Biology Paper 1

• what are examples of eukaryotic cells?


  animal cells and plant cells
• what are examples of prokaryotic cells?

  bacterial cells
• Which is smaller: Prokaryotic or Eukaryotic?

  Prokaryotic
• What do Eukaryotic cells contain that prokaryotic do not?


  Nucleus, chloroplasts and mitochondria
• What do plant cells contain which animal cells do not?


  cell wall, permanent vacuole and chloroplasts
• function of the cytoplasm


  gel-like substance, where chemical reactions happen, contains enzymes, organelles and dissolved ions and nutrients
• cell membrane function


  holds cell together and controls what goes in and out
• mitochondria function


  reactions for aerobic respiration take place - respiration transfers the energy the cell needs
• ribosomes function


  joins amino acids in a specific order during translation for protein synthesis - where proteins are made
• function of cell wall


  made of cellulose - supports and strengthens the cell - plant cell wall prevents the cell bursting when water enters by osmosis
• permanent vacuole function


  contains cell sap - weak solution of sugar and salts, supports the cell maintaining its turgidity
• chloroplasts function


  where photosynthesis occurs which makes food for plant. Contains green substance called chlorophyll which absorbs the light needed for photosynthesis
• sub-cellular structures in a bacterial cell (prokaryote)


  cell wall, cell membrane, cytoplasm, plasmids(small ring of DNA), single circular strand of DNA floating freely in cytoplasm(DNA loop)
• Light microscope vs Electron microscope

  light - see individual cells + large subcellular structures ( nucleus)

  electron - higher magnification and higher resolution, see smaller things in finer detail ( internal structure of mitochondria and chloroplasts, as well as tinier things like ribosomes and plasmids )
• equation for magnification

  Magnification = image size / real size

  1mm=1000micrometres
• The cell cycle stages

  1. Growth and DNA replication
  2. Chromosomes line up at center and one set is pulled to each end of the cell
  3. Nucleus and cytoplasm and cell membrane divide to form two identical cells
• What type of cell is and embryonic stem cell?

  undifferentiated cell = specialised cell
• What can stem cells from bone marrow of a healthy person be used to do?


  replace faulty blood cells as they can differentiate into blood cells
• Embryonic stem cells uses


  replace faulty cells ( make insulin-producing cells to help treat diabetes, or make nerve cells to help treat paralysis )
• Therapeutic cloning


  embryo produced with the same genes as the patient - stem cells from the embryo are not rejected so can be used for medical treatment e.g replace faulty cells
• Risks of stem cell use

  1. Stem cells grown in the lab may become contaminated with a virus which could be passed onto the patient and make them sicker (transfer of viral infection)
  2. ethical or religious objections
• AGAINST stem cell research

  1. human embryos shouldn't be used for experiments as each is a potential human life
  2. concentrate more on finding and developing other sources of stem cells to help people without using embryos
• FOR stem cell research

  1. curing existing patients who are suffering is more important than the rights of embryos
  2. embryos used are unwanted ones from fertility clinics so will most likely be destroyed if not used
• Stem cells from meristems in plants

  • produce identical plants quickly + cheaply
  • Rare species can be cloned to protect from extinction
  • Grow crops of identical plants that have desired/special features such as disease resistance - cloned to produce large numbers of identical plants for farmers
  • high yield of plants produced = sell more = more money
• Plant cells are ?

  undifferentiated cells
• What are cells that differentiate in mature animals used for?

  repairing and replacing cells such as skin or blood cells
• Stem cells =


  undifferentiated cells
• Specialised cells
• Sperm cells - reproduction - how are they adapted to their function?

  • long tail + streamlined head to help it swim to egg
  • lots of mitochondria to provide energy needed
  • carries enzymes in its head to digest through egg cell membrane
• Nerve cells - rapid signaling - adaptations

  • carry electrical signals from one part of the body to another
  • long (up to 2m) to cover more distance and and carry messages
  • have branched connections at their ends to connect to other nerve cells and form a network throughout the body
• Muscle cells - contraction - adaptations

  • long (space to contract)
  • contain lots of mitochondria to generate energy needed for contraction
• Root hair cells - absorbing water + minerals - adaptations

  • gives a bigger surface area to take in water from the soil
  • long "hair" like projections that stick out into the soil which gives plant a big surface area for absorbing water and mineral ions from the soil
• Palisade cell - absorbs light for photosynthesis - adaptations

  • contain lots of chloroplasts to help the plant make food by photosynthesis as more light absorbed
  • long and thin gives a large surface area = more photosynthesis
  • vacuole pushes chloroplasts to edge of cell = less distance for light to travel = more photosynthesis
• Red blood cell adaptations

  • no nucleus so more space for haemoglobin to fit - carry more haemoglobin which leads to increased transport of oxygen
  • circular biconcave disk - increase surface area to volume ratio of the cell = increased transport of oxygen
  • contains haemoglobin which transports oxygen from the lungs to all parts of the body
  • carry oxygen to cells and carbon dioxide away from them
• Ciliated Epithelial cell adaptations

  • your airways are lined with them
  • found in tubes leading to the lungs and in the oviduct
  • have "hairs" (cilia) which move dirt out of the lungs to help to move eggs along the oviduct
• Phloem cells -translocation - adaptations

  • Function: transport of dissolved sugars (e.g. sucrose) and amino acids
  • Adaptations:
  • Made of living cells (as opposed to xylem vessels, which are made of dead cells) that are supported by companion cells
  • Cells are joined end-to-end and contain holes in the end cell walls (sieve plates) forming tubes which allow sugars and amino acids to flow easily through (by translocation)
  • Cells also have very few subcellular structures to aid the flow of materials
• Xylem cells - transpiration - adaptations

  • Function: transport tissue for water and dissolved mineral ions
  • Adaptations:
  • No top and bottom walls (no end walls so water flows easily) between cells to form continuous hollow tubes (so no obstruction to water flow) through which water is drawn upwards towards the leaves by transpiration
  • Cells are essentially dead, without organelles or cytoplasm, to allow free passage of water
  • Outer walls are thickened with a substance called lignin, strengthening the tubes, which helps support the plant
• What is diffusion?


  The movement of particles from an area of higher concentration to an area of lower concentration
• What are some substances transported in and out of cells by diffusion?

  • oxygen and carbon dioxide in gas exchange
  • waste product urea from cells into the blood plasma for excretion in the kidney
• Factors which affect the rate of diffusion

  • concentration gradient - the bigger the gradient the faster the diffusion rate
  • temperature - higher temp = faster diffusion rate because particles have more energy so move around faster
  • surface area of the membrane - larger SA = faster rate of diffusion because more particles can pass through at once