Biology Chapter: Cell Functions and Structure

Cellular Basics

• Cells can sense, respond to their environment, transform matter and energy, and reproduce.
• Approximately 200 types of cells exist in the human body, each performing various functions while sharing fundamental characteristics.
• All cells possess a membrane that separates them from their surroundings and are composed of similar molecular structures.

Key Concepts in Biochemistry

• Understanding biochemical processes in a biological context involves these key themes:
  • Water
  • Biological membranes
  • Self-assembly
  • Molecular machines
  • Macromolecular crowding
  • Proteostasis
  • Signal transduction, including calcium ions as signals and their relationship with metabolism.

Water

• Water has a unique polar structure and interacts with a diverse range of substances, making it essential for biological functions.

Biological Membranes

• Membranes are thin, flexible, stable structures that serve as selective barriers.
• Composed of a phospholipid bilayer, they contain integral and peripheral membrane proteins.

Self-Assembly

• Living organisms consist of supramolecular structures formed through self-assembly processes.

Prokaryotic Cells

• Prokaryotes encompass bacteria and archaea, characterized by:
  • Common features: cell wall, plasma membranes, circular DNA, absence of membrane-bound organelles.

Prokaryotic Cell Wall

• The cell wall is a complex semi-rigid structure that provides support and protection, composed of peptidoglycan.
• The lipid outer membrane contains lipopolysaccharide, which acts as an endotoxin influencing symptoms in infections.
• Small molecules cross the outer membrane via porins.

Eukaryotic Cells Overview

• The plasma membrane consists of a lipid bilayer with various integral proteins embedded, offering mechanical strength and defining cell shape through a protein meshwork known as the membrane skeleton.

Endoplasmic Reticulum (ER)

• The ER consists of membranous tubules, vesicles, and flattened sacs containing the ER lumen.
• Rough ER is involved in protein synthesis, folding, and glycosylation, while Smooth ER focuses on lipid biosynthesis and calcium storage.
• ER stress occurs from the accumulation of misfolded polypeptides due to various environmental and genetic factors.

Lysosomes

• Lysosomes contain acid hydrolases, enzymes responsible for degrading cellular debris and participating in autophagy.

Nucleus

• The nucleus is the most prominent organelle, housing hereditary information and serving as the transcription site.
• Contains components like nucleoplasm, chromatin, nuclear matrix, nucleolus, and an envelope with nuclear pore complexes for molecular exchange.

Mitochondria

• Mitochondria serve as the site for aerobic metabolism and are the principal source of cellular energy.
• Composed of inner and outer membranes surrounding the matrix, they contain their own DNA and ribosomes.
• They form stable contact sites with the endoplasmic reticulum, known as mitochondria-associated membranes (MAMs).

Explore the fascinating world of cells in this quiz based on McKee and McKee's biology textbook. Learn about the similarities and variations among the approximately 200 types of cells present in the human body, including their functions and structural components. Test your understanding of cellular biology and the essential roles cells play in life.