Cell Structures, Microscope Identification, and Photosynthesis Pigments

What is the primary function of the nucleus in a cell?

The nucleus stores DNA and controls cell activities.

Why do mature human red blood cells lack a nucleus?

They eject their nucleus during development to make more room for hemoglobin.

What distinguishes skeletal muscle fibers in terms of nuclei?

Skeletal muscle fibers are multinucleated, with nuclei located at the edge of the fiber.

How is the nucleus of an adipocyte (fat cell) characterized?

The nucleus is flattened and pushed to the side by a large central fat vacuole.

What is a key feature of white blood cells that helps distinguish them from red blood cells?

White blood cells have a large, dark-staining, often lobed nucleus.

What structures are found in guard cells of leaf epidermis?

Guard cells contain a visible nucleus and chloroplasts.

What is typically the most visible feature in Spirogyra algae slides?

The spiral chloroplast is the most visible feature; a distinct nucleus is usually not visible.

What is the function of ribosomes in a cell?

Ribosomes carry out protein synthesis and can float freely or attach to the rough ER.

What is the role of the Golgi apparatus?

The Golgi apparatus modifies, sorts, packages, and ships proteins and lipids.

What is the primary function of mitochondria?

Mitochondria are the site of cellular respiration, converting glucose energy into ATP.

What is the function of chloroplasts?

Chloroplasts are the site of photosynthesis and contain chlorophyll.

What is the role of the central vacuole in plant cells?

The central vacuole stores water and nutrients and maintains turgor pressure.

What is the composition of a plant cell wall?

The plant cell wall is made of cellulose and provides support and protection.

What is the difference between prokaryotic and eukaryotic cells?

Eukaryotic cells have a true nucleus and membrane-bound organelles; prokaryotic cells do not.

What is the function of the plasma membrane?

The plasma membrane is a selectively permeable bilayer that controls what enters and exits the cell.

What is diffusion?

Diffusion is the movement of particles from an area of high concentration to an area of low concentration.

What is osmosis?

Osmosis is the diffusion of water across a selectively permeable membrane.

What happens to a cell in a hypotonic solution?

Water moves into the cell, causing it to swell and gain mass.

What is the function of lysosomes?

Lysosomes contain digestive enzymes that break down waste and worn-out organelles.

What is the role of the cytoskeleton?

The cytoskeleton provides shape, support, and enables movement within the cell.

What are centrioles and where are they found?

Centrioles organize spindle fibers during cell division and are found in animal cells.

What are the unique structures found in plant cells?

Unique structures in plant cells include the cell wall, chloroplasts, and large central vacuole.

What are the unique structures found in animal cells?

Unique structures in animal cells include centrioles and usually lysosomes.

What is the typical appearance of skeletal muscle under a microscope?

Skeletal muscle is identified by long, parallel fibers with visible striations.

How are adipocytes identified in a microscope slide?

Adipocytes appear as large, empty-looking round cells resembling bubble wrap.

What is the identifying feature of human blood cells under a microscope?

Human blood is identified by pale, donut-shaped red blood cells and larger, darker white blood cells.

What is the appearance of leaf epidermis under a microscope?

Leaf epidermis shows a single layer of irregular cells with small pores (stomata) and guard cells.

What are the drawing rules for labeling microscope slides?

Use pencil, draw clean lines, use a ruler for labels, and include a title and total magnification.

What is an isotonic solution?

A solution with the same solute concentration as the cell, resulting in no net change in mass.

What occurs in a hypertonic solution?

Water moves out of the cell, causing it to shrink and lose mass.

What is the memory rule for water movement?

Water always moves toward the side that has more solute.

What effect does a hypotonic solution have on plant cells?

It makes the cell turgid, pressing against the cell wall.

What is plasmolysis in plant cells?

It occurs when the plasma membrane pulls away from the cell wall due to water loss in a hypertonic solution.

What happens to animal cells in a hypotonic solution?

They can undergo lysis, where the cell takes in too much water and bursts.

What is crenation in animal cells?

It is the shriveling of the cell due to water loss in a hypertonic solution.

What are Orbeez?

Superabsorbent polymers (hydrogels) that act like a concentrated solute.

What is the isotonic point for Orbeez?

The concentration that produces zero percent change in mass.

How is percent change in mass calculated?

(final mass - initial mass) / initial mass x 100.

What does a line going up on a graph of percent change in mass indicate?

The object gained water, meaning it was hypertonic relative to the surrounding solution.

What does a flat line on a graph of percent change in mass indicate?

Isotonic condition — no net water movement.

What does a line going down on a graph of percent change in mass indicate?

The object lost water, meaning it was hypotonic relative to the surrounding solution.

What is an enzyme?

A protein that acts as a catalyst, speeding up chemical reactions without being used up.

How do enzymes lower the activation energy?

By providing an active site for substrates to bind and facilitating the reaction.

In the Toothpickase lab, what do your hands represent?

The enzyme, called 'toothpickase.'

What do paperclips represent in the Toothpickase lab?

A competitive inhibitor that blocks the active site.

What was the purpose of Part A in the Toothpickase lab?

To establish the normal, unobstructed reaction rate with no inhibitors.

What effect does icing the hands have in Part C of the lab?

It models a drop in temperature, slowing molecular motion and enzyme activity.

What does denaturation refer to in enzymes?

A permanent change in the enzyme's shape that destroys its function.

What is the expected ranking of reaction rates from fastest to slowest in the lab?

Part A (baseline) → Part B (competitive inhibitor) → Part C (cold temperature) → Part D (denatured).

What does a shorter time in the Toothpickase lab indicate?

A faster reaction rate and more active enzyme.

What does a longer time in the Toothpickase lab indicate?

A slower reaction rate and less active/more hindered enzyme.

What is the role of the active site in enzymes?

The active site is specific to certain substrates, allowing only compatible ones to bind.

What is a competitive inhibitor?

A substance that occupies the active site, preventing the substrate from binding.

What causes denaturation of an enzyme?

Denaturation is caused by high temperature or extreme pH, leading to loss of the enzyme's three-dimensional shape.

How does cooling affect enzyme activity?

Cooling slows enzyme activity without destroying its shape, unlike denaturation.

Describe the shape of a substrate concentration vs. rate graph for enzymes.

It rises and then plateaus, indicating saturation where all active sites are occupied.

What does a temperature vs. rate graph for enzymes look like?

It rises to an optimum temperature and then drops sharply due to denaturation.

What is the shape of a pH vs. rate graph for enzymes?

It is a bell curve peaking at the enzyme's optimum pH.

What is the purpose of paper chromatography in photosynthesis?

It is used to separate and identify pigments absorbed by plants.

How do pigments move in paper chromatography?

Pigments move at different rates due to varying solubility and attraction to the paper.

What happens to pigment colors in leaves during autumn?

Chlorophyll breaks down, revealing hidden pigments like yellow, orange, and red.

What materials are needed for a chromatography experiment?

Chromatography paper, a chamber, isopropyl alcohol, toothpicks, and a pencil.

What is the procedure for applying pigment samples in chromatography?

Make a concentrated dot with a toothpick on a pencil-drawn origin line, avoiding solid chunks.

Why must the origin line in chromatography be drawn in pencil?

Pen ink would dissolve in alcohol and ruin the results.

What does the solvent front indicate in chromatography?

It marks the highest point the solvent reached and must be recorded immediately.

How is the Rf value calculated?

Rf = distance traveled by pigment / distance traveled by solvent front.

What does a higher Rf value indicate about a pigment?

It indicates that the pigment is less polar and more soluble in the solvent.

What are the expected pigments in a spinach leaf?

Chlorophyll a, chlorophyll b, beta carotene, and lutein.

What pigment is responsible for red, purple, and pink coloration in fruits and vegetables?

Anthocyanin.

What distinguishes chlorophyll a from anthocyanin in chromatography?

Chlorophyll a is blue-green, while anthocyanin is blue-purple or pink.

What are accessory pigments and their function?

Accessory pigments like chlorophyll b, beta carotene, and lutein absorb additional light wavelengths and pass energy to chlorophyll a.

Why are Rf values important in chromatography?

They help identify unknown pigments based on their solubility and color under consistent conditions.

What is the significance of the solvent level in chromatography?

The solvent level must be below the origin line to ensure proper pigment dissolution into the moving solvent.

What does it mean if multiple pigment bands appear on one chromatography strip?

It indicates that the original sample was a mixture of several different pigments.

What is the effect of polarity on pigment movement in chromatography?

Less polar pigments travel farther, while more polar pigments travel shorter distances.