Cellular Energy
Chloe Sanchez
6 min read
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Study Guide Overview
This study guide covers energy and metabolism, focusing on ATP, cellular respiration, and photosynthesis. It explains the second law of thermodynamics, entropy, and the importance of energy balance for maintaining order in living systems. The guide also touches upon metabolic pathways, energy flow, and provides practice questions and exam tips.
AP Biology: Energy and Metabolism - The Night Before 🚀
Hey there, future AP Bio master! Let's get you feeling confident and ready to crush this exam. We're going to break down energy and metabolism into bite-sized pieces, connect the dots, and make sure you're not just memorizing, but understanding. Let's dive in!
Energy: The Fuel of Life
The Basics
- All living systems need a constant input of energy to power life processes like growth, repair, and reproduction. Think of it like charging your phone – without it, nothing works! 🔋
- This energy is used to maintain the internal environment of the organism.
- Most energy originates from the sun 🌞.
Energy is converted into cellular energy by photosynthetic organisms, and then further into ATP, the most basic form of cellular energy.
Order, Entropy, and You
- Life requires a highly ordered system.
The second law of thermodynamics states that entropy (disorder) in a closed system always increases.
Energy input must exceed energy loss to maintain order and power cellular processes.
Energy & Metabolism
Energy is neither created nor destroyed, but it is often “lost” as heat.
Energy is stored in molecules and converted through chemical reactions in metabolic pathways.
Cellular Respiration: Breaking Down Glucose 🍬
- Cellular respiration converts glucose and oxygen into carbon dioxide, water, and ATP.
- Glycolysis: Glucose is broken down into pyruvate.
- Pyruvate enters the citric acid cycle, where it's converted into CO2 and H2O, releasing energy.
- The electron transport chain uses energy from the citric acid cycle to produce ATP via oxidative phosphorylation.
Remember Glycolysis comes first, then Citric Acid Cycle, then the Electron Transport Chain
Photosynthesis: Capturing Light Energy 🌿
- Photosynthesis converts light energy into chemical energy (glucose).
- Light-dependent reactions: Light energy is converted into ATP and NADPH.
- Light-independent reactions (Calvin cycle): CO2 is converted into glucose using ATP and NADPH.
Think of photosynthesis as the opposite of cellular respiration. Plants use light to make sugar, while animals break down sugar for energy.
Energy from Food 🥩
- Energy is gained through eating.
- All organisms get their energy from plants, directly or indirectly.
- Carnivores obtain energy from plants by consuming other organisms that have consumed plants.
Practice Question
Practice Questions
Multiple Choice Questions
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Which of the following best describes the flow of energy through living systems? (A) Energy is created by producers and destroyed by consumers. (B) Energy is captured by producers and transferred to consumers. (C) Energy is recycled within ecosystems. (D) Energy is lost as it moves through trophic levels.
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The second law of thermodynamics states that: (A) Energy cannot be created or destroyed. (B) Entropy in a closed system always decreases. (C) Entropy in a closed system always increases. (D) Energy can be converted from one form to another with 100% efficiency.
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Which of the following metabolic processes directly produces the most ATP? (A) Glycolysis (B) Fermentation (C) Citric acid cycle (D) Oxidative phosphorylation
Free Response Question
A group of students is studying the effects of varying light intensities on the rate of photosynthesis in Elodea plants. They set up three experimental groups, each with a different light intensity, and measure the amount of oxygen produced over a 30-minute period.
a) Identify the independent and dependent variables in this experiment. b) Explain how the light-dependent and light-independent reactions of photosynthesis contribute to the production of oxygen. c) Describe how the rate of ATP production would differ in high and low light intensities. d) Explain how the second law of thermodynamics applies to the process of photosynthesis and the overall flow of energy in the ecosystem.
Scoring Breakdown
a) (2 points) * Independent variable: light intensity (1 point) * Dependent variable: amount of oxygen produced (1 point) b) (3 points) * Light-dependent reactions split water molecules, releasing oxygen (1 point) * The electrons from water are used to create ATP and NADPH (1 point) * These products are then used in the Calvin cycle (light-independent reactions) to make glucose (1 point) c) (2 points) * High light intensity would result in a higher rate of ATP production (1 point) * Low light intensity would result in a lower rate of ATP production (1 point) d) (3 points) * Photosynthesis increases order by converting light energy into chemical energy (1 point) * While photosynthesis creates order, some energy is lost as heat, increasing entropy in the system (1 point) * The overall flow of energy in the ecosystem is not 100% efficient, and there is a continuous increase in entropy (1 point)
Final Exam Focus
- Key Topics: ATP, cellular respiration, photosynthesis, thermodynamics, metabolic pathways.
- Common Question Types:
- MCQs on energy flow, ATP production, and metabolic processes.
- FRQs on experimental design, comparing photosynthesis and respiration, and applying thermodynamic principles.
Time Management: Quickly identify the main topic of each question, and don't spend too much time on a single question.
Common Pitfalls: Confusing the light-dependent and light-independent reactions, not understanding the role of enzymes, and misinterpreting the second law of thermodynamics.
You've got this! Go ace that exam! 🌟
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Question 1 of 12
Ready to fuel your brain? 🧠 What is the primary source of energy for most living systems?
The Earth's core
The moon
The sun
Volcanoes