真核與原核細胞的結構與功能：练习题

In a eukaryotic cell, a protein intended for secretion into the extracellular environment is synthesized. Which of the following represents the correct sequence of organelles and structures involved in the synthesis and transport of this protein?

Comparison of two specialized human cells reveals that Cell A has an extensive network of smooth endoplasmic reticulum (SER), while Cell B has a very high density of rough endoplasmic reticulum (RER) and a large Golgi apparatus. Which of the following is the most likely identity and function of these cells?

A microbiologist performs a Gram stain on a sample of unknown bacteria. After the final staining step with safranin, the cells appear pink under a light microscope. Which statement correctly describes the cell wall structure of these bacteria?

The maximum resolution of a standard light microscope is approximately \(200\text{ nm}\), while an electron microscope can achieve a resolution of less than \(1\text{ nm}\). Which statement best explains why electron microscopes have a significantly higher resolution?

Penicillin is an antibiotic that inhibits the enzymes responsible for cross-linking peptidoglycan chains. Why are Gram-negative bacteria generally more resistant to the effects of penicillin than Gram-positive bacteria?

State the specific function of the nucleolus within a eukaryotic nucleus and identify the primary biomolecule synthesized there.

An unknown cell is found to contain a peptidoglycan cell wall but no membrane-bound organelles. Contrast the structure and location of the genetic material in this cell with that found in a human cheek cell.

A micrograph of a plant cell shows a chloroplast that measures \(25\text{ mm}\) in length. If the actual length of the chloroplast is \(5\mu\text{m}\), calculate the magnification used for this image.

An electron micrograph shows a section of a hepatocyte. A mitochondrion in the image measures 35 mm in length. The magnification of the micrograph is \( \times 20,000 \).

(a) Calculate the actual length of the mitochondrion in micrometres (\( \text{μm} \)). Show your working.
(b) Explain why an electron microscope is required to view the internal ultrastructure of a mitochondrion, such as the cristae, whereas a light microscope is not sufficient.

Epithelial cells in the mammalian small intestine are highly specialized for the absorption of nutrients.

(a) Explain how the presence of microvilli and a high density of mitochondria relate to the function of these cells.
(b) These cells are organized into a tissue. Define the term tissue and explain how the structure of the plasma membrane (fluid mosaic model) facilitates the transport of polar glucose molecules into the cell against a concentration gradient.