Cells Definitions Flashcards
(34 cards)
What is an Enzyme?
A biological catalyst (catalysts increase the rate of reaction)
How does substrate concentration affect the rate of enzyme activity?
Speeds it up until saturation occurs, because the are no free enzymes for the substrate to bind to.
How does enzyme concentration affect the rate of enzyme activity?
Speeds it up until saturation occurs, because the are no free substrate molecules for the enzyme to catalyse.
How does temperature affect the rate of enzyme activity?
- Up until the optimum temperature, increasing the temperature will increase the rate of enzyme activity because adding the heat makes the enzymes move faster, increasing the kinetic energy.
- Past the optimum temperature, the bonds holding the active site together will begin to break, which will change the shape of the active site and cause the enzyme to denature.
How does pH affect the rate of enzyme activity?
- Each enzyme has an optimum pH. Most enzymes have an optimum pH of 7 except for some like pepsin (in your stomach), which has an optimum pH of 1.5-2.
- Outside the optimum pH level, the enzyme will denature as the active site shape will change.
What are enzyme inhibitors and how do they work?
They prevent the enzyme from functioning, thus denaturing it.
Competitive inhibitor - blocks the active site.
Non-competitive inhibitor - binds to another part of the enzyme, causing the shape of the active site to change.
Examples: any heavy metal - cadmium, mercury
What are co-enzymes?
They bind to the active site in order for the substrate to fit.
What is cellular respiration?
Converting glucose to ATP
glucose + oxygen ==> ATP + CO2 + water
Where does cellular respiration take place?
Mitochondria
Why do some cells have more mitochondria than other cells?
Because they need more energy.
e.g. liver cells because they are metabolising many toxins and other chemicals
whereas bone cells would have little mitochondria
What is in the mitochondria that makes respiration happen at a faster rate?
Cristae - folds in the inner membrane. Increases surface area to volume ratio, increasing rate of reaction.
Matrix - fluid inside the inner membrane. Contains enzymes, which speed up the rate of reaction.
What is the difference between aerobic and anaerobic respiration?
Aerobic respiration - respiration with oxygen. Produces more ATP than anaerobic.
Anaerobic respiration - respiration without oxygen. Produces very little ATP. Produces lactic acid.
What affects the rate of cellular respiration?
Amount of mitochondria
Anything that affects the rate of enzyme activity, as cellular respiration is mediated by enzymes
What is cell division?
A cell copies itself and splits into two.
When would cell division happen at a greater rate for an organism?
When the organism is younger and undergoing rapid growth, the cells need to divide quickly to accomodate this.
When the organism is hurt/tissue is damaged, the cell needs to divide quickly to repair it.
What are the different phases of the cell cycle?
G1 - preparing the cell for replication, chromosomes begin replicating, organelles replicate.
S - synthesis of DNA - DNA replication
G2 - enzymes, proteins replication
M - cell divides (mitosis)
Why is the cell cycle important?
The cell cycle is important because there are different checkpoints, and these are important because they are there to prevent the onset of uncontrollable cell growth (essentially cancer)
Without it, we would not be able to get new cells.
Checkpoints are used by the cell to monitor and regulate the progress of the cell cycle. If a cell fails to meet the requirements of a phase it will not be allowed to proceed to the next phase until the requirements have been met. Several checkpoints are designed to ensure that damaged or incomplete DNA is not passed on to daughter cells. At the end of the G1 phase, G2 phase and after DNA has been replicated in the S phase it is checked for damages. At the end of the M phase a checkpoint is present to stop cytokinesis in case the chromosomes are not properly aligned on the mitotic spindle
What is Mitosis?
Cells divide into two identical daughter cells
What are stages of Mitosis?
- The replicated chromosomes are pulled apart/separate
- A new nucleus is formed, giving the cell two nuclei
- The cell then splits into two daughter cells
Why is Mitosis important?
Mitosis is important because cells need to divide in times of growth and repair.
Also, it divides the cell when the cell starts getting too big, which keeps the surface area:volume ratio high. Maximum rate of reaction for cell processes.
What are the stages of DNA replication?
- The DNA double helix unzips using an enzyme (helicase).
- This results in exposed bases. Free nucleotides bond to the exposed bases using the complementary base pairing rule (A and T & G and C)
- This creates two DNA molecules. Each DNA molecule has one existing strand and one new strand (semi-conservative replication).
How does semi-conservative replication work? Why is it important?
- Semiconservative replication is when two DNA copies are produced that each contain one original strand and one new strand.
- Semiconservative replication is important as it keeps the DNA exactly the same. The existing strand is a template for the new strand of DNA to bond to. This prevents any errors because it has the existing strand to check for errors with.
What is cell transport? Where does it happen?
Done through the cell membrane and is the movement of particles in and out of a cell.
What are the two different categories of cell transport?
Active transport and passive transport
