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What is the primary characteristic of passive transport?
What is the primary characteristic of passive transport?
Oxygen and carbon dioxide can diffuse easily across the phospholipid bilayer of a membrane.
Oxygen and carbon dioxide can diffuse easily across the phospholipid bilayer of a membrane.
True
What happens to the concentration of dye molecules when they diffuse across a permeable membrane?
What happens to the concentration of dye molecules when they diffuse across a permeable membrane?
The concentration balances on both sides of the membrane.
The diffusion of water across a membrane is called __________.
The diffusion of water across a membrane is called __________.
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Match the following terms with their descriptions:
Match the following terms with their descriptions:
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Why is diffusion across a membrane termed 'passive transport'?
Why is diffusion across a membrane termed 'passive transport'?
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Transport proteins are unnecessary for all types of molecules to cross the membrane.
Transport proteins are unnecessary for all types of molecules to cross the membrane.
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What is the net movement direction of molecules during diffusion?
What is the net movement direction of molecules during diffusion?
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What is osmosis?
What is osmosis?
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A selectively permeable membrane allows all substances to cross freely.
A selectively permeable membrane allows all substances to cross freely.
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In which direction does water move when comparing a 0.5% sucrose solution to a 2% sucrose solution?
In which direction does water move when comparing a 0.5% sucrose solution to a 2% sucrose solution?
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The term __________ refers to the ability of a surrounding solution to cause a cell to gain or lose water.
The term __________ refers to the ability of a surrounding solution to cause a cell to gain or lose water.
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Match the following terms related to osmosis with their definitions:
Match the following terms related to osmosis with their definitions:
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What happens to an animal cell in an isotonic solution?
What happens to an animal cell in an isotonic solution?
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Water molecules are considered hydrophilic when they cluster around solute molecules.
Water molecules are considered hydrophilic when they cluster around solute molecules.
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What effect does a hypertonic solution have on cells?
What effect does a hypertonic solution have on cells?
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What process causes plant cells to wilt in hypertonic environments?
What process causes plant cells to wilt in hypertonic environments?
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Facilitated diffusion requires energy to transport substances across membranes.
Facilitated diffusion requires energy to transport substances across membranes.
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What role do transport proteins play in cell membranes?
What role do transport proteins play in cell membranes?
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In freshwater Paramecium, the contractile vacuoles help maintain _____ balance.
In freshwater Paramecium, the contractile vacuoles help maintain _____ balance.
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Which of the following substances uses facilitated diffusion?
Which of the following substances uses facilitated diffusion?
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Concentrated salt solutions can be used to preserve foods by causing bacteria to plasmolyze.
Concentrated salt solutions can be used to preserve foods by causing bacteria to plasmolyze.
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What is the main driving force behind passive transport such as facilitated diffusion?
What is the main driving force behind passive transport such as facilitated diffusion?
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Which type of energy is associated with the motion of objects?
Which type of energy is associated with the motion of objects?
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Chemical energy is a type of kinetic energy that is important for cellular work.
Chemical energy is a type of kinetic energy that is important for cellular work.
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What is the primary form of energy that cells transform to perform work?
What is the primary form of energy that cells transform to perform work?
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The first law of thermodynamics states that the energy in the universe is __________.
The first law of thermodynamics states that the energy in the universe is __________.
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Which of the following best describes potential energy?
Which of the following best describes potential energy?
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Thermal energy is related to the random movement of molecules.
Thermal energy is related to the random movement of molecules.
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What is thermodynamics?
What is thermodynamics?
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Match the following types of energy with their descriptions:
Match the following types of energy with their descriptions:
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What occurs during energy transfer or transformation?
What occurs during energy transfer or transformation?
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According to the second law of thermodynamics, energy conversions decrease the entropy of the universe.
According to the second law of thermodynamics, energy conversions decrease the entropy of the universe.
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What is the primary waste product released by both automobile engines and cellular respiration?
What is the primary waste product released by both automobile engines and cellular respiration?
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Cells convert approximately ______% of the chemical energy in their fuel to energy for cellular work.
Cells convert approximately ______% of the chemical energy in their fuel to energy for cellular work.
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Match the following processes with their respective energy transformation efficiency:
Match the following processes with their respective energy transformation efficiency:
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Why can't organisms recycle their energy completely?
Why can't organisms recycle their energy completely?
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Entropy is a measure of order in a system.
Entropy is a measure of order in a system.
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What term is used to describe the measure of disorder within a system?
What term is used to describe the measure of disorder within a system?
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What is the total of an organism's chemical reactions called?
What is the total of an organism's chemical reactions called?
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Cellular respiration is an endergonic process.
Cellular respiration is an endergonic process.
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What molecule is primarily responsible for energy coupling in cells?
What molecule is primarily responsible for energy coupling in cells?
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The process of transferring a phosphate group from ATP to another molecule is called __________.
The process of transferring a phosphate group from ATP to another molecule is called __________.
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Match the following forms of cellular work with their descriptions:
Match the following forms of cellular work with their descriptions:
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What happens to a phosphate group when ATP is hydrolyzed?
What happens to a phosphate group when ATP is hydrolyzed?
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The bonds connecting the phosphate groups in ATP are stable.
The bonds connecting the phosphate groups in ATP are stable.
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What type of reactions do cells use to obtain energy from complex molecules?
What type of reactions do cells use to obtain energy from complex molecules?
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Study Notes
The Working Cell - Water Flow Through Membranes
- Computer models illustrate a small section of a human cell membrane, showing water molecules flowing across the membrane.
- Phospholipids form a lipid bilayer; yellow balls represent phosphate heads, and green squiggles represent fatty acid tails.
- Aquaporins, represented by blue ribbons, are membrane proteins functioning as water channels.
- A single aquaporin protein facilitates the flow of billions of water molecules per second through the membrane.
- Aquaporins are crucial for kidney function, enabling water reabsorption.
- Some individuals with defective aquaporins require substantial water intake to prevent dehydration.
Membrane Structure and Function
- Cell membranes have a fluid mosaic structure, containing diverse protein molecules embedded in a phospholipid bilayer.
- Membranes exhibit selective permeability, allowing some substances to cross more easily than others.
- Various membrane proteins perform diverse functions, such as:
- Enzymes
- Attachment proteins
- Signal molecules
- Receptor proteins
- Channel proteins
- Active transport proteins
- Junction proteins
- Glycoproteins
Energy and the Cell
- Cellular metabolic reactions transform energy, utilizing ATP as a driving force.
How Enzymes Function
- Enzymes speed up cellular chemical reactions by lowering activation energy.
- Enzymes are proteins whose structure enables them to selectively bind to specific reactants, called substrates, in a region called the active site.
The Spontaneous Formation of Membranes
- Phospholipids were likely among the first organic molecules spontaneously forming membranes.
- In a test-tube, phospholipids and water mixtures assemble into bilayer membranes (bubbles).
- These simple membranes were a critical step in the evolution of the first cells.
Passive Transport
- Diffusion is the net movement of particles from a higher concentration to a lower concentration area driven by thermal energy.
- Diffusion across a membrane is called passive transport.
- The membrane must be permeable, having channels or pores, for molecules to pass through.
- Oxygen (O₂) and carbon dioxide (CO₂) readily diffuse across the hydrophobic interior of the membrane.
- Ions and polar molecules often need transport proteins.
Osmosis
- Osmosis is the diffusion of water across a selectively permeable membrane.
- Water moves from a solution with a higher water concentration (lower solute concentration) to a solution with lower water concentration (higher solute concentration).
- Tonicity describes how a solution affects cell volume.
- An isotonic solution has an equal solute concentration to the cell.
- A hypotonic solution has a lower solute concentration than the cell, causing water influx.
- A hypertonic solution has a higher solute concentration than the cell, causing water efflux.
Water Balance
- Maintaining proper water balance is crucial for all organisms.
- Organismal osmoregulation (control of water balance) is vital.
- Plant cells have cell walls; animal cells may swell or shrink in various solutions.
Transport Proteins
- Facilitated diffusion utilizes transport proteins to rapidly move substances across a membrane.
- Aquaporins are a type of transport proteins that facilitate rapid water movement.
Enzyme Inhibition
- Enzyme inhibitors are substances that reduce or prevent enzyme activity.
- Competitive inhibitors resemble substrates, competing for the active site.
- Noncompetitive inhibitors bind to a different site (allosteric site).
- Inhibitors are crucial in regulating metabolic pathways or controlling reactions.
Active Transport
- Active transport moves substances against their concentration gradient, requiring energy (ATP).
- This is vital for maintaining specific concentrations within the cell.
- Active transport mechanisms include pumps and other transport proteins.
Cellular Transport Mechanisms
- Exocytosis and endocytosis remove large molecules or bring large particles into the cell.
- Exocytosis involves vesicles fusing with the plasma membrane to release substances.
- Endocytosis involves the cell taking substances in by forming vesicles from the plasma membrane.
- Phagocytosis is a type of endocytosis.
- Receptor-mediated endocytosis is a selective type of endocytosis using receptors.
Energy and the Cell
- Cells use energy transformations (e.g., cellular respiration) to drive cellular work.
- Thermodynamic principles govern energy transformations in living systems.
- ATP is the primary energy currency in cells; it drives endergonic reactions.
- Cells couple exergonic and endergonic reactions to utilize energy.
Enzyme Function
- Enzymes accelerate metabolic reactions by lowering activation energy.
- Enzymes are highly specific for their substrates and display optimal temperature and pH levels.
- Cofactors, including coenzymes, are non-protein molecules that aid in enzyme catalysis.
- Factors affecting enzyme function include temperature, pH, and cofactor availability.
- Enzyme-catalyzed reactions proceed in a specific direction through a multi-step pathway, and regulation of enzymes is vital.
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Description
Explore the fundamental concepts of passive transport in this quiz, including diffusion, osmosis, and the role of selectively permeable membranes. Test your understanding of how molecules move across cell membranes and the significance of concentration gradients in biological systems.
