REVISION 1

• How is the dicotyledonous root an organ?

  The dicotyledonous root is made up of different types of tissues working together so that the root can absorb water and mineral ions.
• Define organ.

  An organ is a structure within a multicellular organism that is made up of different types of tissues working together to perform a particular function.
• Define tissue.

  A tissue is a group of cells grouped together to carry out the same function.
• Compare the structure of prokaryotic cells with that of eukaryotic cells in terms of cell walls.


  In prokaryotic cells the cell wall is always present and made up of peptidoglycan however in eukaryotic cells cellulose cell walls are present in plant cells.
• Compare the structure of prokaryotic cells with that of eukaryotic cells in terms of flagella.

  If flagella is present essential in prokaryotic cells then it would not have internal 9+2 fibril arrangements however in eukaryotic cells the flagella has 9+2 plus two internal fibril arrangement.
• Compare the structure of prokaryotic cells with that of eukaryotic cells in terms of ribosomes.

  Ribosome in prokaryotic cells are smaller than the ribosomes in eukaryotic cells.
• Compare the structure of prokaryotic cells with that of eukaryotic cells in terms of chloroplasts.

  In prokaryotic cells there are no chloroplasts present but only photosynthetic lamellae however in eukaryotic cells there are chloroplasts usually presents normally in plants and algae.
• Compare the structure of prokaryotic cells with that of eukaryotic cells in terms of organelles.

  In prokaryotic cells, there is no membrane bound organelles, however in eukaryotic cells there are membrane bounded organelles present.
• Compare the structure of prokaryotic cells with that of eukaryotic cells in terms of chromosomes.

  In prokaryotic cells, there is no chromosomes but there are circular strands of DNA however in prokaryotic cells there are chromosomes present on which DNA is located.
• Compare the structure of prokaryotic cells with that of eukaryotic cells in terms of the nucleus.

  In prokaryotic cells, there is no distinct nucleus but only diffused areas of nucleoplasm with no nuclear envelope, however in eukaryotic cells there is a distinct, membrane bound nucleus.
• States the evidence which supports the endosymbiotic theory. (5)

  1. Mitochondria and chloroplasts each have a pair of membranes that is an envelope surrounding them. The outer membrane is similar to other membranes of eukaryotic cells, while the inner one has similarities with membranes of prokaryotes.

  2. Mitochondria and chloroplasts each have their own small piece of DNA, which is circular like that of prokaryotes and is not enclosed in a nucleus.

  3. Mitochondria and chloroplasts each have their own ribosomes, which are the same size as those of prokaryotes.

  4. Mitochondria and chloroplasts reproduce by binary fission, like bacteria, before the whole eukaryotic cells divide by mitosis.

  5. Mitochondria and chloroplasts are often very similar in size to prokaryotic cells.
• Outline the basis of the endosymbiotic development of eukaryotic cells.

  The theory states of that mitochondria and chloroplasts where once prokaryotic cells that invaded a eukaryotic cell and lived inside it. A symbiotic relationship was formed as the prokaryotes carried out complex metabolic reactions such as respiration and photosynthesis that provided the eukaryotic cell with energy. The eukaryotes provided the prokaryotes with nutrients.
• With the use of annotations describe the structure of a prokaryotic cell showing structures that may or may not be present. ...
• Comapre the structure of a typical animal and plant cell in terms of carbohydrate storage.

  Plant cells may contain starch grains in plastids while animal cells may contain glycogen granules.
• Comapre the structure of a typical animal and plant cell in terms of the structure lysosome.

  Lysosomes are not usually evident in plant cells but are usually present in animal cells.
• Comapre the structure of a typical animal and plant cell in terms of the structures cillia and flagella.

  They are not present in most plant cells but they may be present in some animal cells.
• Comapre the structure of a typical animal and plant cell in terms of the structure centriole.

  Plant cells have no centrioles while animal cells usually have a pair of centrioles present.
• Comapre the structure of a typical animal and plant cell in terms of the structure vacuole.

  Plant cells have large, permanent vacuoles often present surrounded by a single membrane called a tonoplast and the vacuole contains cell sap. On the other hand, animal cells have temporary small vacuoles or vesicles.
• Comapre the structure of a typical animal and plant cell in terms of the structure plastids (eg. Chloroplasts)

  Chloroplasts are present in some plant cells and leucoplasts are present in tissues such as potato tubers, however animal cells have no plastids.
• Comapre the structure of a typical animal and plant cell in terms of the structure plasmodesmata.

  Plasmodesmata link adjacent cells, providing continuous membrane-lined passageway between them in plant cells, while animal cells have no plasmodesmata.
• Comapre the structure of a typical animal and plant cell in terms of the structure cell wall.

  The plant cell has a tough, elastic cell wall made of mainly cellulose, hemicellulose and sometimes lignin, while animal cells have no cell wall.
• What is the function of the nucleolus?

  It contains DNA that is used to make ribosomal RNA which is a component of ribosomes, thus producing ribosomes.
• What is the function of the nucleus?

  It contains store of genetic information as DNA in chromosones.
• What is the function of centrioles?

  It assembles the spindle to move chromosones when the nucei divides.
• What is the function of the nuclear envelope?


  To separarte the nucleus from the cytoplasm and allow movement between the nucleus and cytoplasm.
• What is the function of the cell membrane?

  It controls what entires and leaves the cell. It retains the cell contents.
• What is the function of chloroplasts?

  It is the site of all the reactions of photosynthesis.
• What is the function of lysosomes?

  The destroy worn out parts of the cell and digest food particles and bacteria with enzymes by fusing with vesicles in the cell.
• What is the function of ribosomes?

  To assemble amino acids to make proteins.
• What is the function of the mitochondria?

  It is the site for aerobic respiration.
• What is the function of the golgi body?

  It modifies and packages proteins and it makes secretory vesicles and lysosomes.
• What is the function of the smooth endoplaismic reticulum?

  It is the site for the synthesis of lipids and the site for the production of steroid hormones and it is the site where toxins are broken down to make them harmless.
• What is the function of the rough endoplaismic reticulum?

  It is the site for protein synthesis and it transports protein to the golgi body.
• How does the structure of collagen relates to it being an extra cellular protein that provides toughness?

  Polypeptides are long, consisting of about 1000 amino acids with glycine on every third amino acid. Glycine has the smallest R group so it does not take up much space. This means that helices can be wound tightly together and form many hydrogen bonds between them. The triple helices are joined together by covalent bonds which are very strong bonds causing the toughness of collagen thus forming network of fibers.
• Collagen is a fibrous protein, what does this mean?


  It means that collagen is insoluble in water and have simple shapes, such as a helix.
• State the function of collagen.

  A collegen is an extracellular protein that provides toughness to skin, bone, cartilage, tendons, ligaments and muscles.
• Outline the molecular structure of collagen.

  Collagen consists of three identical polypeptide chains, each in the shape of a left handed helix. These three helical polypeptides wind around each other to form a rope like structure called a triple helix.
• How does the structure of hemoglobin enable it to transport oxygen?

  The haeme group is covalently bonded to a nitrogen atom that belongs to a nearby histidine group. Oxygen molecules bind to the side of the iron ion that is opposite of the proximal

  histidine. Because histidine is positively charged, its proximity to the negatively charged iron ions prevents the iron ions from becoming too oxidized, which would inhibit the binding of oxygen molecules.
• What is the function of hemoglobin and how does it perform the function ?


  Hemoglobin is used to transport oxygen. Eats iron 2 + ion can combine with one oxygen molecule.
• Hemoglobin is a globular protein, what is a globular protein?

  A globular protein is a protein with a roughly spherical three-dimensional shape, thus it is folded into complex 3D shapes.