CB1 - Key Concepts in Biology

• What is the difference between eukaryotic and prokaryotic cells?

  Eukaryotic cells have a nucleus while prokaryotic cells do not.
• Who discovered cells?

  Robert Hooke
• What is the definition of magnification?


  The number of times an image/object is larger compared to its original size.
• Equation for magnification:

  eyepiece lens magnification x objective lens magnification
• What is the definition of resolution?

  The smallest distance between two points so that they are still recognisable as two points.
• How do electron microscopes work and how did they help us to improve our understanding of cell structures?

  Electron microscopes use, instead of light, beans of electrons that passes through the specimen to build an image. They increased the amount of magnification and resolution possible, allowing us to see cells with great detail and clarity.
• State all organelles in a animal cell:

  Mitochondria, nucleus, cytoplasm, ribosomes, cell membrane.
• State all organelles in a plant cell:

  Mitochondria, nucleus, cytoplasm, ribosomes, cell membrane, cell wall, vacuole, chloroplasts.
• What is the function of the mitochondria?

  Energy is produced through aerobic respiration.
• What is the function of ribosomes?

  They produce new proteins for a cell.
• What is the function of the cell wall?

  It provides support and structure for the cell.
• What is the function of chloroplasts?

  They contain chlorophyll, trapping energy from the Sun and using it for photosynthesis.
• What is the function of the vacuole?

  The vacuole stores cell sap, and helps in the structure of the cell.
• State all the organelles within a bacterial cell:

  Flagellum, ribosomes, cell wall, plasmids, chromosomal DNA
• What is the function of the flagellum within a bacterial cell?

  It helps the bacteria to move.
• What is the function of the chromosomal DNA?

  It controls cell activities.
• What are plasmids?

  Rings of DNA
• What are specialised cells?

  Cells with a specific function within the body, being adapted to such function.
• What are examples of specialised cells?

  Sperm cells, egg cells, and ciliated epithelial cells.
• How is the sperm cell adapted to its function?

  The sperm cell contains a flagellum which allows it to swim towards the egg, an acrosome, which contains enzymes and many mitochondria, to allow the sperm to swim for a long time, providing energy.
• What is the function of the acrosome?

  The acrosome is at the front of the sperm cell, containing enzymes that break down the outer membrane of the egg, allowing the sperm inside it for fertilisation.
• How many chromosomes do sperm and egg cells have?

  23 chromosomes
• What is a cell that only contains 23 chromosomes called?

  Haploid
• What are the adaptations of the egg cell?

  • large cytoplasm: stores many nutrients needed for fertilisation
  • cell membrane changes after fertilisation to prevent other sperm cells from entering it.
• What is the function of ciliated epithelial cells in the oviducts?


  They transport the egg from the ovary towards the uterus by moving their cilia (hair-like structures)
• What are enzymes?

  Enzymes are biological catalysts that increase the rate of reaction within the body - e.g. digestive enzymes speed up digestion.
• What is the mechanism of enzyme action?

  Enzymes are specific to one substance - they have differently shaped active sites, where a substance binds perfectly for breakdown or synthesis (lock-and-key model).
• Explain the effect of temperature on enzymes:

  The optimum temperature for enzymes is body temperature, 37°C, which is when the rate of reaction is the highest. The higher the temperature, the faster molecules are moving around and easier it is for them to bind with enzymes however, enzymes become denatured at a temperature too high.
• Explain the trend between enzyme activity and substrate concentration:

  The higher the substrate concentration, the higher the rate of reaction as most enzyme active sites contain substrate molecules (most active sites are full).
• What is the difference between active transport and other transportations?

  Active transport goes against the concentration gradient, transporting substances which are too big to diffuse through the cell membranes. Active Transport requires energy, differently from osmosis and diffusion.
• What does amylase do?

  Found in the saliva and small intestine, it breaks down starch to small sugars.
• What does catalase do?

  Found in liver cells, is breaks down hydrogen peroxide made in many cells into water and oxygen.