biology paper 1

• What are the two types of cells?

  ● Eukaryotic (plant and animal) ● Prokaryotic (bacteria)
• What are the differences between eukaryotic and prokaryotic cells?

  
  

  Prokaryotic cells are much smaller than eukaryotic cells. Eukaryotic cells contain membrane bound-organelles and a nucleus containing genetic material, while prokaryotes do not
• What is the prokaryotic cell wall composed of?

  Peptidoglycan
• How is genetic information stored in a prokaryotic cell

  Found free within the cytoplasm as: ● Chromosomal DNA (single large loop of circular DNA) ● Plasmid DNA
• What are plasmids?

  ● Small, circular loops of DNA found free in the cytoplasm and separate from the main DNA. ● Carry genes that provide genetic advantages e.g. antibiotic resistance.
• List the components of both plant and animal cells

  ● Nucleus ● Cytoplasm ● Cell membrane ● Mitochondria ● Ribosomes
• List the additional cell components found in plant cells

  ● Chloroplasts ● Permanent vacuole ● Cell wall
• Other than storing genetic information, what is the function of the nucleus?

  Controls cellular activities
• Describe the structure of the cytoplasm

  ● Fluid component of the cell. ● Contains organelles, enzymes and dissolved ions and nutrients.
• What is the function of the cytoplasm?

  Site of cellular reactions e.g. first stage of respiration. Transport medium.
• What is the function of the cell membrane?

  Controls the entry and exit of materials into and out of the cell.
• What is the function of the mitochondria?

  Site of later stages of aerobic respiration in which ATP is produced
• What is the function of the ribosomes

  Joins amino acids in a specific order during translation for the synthesis of proteins.
• What is the plant cell wall made of?

  Cellulose
• What is the function of the plant cell wall?

  Provides strength. ● Prevents the cell bursting when water enters by osmosis.
• What does the permanent vacuole contain?

  Cell sap (a solution of salts, sugars and organic acids)
• What is the function of the permanent vacuole

  Supports the cell, maintaining its turgidity.
• What is the function of chloroplasts

  Site of photosynthesis
• Describe how sperm cells in animals are adapted to their function Haploid nucleus contains genetic information. ● Tail enables movement. ● Mitochondria provide energy for tail movement. ● Acrosome contains enzymes that digest the egg cell membran
• Describe how nerve cells in animals are adapted to their function ● Long axon allows electrical impulses to be transmitted all over the body from the central nervous system. ● Dendrites from the cell body connect to and receive impulses from other nerve cells, muscles and glands. ● Myelin sheath insulates the axon and speeds up the transmission of impulses along the nerve cell
• Describe how muscle cells are adapted to their function ● Arrangement of protein filaments allows them to slide over each other to produce muscle contraction. ● Mitochondria to provide energy for muscle contraction. ● Merged cells in skeletal muscle allow muscle fibre contraction in unison.
• Describe how root hair cells in plants are adapted to their function ● Large surface area to absorb nutrients and water from surrounding soil. ● Thin walls that do not restrict water absorption.
• Describe how xylem cells in plants are adapted to their function ● No upper or lower margins between cells to provide a continuous route for water to flow. ● Thick, woody side walls strengthen their structure and prevent collapse
• Describe how phloem cells in plants are adapted to their function ● Sieve plates let dissolved amino acids and sugars be transported up and down the stem. ● Companion cells provide energy needed for active transport of substances along the phloem.
• What is cell differentiation? The process by which cells become specialised.
• Why is cell differentiation important? Allows production of different tissues and organs that perform various vital functions in the human body
• At what point in their life cycle do most animal cells differentiate? Early in their life cycle
• For how long do plant cells retain the ability to differentiate Throughout their entire life cycle
• What is the purpose of cell division in mature animals? Repair and replacement of cells
• What changes does a cell go through as it differentiates Becomes specialised through acquisition of different sub-cellular structures to enable a specific function to be performed by the cell.
• Define magnification The number of times bigger an image appears compared to the size of the real object.
• Define resolution The smallest distance between two objects that can be distinguished.
• How does a light microscope work? Passes a beam of light through a specimen which travels through the eyepiece lens, allowing the specimen to be observed
• What are the advantages of light microscopes? ● Inexpensive ● Easy to use ● Portable ● Observe both dead and living specimens
• What is the disadvantage of light microscopes Limited resolution
• How does an electron microscope work? It uses a beam of electrons which are focused using magnets. The electrons hit a fluorescent screen which emits visible light, producing an image
• Name the two types of electron microscope Transmission electron microscope (TEM) Scanning electron microscope (SEM
• What is the advantage of electron microscopes? Greater magnification and resolution.
• Why do electron microscopes have a greater magnification and resolution? They use a beam of electrons which has a shorter wavelength than photons of light.
• How have electron microscopes enabled scientists to develop their understanding of cells? ● Allow small sub-cellular structures (e.g. mitochondria, ribosomes) to be observed in detail. ● Enable scientists to develop more accurate explanations about how cell structure relates to function