Mission X Flashcards
Chap 1-4, ref to back of book for unFC Q
With reference to the cohesive and adhesive properties of water, suggest and explain how the formation of small clumps of soil helps to maintain the soil water around the root tip.
Water molecules form hydrogen bonds which creates cohesion between water molecules. The water molecules adhere to the soil clumps. Clumps provide small places in which water collects.
State the term used to describe enzymes that act outside the cells that synthesise them.
extracellular enzymes
Explain what is meant by a polysaccharide.
More than two monosaccharides joined by glycosidic bonds. Eg: sucrose.
In liver cells, enzymes are attached to the membrane of smooth endoplasmic reticulum.
With reference to the functions of smooth endoplasmic reticulum, suggest the advantages of having enzymes attached to the membrane rather than free in the lumen.
- There is more efficient synthesis of products such as lipids (Eg: cholesterol), and steroid hormones such as oestrogen and testosterone.
(synthesis of products require more than one enzyme)
- The membrane gives the enzymes greater protection against degradation.
Explain the advantages of using a transmission electron microscope compared with a light
microscope when viewing a liver cell.
It has a higher resolution (of 5nm compared to 200nm) and so higher magnification without loss of detail. Organelles such as ribosomes are visible.
Explain why this protein is described as globular.
This protein is spherical and soluble. Amino acids with hydrophilic R groups are on the outside of the molecule. Hydrophobic R groups in the centre. Has a physiological role. (Is an enzyme)
State the function of carbonic anhydrase in red blood cells.
Carbonic anhydrase catalyses the reaction between water and carbon dioxide to form carbonic acid.
Different strains of a virus have been formed by mutation. In each strain, the primary structure of the active site of the enzyme (which allows the virus to leave host cells) remains unchanged.
Suggest why the primary structure of the active site remains unchanged in each strain of the influenza virus.
The substrate is able to bind to the active site, so viruses can leave host cells to infect other cells.
The gene mutation is not occuring in the gene coding for the amino acids in the active site for the enzyme. The gene for the enzyme is essential for survival.
State the differences between the structure of a virosome and a virus
Virosome has no genetic material or a protein coat.
(Of a plant cell) Enzymes contained in the vacuole are released into the cytoplasm.
Name an organelle found in animal cells that has a similar function to the vacuole in the developing xylem vessel elements.
Lysosome
During development of the xylem vessel elements the pH of the cytoplasm decreases.
This change in pH activates enzymes in the cytoplasm that cause organelles to swell.
Suggest how a change in pH of the cytoplasm can activate enzymes.
Active site becomes complementary to substrate, because hydrogen/ionic bonds altered between R groups of amino acids.
State one role of cholesterol in phospholipid bilayers.
Cholesterol in phospholipid bilayers maintains the fluidity of the membrane. (Eg: Reducing fluidity at high temperatures).
It maintains the stability of the membrane. Without cholesterol, membranes would easily rupture. Its flat ring structure interferes with the movement of fatty acid tails and reduces the lateral movement of phospholipids.
It prevents the entry of hydrophilic substances.
Explain why sodium ions cannot cross phospholipid bilayers by simple diffusion.
Sodium ions are positively charged and so are repelled by the hydrophylic tails.
No. 3 Number circled blue (need to ask about ms)
Compare facilitated diffusion and active transport by stating ways in which they are different.
Both involve a transport protein,
No 3 Number circle blue
Compare facilitated diffusion and active transport by stating ways in which they are similar.
Suggest an advantage for this reaction pathway occurring in the smooth endoplasmic reticulum of a cell rather than in the cytoplasm.
phospholipid–>arachidonic acid with enzyme, COX–>prostagladin (small lipids formed from phospholipids)
SER is membrane-bound and so can provide the arachidonic acid/phospholipids. The reaction is separated from the cytoplasm, so the cell chemistry is not disturbed.
SER is involved in lipid transport: prostaglandins are lipids therefore they can be transported from the SER or stored in the SER.
Suggest how modifying the R-group of an amino acid in the COX enzyme can reduce the catalytic activity of the enzyme.
The shape of the active site is changed, so the active site is no longer complementary to the substrate. The enzyme-substrate complex could be formed at a reduced rate or not at all.
Outline the role of the tissue that the endodermis is found.
The endodermal tissue stops water moving through the apoplast, so that water moves from the cell wall to the cytoplasm. It controls the substances into the root’s stele.
State an example of an organic compound that is translocated in the root of an iris.
Sucrose, amino acids and auxin.
Name four polysaccharides.
Glycogen, cellulose, amylose and amylopectin.
What specific monomers are the four polysaccharides made up of?
They are all made up of alpha-glucose, except cellulose which is made up of beta-glucose.
Discuss the glycosidic bonds of the four polysaccharides.
Amylose and cellulose have 1,4 bonds. Glycogen and amylopectin have 1,4 and 1,6 bonds.
What is the function of amylopectin and amylose?
Energy storage in plants
What is the function of glycogen?
Energy storage in animals
What is the function of cellulose?
Structural role in plant cell walls
What are prokaryote cell walls made of?
Peptidoglycan, not cellulose
Explain how proteins that have not folded correctly are broken down in the vacuole.
By the action of proteases and the process of hydrolysis, the peptide bonds are broken to form amino acids.
Describe how a molecule of cellulose differs from a molecule of glycogen.
Glycogen is branched. Its monomers are alpha-glucose. Has 1,4 and 1,6-glycosidic bonds. (Cellulose only has 1,4) The 1,4-bonds are not rotated unlike in cellulose where they are rotated 180 degrees.
Explain how the structure of glycogen is related to its function in cells.
Glycogen stores energy. Glycogen has many branching points for easy release of glucose. It is compact, so it stores much glucose in a cell. Glycogen has no osmotic effect in a cell. It prevents loss of glucose from the cell.
Explain how the arrangement of cellulose molecules in plant cell walls is related to their function.
Cellulose is linear, with its molecules arranged in parallel. It has a large number of OH- groups projecting in all directions, making the molecule hydrophylic. Cellulose molecules are joined by hydrogen bonds. They form microfibrils. The many H bonds gives high tensile strength to microfibrils.
Convert micrometre to mm
divide by 1000
Convert metres to nanometres.
multiply by 10^9
After final processing in the Golgi body, collagen is released to the outer surface of the cell by exocytosis.
Complete the passage to describe the process of exocytosis…
After final processing in the Golgi body…
The Golgi vesicles containing the collagen , bud off the Golgi body. These vesicles are moved by microtubules to the cell surface membrane and ATP is required for this.
The vesicle then fuses with the cell surface membrane. Phospholipid bilayers merge into one.
State and explain what the outcome will be for the composition of the extracellular matrix if collagenase inhibitor activity is needed. (Process is breaking down collagen)
Collagen will not be broken down. The inhibitor will bind with the enzyme often, so few enzyme-substrate complexes form. There is an increase in collagen.
State the effect that a non-competitive inhibitor will have on the maximum rate of reaction, Vmax, and the Michaelis–Menten constant, Km, of collagenase.
Vmax decreases.
Km stays the same.
Explain why water is the main component of xylem sap and phloem sap.
Water is a good solvent, so substances that is transported in the sap such as ions ,dissolve in water. There is cohesion between the water molecules and adhesion between the water and xylem wall due to H bonds.
Water is used to build up hydrostatic pressure for translocation. Water moving down the transpiration stream contributes to transpiration stream.
Outline how changing one amino acid in the β-globin polypeptide of haemoglobin may change the structure and function of a molecule of haemoglobin.
A different amino acid will have a different R-group, which may prevent the formation of bonds between R-groups or may form different bonds between R-groups. This can change the folding of the β-globin polypeptide, altering haemoglobin’s globular shape.
If the new group is non-polar instead of polar, its ability to bind with O2 and CO2 will change.
Explain how molecules of cellulose are arranged into a microfibril.
Cellulose molecules are linear (unbranched) chains arranged in parallel. There are H bonds between the cellulose molecules, specifically between the -OH groups.
Explain why channel proteins are needed for the movement of ions into and out of cells.
Ions are hydrophilic, meaning they cannot pass through the hydrophobic core of the phospholipid bilayer. Channel proteins allow facilitated diffusion to occur, providing a hydrophilic, water-filled pathway, allowing ions to move into and out of the cell.
What are the elements of collagen?
CHON
What are the elements of DNA?
CHONP
What are the monomers of collagen?
amino acids
What are the monomers of DNA?
nucleotides
Name the bond between the DNA monomers.
phosphodiester
Name the bond between collagen monomers.
peptide
Where is the site of production of DNA in eukaryotic cells?
nucleus
Where is the site of production of collagen in eukaryotic cells?
ribosomes
State how the structure of a nucleus is suited to its function of containing DNA.
The nucleus has a double membrane, known as the nuclear envelope, which contains nuclear pores that are too small for DNA to pass through. This helps protect DNA from being broken down by enzymes. The nuclear envelope also separates the nucleus from the rest of the cell, creating a barrier between the nucleus and the cytoplasm.
What is the thickness of a cell membrane?
7nm
What is the function of a channel protein of the membrane?
Facilitated diffusion: transport of polar molecules.
What is the function of phospholipid of the membrane?
Phospholipids form the bilayer, forming a hydrophobic core which acts as a barrier to hydrophilic molecules.
What is the function of glycoproteins and glycolipids?
They act as receptors for cell signaling.
What is the function of cholesterol?
Cholesterol gives mechanical stability by maintaining the fluidity of the membrane. (Eg: at low temperatures, it prevents the hydrophobic tails of the phospholipid molecules from getting too close)
Explain how the properties of water make it suitable as the main component of blood.
Water is a good solvent. Urea is a polar molecule that can dissolve and get transported in the water component of the blood, so that it can be excreted. Water has a high specific heat capacity, so the temperature of the blood remains fairly constant.
