Cell Structure

Plasma membrane: semi-permeable membrane that surrounds the cell, regulating what enters and leaves
Cytoplasm: jelly-like substance inside the cell where metabolic processes occur
Nucleus: control center of the cell where DNA is stored
Mitochondria: organelles responsible for generating energy for the cell through cellular respiration
Endoplasmic reticulum (ER): network of membranous tubules and cisternae involved in protein synthesis and transport
Ribosomes: small organelles found throughout the cytoplasm, responsible for protein synthesis
Lysosomes: membrane-bound sacs that contain digestive enzymes, responsible for breaking down and recycling cellular waste and foreign substances
Golgi apparatus: complex of flattened sacs and tubules that process and modify proteins and lipids synthesized by the ER

Phospholipid bilayer: main component of the cell membrane, composed of hydrophilic heads and hydrophobic tails
Selective permeability: ability of the cell membrane to allow certain substances to pass through while keeping others out
Passive transport: movement of molecules from high to low concentration without energy input (diffusion, osmosis, facilitated diffusion)
Active transport: movement of molecules from low to high concentration with energy input (pumps, transport proteins)

Cellular respiration: process by which cells generate energy from glucose, resulting in ATP production
Photosynthesis: process by which plants and some other organisms convert light energy into chemical energy
Cell division: process by which cells reproduce, resulting in daughter cells with identical genetic material
Mitosis: process of cell division that results in two daughter cells with identical genetic material
Meiosis: process of cell division that results in four daughter cells with unique genetic material (gametes)

Signal transduction pathways: series of molecular interactions that allow cells to respond to signals
Receptors: proteins on the surface of cells that bind to specific signaling molecules (ligands)
Second messengers: molecules that transmit signals from the receptor to the target molecule
Hormones: signaling molecules that are produced by endocrine glands and travel through the bloodstream to target cells

Plasma membrane acts as a semi-permeable barrier that controls the entry and exit of substances, maintaining homeostasis.
Cytoplasm provides a medium for biochemical reactions, facilitating metabolic processes crucial for cell survival.
Nucleus serves as the cell's control center, housing DNA that contains genetic information for organismal development and function.
Mitochondria are known as the powerhouses of the cell, generating adenosine triphosphate (ATP) through cellular respiration.
Endoplasmic reticulum (ER) is divided into rough (with ribosomes) and smooth (without ribosomes) regions, integral for protein synthesis and lipid transport.
Ribosomes are essential for translating mRNA into proteins, functioning either free in the cytoplasm or bound to the ER.
Lysosomes contain hydrolytic enzymes that digest cellular waste, foreign materials, and cellular debris, recycling essential components.
Golgi apparatus modifies, sorts, and packages proteins and lipids synthesized in the ER, preparing them for secretion or use within the cell.

The phospholipid bilayer forms the fundamental structure of the cell membrane, exhibiting hydrophilic heads that face outward and hydrophobic tails that face inward.
Selective permeability enables the cell membrane to regulate substances that enter or exit the cell, ensuring necessary nutrients are absorbed while waste products are expelled.
Passive transport processes like diffusion and osmosis allow substances to move along concentration gradients without energy expenditure.
Active transport mechanisms utilize energy (ATP) to move substances against their concentration gradients, facilitated by specific transport proteins or pumps.

Cellular respiration involves a multi-step metabolic pathway that converts glucose into ATP, essential for energy-requiring cellular functions.
Photosynthesis occurs primarily in chloroplasts of plant cells, transforming sunlight into chemical energy stored in glucose, vital for plant growth.
Cell division is critical for growth, repair, and reproduction, ensuring continuity of genetic information through daughter cells.
Mitosis is a type of cell division producing two genetically identical daughter cells, important for somatic growth and maintenance.
Meiosis reduces the chromosome number by half, creating four genetically diverse gametes, essential for sexual reproduction and genetic diversity.

Signal transduction pathways facilitate cellular responses to external stimuli through a series of molecular interactions initiated by receptor-ligand binding.
Receptors are specific proteins located on the cell surface that interact with signaling molecules, triggering internal cellular responses.
Second messengers amplify the signal transduced from receptors, linking the reception of the signal to the appropriate cellular response.
Hormones are specialized signaling molecules produced by endocrine glands; they circulate through the bloodstream to elicit responses in target cells, influencing various physiological processes.