human bio week2

Organelles in Cell Cytoplasm

Nucleus

• Control Center of the Cell: The nucleus is fundamental in regulating cellular activities. It houses the genetic material, or DNA, which determines the cell's function and characteristics.

• Nuclear Structure: Encased by a nuclear envelope, it separates the DNA from the cytoplasmic contents. Embedded within this membrane are nuclear pores that regulate the movement of substances in and out of the nucleus.

• Function in Genetic Processes: The nucleus plays a critical role in transcription—the process where DNA is transcribed into messenger RNA (mRNA).

Nucleolus

• Structure within the Nucleus: The nucleolus is situated inside the nucleus and is essential for producing ribosomal RNA (rRNA), which is necessary for protein synthesis during translation of mRNA into proteins.

Endoplasmic Reticulum (ER)

• Membranous Network: The endoplasmic reticulum is a complex network of membranes with an inner compartment known as the lumen.

• Types of Endoplasmic Reticulum:

  • Rough Endoplasmic Reticulum (Rough ER): Studded with ribosomes, it is the site where mRNA is translated into proteins, hence the rough appearance. Its primary function is protein synthesis.

  • Smooth Endoplasmic Reticulum (Smooth ER): Lacks ribosomes, it is involved in lipid synthesis, therefore presenting a smooth appearance under the microscope.

Ribosomes

• Protein Synthesis Machinery: Ribosomes are small structures made primarily of rRNA along with proteins. They exist in two locations:

  • Free Ribosomes: Float in the cytoplasm, synthesizing proteins that function within the cytosol.

  • Bound Ribosomes: Attached to the Rough ER, synthesizing proteins that are typically exported from the cell or sent to organelles.

• Structure of Ribosomes: Composed of two subunits—a large 50S ribosomal subunit and a small 30S ribosomal subunit that come together to form a functional ribosome.

Mitochondria

• Powerhouse of the Cell: Known for being the site of ATP production, mitochondria are essential for energy metabolism.

• Structural Features: Composed of an outer membrane and an inner membrane, which is highly folded into structures known as cristae. The energy generation process occurs across these folded membranes

• Function: Converts biochemical energy from nutrients into adenosine triphosphate (ATP), the energy currency of the cell.

Golgi Apparatus

• Packaging and Distribution Center: The Golgi apparatus resembles a post office, consisting of flattened membrane-bound sacs called cisternae.

• Structural Faces: The side facing the Rough ER is known as the cis face, and the side facing the plasma membrane is referred to as the trans face.

• Function: Processes, packages, and sorts proteins synthesized in the Rough ER. It prepares them for transport to other organelles or for secretion from the cell.

Lysosomes and Peroxisomes

• Recycling Centers: Both organelles are involved in the breakdown and recycling of cellular debris. Lysosomes contain enzymes that degrade waste material and old organelles, recycling usable components.

• Lysosomes: Engulf and digest debris through hydrolysis, breaking down materials into simpler molecules.

• Peroxisomes: Specialized in the oxidation of fatty acids, and breaking down hydrogen peroxide (a toxic byproduct) into water and oxygen, thereby detoxifying the cell.