Cells and Organelles
This organelle is surrounded by a double membrane with pores and contains the cell's chromosomes. Besides "holding DNA," what is its main job in the cell?
The nucleus stores and protects DNA and controls gene expression, acting as the command center that regulates which proteins the cell makes.
What type of transport moves molecules from low to high concentration using energy?
Active transport
What is the main product of glycolysis?
2 pyruvate molecules (and a small amount of ATP and NADH)
During which phase of mitosis do chromosomes line up along the middle (equator) of the cell, and why is this alignment important?
Metaphase; alignment ensures each daughter cells gets one copy of every chromosome when sister chromatids separate.
A cell needs to secrete large amounts of digestive enzymes. Which two organelles will be especially abundant? (Hint: Ribosomes are not an answer)
Rough Er and Golgi apparatus.
Why do muscle cells contain far more mitochondria than skin cells?
they require more ATP for contraction
Both channel proteins and carrier proteins help substances cross the membrane. What is one key way they are different?
Channel proteins form open pores for specific ions or water to flow through; carrier proteins change shape to move specific molecules across one at a time (like a revolving door)
What molecule is the final electron acceptor in aerobic respiration?
Oxygen (forms water)
What is the main differences between haploid and diploid cells, and give one example of each in humans
Diploid (2n): two sets of chromosomes (one from each parent); example: body/somatic cells like skin or liver or neruon or muscle, etc.
Haploid (n): one set of chromosomes; examples: gametes like sperm or egg
A muscle cell is low on oxygen. How does this affect ATP production and pH
Fermentation makes less ATP and produces lactic acid, lowering pH within the cell.
A researcher observes a cell that has a large Golgi Apparatus and many vesicles. What does this tell you about its function?
It likely secretes lots of proteins (ex: hormones, enzymes)
A cell is placed in pure distilled water. What happens?
Water enters; the cell swells and may lyse.
Why is ATP often described as "coupling" exergonic and endergonic reactions in the cell?
ATp stores energy from exergonic rections (like breaking down glucose) in its phosphate bonds and then releases that energy to power endergonic reactions (like active transport or building macromolecules), linking ("coupling") the two.
What is the role of the spindle fibers during mitosis and where do they come from?
Separate sister chromatids, and they emerge from the centrosomes
A scientist test how different light intensities affect the rate of photosynthesis in a plant.
Name the independent variable, dependent variable, and one control variable they should keep constant.
IV: light intensity
DV: rate of photosynthesis
Control: same plant species, same temp, same CO levels, same type/volume of water, same fertilizer, etc.....
Plant cells have both mitochondria and chloroplasts. Explain why both are necessary.
Chloroplasts make glucose during photosynthesis; mitochondria make ATP from glucose in respiration.
A plant cell is placed in a very hypotonic solutions. What happens to the cell, and why doesn't it react the same way an animal cell might?
Water enters by osmosis, the plant cell becomes turgid (swollen), but it doesn't burst because the rigid cell wall resists further expansion and provides structural support.
During exercise, hy might your muscle cells switch to lactic acid fermentation?
Oxygen becomes limited; fermentation regenerates NAD+ so glycolysis can continue making ATP.
Nondisjunction is an error in meiosis.
What happens during nondisjunction, and what is one possible consequence in a human offspring?
Homologou chromosomes (in meiosis 1) or sister chromatids (in meiosis 2) fail to separate, leading to gametes with extra or missing chromosomes. If such a gamete is involved in fertilization, it can result in chromosomal disorders like trisomy 21, klinefelters, or Turner syndrome (XO).
A researcher measures the rate of mitosis in two tissues: leaf cells exposed to sunlihgt and root cells kept underground.
Predict which tissue divides faster and explain why, using ideas from photosynthesis, cellular respiration, and cell division.
Leaf cells divide faster because they make glucose through photosynthesis, giving them immediate access to fuel for cellular respiration, which produces the ATP needed for mitosis.
Root cells rely only on sugars transported from the leaves, so they have lower energy availability, and therefore slower division.
A mutation prevents lysosomes from functioning. Predict two consequences for the cell.
1. Waste and damaged organelles accumulate
2. cell may die due to buildup of toxic material.
A marine fish is accidentally placed in freshwater. Predict what happens to its cells in terms of osmosis and homeostasis, and explain why this is dangerous.
Freshwater is hypotonic to the fish's body fluids, so water rushes into its cells by osmosis, swelling the cells, and potentially disrupting membranes and overall function. The fish's normal osmoregulation cannot keep up, so it may experience cell damage or death and lose homeostasis
A plant cell receives plenty of sunlight but has a malfunctioning Calvin cyle. Explain why the light reactions alone cannot keep the plant alive, even if ATP and NADPH are being produced.
Because ATP and NADPH made in the light reactions cannot be stored, they must be used immediately in the Calvin cycle to build glucose, which is the molecule the plant uses for long-term energy storage, growth, and cellular respiration. Without the Calvin cycle, the plant cannot make sugar, so it cannot power its mitochondria or build new cells, therefore the plant will eventually die.
Compare a proto-oncogene and a tumor suppressor gene in terms of their normal role and what happens when each is mutated in a way that leads to cancer.
Proto-oncogene: normally promotes cell division in a controlled way. When mutated to an ONCOGENE, it becomes overactive and pushes cells to divide too much.
Tumor suppressor gene (ex: p53, RB): Normally slows the cell cycle, repairs DNA, or triggers apoptosis. When inactivated or lost, cells do not stop at checkpoint and can divide with DNA damage and avoid apoptosis.
A group of cells has the following characteristics: extremely high ribosome numbers, low levels of oxygen (yet they continue to divide), and signs of significant DNA damage (yet the division does not stop).
Using concepts from organelles, energy metabolism, and cell division/cancer biology, explain how all four observations fit together into one biological explanation.
High ribosome numbers = the cells are making proteins at a very high rate, which is typical of fast-dividing cells.
Low oxygen but continued division suggests the cells likely relying on glycolysis/fermentation instead of oxidative phsophorylation to get ATP quickly (a cancer-like trait)
DNA damage with no pause in division suggests checkpoint genes (like p53 or Rb) are likely mutated or nonfunctional, so damaged cells continue through the cycle.
Ultimately, these traits indicate a cancer like cell population.