Cells 🧫

• Cell Membrane


  • Outer boundary of the cell
  • Controlling substance entry and exit
• Cytoplasm


  Thick fluid containing organelles and suspended structures
• Organelles


  Specialized structures in the cytoplasm performing specific functions
• Nucleus


  • Contains genetic material
  • Separated from cytoplasm by a nuclear membrane
• Organelles Overview


  • Mitochondria
  • Endoplasmic Reticulum
  • Ribosomes
  • Lysosomes
• Mitochondria


  • Powerhouses of the cell
  • Producing energy through respiration
• Endoplasmic Reticulum


  • Network of membranes
  • Aiding in chemical reactions
• Ribosomes


  • Sites for protein synthesis
  • Either free or attached to membranes
• Lysosomes


  • Contain enzymes for breaking down materials within the cell
• Cell Membrane


  Separates cell contents from the external environment
• Cytoplasm


  Jelly-like material containing organelles and suspended structures
• Cytosol


  Liquid part of cytoplasm, aiding in metabolic reactions and chemical flow
• Organelles


  Specialized structures within cells formed by internal membranes
• Nucleus


  Contains DNA, controls cell functions and protein production
• Nucleolus


  Composed mainly of RNA, suspended in nucleoplasm
• Ribosomes


  Sites for protein synthesis, crucial for cell function
• Endoplasmic Reticulum


  Aids in chemical reactions, with or without attached ribosomes
• Cells consist of various components like cilia, flagella, nucleus, mitochondria and microtubles.
• Cell functioning:

  • Cells require a stable environment for normal functioning
  • Homeostasis maintains constant cellular conditions like temperature and fluid concentration
  • Cells need oxygen and glucose for cellular respiration, producing carbon dioxide, water, and energy.
  • Different cells have varying requirements and produce different materials.
• Functions of the cell membrane:

  • Separates the cell cytoplasm from the extracellular fluid around the cell.
  • It regulates the passage of materials
  • It is sensitive to change
  • It helps support the cell.
• Connective tissue:

  • Provides support and connection
  • E.g., bone, cartilage, tendons, ligaments, fat storage, blood
  • Characteristics: spaced apart, separated by large amounts of liquid called matrix
• Epithelial tissue:

  • Provides secretion and protection
  • E.g., covers the inside of the heart, stomach, intestines, heart, kidneys, liver, intestine and lungs
  • Characteristics: Closely joined together, thin and flat/column shaped/cube-shaped
• Nervous tissue:

  • When part of a neuron is stimulated, messages can be carried along these projections from one part of the body to another.
  • E.g., the brain, spinal cord, and nerves
  • Characteristics- Made up of specialized nerve cells (neurons), neurons have long projections from the body of a cell
• Skeletal muscle:

  • Makes up the muscles that are attached to bones.
  • Voluntary muscle
• Cardiac muscle:

  • Makes up most of the heart
  • Contracts to stop blood
  • Involuntary muscle
• Simple diffusion

  • Diffusion is the spreading out of particles so they are evenly distributed over the space available
  • High concentration --> Low concentration
  • Passive process
  • Water, oxygen, CO2, alcohol, fatty acids, steroids; ions, lipids; soluble drugs
• Osmosis:

  • Osmosis can be considered to be the diffusion of water across a differentially permeable membrane.
  • High concentration --> low concentration
  • Passive process
  • transports water
• Facilitated diffusion:

  • High concentration --> low concentration
  • Passive process
  • Glucose, amino acids
  • Protein channels, carrier-meditated transport
• Active transport:

  • Low concentration --> High concentration
  • Active process
  • Certain ions, glucose, amino acids
  • Carrier meditated transport
• Endocytosis:

  • Into the cell
  • Active process
  • Micro-organisms and cell debris but only by certain specialized cells
• Exocytosis:

  • Out of the cell
  • Active transport
  • Secretions, such as mucus or digestive juice
• cells —> tissues —> organs —> systems
• Smooth muscle

  
• Cardiac muscle

  
• Skeletal muscle

  
• Muscular tissue

  • Skeletal - Voluntary
  • Smooth - Involuntary
  • Cardiac - Involuntary
• The size of cells is limited by the surface area required to supply the needs of the volume. As the cell gets larger, the surface-area-to-volume ratio decreases, and therefore larger organisms are made up of many cells rather than one large cell.
• Active process


  Needs energy
• Active process examples:

  • active transport
  • exocytosis
  • endocytosis
  • pinocytosis
  • phagocytosis
• Passive process example

  • Diffusion
  • Osmosis