Biology Past Paper Notes PDF

### **1. Osmosis vs. Diffusion** - **Diffusion**: Movement of molecules from high to low concentration. Example: Oxygen spreading in the air. - **Osmosis**: Movement of water across a membrane from low to high solute concentration. ### **2. Concentration Gradient** - Cells use grad...

### **1. Osmosis vs. Diffusion** - **Diffusion**: Movement of molecules from high to low concentration. Example: Oxygen spreading in the air. - **Osmosis**: Movement of water across a membrane from low to high solute concentration. ### **2. Concentration Gradient** - Cells use gradients to move substances: - **Passive transport**: Moves substances from high to low concentration (no energy needed). - **Active transport**: Moves substances from low to high concentration (needs energy). ### **3. Semipermeable Membrane** - A membrane that only lets certain things pass through, like water, but not large molecules. ### **4. Hypotonic, Isotonic, and Hypertonic Solutions** - **Hypotonic**: More water outside; water enters the cell, and it swells. - **Isotonic**: Same water inside and outside; the cell stays the same. - **Hypertonic**: More water inside; water leaves the cell, and it shrinks. ### **5. Positive and Negative Controls** - **Positive control**: A test you expect to work (shows a known result). - **Negative control**: A test you expect not to work (no result). ### **1. What is an Enzyme? How does it function?** - An **enzyme** is a protein that speeds up chemical reactions in the body. - It works by lowering the energy needed for the reaction to happen, acting like a \"helper.\" ### **2. Factors Affecting Enzyme Function** - Factors that can affect enzyme activity: - **Temperature**: Too hot or cold can reduce activity or damage the enzyme. - **pH**: Enzymes work best at a specific pH. Too acidic or basic can stop them. - **Substrate concentration**: More substrate can increase activity, but only up to a limit. - **Optimal conditions**: Enzymes function best at their specific temperature and pH because these conditions keep their shape stable. ### **3. What is an Inhibitor?** - An **inhibitor** is a molecule that slows down or stops enzyme activity. - **Competitive inhibitors** block the active site. - **Non-competitive inhibitors** change the enzyme\'s shape. ### **4. Measuring Enzyme Activity** - Enzyme activity is measured by tracking: - How quickly the product is made. - How fast the substrate is used up.\ Example: Watching bubbles form when enzymes break down hydrogen peroxide. ### **1. Aerobic vs. Anaerobic Respiration** - **Aerobic Respiration**: - Uses oxygen to break down glucose into energy (ATP). - Happens in the **mitochondria**. - Produces carbon dioxide and water as waste. - **Anaerobic Respiration**: - Does **not** use oxygen. - Happens in the **cytoplasm**. - Produces less ATP and waste products like lactic acid (in animals) or alcohol and CO₂ (in yeast). - **Differences**: Aerobic makes more energy and requires oxygen; anaerobic works when oxygen is low. - **Measurement**: - Aerobic: Measured by oxygen use or CO₂ production. - Anaerobic: Measured by CO₂ production or pH changes. ### **2. Fermentation** - **When it happens**: When no oxygen is available. - **Waste products**: - Animals: Lactic acid. - Yeast: Alcohol and CO₂. - **Testing**: - Measured CO₂ bubbles or alcohol content. ### **3. Respiration in Boiled vs. Live Peas** - **Live peas**: Active respiration, producing CO₂. - **Boiled peas**: No respiration because the enzymes were destroyed by heat. ### **4. Respiration in Yeast with Different Sugars** - Yeast breaks down sugars to produce energy. - **Effect of sugar type**: - Simple sugars (like glucose) are broken down faster, producing more CO₂. - Complex sugars (like starch) take longer, producing less CO₂. ### **. Absorbance Spectrum vs. Action Spectrum** - **Absorbance Spectrum**: Shows how much light a pigment absorbs at different wavelengths. - **Action Spectrum**: Shows the rate of photosynthesis at different wavelengths of light. **Relationship**: The action spectrum aligns closely with the absorbance spectrum because pigments that absorb more light at certain wavelengths drive photosynthesis more effectively. ### **2. How to Determine a Pigment's Color** - The pigment's color is the light it **reflects**, not the light it absorbs. - Example: If a pigment absorbs blue and red but reflects green, it looks green. ### **3. Photosynthetic Rate Under Different Light Conditions** - **Light vs. No Light**: - **Light**: Photosynthesis occurs, producing oxygen and glucose. - **No Light**: No photosynthesis; only respiration happens, consuming oxygen. - **Red vs. Green Light**: - **Red Light**: High photosynthesis rate because pigments like chlorophyll absorb red light well. - **Green Light**: Low photosynthesis rate because chlorophyll reflects green light. **Cellular Level**: - **With light**: Chloroplasts use light to power the light reactions, making ATP and NADPH for the Calvin cycle. - **Without light**: Only respiration occurs, breaking down stored sugars for energy. Share User ##### **You said:** What is the difference between Osmosis and Diffusion? How do cells utilize a Concentration Gradient? What is a Semipermeable membrane? What is the difference between Hypotonic, Isotonic, and Hypertonic solutions? What happens to the shape of the cells placed into each and how does the solution move? What are Positive and Negative Controls? ###### **ChatGPT said:** ChatGPT Here's an explanation of each concept: ### **1. Difference between Osmosis and Diffusion** - **Diffusion**: The movement of molecules (e.g., gases, small solutes) from an area of higher concentration to an area of lower concentration until equilibrium is reached. It does not require a semipermeable membrane. Example: Oxygen moving from lungs into blood. - **Osmosis**: A specific type of diffusion where water moves across a semipermeable membrane from an area of low solute concentration to an area of high solute concentration. Example: Water entering plant roots. ### **2. How Cells Utilize a Concentration Gradient** - Cells rely on **concentration gradients** to transport substances: - **Passive transport** (e.g., diffusion, osmosis): Substances move down the gradient (high to low concentration) without energy. - **Active transport**: Substances move against the gradient (low to high concentration) using energy ( 4o ##### **You said:** can you keep the answers simplem ###### **ChatGPT said:** ChatGPT Sure! Here\'s a simpler version: ### **1. Osmosis vs. Diffusion** - **Diffusion**: Movement of molecules from high to low concentration. Example: Oxygen spreading in the air. - **Osmosis**: Movement of water across a membrane from low to high solute concentration. ### **2. Concentration Gradient** - Cells use gradients to move substances: - **Passive transport**: Moves substances from high to low concentration (no energy needed). - **Active transport**: Moves substances from low to high concentration (needs energy). ### **3. Semipermeable Membrane** - A membrane that only lets certain things pass through, like water, but not large molecules. ### **4. Hypotonic, Isotonic, and Hypertonic Solutions** - **Hypotonic**: More water outside; water enters the cell, and it swells. - **Isotonic**: Same water inside and outside; the cell stays the same. - **Hypertonic**: More water inside; water leaves the cell, and it shrinks. ### **5. Positive and Negative Controls** - **Positive control**: A test you expect to work (shows a known result). - **Negative control**: A test you expect not to work (no result). 4o ##### **You said:** What is an enzyme? How does it function? Which factors can affect enzyme function? Under what conditions do enzymes function best? Why? What is an inhibitor? How we measured enzyme activity? ###### **ChatGPT said:** ChatGPT ### **1. What is an Enzyme? How does it function?** - An **enzyme** is a protein that speeds up chemical reactions in the body. - It works by lowering the energy needed for the reaction to happen, acting like a \"helper.\" ### **2. Factors Affecting Enzyme Function** - Factors that can affect enzyme activity: - **Temperature**: Too hot or cold can reduce activity or damage the enzyme. - **pH**: Enzymes work best at a specific pH. Too acidic or basic can stop them. - **Substrate concentration**: More substrate can increase activity, but only up to a limit. - **Optimal conditions**: Enzymes function best at their specific temperature and pH because these conditions keep their shape stable. ### **3. What is an Inhibitor?** - An **inhibitor** is a molecule that slows down or stops enzyme activity. - **Competitive inhibitors** block the active site. - **Non-competitive inhibitors** change the enzyme\'s shape. ### **4. Measuring Enzyme Activity** - Enzyme activity is measured by tracking: - How quickly the product is made. - How fast the substrate is used up.\ Example: Watching bubbles form when enzymes break down hydrogen peroxide. 4o ##### **You said:** What are Aerobic and Anaerobic Respiration, where do they happen, why do they happen, and what are the differences between the two? How did we measure each of them? When does fermentation occur? What are the waste products and how did we test for them? Explain the difference in respiration between the boiled and the live peas. Explain the difference in respiration of yeast with the addition of various sugar treatments ###### **ChatGPT said:** ChatGPT ### **1. Aerobic vs. Anaerobic Respiration** - **Aerobic Respiration**: - Uses oxygen to break down glucose into energy (ATP). - Happens in the **mitochondria**. - Produces carbon dioxide and water as waste. - **Anaerobic Respiration**: - Does **not** use oxygen. - Happens in the **cytoplasm**. - Produces less ATP and waste products like lactic acid (in animals) or alcohol and CO₂ (in yeast). - **Differences**: Aerobic makes more energy and requires oxygen; anaerobic works when oxygen is low. - **Measurement**: - Aerobic: Measured by oxygen use or CO₂ production. - Anaerobic: Measured by CO₂ production or pH changes. ### **2. Fermentation** - **When it happens**: When no oxygen is available. - **Waste products**: - Animals: Lactic acid. - Yeast: Alcohol and CO₂. - **Testing**: - Measured CO₂ bubbles or alcohol content. ### **3. Respiration in Boiled vs. Live Peas** - **Live peas**: Active respiration, producing CO₂. - **Boiled peas**: No respiration because the enzymes were destroyed by heat. ### **4. Respiration in Yeast with Different Sugars** - Yeast breaks down sugars to produce energy. - **Effect of sugar type**: - Simple sugars (like glucose) are broken down faster, producing more CO₂. - Complex sugars (like starch) take longer, producing less CO₂. 4o ##### **You said:** What is an Absorbance spectrum? What is an action spectrum? Understand the relationship between action spectrum and absorbance spectrum. How can you tell what color a pigment is based on its spectra? Be able to compare and explain photosynthetic rate under different light conditions (light vs. no light, red vs. green). What is happening at the cellular lever during each light treatment? ###### **ChatGPT said:** ChatGPT ### **1. Absorbance Spectrum vs. Action Spectrum** - **Absorbance Spectrum**: Shows how much light a pigment absorbs at different wavelengths. - **Action Spectrum**: Shows the rate of photosynthesis at different wavelengths of light. **Relationship**: The action spectrum aligns closely with the absorbance spectrum because pigments that absorb more light at certain wavelengths drive photosynthesis more effectively. ### **2. How to Determine a Pigment's Color** - The pigment's color is the light it **reflects**, not the light it absorbs. - Example: If a pigment absorbs blue and red but reflects green, it looks green. ### **3. Photosynthetic Rate Under Different Light Conditions** - **Light vs. No Light**: - **Light**: Photosynthesis occurs, producing oxygen and glucose. - **No Light**: No photosynthesis; only respiration happens, consuming oxygen. - **Red vs. Green Light**: - **Red Light**: High photosynthesis rate because pigments like chlorophyll absorb red light well. - **Green Light**: Low photosynthesis rate because chlorophyll reflects green light. **Cellular Level**: - **With light**: Chloroplasts use light to power the light reactions, making ATP and NADPH for the Calvin cycle. - **Without light**: Only respiration occurs, breaking down stored sugars for energy. 4o ##### **You said:** Know the parts of and how to properly use the microscope Be able to identify stages of mitosis and parts of the cell using a microscope Be able to explain what happens in each stage of mitosis Understand the differences between plant and animal mitosis What is a histogram? Understand how to read and interpret data presented on a histogram. Be able to calculate the average and standard deviation of sample data for number of chromosomes per cell ###### **ChatGPT said:** ChatGPT ### **1. Parts of and How to Properly Use the Microscope** - **Parts of the Microscope**: 1. **Eyepiece (ocular lens)**: Where you look through. 2. **Objective lenses**: Different magnification levels (4x, 10x, 40x, 100x). 3. **Stage**: Where the slide is placed. 4. **Coarse and fine focus knobs**: Used to adjust the focus. 5. **Diaphragm**: Controls the amount of light. 6. **Condenser lens**: Focuses light on the sample. 7. **Base and Arm**: Support the microscope. - **How to Use**: 8. Start with the lowest magnification (4x). 9. Place the slide on the stage and secure it with clips. 10. Use the coarse focus knob to bring the image into focus. 11. Switch to higher magnifications (10x, 40x) and adjust the fine focus. ### **2. Stages of Mitosis and Parts of the Cell Using a Microscope** - **Mitosis Stages**: - **Prophase**: Chromosomes condense, nuclear membrane breaks down, spindle fibers form. - **Metaphase**: Chromosomes align in the center of the cell. - **Anaphase**: Sister chromatids are pulled to opposite poles. - **Telophase**: New nuclear membranes form around the two sets of chromosomes. - **Cytokinesis**: Cytoplasm divides, resulting in two daughter cells. - **Parts of the Cell**: - **Nucleus**: Contains the genetic material (DNA). - **Cytoplasm**: Gel-like substance that fills the cell. - **Cell membrane**: Outer layer that controls what enters and leaves the cell. ### **3. Differences Between Plant and Animal Mitosis** - **Plant Mitosis**: - **Cell plate** forms during cytokinesis, dividing the plant cell into two. - No centrioles present in plant cells. - **Animal Mitosis**: - **Cleavage furrow** forms during cytokinesis, pinching the cell into two. - **Centrioles** are present and help organize the spindle fibers. ### **4. What is a Histogram? How to Read and Interpret Data** - A **histogram** is a type of graph that shows the distribution of data. It uses bars to represent the frequency of data within certain ranges (bins). - **Reading a histogram**: - The **x-axis** shows the data ranges (e.g., number of chromosomes). - The **y-axis** shows the frequency (how many times a value appears). - The height of each bar tells you how common a certain value is in the data. ### **5. Calculating the Average and Standard Deviation** - **Average (Mean)**: - Add all the values (e.g., number of chromosomes per cell) and divide by the number of values. - Formula:\ Average=Sum of all valuesNumber of valuesAverage=Number of valuesSum of all values​ - **Standard Deviation**: - Measures how spread out the data is from the mean. - Formula:\ Standard Deviation=∑(xi−μ)2nStandard Deviation=n∑(xi​−μ)2​​\ Where: - xixi​ = each value, - μμ = mean, - nn = number of values. ### **1. Meiosis: Haploid and Diploid Stages** - **Meiosis I**: - **Diploid**: The cell starts as diploid (2n) at the beginning of meiosis I. - **Haploid**: At the end of meiosis I, the cell is haploid (n), as homologous chromosomes are separated. - **Meiosis II**: - **Haploid**: The cells remain haploid throughout meiosis II, as sister chromatids are separated. ### **2. Homologous Chromosomes** - **Homologous chromosomes** are chromosome pairs, one from each parent, that are similar in shape, size, and genetic content. They pair up during meiosis. ### **3. What is Meiosis?** - **Meiosis** is a type of cell division that reduces the chromosome number by half to produce **gametes** (sperm and eggs). - It happens in **germ cells** (cells that give rise to gametes). - **Why it happens**: To ensure that offspring have the correct number of chromosomes when gametes combine during fertilization. ### **4. Independent Assortment** - **Independent assortment** is the random distribution of homologous chromosomes into gametes during meiosis I. This leads to genetic variation. - It occurs during **Metaphase I** of meiosis. ### **5. Phases of Meiosis I and II** - **Meiosis I** (reduces chromosome number by half): - **Prophase I**: Chromosomes condense, homologous chromosomes pair up, crossing over occurs. - **Metaphase I**: Homologous pairs align at the center. - **Anaphase I**: Homologous chromosomes are separated. - **Telophase I**: Two haploid cells form. - **Meiosis II** (similar to mitosis): - **Prophase II**: Chromosomes condense in two haploid cells. - **Metaphase II**: Chromosomes align. - **Anaphase II**: Sister chromatids are separated. - **Telophase II**: Four haploid cells form, each with a single set of chromosomes. - **Differences**: - Meiosis I reduces chromosome number, while Meiosis II separates sister chromatids. ### **6. Reading, Interpreting, and Constructing a Pedigree** - **Pedigree**: A family tree showing the inheritance of traits across generations. - **Dominant trait**: Appears in every generation and only one copy of the allele is needed to show the trait. - **Recessive trait**: May skip generations and requires two copies of the allele to show the trait. - **X-linked traits**: Typically affect males more than females, as males have only one X chromosome. - **Autosomal traits**: Affected equally by both sexes. ### **7. Blood Typing: Genotypes, Phenotypes, Donors, and Recipients** - **Blood type**: Determined by the presence of antigens on red blood cells. - **Type A**: Has A antigen, anti-B antibodies. - **Type B**: Has B antigen, anti-A antibodies. - **Type AB**: Has both A and B antigens, no antibodies. - **Type O**: No antigens, has both anti-A and anti-B antibodies. - **Genotype**: A person's blood type can be determined by their genotype (e.g., AA or AO for type A). - **Donors/Recipients**: Type O is the universal donor, and type AB is the universal recipient. ### **8. Rh Factor** - **Rh** is a protein on red blood cells. If present, you are **Rh+**; if absent, you are **Rh-**. - The Rh factor is important for blood transfusions and pregnancy (Rh incompatibility can occur if the mother is Rh- and the baby is Rh+). ### **9. Converting Microliters to Milliliters** - **1 milliliter (mL) = 1,000 microliters (µL)** - To convert: divide microliters by 1,000 (e.g., 500 µL = 0.5 mL). ### **10. Restriction Enzymes** - **Restriction enzymes** are proteins that cut DNA at specific sequences called **recognition sites**. - They are used in genetic engineering, cloning, and DNA analysis. ### **11. Recognition Site/Sequence** - A **recognition site** is a specific sequence of nucleotides in DNA where a restriction enzyme cuts. ### **12. Gel Electrophoresis** - **Gel electrophoresis** is a technique used to separate DNA fragments based on size. - **How it works**: DNA is loaded into a gel and an electric current is applied. DNA, being negatively charged, moves towards the positive end of the gel. Smaller fragments move faster, while larger ones move slower. - **Scientific Evidence**: It can be used for DNA profiling, identifying genetic mutations, or comparing DNA samples. ### **13. How DNA Migrates in Gel Electrophoresis** - The **molecular structure of DNA** (its negative charge) causes it to move towards the positive electrode when an electric current is applied. ### **14. Separating Molecules in Gel** - Molecules are separated based on their **size**: smaller molecules move faster through the gel matrix, while larger molecules move slower.