Topic 1- cell biology

• Active transport


  The movement of substances from a more dilute solution to a more concentrated solution (against a concentration gradient) with the use of energy from respiration
• Adult stem cell


  A type of stem cell that can form many types of cells
• Agar jelly


  A substance placed in petri dishes which is used to culture microorganisms on
• Cell differentiation


  The process where a cell becomes specialised to its function
• Cell membrane


  A partially permeable barrier that surrounds the cell
• Cell wall


  An outer layer made of cellulose that strengthens plant cells
• Chloroplast


  An organelle which is the site of photosynthesis
• Chromosomes


  DNA structures that are found in the nucleus which are made up of genes
• Diffusion

  The spreading out of the particles of any substance in solution, or particles of a gas, resulting in a net movement from an area of higher concentration to an area of lower concentration
• Magnification

  How much bigger an image appears compared to the original object
• Mitosis

  A type of cell division which produces two genetically identical daughter cells from one parent cell
• Plasmid

  Loops of DNA found in the cytoplasm of prokaryotic cells
• Resolution

  The ability to distinguish two different points in a specimen
• Specialised cells

  Cells that are adapted to perform a specific function
• Stem cell

  An undifferentiated cell that can divide to produce many specialised cells of the same type
• Surface area to volume ratio (SA:V)

  The size of the object compared with the amount of area where it contacts its environment
• Therapeutic cloning

  Producing an embryo that has the same genes as a patient
• Cell membrane- controls what can enter or leave the cell, holds the cell together
• cytoplasm- a jelly like substance where chemical reactions (including anaerobic respiration) take place, surrounds the subcellular structures
• DNA- genetic material that controls the activities of the cell (found in the nucleus in Euk cells)
• Ribosomes- the site of protein synthesis in the cell
• plant and animal cells are both

  Eukaryotic- defining feature is that DNA is found in an enclosed nucleus
• Eukaryotic cell diagram

  Sub-cellular structure

  A) animal cell

  B) ribosomes

  C) cytoplasm

  D) mitochondria

  E) cell membrane

  F) nucleus

  
• Eukaryotic cell 2

  sub-cellular structures

  A) plant cell

  B) chloroplast

  C) nucleus

  D) cytoplasm

  E) mitochondria

  F) permanent vacuole

  G) ribosomes

  H) cell wall (made from cellulose)

  I) cell membrane

  
• muscle cell adaptations- functions


  • There are three different types of muscle in animals: skeletal, smooth and cardiac (heart)
  • All muscle cells have layers of protein filaments in them. These layers can slide over each other causing muscle contraction
  • Muscle cells have a high density of mitochondria to provide sufficient energy (via respiration) for muscle contraction
  • Skeletal muscle cells fuse together during development to form multinucleated cells that contract in unison
  • contain layers of fibres- helps them contract
• root hair cell adaptations- functions

  • Root hair to increase surface area (SA) so the rate of water uptake by osmosis is greater (can absorb more water and ions than if SA were lower)
  • Thinner walls than other plant cells so that water can move through easily (due to shorter diffusion distance)
  • Permanent vacuole contains cell sap which is more concentrated than soil water, maintaining a water potential gradient
  • Mitochondria for active transport of mineral ions
• xylem cell adaptations- functions

  • dont have top and bottom walls to form a continuous tube where water moves from roots>leaves by transpiration
  • Cells are essentially dead -allows free passage of water
  • Outer walls are thickened with a substance called lignin, strengthening the tubes, which helps support the plant
• Differentiation

  Structural differences between different types of cells enables them to perform specific functions within the organism
• Cell differentiation

  A cell changes to become specialised
• Almost all of the cells in a multicellular organism will contain the same genetic information
• In an animal, most cells differentiate at an early stage of its development
• Cell division is mainly restricted to repair and replacement in mature animals
• Animal cells therefore lose their ability to differentiate after they have become specialised early in the life of the animal
• Adult stem cells

  • Cells in various locations throughout the body of an animal that retain the ability to differentiate throughout the life of the animal
  • Mainly involved in replacing and repairing cells (such as blood or skin cells)
• Plants differ from animals


  Many types of plant cell retain the ability to fully differentiate throughout the life of a plant, not just in the early stages of development
• electron microscope

  • An electron microscope has much higher magnification and resolving power than a light microscope
  • They can therefore be used to study cells in much finer detail, enabling biologists to see and understand many more subcellular structures such as the mitochondrion
  • They have also helped biologists develop a better understanding of the structure of the nucleus and cell membrane
• Magnification = image size ÷ Actual size
• light microscope

  • use light and lenses to form a magnified image of a specimen
  • With a light microscope it is possible to see images of cells and large subcellular structures ,although stains are often required to highlight certain parts of cells
  • They have a much lower resolution and magnification than electron microscopes
• • Binary fission
  • Bacteria multiply by a type of simple cell division- binary fission
  • In the right conditions, a bacterial cell prepares to divide by replicating its genetic material before it increases in size
  • A copy of each piece of circular DNA moves to each end of the cell before the cytoplasm divides, and new cell walls form around each daughter cell
• Growing bacterial cultures in a lab

  • The effect of disinfectants and antibiotics on microorganisms can be investigated using cultures of bacteria grown in the lab
  • bacteria need an adequate supply of nutrients (carbs, minerals, vitamins) and appropriate temp (depends on species)
  • Warmer temperatures promote faster growth, but in a school lab the maximum allowed temperature for growth is 25°C
  • Above this temperature, more harmful pathogens are likely to grow
  • Bacteria can be grown as colonies on an agar gel plate