas exchange occurs in an organism.

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SA:V ratio in larger organisms

Larger organisms have a lower SA:V ratio, making it harder for them to exchange gases efficiently.

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What are phospholipids?

Phospholipids are a type of lipid that forms the basic structure of cell membranes. They consist of a glycerol molecule, a phosphate group, and two fatty acid tails.

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What are the key properties of a phospholipid?

The phosphate head of a phospholipid is hydrophilic, meaning it can interact with water molecules, while the lipid tails are hydrophobic, meaning they repel water.

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What is the function of phospholipid bilayers?

A phospholipid bilayer is a double layer of phospholipids arranged with their hydrophilic heads facing outwards and hydrophobic tails pointing inwards, forming the basis of cell membranes.

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Distinguish between intrinsic and extrinsic proteins in cell membranes.

Intrinsic proteins are embedded within the membrane, while extrinsic proteins are found on the outer or inner surface.

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What is the role of cholesterol in the cell membrane?

Cholesterol is a lipid molecule that helps regulate the fluidity and stability of cell membranes.

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What are glycolipids and glycoproteins, and what are their roles?

Glycolipids and glycoproteins are found on the cell surface and play crucial roles in cell-to-cell communication, recognizing other cells, and binding hormones.

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What are antigens and what is their function?

Antigens are unique markers on the surface of cells that help the immune system recognize and differentiate between self and non-self cells.

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What is the importance of the cell membrane?

The cell membrane is a selectively permeable barrier that controls what enters and exits the cell. It plays a vital role in maintaining the cell's internal environment and ensuring its survival.

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Fluid Mosaic Model

A model of cell membrane structure suggesting a fluid, dynamic bilayer of phospholipids with embedded proteins.

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Phospholipids

Lipids with a phosphate group, forming the core of cell membranes. They are arranged as a bilayer with a hydrophilic head and hydrophobic tail.

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Non-polar Molecules

Substances that are soluble in lipids, like fats and oils.

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Polar Molecules

Substances that are attracted to water.

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Integral Proteins

Proteins embedded within the phospholipid bilayer. They have roles in transport, signaling, and structure.

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Peripheral Proteins

Proteins attached to the surface of the phospholipid bilayer. They may be involved in enzymatic activity or as binding sites.

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Channel Protein

A type of integral protein that creates a channel through the membrane for the passage of specific molecules.

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Carrier Protein

A type of integral protein that binds to specific molecules and facilitates their movement across the membrane.

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Selective Permeability

The ability of a membrane to control the movement of substances in and out of the cell.

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Fick's Law of Diffusion

The rate of diffusion is proportional to the surface area and the concentration difference, but inversely proportional to the thickness of the membrane. It describes how quickly substances move across a membrane.

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Permeability Constant (P)

A quantitative measure of how quickly a particular molecule can cross a specific membrane.

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Lungs

The organ responsible for gas exchange in mammals, maximizing the uptake of oxygen and the removal of carbon dioxide.

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Trachea

The tube that carries air from the nose and mouth to the lungs, ensuring a constant flow of air.

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Bronchioles

Small, thin-walled tubes that branch off from the bronchi, leading to the alveoli. They help regulate airflow to the lungs.

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Alveoli

Tiny air sacs at the end of the bronchioles, where gas exchange occurs. They have thin walls for efficient diffusion and are surrounded by capillaries.

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Squamous Epithelium

The layer of cells that forms the walls of the alveoli, allowing for the easy passage of gases.

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Cell Surface Membrane

The membrane that surrounds the cell, controlling what enters and exits.

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Active Transport

A type of transport across a membrane that requires energy, moving substances from an area of low concentration to high concentration.

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Study Notes

Gas Exchange Surfaces

  • Organisms exchange gases for aerobic respiration (O₂ intake, CO₂ output) and photosynthesis (CO₂ intake, O₂ output).
  • Gas exchange occurs via diffusion across exchange surfaces.
  • Exchange surfaces have high SA:V ratios for efficient exchange.
  • SA:V ratio decreases with increasing organism size.
  • Single-celled organisms have high SA:V, allowing efficient diffusion-based exchange.
  • Multicellular organisms have adaptations like alveoli (lungs), lamellae (fish gills), and spongy mesophyll (leaves) to increase surface area.
  • Diffusion pathway is minimized by a single layer of flattened epithelial cells.
  • Diffusion rate depends on the concentration gradient between exchange surfaces and environment.
  • Maintaining a concentration gradient relies on movement of substances, e.g. ventilation systems, blood flow in alveoli.
  • Fick's Law of Diffusion: Rate ∝ (SA x ΔC) / thickness.

Fick's Law of Diffusion Equation

  • Rate = P x A x ((C₁ - C₂) / T)
  • P = permeability constant
  • A = surface area
  • C₁ - C₂ = concentration difference
  • T = thickness of membrane

Lungs and Gas Exchange

  • Lungs maximize gas exchange, minimizing water loss in air-breathing animals.
  • Located in the thorax (chest cavity).
  • Air enters trachea, branching into bronchi & bronchioles, ending in alveoli.
  • Trachea has C-shaped cartilage rings to prevent collapse and for flexibility during swallowing.
  • Trachea and bronchi have mucus and cilia to trap and remove dust & pathogens.
  • Bronchioles have smooth muscle for adjusting airflow.
  • Alveoli have a single layer of squamous epithelium for rapid diffusion.
  • Alveoli surrounded by capillaries for efficient gas exchange (O₂ in, CO₂ out).
  • Moist surface in alveoli allows gas exchange in solution.

Cell Membranes

  • Membranes are vital for all cells.
  • The cell surface membrane separates the interior from exterior.
  • Membranes control substance exchange.
  • Phospholipid bilayer forms the basic membrane structure.
    • Phospholipid composed of glycerol, phosphate head (hydrophilic), and fatty acid tails (hydrophobic).
    • Bilayer forms due to hydrophilic/hydrophobic interactions with water.
  • Membrane proteins (intrinsic/extrinsic): transport & communication.
  • Cholesterol regulates membrane fluidity and stability.
  • Glycolipids and glycoproteins aid cell-to-cell communication and recognition (e.g. blood groups).
  • The fluid mosaic model describes the dynamic nature of membrane components.
  • Membranes are selectively permeable, allowing some molecules to pass more readily than others.

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Description

This quiz covers the mechanisms of gas exchange in organisms, including the role of diffusion and the significance of surface area to volume ratios. Explore the adaptations of multicellular organisms and the application of Fick's Law of Diffusion in understanding respiratory efficiency. Test your knowledge on how different structures facilitate gas exchange in various organisms.

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