Cell Structure, Metabolism & Transport

Cell Structure, Metabolism & Transport

1. Cell Structure

   • Cell Membrane
     • surrounds cell and fills outer boundary
     • made up of a double layer of lipid molecules and proteins
   • Cytoplasm
     • thick fluid, fills inside of cell
   • Organelles
     • Golgi Body
       • stack of flattened channels; packages proteins for secretion from the cell
     • Mitochondria
       • 'powerhouses' of the cell
       • working organelles that keep the cell full of energy
     • Nucleus
       • large organelle, contains DNA
     • Lysosomes
       • break down materials that are taken into cell, break down worn-out organelles
     • Centrioles
       • located near nucleus, involved in cell division
     • Endoplasmic reticulum
       • forms channels through cytoplasm, used for storage, support, synthesis and transport within the cell
       • rough ER contains ribosomes attached to outside of membrane
     • Ribosomes
       • amino acids joined together at ribosomes to make proteins
   • Cytoskeleton
     • assists in cell movement, protein fibres

2. Structure of Cell Membrane

   • fluid mosaic model
   • phospholipid bilayer; main structure
     • contains hydrophilic and hydrophobic heads and tails
   • cholestrol and protein molecules embedded in phopholipid bilayer
   • channel proteins, pore that allows ions, water and small molecules to pass through

3. Types of Transport

   • Diffusion
     • passive, high conc -> low conc
     • substances: alcohol, steriods, fat-soluble substances, O2, CO2
     • results in random movement of particles
   • Osmosis
     • passive, diffusion of water, high conc -> low conc
     • important for living cells, results in osmotic pressure
   • Carrier- Mediated
     • carrier proteins bind to molecules for transport, proteins are specific
     • can become saturated -> max rate of transport
     • carrier proteins can be regulated by hormones
   • Facilitated-Diffusion
     • passive; still diffusion, high -> low conc
     • substances: glucose, amino acids
   • Active Transport
     • needs energy, happens against conc. gradient, low -> high conc
     • substances: glucose, certain ions, amino acids
   • Vesicular Transport
     • always active, needs energy as vesicles (memranous bags) need to be built
       • Endocytosis (into cell) -> cholestrol, iron ions
       • Pinocytosis (liquids) Phagocytosis (solids - cell debris, microrganisms)
       • Exocytosis (out of cell), contents of vesicles are pushed out through cell membrane
         • mucus, enzymes, breastmilk

4. Tissues

   • Epithilium
     • covers and lines organs/hollow organs, ducts
     • location: outer layer of skin, lining of stomach, covering of heart
   • Connective
     • provides support and helps hold all body parts together
     • location: bone, ligaments & tendons, fat storage, tissue, cartilage
     • non-cellular material - matrix, cells not close together
   • Muscular
     • responds to a stimulus by contracting, becoming shorter
     • skeletal (voluntary, striated), attaches to bones
       • involuntary (smooth, non-striated), iris, uterus, stomach, intestines, walls of blood vessels
   • Nervous
     • when part of a neuron is stimulated messages are carried along these projections
     • location: brain, spinal cord & nerves

5. Cell Metabolism

   • Anabolism - needs energy, e.g Protein synthesis
     • Catabolism - releases energy, e.g Cellular respiration
     • also known as Synthesis
   • Organic Compounds
     • Carbohydrates
       • main source of energy, contains C, H, O2
       • simple unit: Monosaccharides (glucose), Disachharides (lactose)
         • complex unit: Polysaccharides (starch, glycogen)
     • Proteins
       • enzymes and structural materials, brokendown for energy, contains C, H, O2, N - often P, S
       • simple unit: Amino acids (glycine, alanine), Peptides (dipeptide)
         • complex unit: all Enzymes, Proteins contain 100+ Amino acids
     • Lipids
       • store energy, phopholipid bilayer, steriods, contains C, H, O2
       • simple unit: Glycerol, Fatty acids
         • complex unit: Triglyceride
     • Nucleic Acids
       • RNA, DNA, large molecules, contains C,H, O2, N ,P, made of nucleotides
       • simple unit: RNA
         • complex unit: DNA
   • Cellular Respiration
     • glucose + oxygen -> carbon dioxide + water + energy
   • ATP/ADP
     • tranporter of energy, Adenosine Triphosphate, continually recycled
     • formed when energy releases, Adenosine Diphophate can be reused to store energy from Cellular Respiration
   • Anaerobic Respiration
     • respiration that does not require energy, allows cells to produce energy when no oxygen
     • glucose -> lactic acid + energy
   • Aerobic Respiration
     • glucose + oxygen -> carbon dioxide + water + energy
     • requires oxygen