biology unit 1

• electron microscopes advantages:

  -higher magnification than light microscopes

  -can see the structures inside the cells
• electron microscope disadvantages:

  -much more expensive

  -you can only examine dead material

  -they need special training to use
• simple to complex:

  cells

  tissue

  organs

  systems

  organism
• the plasma membrane protects the the cell from its surroundings and allows substances in and out
• the cytoplasm is the liquid that fills the cell, it contains many dissolved substances and lots of chemical reactions happen here
• the nucleus is surrounded by a double membrane and contains the genetic material of the cell and controls the activities of the cell by it’s nuclear pores which allow substances to enter and leave the nucleus
• the nucleolus is a region of dense DNA, ribosomes are also made here
• ribosomes make proteins

  • 80S in eukaryotic cell
  • 70S in prokaryotic cell
• rough ER is flattened sacs with a membrane covered in ribosomes where proteins are made
• smooth ER are membrane tubes where lipids are made
• vesicles are membrane bound sacs for storing and transporting substances around in the cell
• the golgi apparatus modifies proteins and packages them in vesicles for transport
• lysosomes are enclosed by a single membrane and contain digestive enzymes, they destroy old organelles and pathogens
• centrioles make the spindle in cell division and are involved in cell division
• in mitochondria respiration takes place and ATP is produced. they are surrounded by a double membrane and the inner membrane has folds to increase surface area. the central area contains a jelly called the matrix where chemical reactions happen which produce ATP
• plant cell

  
• a eukaryotic cell is a cell that contains a nucleus and membrane bound organelles eg: plant and animal cells
• a prokaryotic cell is a single celled organism with no membrane bound organelles

  eg: bacteria
• a nucleoid is a single circular length of DNA that is folded
• the slime capsule prevents the cell from drying out, helps to protect from white blood cells and helps it to stick to surfaces
• cell wall (bacteria) is made of peptidoglycan which helps with cell shape and strength
• plasmids are double stranded DNA in a circular structure which contain additional genes that aid in survival eg: antibiotic resistance
• in a gram test the peptidoglycan absorbs the stain
• gram positive (purple) do not have an outer membrane and have a thick peptidoglycan wall to absorb the stain
• gram negative (pink) bacteria have a outer membrane and a thin peptidoglycan cell wall so they do not retain the stain
• gram negative bacteria are more resistant to antibiotics as they have more protection (outer membrane)
• the flagella are made of microtubules and are used for movement
• chloroplasts (plant) where photosynthesis happen, they contain chlorophyll
• vacuole (plant) sac of liquid which stores water and other dissolved substances
• cell wall (plant) for support and protection
• tonoplast membrane (plant) controls the movement of molecules in and out of the vacuole
• amyloplasts (plant) store starch
• plasmodesmata and pits (plant) to allow communication between one cell and another
• palisade mesophyll cells do photosynthesis because they contain lots of chloroplasts and a large vacuole so that the chloroplasts are in the outer region of the cell so they can absorb the most light. they have thin cell walls to allow diffusion of substances
• root hair cells collect water and minerals from the soil, they have many long projections which reach out into the soil, they have a large surface area, they have no chloroplasts because no photosynthesis takes place here
• egg cells carry the genetic information from the female in the haploid nucleus, the zona pellucida is a jelly layer that stops more than one sperm getting in
• the sperm cell carries genetic information from the male in the haploid nucleus, mid region contains mitochondria to provide energy needed to swim to the cell
• white blood cells protect the body against infection and disease by producing antibodies, antitoxins and destroying pathogen, they can change shape to squeeze through gaps and get to sites of infection and engulf the invaders
• red blood cells carry oxygen in the blood stream and contain haemoglobin which carry's the oxygen. they have a biconcave disc shape and no nucleus which gives them a large surface are to volume ratio, they are small and flexible so they can squeeze through capillaries
• epithelial tissue any surface in contact with the external environment, may line the outer surface of internal organs and blood vessels and also the inner surface of organs with cavities