Cell Physiology: Biomolecules & Water

• Topic 1 is called Foundation of Cell Physiology and Function

Biomolecules and their Function

• In living organisms, the three most common elements are carbon (C), oxygen (O), and hydrogen (H)
• These three elements compose all biomolecules
• Biomolecules include water, carbohydrates, proteins, lipids, and nucleic acids

Water

• Water molecules have a V-shaped structure
• The general rule is "like dissolves like"
• Polar substances dissolve well in polar solvents
• Non-polar substances dissolve well in non-polar solvents
• Water is considered a polar solvent
• Water solid (ice) is less dense than water liquid
• Water requires a lot of energy to change one degree
• Water is transparent

Carbohydrates

• Carbohydrates contain carbon, hydrogen, and oxygen
• Sugars are small molecules, sweet, soluble in water, crystalline, and end with -OSE (e.g., glucose)
• Polysaccharides are macromolecules, not sweet, insoluble, or only slightly soluble, non-crystalline, and include starch

Proteins

• Proteins are of primary importance to the life of cells

Nucleic Acids

• By dry weight, proteins are the major components of an actively growing cell
• Proteins are constructed of amino acid monomers
• There are 20 amino acids in humans
• A number and sequence of amino acids determine the protein and results in a precise and specific shape
• Virtually all enzymes are proteins
• Structural proteins include collagen and elastin in connective tissue
• Keratin can be found skin, hair, and nails
• Contractile proteins include actin and myosin in muscles, which allow contraction and movement
• Hormones may have a protein structure (e.g., insulin, glucagon, growth hormone)
• Hemoglobin facilitates oxygen transport
• Albumin in the blood transports fatty acids
• Carrier and channel proteins in the cell membrane regulate movement across it
• Immunoglobulins (antibodies) protect the body
• Fibrinogen in the blood is vital for clotting
• Enzymes are proteins with a specific shape and catalyze reactions
• One enzyme will react with molecules of one substrate
• Enzymes are biological catalysts that increase the rate of a reaction
• There are about 40,000 different enzymes in human cells
• Lipids are water-insoluble organic substances that are readily soluble in organic solutions.
• In essence is anything that dissolves in fat
• Lipids are non-polar therefore insoluble in water
• They serve as a high-energy store which contains a high proportion of hydrogen
• Fat conducts heat very slowly.
• Lipids provide electrical insulation.
• Lipids are waxy allowing for waterproofing
• Hormones in lipids allow for hormone production
• Lipids allow for buoyancy

Nucleic Acids

• Nucleic acids are biopolymers essential for all known forms of life
• Nucleic acids include DNA and RNA made from monomers known as nucleotides
• DNA carries genetic information for the development and functioning of organisms to produce proteins

The Cell

• It is the basic unit of structure and function and the smallest component that can have the properties of life.
• Cells can grow and function if placed in a Petri dish under the right conditions, such as bacteria like Eschericia coli
• A single cell has molecules that transforms matter/energy, and allows growth/reproduction
• The cell contains a membrane known as the cell membrane
• The first requirement is information to make cellular components with the instructions for producing found in DNA
• The cell requires energy in the form of ATP
• The cell divides into exact replicas of itself.
• All living things are made of one or more cells

Cell Theory

• Each cell is a basic living unit
• A new cell arises only from other cells
• All plants and animal cells are eukaryotic, where the DNA is contained within a nucleus.
• A single-celled (unicellular) organisms like amoebas
• Multicellular organisms are made up of many cells and cells are the fundamental units of life
• Cell diameters are typically in the range of 1-100 μm

Surface area to Volume ratio

• The main factor of cell size is the amount of substances it can take from its outside environment and the waste products it can release
• The amount of chemical activity cell carries out determines the size of its volume
• Surface area and volume is a considered a ratio
• Most body cells adapted to increase its surface area to volume ratio.
• Exchange is limited by the distance from the center of the cell and its surface area
• Genetic material (DNA), cytoplasm, ribosomes and a plasma membrane are features that all cells have in common
• Cytoplasm is a semifluid matrix containing organelles
• Ribosomes synthesise proteins
• Compartmentalisation is important so eukaryotic cells specialise, forming the organs and tissues.
• Biochemically distinct organelles can thrive in compartimentalised sections

Organelles

• A specialized subunit within a cell has a specific function and is separately enclosed.
• Organelles such as ribosomes, centrioles and the cytoskeleton that all have a separate membrane
• A smaller cell molecule meet more effectively when there are no compartments
• Organelles with membranes include: nucleus, endoplasmic reticulum, golgi apparatus, lysosomes, mitochondria, chloroplasts, peroxisomes, vacuoles
• Organelles without membranes include: ribosomes, centrioles, cytoskeleton

Nucleus

• It is the largest organelle
• Controls the activities as it contains the DNA
• Found in all eukaryotic cells except mature red blood cells
• Surrounded by a nuclear envelope that allows communication between the nucleus and cytoplasm
• The nucleolus covers 25% of the volume in the nucleus
• Made by the union of subunits to form ribosomes.
• Plays an important role in the synthesis of proteins in eukaryotic cells
• Rich in RNA
• Chromatin are mainly coils of DNA bound and histones (proteins) and condenses into coiled threads called chromosomes.
• A membrane of a rough endoplasmic reticulum with ribosomes surrounds the nucleus.

Endoplasmic Reticulum (ER)

• Lined with ribosomes (Rough ER)
• No ribosomes (Smooth ER)
• Rough ER transports proteins made by ribosomes found on its surface.
• The proteins enter the ER via a channel and moves through the cisternae where it can be modified as it moves
• Small transmembrane, soluble and large proteins can be secreted to the Golgi Apparatus from the ER
• It is made up of tubular cavities which occupies smaller area.
• Smooth ER Makes lipids from fatty acids, glycerol absorbed from the gut and passes them to the Golgi apparatus for export.
• Smooth ER can makes steroids a type of lipid) - hormones such as testosterone and aids the hydrolysis of glycogen

Golgi Apparatus

• it is made of Golgi vesicles and cisternae and aids the transfer of secretions, proteins amongst other things.
• Proteins from the ER are modified and then secreted as vesicles or lysosomes to outer body.

Lysosomes

• Contains digestive enzymes, proteases. nucleases, and lipesases
• These enzymes breakdown molecules by hydrolysis best in acidic conditions

Mitochondria

• Is is also nicknamed as the powerhouse of the cell due to the forming of ATP
• ATP is the energy currency that drives most reactions in the cells

Peroxisome

• These are spherical organelles that contain single membranes-containing catalase which break down the enzyme hydorgen perioxide

Vacuoles

• A vacuole is a fluid-filled sac bounded by a single membrane.
• It can help sequester waste products or allow digestion of food particles using food vacuoles

Ribosome

• This is the site of protein synthesis
• Made of two subunits being larger and smaller subunits
• Located bound to close to nucleus, cytoplasm and in mitochondria

Cytoskeleton

• Its transports organelles using filaments, maintains its shape, provdes strength, chromosome seperaration in mitosis and meiosis

Cell Membrane

• Membranes are composed of a phospholipid bilayer with proteins floating around inside it. Parts of the membranes that are not directly cell components, can freely move through, therefore making it 'fluid'.
• Cell receptors: Activate or Deactivate Transport Proteins
• Channel Proteins and Carrier Proteins
• Cholesterol: increases membrane stability, the elasticity
• Cell Membrane Functions selectively permeable membrane/barrier, structural, communication, site of reactions, mobility
• Intracellular fluid – fluid inside the cell, i.e. the cytoplasm
• The main fluids include interstitial fluid, blood plasma and transcellular
• There is transport across cell membranes due to need to provide nutrients, excrete substances/toxic metabolites
• Transport across cell membranes: Macro-transfer, moving large proteins in the process of endocytosis and exoytosis
• The transferal of smaller molecules where membranes act as osmotic and transport carriers
• Endocytosis' is an active transport mechanism, allowing large molecules to move parts of the cell

Exocytosis

• Material can be expelled from fluid surrounding.
• Transport-Osmosis is a diffusion across a permeable membrane where water travels for high to low conceration

Transport of diffusion

• Diffusion acts under concentration of gradients, reaching a equilibrium
• Allows for cell transport of: steroids, hormones, oxygen, carbon, ethanol.
• The main factors that allow for cell rate is size of diffusing cell, pores present within cell, concentration and temperature gradiants, thickness and surface area

Facilitated Diffusion

• Polar and charged molecules that need intrinsic molecules called ligands
• Facilitated diffusion is the act of using carriers to transport molecules
• Ligands will only allow certain molecules that saturate on them therefore any larger concerations does not increase transport rate.

Active transport

• Moves substances against concentration gradients and involves energy and a carrier.
• It is highly specific and demonstrates full saturation, allowing full ocupation in points.
• Active transport includes protein synthesis, muscle contraction,amino acids in the gut, absorption of mineral salts by plant roots

Exploring cell physiology with a focus on biomolecules and water. Covers the composition and function of carbohydrates and the unique properties of water. Water's structure, polarity, and role as a solvent are examined.