bio

• personal error = includes mistake or miscalculations
• random errors = affect the precision of measurement
• systematic errors = affect the accuracy of measurement, and cause readings to differ from the true value by a consistent amount each time a measurement is made.
• Organisms = for something to be considered alive it must meet ALL of the following criteria: MRS GREEN

  1. Movement
  2. Respiration
  3. Sensitivity (to stimuli)
  4. Growth
  5. Reproduction
  6. Equilibrium (homeostasis)
  7. Excretion
  8. Nutrition
• Viruses:

  • is not a living thing
  • an infectious agent that can only replicate with a host organism
  • can infect a variety of living organisms, including bacteria, plants and animals
  • can only be seen with a microscope
• Cell theory:

  • all living things are made up of cells
  • cells are the smallest and most basic unit of life
  • all cells come from pre-existing cells
• Prokaryotic cells:

  • minimal defined internal structure
  • no membrane-bound organelles
  • lack a defined structure (nucleus) to house DNA
  • form unicellular organisms e.g kingdom Bacteria and Archaea
• Eukaryotic cells:

  • more complex structure
  • contain many different membrane-bound structures (organelles)
  • contain a nuclear envelope
  • some are unicellular organisms
  • some are from multicellular organisms
  • organelles are held in place by a network of fine protein filaments and microtubules within the cell (cytoskeleton)
• Unicellular and Multicellular organisms:

  • cell = most basic unit of life
  • tissue = a group or collection of cells in an organism that has similar structure and function
  • organ = a grouping of tissues into district structure, (such as a heart or kidney in animals or a leaf or stamen in plants), that perform a specialist job.
  • system = a group of organs that work together to carry out a particular task
• Biomolecules include:

  • proteins
  • carbs
  • lipids
  • nucleic acid
• Polymers and monomers:

  • biomolecules are polymers
  • polymer's are large organic molecules composed of many smaller repeating units (monomers) joined together in a long linear chain
  • monomer = single unit of a polymer
• Carbohydrates (made up of CHO):

  • carbs are polymers
  • the monomers of carbs are monosaccharides
  • carbs are an important source of energy
  • glucose + frutcose = sucrose
• Nucleic acids (made up of CHONP):

  • main information-carrying molecule in the cell
  • two main classes = DNA and RNA
  • made up of nucleotides (monomers) which contain a nitrogenous base, a phosphate and a sugar (ribose - RNA, Deoxyribose - DNA)

  
• Lipids (made up of CHO):

  • lipids are not true polymers
  • lipids are insoluble in water
  • made from fatty acids and glycerol
  • make up membranes in the cell like the cell membrane
  • some human hormones are made of lipids e.g sex cells
• Proteins (made up of CHONS):

  • proteins (polypeptides) are chains formed from the joining of monomers called amino acids
  • the joining of amino acids to form proteins, occurs in the ribosomes
  • each protein has its own specific sequence/chain of amino acids and the protein has a unique function
  • some functions of proteins: enzymes to speed up reactions, antibodies in the immune response, assist with transport across cell membranes, and carry oxygen in red blood cells.
• Water:

  • water is the most abundant compound in organisms
  • water molecule are highly cohesive (attracted to each other) and adhesive (attracted to other things)
  • water acts as a solvent, substances that dissolve in a solvent or called a solute
  • water is found in the blood, tissue fluid and lymph outside the cells
  • inside a cell, water is found in the cytosol and organelles.
• Nucleus:

  • control centre of the cell
  • enclosed in a nuclear membrane made of phospholipid and protein - the nuclear envelope
  • pores are present in the eukaryotic nucleus
  • contains the genetic material of the cell (DNA)
  • DNA found in chromosomes
  • The nucleus contains a nucleolus - responsible for producing and assembling the cell's ribosomes.
• Ribosomes:

  • NOT enclosed in a membrane
  • made from protein and ribosomal RNA (rRNA)
  • function is protein production
  • found in cytosol as well as attached to the endoplasmic reticulum (ER)
  • ribosomes are found in both prokaryotes and eukaryotes
• Endoplasmic reticulum:

  • channels formed by membranes
  • used to transport material within cells
  • ROUGH ER had ribosomes attached and proteins produced are transported have to be exported out of the cell
  • SMOOTH ER does not have ribosomes attached, lipids are produced in the smooth ER
• Golgi complex (AKA Golgi apparatus/Golgi body)

  • membrane-bound structure
  • stores and packages material for export of cells
  • creates vesicles for exocytosis
• Vesicles:

  • membrane-bound structure
  • transport proteins around the cell or to the outside of the cell
• Lysosome:

  • small sac-like organelles
  • found in animal cells
  • surrounded by a membrane
  • filled with fluid containing enzymes to break and digest substances
  • destroys unwanted or damaged cell parts
  • important for Apoptosis - programmed cell death
• Vacuole:

  • larger in plant cells
  • stores water and provides physical support (turgor)
  • movement of substances in and out is controlled by vacuole membrane
  • stores waste e.g salt, toxic substances, etc
• Mitochondria:

  • source of energy for the cell by producing adenosine triphosphate (ATP)
  • enclosed in a double membrane
  • The inner membrane is highly folded called cristae
  • ATP is produced during cellular respiration, which occurs within these folds
  • has its own DNA and ribosomes
  • breaks down monosaccharides to carbon dioxide and water to release energy
  • Glucose + Oxygen -> Carbon dioxide + Water + Energy
  • C6H12O6 + 6O2 -> 6CO2 + 6H20 + Energy
• Chloroplast:

  • contains the green pigment chlorophyll
  • traps sunlight to create glucose
  • where the process of photosynthesis takes place
  • found in plant and algae cells
  • have their own DNA and ribosomes
• Photosynthesis:

  • produces glucose, the substance that is used to provide energy in nearly all living organisms
  • in the chloroplast, carbon dioxide and water in the presence of light, are combined in a series of chemical reactions to form glucose
  • other products are water and oxygen
  • glucose that is not instantly used by cells can be stored as starch for later use
• Endosymbiotic theory:

  • larger cells have engulfed smaller cells to create current-day mitochondria and chloroplasts
• SA: V:

  • The SA: V ratio is obtained by dividing the area of an object by its volume.
  • For a cell, it is the comparison of the amount of SA available for absorption and secretion of substances, compared to the V of the cell
  • area refers to the coverage of a surface (for a cell it's the cell membrane)
  • volume refers to the amount of space taken up by an object (cytoplasm)
• Size of cells:

  • cells are small so the exchange of materials like oxygen and glucose, between the cell and the environment, through the cell membrane can be exchanged efficiently and quickly
  • when cells are small they have an efficient SA: V ratio and thus exchange is faster
  • the amount of SA (cell membrane) available for the exchange of materials is high compared to the volume of the cell (the cytoplasm)
  • as a cell gets larger, the SA: V ratio decreases and the less efficient the cell becomes at exchanging substances with the environment.
• Size of cell:

  • big cells, such as white blood cells, often grow more nuclei so that they can supply enough proteins and RNA for the cell's requirements
  • big cells with a reduced SA: V ratio can divide to form two smaller cells with increased SA:V ratio
• Shape of cells:

  • the variety of cell shapes seen in prokaryotic and eukaryotic cells reflect the job/function that each cell performs
  • a cell that is smaller and thinner will be able to absorb or secrete substances more efficiently than a cell that is larger and wider
  • this concept is concerned with the speed of exchange of substances not the amount of exchange
• Red blood cells lose their nucleus when becoming mature, to maximise space for oxygen-carrying hemoglobin.
• Cell membrane:

  • all cells exist in a watery environment so a barrier around the cell is needed to separate the inside and outside.
  • the environment of living cells is called the extracellular fluid
  • the cell membrane is the barrier of the cell
• Membrane structure:

  • ALL cells have a plasma membrane (aka cell membrane)
  • all membrane-bound organelles have a membrane e.g vacuole, mitochondria
  • the cristae in mitochondria and thylakoid in chloroplasts is also made of membrane
• Cell membrane structure:

  • it is a phospholipid bilayer with proteins embedded in the layer
  • The phospholipids making up the membrane can rotate on their axis. They can swap places with the phospholipid next to them.
  • the cell membrane is semi-permeable (only allows some substances to move in and out)
• Structure of phospholipids:

  • phospholipids have hydrophobic tails and hydrophilic heads
  • hydrophobic = not attracted to water (non-polar)
  • hydrophilic = attracted to water (polar)
• Phospholipid bilayer:

  • the fluid surrounding most cells is called tissue fluid and is largely composed of water
  • the fluid on the inside of the cell is the cytosol and it is largely composed of water
  • the hydrophobic part of the phospholipid faces away from the water solution
  • the hydrophilic part of the phospholipid faces water solutions
• Embedded proteins:

  • peripheral proteins (attached to the surface or one side of the membrane)
  • transmembrane protein (a type of integral protein that is embedded in the membrane)
  • glycoproteins = proteins with carbs attached
  • glycolipid = lipid with carbs attached
• Protein function in cell membrane:

  • junctions = serve to connect and join two cells together
  • enzymes = catalyse (speed up) metabolic pathways
  • transport = move substances across membranes
  • anchorage = attachment points for the internal cytoskeleton
  • recognition = membrane glycoproteins (protein + sugar) are called antigens that can be recognised by white blood cells as self or non-self
  • antigens = are like little 'flags' on the surface of our cells which allow our body to detect which cells are our own and which cells are foreign and to destroy
• Cholesterol:

  • cholesterol molecules located between the phospholipid molecules makes the membrane more fluid and more stable in lower temperatures - this prevents crystallisation
  • cholesterol is absent in plant cells, as their plasma membranes are surrounded and supported by a rigid cell wall