Cell structure and division

• what are the stages in the cell cycle?

  -Growth 1

  -Synthesis

  -Growth 2

  -mitosis

  -cytokinesis
• what happens to the cell in Growth 1 (stage 1)?

  -the size of the cell has increased

  -the organelles have replicated
• what happens to the cell in Synthesis (stage 2)?

  -DNA replication

  -before DNA replication there are two chromosomes and each chromosome is made from one piece of DNA

  -after DNA replication there are two chromosomes and each chromosome is made from two pieces of DNA - genetically identical
• what happens to the cell in Growth 2 (stage 3)?

  -further growth of the cell
• what are the stages of mitosis?

  -prophase

  -metaphase

  -anaphase

  -telophase
• what happens in prophase?

  -chromosomes condense- they are thickening and visible

  -nucleus membrane begins to breakdown

  -spindles begin to develop
• what happens in metaphase?

  -chromosomes line up on the equator

  -nuclear membrane has fully broken down

  -spindles attach to the centromere of the chromosomes
• what happens in anaphase?

  -the sister chromatids are separated by the spindles attached to the centromeres

  -spindles contract to pull the sister chromatids to opposite poles of the cell
• what happens in telophase?

  -the chromosomes uncoil and therefore uncondense

  -nuclear membrane returns around the chromosomes
• what is the difference between chromatin and chromatid?

  -chromatin = DNA aspect of chromosome in interphase --> uncondense + not visible

  -chromatid = DNA aspect of chromosome when dividing (mitosis/meisosis) --> condensed + visible
• what happens in cytokinesis?

  the cytoplasm divides to create two cells
• what is the mitotic index?


  mitotic index = number of cells in mitosis/ total number of cells
• what is the structure of the nucleus?

  -largest and densest organelle

  -bound by a double membrane with pores - so theres control over what enters and leaves the organelle

  -contains DNA - chromatin and chromosomes
• what is the structure of the nucleolus?

  densely stained region of the nucleus
• what is the structure of the ribosomes?

  -smallest least dense organelle

  -not membrane bound

  -made in the nuclei of the nucleus

  -can be found free in the cytoplasm or attached to the surface of the rough ER
• what is the structure of chloroplasts?

  - surrounded by double membrane

  - grana made from stacks of thylakoid membranes

  - grana (grenum) are linked together by lamellae

  - stoma -- like cytoplasm
• what is the structure of the vesicles?

  -small membrane bound sacs

  -contain fluid that is being transported to the cell surface
• what is the structure of the golgi body?

  -series of flattened cavities (cristernae) that are stacked on top of each other

  -cavity above is not directly connected to the one below
• what is the structure of the rough ER?

  -series of connected, flattened sacs called cristernae that are spread throughout the cytoplasm of the cell

  -have ribosomes attached to the surface
• what is the structure of the smooth ER?

  -series of connected, flattened sacs called cristernae that are spread throughout the cytoplasm of the cell

  -do not have ribosomes on the surface

  -more rounded cristernae
• what is the structure of lysosomes?

  vesicles produced by the golgi that contain enzymes such as proteases and lipases
• what is the structure of the mitochondria?

  -relatively large, rod shaped organelle

  -has a double membrane

  -outer membrane is smooth and controls movement of molecules in and out

  -inner membrane is highly folded to give structures called cristae

  -the fluid interior is called the matrix --- contains enzymes, ribosomes and DNA for replication of the organelle
• what is the function of the ribosomes?

  site of protein synthesis
• what is the function of the nucleolus?

  ribosomes are constructed here
• what is the function of the vesicles?

  -contain fluid which can contain proteins , carbohydrates and lipids which are transported to the cell surface

  -sacs fuse with cell membrane so the contents can be secreted outside the cell -- exocytosis
• what is the function of the golgi body?

  -form lysosomes

  -protein, lipids and carbohydrates produced in the ER are modified by being transported through cavities

  -part of cavity pinches off to form a vesicle. the vesicle then moves and fuses with the cavity above

  -at the top cavity the vesicle formed moves to the cell surface and fuses with it so that secretion occurs -- exocytosis
• what is the function of the rough ER?

  -proteins made by the ribosomes are passed into the lumen and are then transported through the cell

  -vesicles pinch off the cavity and travel to the golgi body
• what is the function of the smooth ER?

  site of lipid and carbohydrate synthesis, storage and transport
• what is the function of the lysosomes?

  -isolates harmful enzymes from the rest of the cell before releasing them to the outside of the cell or into a phagocytic vesicle within a phagocyte

  -enzymes breakdown the component parts of the cell so useful chemicals can be reused

  -release enzymes to outside the cell to destroy material around the cell
• what is the function of the mitochondria?

  site of respiration --- ATP is made here
• where is ATP produced?

  within mitochondria and chloroplasts
• what is chromatin?


  DNA associated with proteins in a form where chromosomes are uncoiled and not visible (chromosomes only become visible when the cell divides)
• what is an organelle?

  a subcellular structure that performs specific functions
• what is ATP?


  - a smaller molecule that stores energy

  - allows smaller, more manageable amounts of energy to be released
• how is ATP broken down?

  when energy is needed, ATP is broken down into ADP and Pi using a hydrolysis reaction

  
  

  ATP + water ---> ADP + Pi

  enzyme = ATP hydrolase
• how is ATP synthesised?

  during respiration, ATP is made using a condensation reaction

  
  

  ADP + Pi ---> ATP + water

  enzyme = ATP synthase
• what is phosphorylation?


  addition of a phosphate to make a molecule more reative
• what is standard deviation?

  the spread of data around the mean
• what does it mean if the standard deviation bars overlap?

  the higher mean is not significantly higher
• why is the solution used in cell fractionation an ice cold , isotonic buffer?

  ice cold = prevents enzymes from breaking / damaging organelles as theres too little kinetic energy, reduce enzyme activity

  isotonic = the water potential is the same as the organelle therefore has no osmotic effect so the organelle will not burst

  buffer = maintain the pH to prevent proteins / enzymes in the organelle denaturing