unit 1 bio exam reicse

Cell Theory

• Cells are the smallest basic unit of life.
• All living things are made up of cells.
• All cells are made from pre-existing cells.

Organelles and Functions

• Nucleus: Houses the DNA in the cell, helps to control the cell processes. Control centre of the cell.
• Rough ER: Helps to make and send proteins off for the cell to use.
• Smooth ER: Production of steroids and hormones, as well as the synthesis of important lipids, like phospholipids and cholesterol.
• Lysosomes: Degrades waste material from within and outside the cell.
• Cytoskeleton: Keeps the cell's shape and helps maintain a strong structure for the cell.
• Mitochondria: Creates energy for the cell to use in all necessary processes. Site of cellular respiration.
• Chloroplast: Where photosynthesis takes place (found in plant cells). Site of photosynthesis.
• Ribosomes: Site of protein synthesis.
• Golgi Apparatus: Processes and transports proteins that can be used in other areas both outside and inside the cell.
• Cytoplasm: Jelly-like fluid found within the cell, where most chemical reactions take place.

Cell Membrane and Wall

• Cell Membrane: Helps with chemical signalling, recognises other cells, and keeps the inside environment of the cell stable.
• Cell Wall: Protects the cell from mechanical or osmotic stress, found on the outside of the cell.

Transport and Movement

• Endocytosis: Plasma membrane folds around and engulfs materials by an infolding of the plasma membrane.
• Exocytosis: A secretory vesicle fuses with the plasma membrane and expels waste from the cell into the extracellular space.
• Passive Transport: Moves along the concentration gradient, including osmosis and simple diffusion.

Cell Size and SA: V Ratio

• Cell size is limited due to the inability of very large cells to provide nutrients and water and remove wastes efficiently.
• Smaller cells have a larger SA: V ratio, allowing for faster diffusion and maintenance of internal environment.

Fluid Mosaic Model

• Phospholipid Bilayer: Created by two layers of phospholipids, which automatically rearrange themselves to avoid the fluids in the extra/intracellular space.
• Fatty Acid Tails: Hydrophobic tails turn away from the water on the outside and inside the cell.
• Phosphate Heads: Hydrophilic heads turn towards the water on the outside and inside the cell.
• Cholesterol: In between phospholipid tails, helps maintain fluidity and prevents freezing or overheating.

Prokaryotic vs Eukaryotic Cells

• Prokaryotic Cells: Lack membrane-bound organelles, have no nucleus (DNA is stored in the nucleoid), and are typically smaller.

• Eukaryotic Cells: Have membrane-bound organelles (such as the nucleus, mitochondria, chloroplast, Golgi apparatus, and Endoplasmic reticulum), and are typically larger.### Cell Biology

• All living organisms are made up of cells, which are the smallest organizational unit of life.

• Cells come from pre-existing cells.

Cell Size and Surface to Volume Ratio

• Cells are microscopic because their surface area to volume (SA:V) ratio is larger, allowing for faster diffusion.
• Diffusion is important for cells to maintain proper exchange of nutrients and waste.

Passive Transport

• Diffusion: the movement of molecules from a high concentration to a low concentration without the use of proteins or energy.
• Examples of molecules that use diffusion:
  • Oxygen and Carbon Dioxide molecules
• Osmosis: the movement of water molecules through a semipermeable membrane from a high concentration to a low concentration.
• Facilitated diffusion: the movement of molecules through a plasma membrane with the help of transport proteins (carrier and channel proteins).
• Examples of molecules that use facilitated diffusion:
  • Amino acids, ions (small polar molecules)

Active Transport

• The movement of molecules through a plasma membrane that uses energy to move against the concentration gradient.
• Examples of molecules that use active transport:
  • Ions, glucose, and amino acids
• Active transport requires energy because it transports molecules against their concentration gradient.

Cell Theory

• All cells are made up of cells
• Cells are the smallest organizational unit of life
• All cells come from pre-existing cells

Cell Cycle

• The cell cycle is the process of cell growth, replication, and division.
• The cell cycle consists of three main stages: interphase, mitosis, and cytokinesis.
• Interphase: the stage of cell growth and preparation for replication.
  • G1 (Gap 1): initial growth phase, where the cell grows to its full size.
  • S (Synthesis): the stage of DNA synthesis, where the DNA is replicated.
  • G2 (Gap 2): the stage of final preparation for cell division, where organelles are replicated.
• Mitosis: the stage of nucleus replication, consisting of four main phases:
  • Prophase: the stage of chromosome condensation and spindle fibre formation.
  • Metaphase: the stage of chromosome alignment at the equator.
  • Anaphase: the stage of chromosome separation.
  • Telophase: the stage of nuclear envelope reformation.
• Cytokinesis: the stage of cytoplasmic division and cell separation.

Cell Division

• Cell division is the process of cell replication and division.
• Reasons for cell division:
  • Cell growth and development
  • Tissue repair
  • Replacement of damaged cells
• Cell division can be affected by:
  • External factors: chemical and physical signals, cell-to-cell contact, and growth factors.
  • Internal factors: cyclins, kinases, and tumour suppressor genes.

Apoptosis

• Apoptosis is the process of programmed cell death.
• Reasons for apoptosis:
  • DNA damage or mutation
  • Infection with a virus
  • Overproduction of cells
  • Wrong or incomplete cell division
• Apoptosis is a controlled process that eliminates unwanted or abnormal cells during embryonic development and tissue homeostasis.

Cancer Cells

• Cancer cells form due to a mutation in the DNA that blocks death signal pathways.

• Cancer cells uncontrollably divide and can stop other cells from working properly.

• p53 is a tumour suppressor gene that helps to regulate cell division and apoptosis.

• Mutation can be caused by physical, chemical, biological, or environmental factors.### Apoptosis and Cell Cycle Regulation

• Apoptosis is a process of programmed cell death, and it's regulated by pro-apoptotic and anti-apoptotic genes.

• BCL-2 family genes (BCL-2, BCL-XL, MCL-1, BFL-1, BCL-W, BCL2L10) possess BH1-4 domains and maintain the outer mitochondrial membrane integrity.

• These genes are involved in controlling the cell cycle and inhibit the pro-apoptotic members.

Proto-Oncogenes and Oncogenes

• Proto-oncogenes are genes that stimulate cell division and promote survival and proliferation in normal cells.
• They code for proteins that act as growth factors, signaling molecules, or transcription factors.
• Mutated proto-oncogenes become oncogenes, which accelerate cell division and promote the growth of cancer cells.
• Oncogenes can cause cancer by stimulating cell division and accelerating cell growth.

Tumor Suppressor Genes

• Tumor suppressor genes (pro-apoptotic genes) code for proteins that inhibit cell division, detect and repair DNA mistakes, and stimulate apoptosis if the cell is irreparable.
• These genes act as brakes to slow down or stop cell division.
• Mutations in tumor suppressor genes can cause cancer by stopping them from inhibiting cell division.

Cell Cycle Regulation

• The cell cycle control system ensures that no abnormalities occur during the cell cycle.
• Checkpoints (M, G1, G2) ensure that the cell cycle pauses if there are any abnormalities.
• The p53 gene is a tumor suppressor gene that attempts to repair DNA damage or induce apoptosis if the damage is irreparable.

Stem Cells

• Stem cells are unspecialized cells that have no specific role or job within the body.
• Types of stem cells:
  • Totipotent: can differentiate into any cell in the body (e.g., Morula cells, 3 days after fertilization).
  • Pluripotent: can differentiate into many different types of cells, but not any type of cell (e.g., Embryonic stem cells, inner cell mass of blastocysts).
  • Multipotent: can differentiate into a limited number of cell types (e.g., Adult stem cells, Ectoderm, Mesoderm, Endoderm).
  • Oligopotent: can differentiate into a few cell types (e.g., Adult lymphoid or myeloid).
  • Unipotent: can differentiate into a specific type of cell (e.g., muscle stem cells).

Apoptosis Pathways

• Intrinsic pathway: DNA damage activates the intrinsic pathway, which involves the activation of ATM protein, p53, and BCL-2 family proteins.
• Extrinsic pathway: involves the activation of natural killer cells or cytotoxic T cells, which release Perforin and Granzyme, leading to the activation of Casp-8 and Casp-3.