Cell Structure and Components

Cell Structure

• Plasma membrane: a thin, semi-permeable membrane that separates the cell from its environment
• Cytoplasm: a jelly-like substance inside the cell where metabolic processes take place
• Nucleus: the control center of the cell where DNA is stored
• Mitochondria: organelles responsible for generating energy for the cell through cellular respiration
• Endoplasmic reticulum (ER): a 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 containing digestive enzymes that break down and recycle cellular waste and foreign substances
• Golgi apparatus: a complex of flattened sacs and tubules involved in protein modification and packaging

Cell Types

• Prokaryotic cells: lack a true nucleus and are typically small and simple in structure (e.g. bacteria)
• Eukaryotic cells: have a true nucleus and are typically larger and more complex in structure (e.g. plants, animals, fungi)

Cell Functions

• Metabolism: the process of converting energy and nutrients into the components that make up living organisms
• Growth and development: the process of increasing in size and complexity
• Response to stimuli: the ability to react to changes in the environment
• Reproduction: the process of producing new cells or organisms
• Cell signaling: the process of communicating with other cells or organisms

Cell Division

• Mitosis: the process of cell division that results in two daughter cells with the same number of chromosomes as the parent cell
• Meiosis: the process of cell division that results in four daughter cells with half the number of chromosomes as the parent cell (occurs in gamete formation)

Cell Transport

• Passive transport: the movement of molecules from an area of high concentration to an area of low concentration without the use of energy (e.g. diffusion, osmosis)
• Active transport: the movement of molecules from an area of low concentration to an area of high concentration using energy (e.g. pumps, transport proteins)

Cell Structure

• The plasma membrane is a semi-permeable membrane that separates the cell from its environment and regulates what enters and leaves the cell.
• Cytoplasm is a jelly-like substance inside the cell where metabolic processes such as glycolysis, protein synthesis, and cell signaling occur.
• The nucleus is the control center of the cell, containing most of the cell's genetic material in the form of DNA.
• Mitochondria are organelles responsible for generating energy for the cell through cellular respiration, which involves the breakdown of glucose and other organic molecules.
• The endoplasmic reticulum (ER) is a network of membranous tubules and cisternae involved in protein synthesis, folding, and transport, and is also responsible for lipid synthesis and detoxification.
• Ribosomes are small organelles found throughout the cytoplasm, responsible for protein synthesis by translating messenger RNA (mRNA) into amino acid sequences.
• Lysosomes are membrane-bound sacs containing digestive enzymes that break down and recycle cellular waste and foreign substances, such as bacteria and viruses.
• The Golgi apparatus is a complex of flattened sacs and tubules involved in protein modification, sorting, and packaging, and is also responsible for the formation of lysosomes and secretion of hormones and enzymes.

Cell Types

• Prokaryotic cells lack a true nucleus and are typically small and simple in structure, with a single circular chromosome and a large surface-to-volume ratio.
• Eukaryotic cells have a true nucleus and are typically larger and more complex in structure, with linear chromosomes and membrane-bound organelles.

Cell Functions

• Metabolism involves the breakdown of nutrients to produce energy and the synthesis of new molecules, and is essential for maintaining cellular homeostasis.
• Growth and development involve the increase in cell size and number, and are regulated by hormonal signals and gene expression.
• Response to stimuli involves the ability to detect and respond to changes in the environment, such as light, temperature, and touch.
• Reproduction involves the production of new cells or organisms, and can occur through mitosis, meiosis, or binary fission.
• Cell signaling involves the communication between cells or organisms through signaling molecules, such as hormones and neurotransmitters.

Cell Division

• Mitosis is the process of cell division that results in two daughter cells with the same number of chromosomes as the parent cell, and is essential for growth and development.
• Meiosis is the process of cell division that results in four daughter cells with half the number of chromosomes as the parent cell, and occurs in gamete formation.

Cell Transport

• Passive transport involves the movement of molecules from an area of high concentration to an area of low concentration without the use of energy, and includes processes such as diffusion, osmosis, and facilitated diffusion.
• Active transport involves the movement of molecules from an area of low concentration to an area of high concentration using energy, and includes processes such as pumps, transport proteins, and ion channels.

Endoplasmic Reticulum (ER)

Structure

• A network of membranous tubules and cisternae (flattened sacs) found in the cytoplasm of eukaryotic cells
• Consists of two types: Rough ER (RER) and Smooth ER (SER)

Functions

• Protein Synthesis and Transport
  • RER: Ribosomes attached to the ER membrane synthesize proteins, which are then inserted into the ER lumen for transport
  • Proteins are modified and folded in the ER before being transported to other organelles or secreted outside the cell
• Lipid Synthesis
  • SER: involved in the synthesis of lipids, such as cholesterol and phospholipids
  • Also involved in the breakdown of lipids
• Detoxification
  • SER: contains enzymes that help detoxify the cell by breaking down toxins and drugs
• Calcium Storage
  • ER is involved in the regulation of calcium levels within the cell

Types of Endoplasmic Reticulum

• Rough Endoplasmic Reticulum (RER)
  • Has ribosomes attached to the surface
  • Involved in protein synthesis and transport
• Smooth Endoplasmic Reticulum (SER)
  • Lacks ribosomes
  • Involved in lipid synthesis and detoxification