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 Double bounded. Which organelles are surrounded by two membranes?

Short answer

(a) 9, (b) 12, (c) 5, (d) 10, (e) 11, (f) 8, (g) 4, (h) 7, (i) 2, (j) 6, (k) 1, (l) 3. Double-bound: Mitochondrion, Chloroplast, Nucleus.

Step-by-step solution

Match Endoplasmic Reticulum

To match parts a, b, and c, let's start with understanding the functions: - (a) Endoplasmic reticulum: A network of membranous tubules within the cell. - Rough endoplasmic reticulum (b) has ribosomes on its surface; hence it matches with "5. Membrane with ribosomes attached." - Smooth endoplasmic reticulum (c) is involved in lipid synthesis and detoxification, matching with "12. Processes exogenous chemicals."

Identify Golgi Complex

The Golgi complex is responsible for modifying proteins and lipids and is primarily involved in adding carbohydrates to proteins, which matches with "10. Site of carbohydrate addition to proteins." Thus, (d) matches with 10.

Link Transport Vesicles

Transport vesicles are responsible for moving materials between organelles. They function by facilitating communication between the rough endoplasmic reticulum and the Golgi complex, which matches 11. Therefore, (e) matches with 11.

Assign Secretory Granules

Secretory granules are vesicles that carry molecules to the plasma membrane for secretion, thus matching with "8. Destined for fusion with the plasma membrane." Therefore, (f) matches with 8.

Determine Endosome Function

Endosomes are involved in the transport of molecules into the cell, which aligns with "4. Carries important biochemicals into the cell." Therefore, (g) matches with 4.

Connect Lysosome

Lysosomes contain digestive enzymes, necessary for breaking down cellular waste, which matches with "7. Contains digestive enzymes." Therefore, (h) matches with 7.

Explain Mitochondrion

Mitochondria are responsible for cellular respiration and energy production, which aligns with "2. Site of fuel oxidation." Therefore, (i) matches with 2.

Function of Chloroplast

Chloroplasts are the organelles where photosynthesis takes place, matching "6. Site of photosynthesis." Therefore, (j) matches with 6.

Identify Nucleus

The nucleus is the control center of the cell housing most of the cell's DNA, matching "1. Location of most of the cell's DNA." Therefore, (k) matches with 1.

Determine Plasma Membrane

The plasma membrane is the boundary of the cell, separating it from its environment, matching "3. Separates the inside of the cell from the outside." Therefore, (l) matches with 3.

Double Membrane Organelles

Organelles surrounded by a double membrane typically include the nucleus, mitochondrion, and chloroplast.

Key concepts

Endoplasmic Reticulum

The endoplasmic reticulum (ER) serve as vital facilities within the cell that process proteins and lipids. This network of membranous tubules extends throughout the cytoplasm. The ER comes in two forms: the rough ER and the smooth ER.

The rough endoplasmic reticulum (RER) is distinguished by the ribosomes studded on its surface, which give it a "rough" appearance under a microscope. These ribosomes are crucial for protein synthesis, making the RER instrumental in producing proteins to be packaged, processed, or secreted outside of the cell. Particularly, after synthesis, proteins may be modified in the RER before being sent to their next destination.

On the other hand, the smooth endoplasmic reticulum (SER) is devoid of ribosomes, providing a "smooth" texture. It plays a key role in lipid production and is involved in detoxification processes. This part of the ER helps process some biochemical substances, facilitating detoxification of exogenous chemicals that enter the body. Therefore, while both types of ER are essential for cellular function, they perform distinct tasks connected to their structural differences.

Golgi Complex

The Golgi complex acts as the cellular post office. It is responsible for modifying, sorting, and packaging proteins and lipids that are transported throughout the cell. This organelle consists of flattened membranous sacs known as cisternae.

One primary function of the Golgi complex is the addition of carbohydrates to proteins. This step is crucial for properly folding and functioning proteins. As proteins pass through different layers of the Golgi, they undergo modifications that make them suitable for their specific roles within or outside the cell.

In addition to its role in protein modification, the Golgi complex is also integral to the creation of lysosomes and certain transport vesicles, which are involved in moving molecules from one part of the cell to another. By packaging materials into vesicles, the Golgi ensures that they reach their destined location efficiently, playing a substantial role in maintaining proper cellular operations.

Lysosome

Lysosomes are the cell's digestive system, filled with enzymes that break down macromolecules, cellular debris, and even invading pathogens. These membrane-bound organelles are pivotal in recycling waste material within the cell.

The enzymes inside lysosomes are capable of degrading proteins, nucleic acids, carbohydrates, and lipids. This ability makes lysosomes essential for cellular homeostasis. By safely housing digestive enzymes, lysosomes prevent the rest of the cell from being damaged by these potent substances.

Additionally, lysosomes play a role in programmed cell death, or apoptosis, making them crucial for development and disease prevention. Dysfunction in lysosomal activity can lead to a range of diseases, highlighting their importance in cellular health.

Mitochondrion

Mitochondria are the powerhouse of the cell, primarily responsible for producing the energy currency of the cell, adenosine triphosphate (ATP), through cellular respiration. They are unique among cell organelles due to their double membrane structure; the inner membrane folds into projections called cristae, which increase the surface area for energy production.

In each mitochondrion, fuel molecules such as glucose undergo oxidation to extract energy, which is then used to produce ATP. This process occurs mostly in the inner membrane, where a variety of enzymes manage the electron transport chain and ATP synthesis.

Interestingly, mitochondria have their own DNA, separate from the cell's nuclear DNA, which suggests a unique evolutionary history. This separate DNA allows mitochondria to produce some of their own proteins independently. Due to their central role in energy production, dysfunctions in mitochondria are linked to numerous diseases and are standing subjects of medical research.