Biology P1

• Describe how xylem is adapted for the transportation of mineral ions and water around a plant:

  -Made of dead cells/ Form hollow tubes/ have no organelles

  -Walls are strengthened with lignin
• Describe the method used to prepare an onion cell specimen on a microscope slide for observation with a light microscope


  -Use tweezers to peel back a layer of epidermal tissue

  -Spread tissue onto a clean slide

  -With a pipette add iodine solution to stain the structures to appear visible

  -Place cover slip over the top

  -Dab away any excess dye
• Rules which should be observed when creating a biological drawing:


  -No shading/ use clean lines

  -Draw structures in proportion

  -Label features with clear uncrossed lines
• The nucleus of a sperm cell is different from the nucleus of a muscle cell in that:

  -sperm cell is haploid, muscle cell is diploid

  -sperm cells contain 23 chromosomes, muscle cells contain 46 chromosomes
• Compare the process of differentiation in animals and plants

  -In animals differentiation occurs at an early stage/ early development

  -In plants differentiation, unspecialised cells are capable of forming any cell required when mature
• The function of mitochondria


  -Where energy is released by aerobic respiration
• Failure of a root hair cell to develop properly in the cells of a plant root could be catastrophic to a plant because:


  -The function/purpose of a root hair cell is to increase the surface area

  -For the absorption of water, mineral ions,

  -Less root hairs means less absorption of mineral ions

  -Water is essential for photosynthesis

  -Leading to stunted growth
• Prokaryotic cells


  • Contain cytoplasm and a cell membrane
  • Do not contain mitochondria or chloroplasts
  • Contain plasmids
• Eukaryotic cells


  • Contain cytoplasm and a cell membrane
  • Contain mitochondria and chloroplasts
  • Do not contain plasmids
• Prokaryotic cells


  Have more than one flagellum
• Prokaryotic cells


  Are generally smaller than eukaryotic cells
• Organelles such as mitochondria or chloroplasts


  Would not fit into a prokaryotic cell due to the size difference
• Describe how cell specialisation results in a zygote developing into a baby.


  -The single cell/ fertilised egg divides by mitosis

  -Different cells are required to form different tissues

  -Cells in the embryo differentiate
• Different parts of the human digestive system break down molecules of fat so that they can be absorbed into the body. (6m)

  -mechanical breakdown (of food) in mouth

  -Lipase, which is produced by the pancreas, breaks down molecules of fat into fatty acids and glycerol

  -Bile is produced by the liver, and neutralises acid in stomach and also emulsifies fats

  -Fat digestion happens in the small intestine and small molecules are absorbed
• Give two reasons why we cannot make our cells even warmer to increase the rate of reactions


  -Heating our cells even more would require a lot of energy

  -Higher temperatures could damage our cells
• Explain how a high temperature can cause an enzyme to denature


  -A high temperature will break the bonds holding the enzyme together

  -This means the enzyme will change shape and so will its active site

  -The active site will no longer be complementary to the substrate

  -No longer able to catalyse a reaction
• What are 6 features of leafs?


  -Large surface area

  -Thin, quick diffusion of carbon dixoide to palisade mesophyll cells quickly

  -Chlorophyll, absorbs light energy

  -Stomato

  -Thin cuticle made of wax, protects leaf without blocking sunlight

  -Spongy layer, air spaces allow carbon dioxide to diffuse through the leaf increasing the surface area
• Factors which affect transpiration


  -Air movement

  -Temperature

  -Light intensity

  -Humdity
• How does air movement affect transpiration rate?


  Good airflow removes water vapour from the air surrounding the leaf, setting up a concentration gradient between the leaf and the air, increasing water loss.
• How does temperature effect transpiration rate?


  At higher temperature, particles have more kinetic energy so transpiration occurs at a faster rate as water molecules evaporate from the mesophyll and diffuse away faster than at lower temperatures.
• How does light intensity effect transpiration rate?

  More- guard cells are responsive to light intensity; when it is high they are turgic and the stomata open allowing water to be lost
• How does humidity affect transpiration rate?


  More humid air, causes transpiration to happen at a slower/less rate as the air is saturated with water vapour, therefore concentration gradient is weaker, less water is lost.
• What happens to to translocation during winter?

  Winter- phloem tubes transport dissolved sucrose and amino acids from the storage organs to other parts of the plant so that respiration can continue
• What happens to translocation during a growing period?


  The storage organs, e.g. roots would be the source and the many growing areas of the plant would be sinks
• What happens to translocation after the growing period?

  After the plant has grown, the leaves are photosynthesising and producing large quantities of sugars so they become the source and the roots become the sink storing sucrose as starch until it is needed again.
• The new plant is reproduced by _______ reproduction. In this type of reproduction body cells divide by _______. The new plant has the same _____ as the parent cells.

  asexual,mitosis,genes
• Name 3 ways in which infectious diseases can spread

  -Water, pathogens contaminate water supplies,organisms drinking this contaminated water can be infected by pathogens ;Cholera is spread this way

  -Direct Contact, Pathogens live on the surface of other organisms, such as your skin. If the infected skin makes contact with another surface, pathogens will transfer from the infected skin to the surface. Anybody who touches this surface, will have pathogens spread to them; Athletes foot is spread this way
• Last way infectious diseases are spread

  -Air, Pathogens are released into the air inside droplets when an organism coughs/sneezes. These can be inhaled by other organisms; flu common colds spread
• Ways of preventing infections:

  -Decrease vectors

  -Improve hygiene

  -Isolate/isolation of infected individuals
• Define cell differentiation


  -When a cell develops/ acquires new sub-cellular structures to let it perform a specific function, cell is now specialised
• Embryos


  -Cell differentiation occurs during an organisms development

  -Organisms start as one cell

  -Cells divide to form embryos that differentiate (specialise) to produce cells that perform all the bodys functions
• Plants differentiation


  -Plants keep their ability to differentiate throughout their life.

  -Always able to create new tissues
• Adult animals differentiation


  -Differentiation is rare in adult animals

  -Cells will mostly divide in order to replace cells and repair tissues

  -New tissues are rarely created
• What are sperm cells function?

  Specialised to fertilise egg cells.
• Name important specialised features in the sperm cells head

  1)Found at tip of head, Acrosome- contains digestive enzymes which allow it to penetrate the egg cell

  2) Nucleus- carries one half of organisms genetic material, which combines with one half of the egg cells genetic material to fertilise the egg cell
• Sperm cell: Flagellum

  Used for cells motion, allowing the sperm to travel towards the egg cell
• Sperm cell: Middle section

  Contains many mitochondria to release the energy needed/ give energy to sperm cell to travel long distances to reach the egg cell
• What are nerve cells function?


  Specialised to transmit electrical messages around the body
• Name specialised functions of a nerve cell:

  1)Axon- Part of the cell that electrical signals travel along; Long axon to increase the distance elctrical signals travel

  2)Dendrites- Branches of a nerve cell, Several dendrites spread outwards from cell body to to transfer electrical signals to other neurones, Electrical messages travel between neurones and synapses

  3)Myelin Sheath- made of myelin to stop electrical nerve signal from leaking out of nerve cell and also increase speed of transmission
• What are muscle cells function?

  Contract to bring about movement, produce force and motion