CAPE Biology unit 1 module 1

Describe and draw the structure of water.

The water molecule is made up of two atoms of hydrogen covalently bonded to one atom of oxygen.

How does the structure of water enables it to be a good solvent?

Water is a solvent. The tiny charges on its molecules attract other molecules or ions thats have charges on them. This is the because of the dipole.

How does water being a solvent and being able to flow play a role in the medium of life?

Cytoplasm contains many different substances dissolved in water. Water can flow and therefore can carry dissolved substances from one place to another. This happens in our blood and in the xylem vessels and phloem sieve tubes. Urea is removed from the body by being dissolved in water as urine.

Draw the structure of beta glucose.

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Draw the structure of alpha glucose.

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What are the functions of glucose?

Glucose is used as an energy source, a transport substance and a monomer to make other organic substances.

How does the structure of glucose enable it to be a good source of energy?

It's carbon atoms are easily oxidized to form carbon dioxide releasing energy in the process.

How does the structure of glucose enable it to be a good transport substance?

The numerous hydroxyl groups in glucose allows it to hydrogen bond with water molecules, thus making it highly soluble in water.

How does the structure of glucose enable it to be a monomer to make other organic substances?

The aldehyde group in glucose is very reactive so it will easily polymerize.

Describe the structure of the sucrose molecule and draw it.

A sucrose molecule is made up of an alpha glucose molecule linked to a beta fructose molecule by a 1-2 glycosidic bond.

What are the functions of sucrose?

Sucrose is used as an energy source, a transporter and a storage material in some plants.

How does the structure of sucrose enables it to be a good energy source?

The enzyme sucrase hydrolyzes sucrose to glucose and fructose since it is unreactive. The fructose molecule is then rearranged to form glucose.

How does the structure of sucrose enable it to be a good storage molecule and a good transport substance ?

The aldehyde group and the ketone group are linked together in the glycosidic bond, thus has no reactive group.

Draw the molecular structure of starch.

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What is starch made up of and what are the types of bonds?

Starch is a mixture of amylose and amylopectin joined together by an alpha 1-4 glycosidic bond. Amylopectin has alpha 1-6 branches which spirals to a lesser extent than the unbranched amylose which coils up into a spiral.

Why is starch insoluble?

Starch is made up of 79% amylopectin. Amylopectin has branched chains and the more branched chains it has, the more insoluble it is.

How does the structure of starch enable to be a good energy reserve?

The enzyme amylase can break down starch into glucose molecules and since it coils to form spirals, it is more compact.

Draw the molecular structure of glycogen.

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Name the types of bonds in glycogen and the and what it is made up of?

Glycogen is made up of alpha glucose. It is made up of alpha 1-4 glycosidic bonds with alpha 1-6 branches.

Why is that glycogen so dense?

It has more branches than amylopectin so it is heavily branched, so it is less able to form spirals

How does the structure of glycogen allow it to be a good energy reserve and source and why is it insoluble?

Because glycogen is so widely branched, it is insoluble and it allows many enzymes to act simultaneously to cut off more glucose molecules. The chains also coil up into helical structures, making their final structure more compact (useful for storage).

What color does glycogen and amylopectin give with iodine?

Faint red

Draw the molecular structure of cellulose

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What is cellulose made up of and what are the bonds?

Cellulose is made up of beta glucose. The molecules are linked with beta 1-4 glycosidic bonds.

How does the structure of cellulose contribute to it being a very strong structure?

The cellulose molecule lies straight because of it's bonding. This allows hydrogen bonds to be formed between with hydroxyl groups of neighboring molecules. This produces bundles of molecules lying side by side called fibrils all held together by thousands of hydrogen bonds which are collectively strong

How does the structure of cellulose contribute in cells?

Bundles of fibrils are called fibres. Fibers are structurally very strong because of the many collectively strong hydrogen bonds and giving the molecule high tensile strength. This makes cell walls able to expand without breaking.

Why is cellulose difficult to digest?

Very few animals have an enzyme that can break its beta 1-4 glycosidic bond.

How does cellulose not being able to digest be of importance in human being?

Its is a good source of dietary fiber in the human beings remaining undigested as it passes through the alimentary canal and stimulating peristalsis.

What color does amylose give with iodine?

Blue-black

Draw the molecular structure of a triglyceride.

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What is triglyceride made up of?

Triglyceride is made up of one molecule of glycerol attached to three fatty acids with 3 hydrophobic hydrocarbon tails attached.

Describe triglycerides' role as a source of energy.

When triglycerides are respired they make compact and efferent stores. Triglycerides are used as thermal insulator.

What is triglycerides role in obesity?

High triglyceride levels contribute to obesity.

Draw the structure of a phospholipid molecule.

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Why are phospholipds amphipathic?

A phospholipid is part hydrophobic because of its long hydrocarbon tails that have non polar bonds. A phospholipid is part hydrophilic in its "head" because the head has a polar phosphate group attached.

Describe the structure of phospholipids.

Phospholipids are made up of two fatty acids attached to a glycerol head. The glycerol molecule is attached to a phosphate group.

What is the role of phospholipids in membrane structure and function?

Phospholipids form a bilayer thats acts as a barrier between the exterior of cells and the cytoplasm.

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How does the structure of phospholipids relate to it's function?

The phosphate head is water soluble and the two fatty acids are insoluble making the molecule have a hydrophobic and hydrophillic region. Two layers of phospholipids will form a bilayer when in contact with water.

Describe the generalized structure of an amino acid.

All amino acids have a central carbon atom, an amine group and a carboxylic acid group. Attached to the central carbon atom is a hydrogen atom, and a group that is specific to the type of amino acid ( R group)

Draw the structure of an amino acid.

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Show the formation of a peptide bond .

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Show the breakage of a peptide bond.

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Explain the meaning of the primary structure of proteins.

The primary structure of proteins is the sequence of amino acids linked together in a polypeptide or protein which determines the position of disulfide bonds by using the position of cysteines in the sequence.

Explain the meaning of the secondary structure of proteins.

This is the interactions among the various amino acids along a polypeptide chain which causes it to fold into a pattern known as the secondary structure.

Name the two types of secondary structures and state what bonds they are held together by.

Alpha helix and beta pleated sheet. They are held together by hydrogen bonds.

Describe the alpha helix.

The polypeptide chain is wound round to form a helix. It is held together by hydrogen bonds running parallel along the long helical axis.

Describe the beta pleated sheet.

Parallel polypeptides with beta chains are held together to form beta pleated sheets with hydrogen bonds which stabilizes the beta chains.

Explain what is meant by the tertiary structure of proteins.

This is the three dimensional structure formed by the folding up a whole polypeptide chain.

What are the bonds that hold together the teritiary structure of proteins?

The tertiary structure is held together by hydrogen bonds, ionic bonds and disulphide bonds and hydrophobic interactions between R groups.

Explain what is meant by the quaternary structure of proteins.

The structure is found only in proteins containing more than one polypeptide chains. The quaternary structure of proteins simply means how the difference polypeptide chains are held together.

What type of bonds are the quaternary structure held together by?

The quaternary structure of proteins is held together by hydrogen, ionic and disulfide bonds and hydrophobic interactions.

Describe the ionic bond that holds the protein molecule in shape and state how it can be broken.

And ionic bond forms between an R group with a full negative charge and one with a full positive charge. The bond is much stronger than a hydrogen bond and can only be broken by changes in pH.

Describe the hydrogen bond that holds the protein molecules in shape and state how it can be broken.

A group with a slight negative charge is attracted to one with a slight positive charge. The hydrogen bond is not very strong and is easily broken by high temperatures or a change in pH.

Describe the disulfide bond that holds the protein molecule in shape and state how it can be broken.

Disulfide bonds form between the R group of the amino acide cysteine . They are very strong covalent bonds, but can be broken by reducing agents.

Describe the hydrophobic interaction holds the protein molecule in shape.

R groups which contain only carbon and hydrogen atoms are hydrophobic. Hydrophobic R groups tend to be found together as water is nearly always present around a protein molecule and its chains. There is a slight attraction between them and this is called hydrophobic interaction. It is very weak.

Outline the molecular structure of haemoglobin.

Each molecule of hemoglobin is composed of four polypeptides , that is, two alpha globins and 2 beta globins. Each polypeptide has alpha helices do but no beta sheets. In the center of each polypeptide is a haem group. A haem group has a Fe 2+ at its centreand is not made of amino acids. Hemoglobin has a quaternary structure.

Hemoglobin is a globular protein, what is a globular protein?

A globular protein is a protein with a roughly spherical three-dimensional shape, that is mostly soluble in water.

What is the function of hemoglobin and how does it perform the function ?

Hemoglobin is used to transport oxygen. Each ferrous ion can combine with one oxygen molecule.

How does the structure of hemoglobin enable it to transport oxygen?

The nitrogen atom in histidine which is covalently bonded to the haem group is positively charged and its proximity to the positively charged iron ions prevents the iron ions from becoming too oxidized, which would inhibit the binding of oxygen molecules.

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.

State the function of collagen.

A collegen is an extracellular protein that provides toughness to skin, bone, cartilage, tendons, ligaments and muscles.

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.

How does the structure of collagen relates to it being an extra cellular protein that provides toughness?

The triple helices are joined together by covalent bonds which are very strong bonds forming fibrils and eventually a network of fibres. Also, the ends of the triple helices are staggered so it will not create a weak spot along the collagen fibrils.

What is the function of the rough endoplaismic reticulum?

It is the site for protein synthesis.

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 golgi body?

It modifies and packages proteins and it makes secretory vesicles and lysosomes.

What is the function of the mitochondria?

It is the site for aerobic respiration.

What is the function of ribosomes?

To assemble amino acids to make proteins.

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 chloroplasts?

It is the site of all the reactions of photosynthesis.

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 the nuclear envelope?

To separarte the nucleus from the cytoplasm and allow movement between the nucleus and cytoplasm.

What is the function of centrioles?

It assembles the spindle to move chromosones when the nucei divides.

What is the function of the nucleus?

It contains store of genetic information as DNA in chromosones which are in chromatins.

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.

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.

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 plastids (eg. Chloroplasts)

Chloroplasts are present in some plant cells and leucoplasts are present in some plant tissues however animal cells have no plastids.

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.

Compare 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.

Compare 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 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 carbohydrate storage.

Plant cells may contain starch grains in plastids while animal cells may contain glycogen granules.

With the use of annotations describe the structure of a prokaryotic cell showing structures that may or may not be present.

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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.

States the evidence which supports the endosymbiotic theory. (5)

1.The outer membrane of the envelope of mitochondria and chloroplasts 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 circular DNA that is not enclosed in a nucleus like that of prokaryotes.
3. Mitochondria and chloroplasts each have their own 70S ribosomes like prokaryotic cells.
4. Mitochondria and chloroplasts reproduce by binary fission, like bacteria which are prokaryotes
5. Mitochondria and chloroplasts are similar in size to prokaryotic cells.
Mebiriside

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.

Compare the structure of prokaryotic cells with that of eukaryotic cells in terms of DNA.

In prokaryotic cells, there are circular strands of DNA however in prokaryotic cells there is linear DNA is located.

Compare the structure of prokaryotic cells with that of eukaryotic cells in terms of membrane bound 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 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 ribosomes.

Ribosome in prokaryotic cells (70S/20nm)are smaller than the ribosomes in eukaryotic cells(80S/30nm).

Compare the structure of prokaryotic cells with that of eukaryotic cells in terms of flagella.

Prokaryotic cells sometimes have flagella but not of the 9+2 internal fibril arrangement, like that in eukaryotic cells.

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.

Define tissue.

A tissue is a group of cells grouped together to carry out the same function.

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.

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.

Draw the dicotyledonous root and label the tissues and state how they assist in the function of the root.

Parenchyma tissue-unspecialized

Vascular tissues- transports material through plants cells: pericycle

Xylem tissue- Transports water, cells: vessel elements

Phloem tissue- transports substances the plant has made. Cells: Phloem sieve elements

Outline the roles of phospholipids in membrane structure and function.

They provide a barrier to large polar molecules and ions, while permeable to non-polar molecules and small substances.

Outline the roles of cholesterol in membrane structure and function.

-maintain the fludity by preventing phospholipis from solidifying at low temperatures or becoming too fluid at high temperatures.
-stabilizes the bilayer by binding to polar heads and non polar tails.