Prokaryotic vs Eukaryotic Cells

• All organisms consist of cells.
• Cells are the fundamental units of life.
• Cells arise from pre-existing cells.

Prokaryotic vs Eukaryotic Cells

• Prokaryotic cells lack a nucleus, while eukaryotic cells possess one.
• Prokaryotic cells typically range around 1 µm in diameter.
• Eukaryotic cells typically range from 10 - 100 µm in diameter.
• Prokaryotic cells lack a cytoskeleton.
• Eukaryotic cells have a cytoskeleton
• Cytoplasmic organelles are absent in prokaryotic cells.
• Cytoplasmic organelles are present in eukaryotic cells.
• Prokaryotic cells have a DNA content of 1 × 10^6 to 5 × 10^6 base pairs.
• Eukaryotic cells have a DNA content of 1.5 x 10^7 to 5 × 10^9 base pairs.
• Prokaryotic cells contain a singular circular DNA molecule as their chromosome.
• Eukaryotic cells' chromosomes are multiple linear DNA molecules.
• Prokaryotic cells are single-celled organisms, e.g., bacteria.
• Eukaryotic cells are found in all animals, plants, and multicellular organisms.

Tissues and Organs

• Cells organize into tissues to perform specific functions.
• Examples of tissue include epithelial, connective, muscle, nervous, and adipose tissue.
• Basic tissues combine to create organs.
• Organs combine to form organ systems.
• Cells grouping together form tissues, multiple tissues form organs, and interacting organs form organ systems.
• Organ systems carry out all the life functions of the organism.

Cell Functions and Body Systems

• Cells provide the basis for various organ functions.
• These organ functions in turn support different body systems.
• Cells provide energy, structure, and propulsion.
• Cells facilitate pumping, ventilation, protection, purification, control, creation, construction, and repair.

Cells and Body Composition

• The human body comprises cells and water.
• There are approximately 37 trillion cells in the human body.
• Red blood cells (RBCs) are the most abundant type of cell.
• Females have approximately 55% water mass in their body.
• Males have approximately 60% water mass in their body.

Fluid Exchange and Surface Area

• Rate of metabolism relies on it's mass to volume ratio.
• Larger cells require more resources to sustain functions.
• The rate of material exchange depends on surface area (plasma membrane).
• A cell will die if its metabolic rate exceeds its material exchange rate.
• Volume increases faster than surface area as a cell grows, making the original state unsustainable.
• A high surface area to volume ratio enables a cell to function more efficiently.
• More membrane is available to serve each unit of volume that needs nutrients or produces waste.
• Shorter diffusion pathways enhance efficiency, reducing use time and energy through active transport.
• Concentration gradients are easier to generate.

Maximizing SA:Vol Ratio

• Cells divide as organisms grow.
• Cells compartmentalize to enable membranes to perform metabolic processes.
• Eukaryotic organelles have membranes.
• Some organs, like intestines, fold up to increase the SA:Vol ratio.
• Cells and tissues specialized for material/gas exchange increase their surface area for optimized transfer; examples of this appear in alveoli, root hairs and micro-villi.

The Cell as a Factory

• The cell is composed of a plasma membrane, cytoplasm, nucleus, and organelles.

Molecular Level

• Investigates the different components and processes occurring within a cell.
• "Genome" constitutes the DNA or RNA.
• "Transcriptome is the RNA.
• "Proteome" is the protein.
• "Metabolome" are the metabolites"

The Genome

• The first fully sequenced human genome was completed between 1990 and 2003.
• The first human sequencing costed $5 billion.
• DNA contains instructions for cell replication, growth, and differentiation.

The Proteome

• Each cell type expresses a unique set of proteins for specific functions.
• 60,000-80,000 proteins exist.
• Proteome= totality of proteins expressed within a cell, tissue, or organism at a certain time.
• The proteome composition varies among individuals.
• The proteome is determined by genome and environmental influences.
• Not all genes produce polypeptides, so the proteome is larger than the genome.
• Polypeptides and prosthetic groups interact.
• Amino acids can be modified.
• Polypeptides fold into various structures.

Control Center: Nucleus

• Nucleolus is the site of RNA transcription and ribosome biogenesis.
• The rough endoplasmic reticulum (rER) is responsible for ribosome and protein synthesis.
• The rER sends proteins produced by ribosomes on its surface to the Golgi apparatus.
• Proteins produced in the ER are usually for outside the cell.
• Smooth endoplasmic reticulum (sER) produces and stores lipids and steroid hormones.

Golgi Apparatus

• Located near the Endoplasmic Reticulum.
• The Golgi Apparatus processes and sorts proteins from the endoplasmic reticulum.
• They are then trafficked to correct destination.

80s Ribosomes

• Site of protein synthesis.
• Free ribosomes produce proteins inside the cell itself

Mitochondria

• The powerhouse of the cell, responsible for generating ATP (adenosine triphosphate).
• They replicate by binary fission and have their own maternal DNA.

Lysosome

• They act as waste disposals to breaks down food in vesicles and damaged organelles.

Cytoskeleton

• Provides structure, support, and transport within the cell.
• Network of filaments and tubules facilitates connections between cell parts.
• Offers cell support for structure and allows movement of items.

Learning Objectives

• Understanding the definition of cells as the basic unit of life.
• Understanding cell specialization in different organs.
• Describing how water regulates the intracellular and extracellular environment.
• Familiarizing the functions of the major cell components like the nucleus, endoplasmic reticulum, golgi apparatus, mitochondria, lysosome, and cytoskeleton.