Biology Paper 1

• What are all living things made up of?

  Cells
• What are eukaryotic cells?

  Are complex and include all animals and plant cells. They have a nucleus.
• What are prokaryotic cells?

  Prokaryotic cells are smaller and simpler. They don't have a nucleus. For example bacteria.
• What are the different parts of a cell called?

  Sub cellular structures
• What do animal cells have?

  Nucleus, cytoplasm, cell membrane, mitochondria and ribosomes
• What is a nucleus?

  Contains genetic material that controls the activities of the cell
• What is a cell membrane?

  Holds the cell together and controls what goes in and out
• What is a ribosome?

  These are where proteins are made in the cell
• What is a mitochondria?

  These are where most of the reactions for aerobic respiration take place. Respiration transfers energy that the cell needs to work
• What is a cell wall?

  Rigid cell wall made of cellulose. It supports the cell and strengthens it
• What are the chloroplasts?

  These are where photosynthesis occurs which makes food for the plant. They contain a green substance called chlorophyll, which absorbs the light needed for photosynthesis.
• What do bacteria cells have instead of a nucleus?

  They have a single circular strand of DNA that floats freely in the cytoplasm.
• What is in a bacteria cell?

  Cell membrane, cell wall, circular strand of DNA, cytoplasm and plasmids
• What do microscopes help us see?

  Microscopes help us see small objects or details that are not visible to the naked eye.
• What do light microscopes use?

  Visible light.
• What do electron microscopes use?

  Electron beams.
• What is the difference between light and electron microscopes?

  Light microscopes are cheap, used in schools, easy to carry, lower magnification and resolution, they let us see individual cells and large sub cellular structures. Whereas Electron microscopes are expensive, used by scientists, not easy to carry, higher magnification and resolution, they let us see internal structures of mitochondria and chloroplasts. They let us see even tinier things like ribosomes and plasmids.
• What is the equation for magnification?

  Magnification= image size/ real size
• Millimetre

  mm, thousandth of a metre, 10^-3m
• Micrometre


  μm, millionth of a metre, 10^-6m
• Nanometre

  nm, billionth of a metre, 10^-9m
• Equipment for microscopy practical (6)

  1. Microscope2. Onion3. Scalpel4. Forceps5. Slide and cover slip6. Iodine
• What must you remember when you are drawing cells from a microscope? (2)

  1. Draw in neat pencil lines2. Note down what magnification you are using
• Microscopy practical

  1. Cut a thin sample of onion with the scalpel and place it on the slide2. Add a few drops of iodine3. Carefully place a cover slip on top, avoiding air bubbles4. Place the slide onto the stage5. Select the lowest-powered objective lens6. Use the coarse adjustment (/focus?) and then fine adjustment knob to focus your image7. If necessary, select a higher-powered objective lens and refocus
• How are sperm cells adapted for their function? (5)

  1. Function: to swim to and fertilise an egg cell2. Lots of mitochondria in middle section provide energy to tail3. Tail is long and contains muscle-like proteins for swimming4. Acrosome (head) stores digestive enzyme for breaking down outer layers of egg5. Large nucleus contains genetic information to be passed on
• How are nerve cells adapted for their function? (4)

  1. Function: to transmit messages from one part of the body to another2. Axon is very long so easier to communicate over further distances3. Dendrites (branched endings) allow connections with many other neurones4. Nerve endings contain lots of mitochondria to provide energy to make transmitter chemicals
• How are root hair cells adapted for their function? (4)

  1. Function: to absorb minerals and nutrients from the soil2. Increased surface are for water to move into the cell3. Large permanent vacuole speeds up the movement of water by osmosis4. Many mitochondria to transfer the energy needed for active transport
• How are xylem cells adapted for their function? (3)

  1. Function: to carry water and mineral ions from the roots to the rest of the plant2. Coated in lignin which kills cells, waterproofs them and creates a long hollow tube3. Spirals of lignin make them strong to withstand water pressure and support stem
• How are phloem cells adapted for their function? (3)

  1. Function: to transport sugar from the leaves to the rest of the plant (translocation)2. Cell walls between cells form sieve plates (tiny holes) which allow dissolved food to move between cells3. Supported by companion cells which have mitochondria to transfer energy for translocation
• Why is cell differentiation important?

  So that cells can become specialised for a particular function and carry out this function in the most efficient way
• When do most types of animal cells differentiate?

  At an early stage
• Light microscopes

  1. Use a beam of light and lens to form an image2. Can magnify up to around 2000 times3. You can see individual cells and nuclei
• Electron microscopes

  1. Invented in 1930s2. Use beams of electrons to form an image2. Can magnify up to 2,000,000 times - subcellular structures3. Transmission microscopes give 2D images with high magnification and low resolution4. Scanning electron microscopes give 3D images but with a lower resolution
• Resolution

  The ability to distinguish between 2 points
• How do bacteria multiply?

  Simple cell division (binary fission)
• How often do bacteria multiply?

  Up to every 20 minutes, if they have enough nutrients and a suitable temperature
• Steps to prepare a slide [Required Practical]

  1. Add a drop of water to the middle of a clean slide

  2. Cut up an onion and separate it out into layers. Use tweezers to peel off some epidermal tissue from the bottom of one the layers

  3. Using the tweezers, place the epidermal tisse into the water on the slide

  4. Add a drop of iodine solution. Iodine solution is a stain which is used to highlight objects in the cell by adding colour to them

  5. Place a cover slip on top. To do this, stand the cover slip upright on the slide, next to the water droplet. Then carefully tilt and lower it so it covers the specimen. Try not to get any air bubbles underneath it - they'll obstruct your view of the specimen
• Steps to use a light microscope to look at a slide

  1. Clip the slide onto the stage

  2. Select the lowest-powered objective lens

  3. Use the coarse adjustment knob to move the stage up to just below the objective lens

  4. Look down the eyepiece, use the coarse adjustment knob to move the stage downwards until the image is roughly in focus

  5. Adjust the focus with the fine adjustment knob, until you get a clear image

  6. If you need greater magnification, swap to a higher-powered objective lens and refocus
• What is cell differentiation?

  Cell differentiation is the process by which a cell changes to become specialised for its job.
• What is cell specialisation?

  The process of cells as they develop depending on their location in a tissue or organ.