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Questions and Answers
What is the primary effect of cyanide on cellular processes?
What is the primary effect of cyanide on cellular processes?
The energy from glucose is mostly delivered in large amounts.
The energy from glucose is mostly delivered in large amounts.
False
What molecule is produced when H+ ions diffuse back through ATP synthase?
What molecule is produced when H+ ions diffuse back through ATP synthase?
ATP
The energy packets produced from food in cells are called __________.
The energy packets produced from food in cells are called __________.
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Match the following terms with their descriptions:
Match the following terms with their descriptions:
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What is the primary effect of adding non-polar molecules to water?
What is the primary effect of adding non-polar molecules to water?
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Separating polar and non-polar phases decreases entropy at the micro-level.
Separating polar and non-polar phases decreases entropy at the micro-level.
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What is the effect of phase separation on the micro-level entropy?
What is the effect of phase separation on the micro-level entropy?
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Systems minimize contact between polar and non-polar components by __________ all the polar in one place.
Systems minimize contact between polar and non-polar components by __________ all the polar in one place.
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Match the following terms with their correct descriptions:
Match the following terms with their correct descriptions:
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Why do systems prefer lower energy states?
Why do systems prefer lower energy states?
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The addition of non-polar molecules helps lower the free energy of water molecules.
The addition of non-polar molecules helps lower the free energy of water molecules.
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Explain how phase separation affects the visible organization of a system.
Explain how phase separation affects the visible organization of a system.
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What role does cholesterol play in lipid bilayers at body temperature?
What role does cholesterol play in lipid bilayers at body temperature?
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Hydrophobic molecules can easily cross lipid bilayers.
Hydrophobic molecules can easily cross lipid bilayers.
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What type of molecules have both hydrophilic and hydrophobic properties?
What type of molecules have both hydrophilic and hydrophobic properties?
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The overall change in entropy is __________ due to the increase at the micro-level.
The overall change in entropy is __________ due to the increase at the micro-level.
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Match the following terms with their descriptions:
Match the following terms with their descriptions:
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What happens to the organization of a system when it separates into two phases?
What happens to the organization of a system when it separates into two phases?
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Large hydrophobic spaces are commonly found in the body.
Large hydrophobic spaces are commonly found in the body.
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Why are large hydrophobic spaces considered rare in the body?
Why are large hydrophobic spaces considered rare in the body?
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What is one purpose of ATP in cellular processes?
What is one purpose of ATP in cellular processes?
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High bandwidth communication is inexpensive.
High bandwidth communication is inexpensive.
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What defines a 'signal' in scientific communication?
What defines a 'signal' in scientific communication?
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Cells maintain distinct compartment contents by using a co-transporter to move solute __________.
Cells maintain distinct compartment contents by using a co-transporter to move solute __________.
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Match the components involved in cellular homeostasis with their functions:
Match the components involved in cellular homeostasis with their functions:
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What is a characteristic of a signal?
What is a characteristic of a signal?
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Making and maintaining organization within cells does not require energy.
Making and maintaining organization within cells does not require energy.
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What is one way the body achieves homeostasis?
What is one way the body achieves homeostasis?
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Which type of signaling involves cells sending signals to themselves?
Which type of signaling involves cells sending signals to themselves?
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Endocrine signaling is used for short-distance communication only.
Endocrine signaling is used for short-distance communication only.
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What are SIMPLE signals used for in biological systems?
What are SIMPLE signals used for in biological systems?
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Juxtacrine signaling involves __________ between neighboring cells.
Juxtacrine signaling involves __________ between neighboring cells.
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Match the following types of signaling with their descriptions:
Match the following types of signaling with their descriptions:
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What is the role of drugs in relation to SIMPLE signals?
What is the role of drugs in relation to SIMPLE signals?
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Hydrophobic molecules cannot cross the cell membrane directly.
Hydrophobic molecules cannot cross the cell membrane directly.
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Name the four main classifications of signaling paths.
Name the four main classifications of signaling paths.
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Which of the following is a key feature of steroid-mediated signaling pathways?
Which of the following is a key feature of steroid-mediated signaling pathways?
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Hydrophilic molecules can freely pass through cell membranes without assistance.
Hydrophilic molecules can freely pass through cell membranes without assistance.
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What is one of the main tradeoffs in signaling regarding sensitivity, speed, and economy?
What is one of the main tradeoffs in signaling regarding sensitivity, speed, and economy?
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To achieve high-speed cellular responses, there must be rapid synthesis and destruction of __________.
To achieve high-speed cellular responses, there must be rapid synthesis and destruction of __________.
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Match the following signaling concepts with their descriptions:
Match the following signaling concepts with their descriptions:
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What is often a consequence of averaging over time in signaling processes?
What is often a consequence of averaging over time in signaling processes?
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High speed in signaling can be achieved with low energy costs.
High speed in signaling can be achieved with low energy costs.
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List one strategy used to avoid false signals from noise in cellular signaling.
List one strategy used to avoid false signals from noise in cellular signaling.
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Study Notes
Body in Motion - Homeostasis
- Energy in biochemical reactions is measured in eV (electron volts), not calories or joules
- Typical biochemical reactions involve energy changes around 0.2 eV
- Many biochemical reactions are driven by 0.3 eV energy packets
- Homeostasis maintains a stable internal environment despite internal and external changes
- Many diseases result from failures of homeostasis
- Examples of homeostatic failures include infection, diabetes, hypertension, cancer, and Alzheimer's disease
Second Law of Thermodynamics
- Entropy (disorder) tends to increase in closed systems
- dS/dt > 0 in any closed system out of equilibrium
- Biological systems are not closed systems and require energy input to maintain order
Energetics of Biochemical Reactions
- Biochemical reactions often run 'downhill' (release energy), but one can be coupled to a 'uphill' reaction (require energy)
- ATP conversion to ADP+Pi is a downhill reaction that provides energy for uphill reactions
- Glucose and fructose are examples of plant-derived molecules used for energy
Phosphorylation in Glucose to Fructose-1,6-Bisphosphate
- Conversion of glucose to fructose-1,6-bisphosphate involves two phosphorylation steps
- ATP is the energy carrier and the glucose molecule undergoes a nucleophilic attack on the ATP
- These processes are enzyme facilitated
Why is Oxidation of Sugars Not “On Fire”?
- The human body needs to carefully manage energy release
- Oxidising glucose releases substantial energy in 29 eV packets, which is too much energy to be safe
A Possible Solution for Energy Transfer
- NADH and FADH2 transfer energy to ATP in the electron transport chain
Summary of Biochemistry
- Glucose processing occurs in small steps
- Some steps release small amounts of energy directly to ATP
- Some steps pass energy to carriers (e.g., NADH)
Membrane Structure and Function
- Hydrophobic spaces (e.g., fat droplets) are relatively rare in the body, except in adipocytes
- Typically hydrophobic regions form barriers between aqueous compartments
- Membranes are largely composed of amphipathic molecules (hydrophilic head and hydrophobic tails) forming stable bilayers.
- Water interacts with hydrophilic substances, and doesn't interact with hydrophobic substances
Transport Across Membranes
- Some molecules can easily cross the membrane bilayer (e.g., water) but others need help
- In order to maintain homeostasis, the membrane must have selective mechanisms to transport substances.
- Mechanisms include direct free diffusion, uniporters, co-transporters, and antiporters
- Different transport mechanisms can transport at varying speeds and may need energy (ATP)
A "Universal" Example: Na+/K+ ATPase
- The Na+/K+ ATPase maintains a concentration gradient of Na+ and K+ across the cell membrane
- This gradient is vital for many cellular processes
Chemical Signals (Hormones/Neurotransmitters):
- Hormones broadcast signals to the whole body; neurons target specific recipients
- Both hormones and neurotransmitters are involved in inter-individual communication.
Types of Signaling in Systems
- Autocrine signaling: signals affect the cell that produced them
- Paracrine signaling: signals affect neighboring cells
- Endocrine signaling: signals travel through the blood to reach distant sites
- Juxtacrine signaling: involves direct cell-to-cell contact
How Do Signals Get Into Cells?
- Hydrophobic molecules (e.g., steroids) can cross the membrane directly
- Cells have receptors for hydrophilic molecules
Signal Transduction
- Signals often initiate a cascade of events involving a series of proteins and enzymes (amplification)
- This cascade often involves 'second messengers'
Ways of Avoiding False Signals/Avoiding Noise
- Average signals over time (temporal averaging)
- Average responses over a group of cells (spatial averaging)
- Speed of response and rapid production and destruction of second messengers
- High speed and high energy costs are often coupled.
Challenges of Long-Distance Communication
- Low speeds (e.g., signals traveling through the bloodstream)
- Dilution of signals
- Sometimes sensitivity vs efficiency of signaling
High-Speed Communication (e.g., Nervous System)
- Uses a "pipe system" to ensure signals are fast and efficient.
- Same chemical signals are used with varying "wires" to target different muscles/organs
Neurons and Neurotransmitters
- Neurons are specialized cells that utilize neurotransmitters for quick communication
Homestasis Mechanisms
- Homeostasis is achieved by closed-loop feedback control systems.
- The system maintains a target value in the face of unpredictable changes.
- Internal variables include wake/sleep cycles, resting/active states, standing/reclining posture
- External variables include warm/cold conditions, injury, hunger, etc;
- Proportional Control (looks at the size of an error) and Integrative Control (looks at the whole history of an error over time) together achieve good homeostasis
Failure of Homeostasis
- Damage to effectors, such as integumentary damage and the problems with kidney malfunction.
- Poorly functioning pacemakers which can become problems for the body.
- Damage to control systems (i.e., damaged feedback loop such as in cases of obesity)
- Inappropriate cellular responses (i.e., inappropriate immune responses or cancer)
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Description
Explore the fascinating concepts of homeostasis and the energetics of biochemical reactions in this quiz. Understand how energy changes and the laws of thermodynamics apply to biological systems. Test your knowledge about diseases linked to homeostatic failures and the balance of energy in biochemical processes.
