Cell Biology Components

Cell Components

• Cytoplasm: site of metabolism of carbohydrates, amino acids, nucleotides, and fatty acid synthesis
• Cytosol: site of metabolism and protein synthesis (free ribosomes)

Endoplasmic Reticulum (ER)

• Rough ER: translation of mRNA into membrane-associated proteins or for secretion out of the cell
• Smooth ER: synthesis of lipids, Ca²⁺ storage, and steroid production
• Nascent protein: a protein as it is being formed by a ribosome before it folds into its active shape

Golgi Apparatus

• Modifies and packages proteins and lipids for delivery to other organelles within the cell or for secretion out of the cell
• Shaped stacks of cisternae with polarity, proteins move from the convex/cis (entry point) to concave/trans end of the stack and are modified as they move
• Vesicles leave from the concave/trans face of the Golgi body

Mitochondria

• Double-membraned organelles with a smooth outer and a folded inner lipid bilayer membrane
• Inner membrane forms folds called cristae, which boost the surface area for ATP production
• Matrix houses the Krebs cycle, mitochondrial DNA, ribosomes, and enzymes crucial for ATP generation through the Krebs cycle and oxidative phosphorylation

Ribosome

• Composed of two rRNA subunits (40s+60s for eukaryotes, 50s +30s for prokaryotes) that wrap around mRNA to begin translation and protein synthesis
• Site of protein synthesis (translation) within the cell

Lysosomes

• Membrane-bound organelles that contain acid hydrolases at pH 5
• Function: intracellular digestion

Peroxisomes

• Membrane-bound organelle that undergoes chemical detoxification and lipid metabolism

Proteosome

• Function: degradation of intracellular proteins

Endosome

• Function: sorting and delivery of lipid vesicles and their contents to and from the plasma membrane

Plasma Membrane

• Acts as a selective barrier, allowing only small, non-polar molecules to pass through passively
• Functions: controls what enters and exits the nucleus

Cell Types

• Prokaryote Cell: no nucleus, membrane-bound organelles, circular plasmid DNA, important for gene modification
• Eukaryotic Cell: has a nucleus, organelle-compartment of a cell with a specific function

Nucleus

• Contains DNA, nucleoproteins, and RNA
• Function: stores DNA and coordinates the cell's activities, such as growth, metabolism, protein synthesis, and cell division
• Heterochromatin: condensed, tightly packed DNA, appears dark, no active RNA synthesis
• Euchromatin: uncondensed DNA, appears light, has active RNA synthesis

Nucleolus

• Found within the nucleus
• Function: site of ribosomal RNA (rRNA) synthesis

Nuclear Envelope

• A double-layered membrane
• Contains nuclear pores, allowing macromolecules to pass through when entering or exiting the nucleus