Problem 13 - Biology Concepts and Applications

Question

No animal cell has a _____ . a. plasma membrane b. flagellum c. lysosome d. cell wall

Step-by-Step Solution

Answer

d. cell wall

Step 1: Identify the Structure Unique to Plants

Review what structures are unique to plant cells but not present in animal cells. Plant cells have a rigid structure called a cell wall, which provides support and shape to the cell.

Step 2: Analyze Each Option

Go through each of the given options to determine if it is present in animal cells: - a. Plasma membrane: All animal cells have a plasma membrane. - b. Flagellum: Some animal cells, like sperm cells, can have a flagellum. - c. Lysosome: Animal cells have lysosomes, which help in digestion of cellular waste. - d. Cell wall: This structure is not found in animal cells; it is a feature of plant cells and some fungi and bacteria.

Step 3: Conclusion

Based on the analysis of the options, determine that the structure not present in animal cells is a cell wall. This feature is indeed unique to plant cells, making option d the correct choice.

Key Concepts

Cell Wall

Animal cells do not have cell walls. Instead, this characteristic is unique to plant cells and some fungi and bacteria. Cell walls are the rigid, outermost layer that surrounds the cell membrane of these organisms. They are made primarily of cellulose in plants, providing the structure necessary for growth and stability. This wall supports the plant's upright position and protects cells from mechanical stress.

In contrast, animal cells rely on the extracellular matrix and cytoskeleton for structural support. The absence of a cell wall allows animal cells to take on a variety of shapes and to engage in more dynamic interactions with their environment. Unlike the more fixed shape of plant cells, animal cells often change shape as they move or grow.

Plasma Membrane

All animal cells have a plasma membrane, also known as the cell membrane. This is a flexible, semipermeable barrier that surrounds the cell's cytoplasm. Made up mainly of a lipid bilayer with embedded proteins, it plays a crucial role in protecting the cell and maintaining homeostasis.

One of the main functions of the plasma membrane is to regulate what enters and exits the cell, maintaining an optimal internal environment by allowing selective passage of ions and molecules.

• This selective permeability ensures essential nutrients enter while waste products are expelled.
• It also keeps harmful substances out, safeguarding the cell's interior.

Additionally, the plasma membrane facilitates communication with other cells through receptor proteins that bind to specific molecules, initiating cellular responses and signaling pathways.

Lysosome

Lysosomes are vital organelles found in animal cells. They are small vesicles filled with digestive enzymes that break down waste materials and cellular debris. When a cell engulfs food or pathogens, lysosomes merge with the vesicles containing these materials, allowing enzymes to digest them effectively.

A critical role of lysosomes is to recycle old or damaged cell components. This recycling process ensures that cells can maintain balance and adapt to their changing environment. Without lysosomes, waste products could accumulate, hindering cell function and leading to cellular damage.

Lysosomes are particularly abundant in animal cells due to their important role in upholding cellular cleanliness and efficiency. They are often referred to as the "garbage disposal" of the cell, highlighting their crucial function in maintaining cellular health and preventing waste buildup.