Cell (Structure & Transport)
What is the function of the cell membrane?
The cell membrane controls what substances can enter and leave the cell.
What molecule carries the genetic information for making proteins?
DNA carries the genetic information for making proteins.
What is meant by an enzyme?
An enzyme is a biological catalyst that speeds up chemical reactions and remains unchanged.
Genetic engineering is the transfer of genetic information from one cell to another.
What is respiration?
Respiration is a series of enzyme-controlled reactions that release energy from glucose in all cells.
What is meant by diffusion?
Diffusion is the movement of molecules from a higher concentration to a lower concentration down a concentration gradient.
State the four bases found in DNA.
Adenine, thymine, cytosine and guanine
State two functions of proteins.
Proteins can function as enzymes, structural components, hormones, antibodies or transport molecules.
What is a plasmid?
A plasmid is a small ring of DNA found in the cytoplasm of bacterial cells.
What molecule transfers energy in cells?
ATP transfers energy for cellular activities.
Describe one difference between plant and bacterial cells.
Bacterial cells lack membrane-bound organelles and have a different cell wall structure.
Explain how complementary base pairing occurs in DNA.
Adenine pairs with thymine and cytosine pairs with guanine.
Describe what happens when an enzyme-substrate complex is formed.
The substrate binds to the active site, the reaction occurs, and products are released.
Describe two stages in genetic engineering.
The required gene is extracted and inserted into a bacterial plasmid.
Describe what happens to glucose during the first stage of respiration.
Glucose is broken down into two molecules of pyruvate, releasing enough energy to produce two ATP molecules.
Explain what happens to animal and plant cells in a high water concentration.
Water enters the cell by osmosis; animal cells may burst and plant cels become turgid.
Explain how the sequences of bases in DNA determine a protein.
The base sequence determines the amino acid sequence, which determines the protein produced.
Explain how temperature can affect enzyme activity.
Identify the stages of genetic engineering that use enzymes.
Extracting the gene and inserting it into the plasmid use enzymes.
Explain what happens to pyruvate when oxygen is absent in animal cells.
Explain why active transport requires energy.
Energy is needed to move substances against their concentration gradient using membrane proteins.
Describe the role of mRNA in protein synthesis.
mRNA carries a complementary copy of the genetic code from the nucleus to a ribosome, where the protein is assembled.
Explain the difference between synthesis and degradation enzyme reactions.
Degradation reactions break large molecules into smaller ones, while synthesis reactions build larger molecules from smaller ones.
Explain why bacteria are suitable host cells for genetic engineering.
Bacteria reproduce rapidly and contain plasmids that can be genetically modified.
Compare aerobic respiration and fermentation in terms of ATP yield and location.
Aerobic respiration produces many ATP molecules and the second stage occurs in the mitochondria. Fermentation produces only two ATP molecules and occurs in the cytoplasm.