Scientific Practices
What is the difference between an observation and an inference?
An observation is information gathered using your senses or measurements; an inference is an explanation or conclusion based on observations.
What is the basic unit of structure and function in all living things?
The cell.
Which organelle controls many of the cell's activities and contains DNA?
Nucleus
In what organelle does photosynthesis occur?
Chloroplast
What molecule acts as a major carrier of usable energy in cells?
ATP
A student tests whether the amount of sunlight affects plant growth. What is the independent variable?
The amount of sunlight.
Name the three major ideas of Cell Theory.
All living things are made of cells; cells are the basic unit of structure and function in living things; all cells come from preexisting cells.
Which organelle produces much of the usable energy needed by a eukaryotic cell?
Mitochondria
What pigment captures light energy for photosynthesis and gives most plants their green color?
Chlorophyll
What is an enzyme?
A protein that speeds up chemical reactions without being used up.
In the same experiment testing sunlights effect on plant growth, the student measures the plant's height every three days. What is the dependent variable?
Plant height/Growth
What major structure do eukaryotic cells have that prokaryotic cells do not?
A nucleus. (Also accept membrane-bound organelles.)
Put these levels of organization in order from smallest to largest: organ, organ system, cell, tissue.
Cell → Tissue → Organ → Organ System.
Name the three inputs needed for photosynthesis and the two major products.
Inputs: carbon dioxide, water, and light energy. Products: glucose and oxygen.
What is the active site, and what binds to it?
The active site is the specifically shaped region of an enzyme where the substrate binds.
A student tests three fertilizers on identical plants. One plant gets 100 mL of water each day, another gets 200 mL, and another gets 300 mL. What is wrong with the experiment?
The amount of water is not controlled, so the student cannot know whether fertilizer or water caused differences in growth.
A scientist observes a cell with a cell membrane, cytoplasm, DNA, and ribosomes but no nucleus. Is it prokaryotic or eukaryotic? Explain.
Prokaryotic because it does not have a nucleus.
A cell needs to make, process, and ship a large amount of protein. Name three organelles that would be especially important.
Ribosomes, endoplasmic reticulum, and Golgi apparatus.
A plant has plenty of water and carbon dioxide but is placed in complete darkness. Which input for photosynthesis is missing, and what will happen to glucose production?
Light energy is missing, so the plant will not be able to continue producing glucose through photosynthesis normally.
An enzyme normally works well at body temperature. It is exposed to extremely high heat, and its active site changes shape. What has happened, and why might the enzyme stop working?
The enzyme has become denatured. Its active site changed shape, so its substrate may no longer fit correctly.
A student claims, “Plants grow faster under blue light.” Their plants under blue light grew an average of 12 cm, while plants under white light grew an average of 8 cm. Identify the claim and the evidence.
Claim: Plants grow faster under blue light. Evidence: Blue-light plants grew 12 cm on average compared with 8 cm under white light.
An unknown cell has a nucleus, chloroplasts, a cell wall, and a large central vacuole. Identify the type of cell and give two pieces of evidence supporting your answer.
Plant cell; evidence can include chloroplasts, cell wall, or large central vacuole.
Muscle cells require large amounts of usable energy because they repeatedly contract. Which organelle would you expect muscle cells to contain in large numbers, and why?
Mitochondria, because they help release energy from food and produce ATP for cellular processes.
Complete and explain the relationship:
Photosynthesis: carbon dioxide + water + light → glucose + oxygen
Cellular respiration: __________ + __________ → carbon dioxide + water + usable energy
Glucose + oxygen. The products of photosynthesis provide materials used in cellular respiration, while cellular respiration releases usable energy from glucose.
Students place equal-sized potato pieces containing catalase into hydrogen peroxide. Sample A produces 7 cm of foam while Sample B produces 1 cm of foam after 60 seconds. What can they conclude about catalase activity in the two samples? Explain using the evidence.
Catalase was more active in Sample A. Catalase breaking down hydrogen peroxide releases oxygen that creates foam, and Sample A produced 7 cm compared with only 1 cm in Sample B.