Question

(a) Endoplasmic reticulum _______ (b) Smooth endoplasmic reticulum ________ (c) Rough endoplasmic reticulum ______ (d) Golgi complex _______ (e) Transport vesicles ______ (f) Secretory granules _____ (g) Endosome _____ (h) Lysosome ____ (i) Mitochondrion ____ (j) Chloroplast ______ (k) Nucleus _____ (l) Plasma membrane ____ 1\. Location of most of the cell's DNA 2\. Site of fuel oxidation 3\. Separates the inside of the cell from the outside 4\. Carries important biochemicals into the cell 5\. Membrane with ribosomes attached 6\. Site of photosynthesis 7\. Contains digestive enzymes 8\. Destined for fusion with the plasma membrane 9\. Common form of cytoplasmic membrane 10\. Site of carbohydrate addition to proteins 11\. Facilitate communication between the rough endoplasmic reticulum and the Golgi complex 12\. Processes exogenous chemicals What is an organelle?

Short answer

An organelle is a specialized structure within a cell that performs specific functions.

Step-by-step solution

Match Endoplasmic Reticulum

(a) Endoplasmic reticulum - 9. Common form of cytoplasmic membrane (b) Smooth endoplasmic reticulum - 12. Processes exogenous chemicals (c) Rough endoplasmic reticulum - 5. Membrane with ribosomes attached

Match Golgi Complex

(d) Golgi complex - 10. Site of carbohydrate addition to proteins

Match Vesicles and Granules

(e) Transport vesicles - 11. Facilitate communication between the rough endoplasmic reticulum and the Golgi complex (f) Secretory granules - 8. Destined for fusion with the plasma membrane

Match Other Organelles

(g) Endosome - 4. Carries important biochemicals into the cell (h) Lysosome - 7. Contains digestive enzymes (i) Mitochondrion - 2. Site of fuel oxidation (j) Chloroplast - 6. Site of photosynthesis (k) Nucleus - 1. Location of most of the cell's DNA (l) Plasma membrane - 3. Separates the inside of the cell from the outside

Define Organelle

An organelle is a specialized structure within a cell that performs a specific function, often enclosed by a membrane. Examples include the nucleus, mitochondria, and chloroplasts.

Key concepts

Endoplasmic Reticulum

The endoplasmic reticulum (ER) is a network of membranous tubules and sacs called cisternae. It plays a vital role in the synthesis, folding, modification, and transport of proteins. There are two types of ER, each with unique functions:

• Rough Endoplasmic Reticulum (RER): This type of ER has ribosomes attached to its surface, giving it a "rough" appearance under a microscope. It is primarily involved in the synthesis of proteins that are either secreted by the cell or embedded in the cell's plasma membrane.
• Smooth Endoplasmic Reticulum (SER): Lacking ribosomes, the SER is smooth in appearance and is responsible for lipid and carbohydrate synthesis, metabolism of lipids, and detoxification of drugs and poisons.

The ER assists in the smooth operation of the cell's internal communication channels by preparing proteins for transfer to the next organelle destination.

Golgi Complex

The Golgi complex, also known as the Golgi apparatus or Golgi body, functions as the cell's "post office." It modifies, sorts, and packages proteins and lipids that have been synthesized in the ER.

• Proteins the Golgi receives are often tagged with small carbohydrate molecules, a process known as glycosylation, which is crucial for proper cell signaling and protein stabilization.
• Once modifications are complete, the Golgi aparatus sends these proteins and lipids to their final destinations inside or outside of the cell in vesicles.

This organelle is essential for the processing and distribution of molecules, ensuring that functional proteins reach their target locations efficiently.

Mitochondrion

The mitochondrion is often referred to as the powerhouse of the cell. Its primary function is the production of adenosine triphosphate (ATP), the cell's main energy carrier, through a process called oxidative phosphorylation.

• This organelle has a unique double-membrane structure, with the inner membrane folded into cristae. These folds increase the surface area for ATP production.
• Mitochondria also play roles in regulating the cell metabolism, signaling, cellular differentiation, and cell death (apoptosis).

Interestingly, mitochondria have their own small circular DNA, similar to bacteria, suggesting an evolutionary past where these organelles were free-living organisms.

Chloroplast

Chloroplasts are specialized organelles found in plant cells and certain algae, where they conduct photosynthesis. They capture light energy from the sun and convert it into chemical energy stored in glucose and other carbohydrates.

• Chloroplasts contain chlorophyll, the green pigment responsible for the absorption of light, particularly in the blue and red wavelengths.
• Like mitochondria, chloroplasts have their own DNA and double membrane, implying a symbiotic origin.

This organelle helps sustain life on Earth by providing organic compounds and oxygen, playing a crucial role in the energy cycle of living organisms.

Nucleus

The nucleus serves as the control center of the cell, safeguarding the cell's genetic material. It houses the majority of the cell's DNA, which is organized into chromosomes.

• DNA in the nucleus contains instructions for building proteins and other critical functions essential for the cell's survival and replication.
• The nucleus is surrounded by a double membrane called the nuclear envelope, which protects the DNA while allowing communication with the rest of the cell via nuclear pores.

This organelle regulates everything from cell growth and reproduction to protein synthesis, emphasizing its critical role in maintaining cellular function and integrity.

Plasma Membrane

The plasma membrane, also known as the cell membrane, is a protective barrier that envelops the cell. It plays a pivotal role in maintaining the cell's homeostasis by regulating the movement of substances in and out of the cell.

• Composed of a lipid bilayer with embedded proteins, the plasma membrane is selectively permeable, allowing certain molecules to pass while barring others.
• This membrane aids in cell communication and signaling, as well as providing structural support.

By controlling the exchange of materials, the plasma membrane helps the cell maintain its proper environment, essential for its survival and function.

Lysosome

Lysosomes are small vesicles filled with digestive enzymes that break down macromolecules into their monomers, which can be reused by the cell. Often referred to as the cell's "waste disposal," lysosomes are involved in both the digestion of food particles and the removal of cellular debris.

• They play an essential role in autophagy, the process of clearing out damaged cell components, aiding in maintaining cell health.
• Lysosomes help protect the cell from invading pathogens by breaking down harmful bacteria and viruses.

This organelle's function ensures the cell's recycling system is efficient, allowing for the constant renewal and maintenance of cellular structures.