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 Polymers. Differentiate between proteins and glycogen in regard to their polymeric structure.

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

Step-by-step solution

Endoplasmic Reticulum

The endoplasmic reticulum is divided into two types: smooth and rough. It serves as a common form of cytoplasmic membrane. Therefore, the corresponding item is: **9. Common form of cytoplasmic membrane.**

Smooth Endoplasmic Reticulum

The smooth endoplasmic reticulum (SER) lacks ribosomes and is the site where carbohydrate addition to proteins occurs. Additionally, it processes exogenous chemicals. Therefore, the corresponding item is: **12. Processes exogenous chemicals.**

Rough Endoplasmic Reticulum

The rough endoplasmic reticulum (RER) has ribosomes attached to its membrane, making it the site of protein synthesis. Therefore, the corresponding item is: **5. Membrane with ribosomes attached.**

Golgi Complex

The Golgi complex is where carbohydrate molecules are added to proteins, modifying them and preparing them for transport. Therefore, the corresponding item is: **10. Site of carbohydrate addition to proteins.**

Transport Vesicles

Transport vesicles are responsible for carrying important biochemicals within the cell, facilitating communication between the RER and the Golgi complex. Hence, the corresponding item is: **11. Facilitate communication between the rough endoplasmic reticulum and the Golgi complex.**

Secretory Granules

Secretory granules are destined for fusion with the plasma membrane to release their contents out of the cell. Therefore, the corresponding item is: **8. Destined for fusion with the plasma membrane.**

Endosome

Endosomes are involved in transporting and carrying important biochemicals into the cell through endocytosis. Therefore, the corresponding item is: **4. Carries important biochemicals into the cell.**

Lysosome

Lysosomes contain digestive enzymes that break down waste materials and cellular debris. Therefore, the corresponding item is: **7. Contains digestive enzymes.**

Mitochondrion

The mitochondrion is known as the powerhouse of the cell and is the site of fuel oxidation where energy is produced. Therefore, the corresponding item is: **2. Site of fuel oxidation.**

Chloroplast

Chloroplasts are involved in photosynthesis, converting light energy into chemical energy. Therefore, the corresponding item is: **6. Site of photosynthesis.**

Nucleus

The nucleus contains most of the cell's DNA and serves as the control center, regulating gene expression and cell division. Therefore, the corresponding item is: **1. Location of most of the cell's DNA.**

Plasma Membrane

The plasma membrane separates the inside of the cell from the outside, controlling the movement of substances in and out of the cell. Therefore, the corresponding item is: **3. Separates the inside of the cell from the outside.**

Key concepts

Endoplasmic Reticulum

The endoplasmic reticulum (ER) is a crucial cell organelle involved in multiple cellular processes. It can be thought of as the cellular factory or transport network. This organelle is divided into two types: the smooth endoplasmic reticulum (SER) and the rough endoplasmic reticulum (RER). Each type has distinct functions.

The SER is involved in synthesizing lipids, detoxifying certain chemicals, and storing ions, specifically calcium, which is crucial for cellular activities. On the other hand, the RER is studded with ribosomes on its surface, which gives it a 'rough' appearance. These ribosomes are the sites of protein synthesis, where amino acids are assembled into proteins.

• RER is often involved in modifying proteins after they're synthesized.
• SER assists in producing lipids and steroid hormones.

In essence, the endoplasmic reticulum serves as a multifunctional organelle that is integral to the production and transport of key biological molecules within the cell.

Nucleus

The nucleus is often referred to as the control center or the brain of the cell. It houses the cell's genetic material, DNA, which contains the instructions needed for the cell's growth, replication, and function. The DNA is organized into structures called chromosomes.

Within the nucleus, we find the nucleolus, which is important for producing ribosomes — the protein-making machinery of the cell. Ribosomes then exit the nucleus and are either free cytoplasmic structures or attached to the RER.

• It maintains the integrity of genes and controls the activities of the cell by regulating gene expression.
• The nuclear envelope, a double membrane, surrounds the nucleus, providing an additional layer of control and separation from the cytoplasm.

Overall, the nucleus plays a key role in storing information and directing various cellular activities necessary for life.

Mitochondrion

The mitochondrion is known as the powerhouse of the cell. This organelle is where cellular respiration takes place, a process that converts nutrients into energy in the form of adenosine triphosphate (ATP). ATP serves as a key energy currency that powers many types of cellular functions.

Mitochondria have a unique structure that includes two membranes – an outer membrane and a highly folded inner membrane. These folds, called cristae, increase the surface area to maximize energy production.

• Mitochondria contain their own DNA, which is separate from the nuclear DNA, suggesting a symbiotic origin.
• They play a critical role in energy metabolism, as well as apoptosis, a type of programmed cell death.

This dual membrane and autonomous DNA allow mitochondria to replicate independently and produce the energy necessary for cell survival.

Plasma Membrane

The plasma membrane acts as the gatekeeper of the cell by controlling which substances come in and out. It is a semi-permeable barrier, composed mainly of a double layer of phospholipids interspersed with proteins.

These proteins serve various functions, such as channels, receptors, and enzymes. They assist in signaling and transport across the membrane.

• The phospholipid bilayer is fundamental in maintaining the delicate balance between the external environment and the internal components of the cell.
• Embedded carbohydrates can serve as identifiers that help cells recognize each other and coordinate bodily processes.

The plasma membrane's role is crucial in maintaining homeostasis within the cell, allowing it to function properly in a constantly changing environment.