B3 - Living and Growing Flashcards
Explain why liver and muscle cells have large
numbers of mitochondria.
Mitochondria is where respiration takes place; respiration provides energy for cell processes. Therefore, areas of the body that needs lots of energy will have large numbers of mitochondria.
- In the liver, lots of energy-demanding metabolic reactions take place. Lots of mitochondria are needed to provide that energy.
- Muscle cells need lots of energy to contract; mitochondria provide this energy.
Where does protein synthesis take place?
They happen in ribosomes, which are found in the cell’s cytoplasm.
Describe the basic structure of DNA.
- Two strands coiled together to form of a double helix.
- Each strand contains chemicals called bases.
- Cross-links between the strands formed by complimentary base pairs.
What is a chromosome?
A long-coiled molecule of DNA, divided up into regions called genes.
List the four bases of DNA and their complimentary base pairings.
A + T
G + C
Explain how a unique protein structure is determined by the
DNA base code.
- The order of the bases in a gene determines the order in which the amino acids join together in a protein.
- Each amino acid is coded for by a sequence of three bases.
- Each gene contains a different sequence of bases, allowing each gene to code for a unique protein.
Explain how code is carried from the nucleus to the ribosomes.
- DNA can’t move out of the nucleus because it is too large.
- mRNA is a messenger that copies the code from the DNA and transports it back to the ribosome.
- The ribosome then can use the bases from the copied genes to produce amino acids and proteins.
Explain how DNA controls cell function by controlling protein production.
- Some proteins determine cell structure, others (such as enzymes) control cell reactions.
- Different cells have different functions because they make different proteins.
- This is because only certain genes are used in any one cell. For example, muscle cells only use the genes that code for muscle proteins.
How did Watson and Crick build a model of DNA? Why wasn’t this model widely accepted straight away?
- X-rays showed that two chains were wound together to form DNA.
- Data showed that bases occurred pairs.
This model wasn’t accepted right away, as it was necessary for other scientists to repeat and test their work.
Describe the functions of different proteins (using examples where possible).
Structural proteins - e.g. collagen
Hormones - e.g. insulin
Carrier molecules - e.g. haemoglobin
Enzymes
Explain why different proteins have different shapes and functions.
Each protein has its own number and sequence of amino acids, resulting in each protein having a different shape/structure. This is why different proteins are better suited to different functions.
What is a substrate?
The molecule changed by catalyzed reaction involving enzymes.
Describe key features of enzymes.
- Biological catalysts
- Catalyze chemical reactions such as respiration and protein synthesis.
- They are highly specific to their substrate (the chemical they are acting upon).
Explain the specificity of enzymes in terms of the
‘lock and key’ mechanism.
- Each enzyme has an active site, which is the part that connects/joins on to the substrate.
- Enzymes are highly specific - usually only working for one substrate.
- The active site has a very specific shape; if the substrate’s shape doesn’t match the shape of the enzyme’s active site, the reaction won’t be catalysed.
Explain how enzyme activity is affected by pH and
temperature.
- Lower collision rates at lower temperatures, meaning the substrate is less likely to meet up with the active site of the enzyme.
- At extremes of pH and high temperatures, the enzymes become denatured.
- This is an irreversible change that alters the enzyme’s function.
- Denaturing changes the shape of the active site, often meaning that it is no longer able to catalyse reactions as it does not match up with the substrate.
What is the Q10 value for a reaction? How can it be calculated?
The Q10 value for a reaction shows how much the rate of reaction changes when the temperature is raised by 10 degrees.
Q10 = rate at higher temperature / rate at lower temperature
Explain how changes to genes alter, or prevent the
production of the protein which is normally made.
- A mutation is a change in the DNA base sequence.
- If the DNA base sequence changes, a different sequence of amino acids will be produced, resulting in a different protein is produced (or no proteins at all).
Mutations occur randomly, but how can their frequency be increased?
- Ionising radiation from EM waves can increase the chance of mutation.
- Chemicals, called mutagens, can increase the chance of a mutation occurring.
What is the symbol equation for respiration?
C6H12O6 + 6O2 —-> 6H2O + 6CO2
In what form does respiration produce energy for the body?
Respiration results in the production of ATP - ATP is used as the energy source (fuel) for lots of processes in cells.
Why can oxygen consumption be used an estimate for metabolic rate?
The metabolic rate is the rate at which energy is used by the body. Since aerobic respiration needs oxygen, the rate of oxygen consumption can be used as an estimate of metabolic rate.
Explain why the rate of respiration is influenced by
changes in temperature and pH.
The rate of respiration is controlled by enzymes. Therefore, at extremes of pH or high temperatures, the enzymes become denatured.
This means that their active sites can change shape and stop interlocking with the substrate. As a result, the reaction can no longer be catalysed as effectively, slowing it down.
Explain why anaerobic respiration takes place during
hard exercise in addition to aerobic respiration.
When you are exercising vigorously, your muscles need a lot more energy. This means more respiration needs to take place; anaerobic respiration requires oxygen. As a result, your body is unable to supply enough oxygen to your body.
Therefore, anaerobic respiration begins to take place - a form of respiration that doesn’t require oxygen.
Explain why anaerobic respiration is less efficient than aerobic respiration.
Anaerobic respiration produces much less energy per glucose molecule than aerobic respiration.
Explain fatigue in terms of lactic acid build up.
- Hard exercise causes a lack of oxygen in cells.
- As a result, glucose can only be partially broken down (incomplete) via anaerobic respiration.
- Lactic acid is built-up, and must be transported back to the liver to be broken down. This means that your heart rate remains high.
- To break down this lactic acid, extra oxygen is needed. This is why you continue breathing heavily (panting) after exercise - in order to repay your oxygen debt.
List the advantages of being multicellular.
- Allows organism to be larger.
- Allows for cell differentiation (specific cells can carry out specific jobs).
- Organism can become more complex.
