biology paper 1

• Eukaryotic cells


  • Eukaryotic cells Have genetic material that forms chromosomes in nucleus
  • Animal and plant cells are eukaryotic
• Animal and plant cells both:


  • Have a nucleus containing DNA
  • Have a cell membrane that controls substances in and out of the cell
  • Have mitochondria that release energy through respiration
  • Have ribosomes as the site of protein synthesis
  • Have cytoplasm as a jelly-like substance for chemical reactions
• Plant cells ONLY 


  • Have a permanent vacuole containing cell sap
  • Have chloroplasts which contains chlorophyll to absorb light
  • Have a cell wall made of cellulose
• Prokaryotic cells (Bacteria)


  • Are single cells with no nucleus
  • Have DNA plasmids
  • Are smaller than eukaryotic cells
  • Have a cell wall, cell membrane, cytoplasm, flagellum, and bacterial DNA loop with no nucleus
• Light microscopes


  • Use light to form images
  • Can view living samples. • light microscopes are also cheap and have low magnification and a low resolution
• Electron microscopes


  • Use a beam of electrons to form images
  • Can view non-living samples
  • Have high magnification and high resolution and are expensive
• Magnification = 


  image size divided by actual size
• Sperm cells


  • Fertilise ovum And Swim to ovum to fertilise it sperm cells also have lots of mitochondria
• Red blood cells


  • Transport oxygen around body and they have no nucleus so they have more room
  • Contains red Pigment which binds to oxygen molecules
• Muscle cells


  • Contract and relax
  • Contains protein fibres
  • Contains mitochondria
• Nerve cells


  • Carry electrical impulses
  • the myelin sheath insulates to make the transmission speed increases
• Root hair cells


  • Absorb mineral ions
  • Contain lots of mitochondria
• Palisade cells


  • Enable photosynthesis in leaf
  • Contain lots of chloroplasts
• Diffusion


  Movement of particles from an area of high concentration to an area of low concentration and requires no energy
• Diffusion occurs in humans, fish, and plants for oxygen
• Osmosis

  Diffusion of water through a partially permeable membrane from a dilute solution to a more concentrated solution, no energy needed osmosis occurs in plants for root hair cells
• Active transport


  Movement of particles from a dilute solution to a more concentrated solution using energy from respiration
• Active transport occurs in humans and plants because they respire
• Energy is required for respiration in active transport
• Chromosomes


  the nucleus of a cell contains chromosomes each chromosome carries genes made of dna molecules
• stem cells in medicine 


  • stem cells are undifferentiated cells that can develop in to one or more types of specialised cells
  • there are two types of stem cells: adult stem cells and embryonic stem cells stem cells can be cloned to produce larger identical cells
• Adult stem cells


  • Found in specific parts of the body eg bone marrow
  • Can only differentiate to form certain types of cells eg stem cells
• Advantages of adult stem cells


  • Fewer ethical issues
  • Already a technique for treating a disease eg Lukemia
  • Relatively safe to use & donors recover and donors recover quickly
• Disadvantages of adult stem cells


  • Requires a donor-Long wait time
  • Only differentiate into certain specialised cells which can be used to treat fewer diseases
• Embryonic stem cells


  • Found in early human embryos
  • Can differentiate into any specialised cell in body eg nerve or muscle cells
• Advantages of embryonic stem cells


  • Wide range of diseases can be treated
  • May be Possible to grow whole replacement organs and there is no donor needed as there are spare embryos from fertility clinics
• Disadvantages of embryonic stem cells


  • Ethical issues
  • Risk of viral infection forming
• another disadvantage of embryonic stem cells is because they are a Newer treatment they are not yet clear if they can cure as many diseases
• Plant meristem


  found in roots and shoots of plants
• Plant meristem


  • Can differentiate into all cell types used to clone plants
  • Advantages of plant meristem is rare species of plants can be cloned so they don’t become extinct and Plants with desirable traits can be cloned
  • they are also a Low cost of production
• disadvantages of plant meristem 


  Crop is At risk of being destroyed by disease as cloned plants are genetically identical
• Cell cycle


  Cell cycle is the split of 2 identical daughter cells. mitosis is important for growth and repair of cells.there are three stages of cell cycle as followed:

  1. DNA replicates

  2. Nucleus divides to form two nuclei

  3. Cytoplasm and cell membrane divide to form two daughter cells
• Binary fission

  Binary fission is Cell division in bacteria
• Bacteria can multiply every 20 minutes if temperature is at optimum and bacteria can bc grown in sterile conditions on agar gel plate or in nutrient broth. The lid must be sealed but not all the way to allow oxygen in this is so harmful bacteria that don’t need oxygen aren’t able to grow
• Therapeutic cloning


  • Cells from a patient's body are used to clone an embryo of themselves. Stem cells from embryo can be used for medical treatments and growing new organs. Stem cells have same Genes as patients so they are less likely to be rejected when transplanted.
• Levels of organisation


  • Cells
  • Tissues
  • Organs
  • Organ systems
  • Organisms
• Organ systems


  Groups of organs working together
• Organisms


  Work together to form an organism
• Digestive enzymes

  • Amylase are produced in salivary glands, pancreas + small intestine. The reaction catalyst is starch → glucose
  • Proteases are produced in stomoch, pancreas and small intestine The reaction catalyst is proteins → amino acids.
  • Lipases are produced in pancreas and small intestine The reaction catalyst is lipids → fatty acids + glycerol
• Enzymes


  Large proteins that speed up reactions