Cell Theory and Cell Structure

• Cell Theory posits all living organisms consist of cells, cells are the basic structural/functional unit, and all cells originate from pre-existing cells via division.
• Cells represent the fundamental unit of life, serving as the building blocks of all living organisms.
• Cells are the smallest structures capable of performing all life processes.

Types of Cells

• Prokaryotic cells are simple cells lacking a nucleus, such as bacteria.
• Eukaryotic cells are more complex, containing a nucleus and organelles, such as plant and animal cells.

The organelles of a Animal cell

• The cell membrane is a selectively permeable barrier enclosing the cell.
• Cytoplasm is a gel-like substance suspending organelles.
• The nucleus houses DNA (genetic material).
• Ribosomes are the sites of protein synthesis.
• Mitochondria are responsible for energy production.
• The endoplasmic reticulum is involved in protein and lipid synthesis.
• The Golgi apparatus modifies and distributes proteins.
• Lysosomes are responsible for cellular digestion.
• The cytoskeleton provides structure and support.
• Centrioles participate in cell division.
• Peroxisomes break down fatty acids and detoxify chemicals.
• Vacuoles are storage compartments, smaller in animal cells.
• Animal cell membranes contain cholesterol, which is typically absent in plant cells.

The organelles of a Plant cell

• The cell wall is a rigid structure around the cell membrane, providing support and protection.
• The cell membrane is a selectively permeable barrier enclosing the cell.
• The nucleus houses DNA (genetic material).
• Chloroplasts are organelles responsible for photosynthesis.
• A large central vacuole serves as a storage compartment.
• Cytoplasm is a gel-like substance suspending organelles.
• Mitochondria are responsible for energy production.
• The endoplasmic reticulum, Golgi apparatus, and ribosomes are involved in protein synthesis and modification.
• Plant cells have unique features such as the cell wall, chloroplasts, and a large central vacuole that distinguish them from animal cells.

Cell Membrane Structure

• Cell membranes are composed of a phospholipid bilayer.
• Embedded proteins are found throughout the membrane.
• Animal cells contain cholesterol in their cell membranes.

Transport Mechanisms

• Passive transport includes diffusion, osmosis, and facilitated diffusion.
• Active transport requires energy (ATP).
• Endocytosis and exocytosis are mechanisms for moving large particles.

Principles of Membrane Transport

• Movement across membranes depends on the concentration gradient.
• Electrochemical gradients influence ion movement.
• Selective permeability controls which substances pass through.

Cellular Respiration

• Glycolysis breaks down glucose.
• The citric acid cycle (Krebs cycle) oxidizes molecules.
• The electron transport chain generates ATP.

Photosynthesis (in Plant Cells)

• Light-dependent reactions capture energy from sunlight.
• The Calvin cycle (light-independent reactions) uses captured energy to produce sugars.

ATP (Adenosine Triphosphate)

• ATP is the cell's energy currency.
• ATP synthesis and hydrolysis drive cellular processes.

Cell Cycle

• The cell cycle has two main phases: interphase and the mitotic (M) phase.

Interphase

• G1 (Gap 1) is for cell growth and preparation of DNA synthesis.
• S (Synthesis) is when DNA replication occurs.
• G2 (Gap 2) allows for further growth and preparation for mitosis.

Mitotic (M) Phase

• The M phase includes mitosis (nuclear division) and cytokinesis (cytoplasmic division).

Stages of Mitosis

• Prophase: Chromatin condenses, the nuclear envelope breaks down, and spindle fibers form.
• Metaphase: Chromosomes align at the metaphase plate.
• Anaphase: Sister chromatids separate and move to opposite poles.
• Telophase: Chromosomes decondense, and nuclear envelopes reform.

Cytokinesis

• Cytokinesis divides the cytoplasm, resulting in two separate daughter cells.

Regulation of the Cell Cycle

• Cell cycle checkpoints (G1, G2, and Metaphase) ensure proper progression.
• Cyclins and Cyclin-Dependent Kinases (CDKs) regulate progression through the cell cycle.
• Growth factors and inhibitors either stimulate or inhibit cell division.

Mitosis vs. Meiosis

• Mitosis produces genetically identical daughter cells.
• Meiosis produces genetically diverse gametes.

Cell Division Regulation

• Checkpoints monitor the cell cycle.
• Cyclins and cyclin-dependent kinases regulate cell cycle stages.
• Apoptosis is programmed cell death.