Cell Organelles and Immune System Overview

Cell Organelles

• Cell membrane surrounds the cell, made of phospholipids
• Cytoplasm is the jelly-like fluid inside the cell
• Ribosomes are small proteins that make proteins for the cell
• Nucleoid is the area where DNA gathers for prokaryotes only
• Nucleus contains the DNA in eukaryotes only
• Nucleolus is a dark area inside the nucleus where ribosomes are made
• Rough ER is connected to the nucleus and has ribosomes on its surface. It makes and processes proteins
• Smooth ER is connected to the rough ER but has no ribosomes. It makes lipids and detoxifies
• Golgi apparatus is a stack of membranes that receives, labels, and sends proteins from the rough ER.
• Mitochondria are organelles responsible for making ATP (energy) in eukaryotes
• Lysosomes are small spheres containing acids and digestive enzymes found in animal cells
• Cytoskeleton is a network of proteins that provide structure and support to cells, also acts as a transport system

Immune System

• Immune cells recognize foreign invaders by their antigens
• Innate immunity is a rapid and nonspecific response
• The first line of defense of innate immunity is the skin and mucous membranes
  • Skin has a low pH, high salt content, is dry, and has a natural microbiome
  • Mucous traps invaders
• The second line of defense of innate immunity includes:
  • Inflammation: redness, swelling, heat, and pain that prevent the spread of invaders
  • Fever: a systemic response that helps fight invaders
  • Phagocytes: macrophages and neutrophils that engulf bacteria and other foreign invaders
• Adaptive immunity is acquired after exposure to disease
• Antibodies are proteins that identify specific antigens on invaders
• T cells and B cells are specialized immune cells that produce antibodies and create immunity
  • B cells make antibodies
  • T cells target infected cells

Cell Membrane Study Guide

• The cell membrane is made of phospholipids, membrane proteins, carbohydrates, and cholesterol
• Phospholipids are fats with a polar, hydrophilic head and two nonpolar, hydrophobic tails. They form a bilayer with the heads facing the extracellular and intracellular spaces.
• Membrane proteins are responsible for the transport of materials in and out of the cell
• Carbohydrates act as signals on the membrane
• Cholesterol helps keep the membrane fluid
• The cell membrane is semi-permeable, meaning it allows some materials to pass through but not others.
• The fluid mosaic model says that the membrane proteins and phospholipids are constantly moving.

Diffusion, Osmosis, Active Transport

• Diffusion: The movement of particles from an area of high concentration to an area of low concentration.
• Osmosis: The movement of water across a semi-permeable membrane to balance the concentration of solutes
• Active Transport: Requires energy to move particles against their concentration gradient.
  • Using a protein: Transport proteins move specific materials in or out of the cell
  • Bulk Transport: Vesicles move larger molecules in or out of the cell
    • Endocytosis: Takes materials into the cell
    • Exocytosis: Releases materials out of the cell

Homeostasis

• The cell/body maintains a steady state for things like temperature, water content.
• Negative Feedback: A signal that causes the cell to counter something undesirable. Examples:
  • Temperature regulation: shivering when cold, sweating when hot
  • Blood glucose regulation: insulin and glucagon
  • Hormone regulation: testosterone and estrogen
• Positive Feedback: A signal that causes the body to continue an action or strengthen a stimulus. Examples:
  • Childbirth: the baby's pressure on the cervix triggers oxytocin release
  • Lactation: baby suckling triggers prolactin and oxytocin release
  • Fruit ripening: ethylene gas triggers ripening genes

The Nervous System

• The central nervous system consists of the brain and spinal cord
• The peripheral nervous system consists of all the nerves in the body.
• Neurons are brain cells that send signals. They are composed of:
  • Dendrites: receive signals
  • Axon: sends signals
  • Myelin sheaths: protect the axon and make signals travel faster
• Action potentials: are how neurons transmit signals. They are caused by the opening of voltage-gated sodium channels, creating a positive charge that propagates down the axon.
• Neurotransmitters: chemical messengers released from the end of an axon into the synapse. They bind to receptors on the next cell to continue the signal.

Endocrine System

• Works with the nervous system to send long-distance chemical signals
• Hormones: Long-distance signal molecules that travel through the bloodstream to target cells.
• Steroid (Lipid) Hormones: Can cross the cell membrane and bind to proteins inside the cell
• Non-Steroidal (Hydrophilic) Hormones: Cannot cross the membrane so they bind to membrane proteins, which trigger a signal cascade inside the cell.

Explore the essential components of cell organelles and their functions, as well as an introduction to the immune system. This quiz delves into the structures responsible for maintaining cell health and the body's defense mechanisms. Test your knowledge and understanding of these vital biological concepts.