B3 Flashcards
What are mitochondia, what do they do and where are they found in their largest numbers?
Mitochondria are tiny structures found in cells (one is called a mitochondrion). Respiration, the chemical reaction that releases energy from glucose, happens in mitochondria.
Tissues and organs that need a lot of energy have large numbers of mitochondria in their cells. For example, liver cells and muscle cells contain a lot of mitochondria.
What are ribosomes, what do they do and why cant they always be seen?
Some cell structures are too small to be seen with the light microscope. Ribosomes are like this. They are found in the cytoplasm and are the site of protein synthesis. They can only be seen using an electron microscope.
Desribe the structure of DNA.
- Each strand of DNA is made of chemicals called bases.
- There are four different types of bases, shown as A, T, C and G in the diagram.
- In DNA, two strands coil together to form adouble helix. There are chemical cross-links between the two strands, formed by pairs of bases.
What bases in DNA match with which and what is that called?
A – T
G – C
This is complimentary Base Pairing
How is a protein structure developed?
The DNA base code
- Protein structure is determined by the DNA base code.
- Proteins are made from lots of amino acids joined together. Each amino acid is coded by the sequence (order) of three bases.
- The sequence of bases determines the sequence of amino acids in a protein molecule.
- DNA controls the functions of a cell by controlling its production of proteins. Some of these proteins are enzymes.
Describe how ribosomes get the genes from the nucleus
Ribosomes are the site of protein synthesis. They are found in the cytoplasm but DNA is found in the nucleus. The genetic code needed to make a particular protein is carried from the DNA to the ribosomes by a molecule called mRNA.
Making:
- mRNA from DNA is called transcription
- Proteins from mRNA is called translation
Proteins are ___________ relatively large molecules made from many smaller molecules. Each protein molecule is built up from amino acids, smaller _________molecules that join end to end to make the protein ___________ molecule. - fill in the blanks
polymers, monomer, polymer
Give 3 examples of reactions sped up by a biological catalyst. What is this biological catalyst?
Enzymes are biological catalysts – protein molecules that speed up chemical reactions.
- Respiration
- Photosynthesis
- Protein synthesis
The shape of an enzyme determines how it works - describe why, and what this is called.
- Enzymes have active sites that substrate molecules (the substances involved in the chemical reaction) fit into when a reaction happens.
- The active site has to be the right shape for the substrate molecules to fit into.
- This means that enzymes have a high specificity for their substrate – a particular type of enzyme will only work with one or a smaller number of substrates.
- The mechanism involved is called the ‘lock and key’ mechanism.
What conditions affect how enzymes work best
particular temperatures and pH values.
Describe breifly how enzmes work with temperature
At low temperatures, enzyme reactions are slow. They speed up as the temperature rises until an optimum temperature is reached. After this point the reaction will slow down and eventually stop.
Describe breifly how enzymes work with pH
- Different enzymes work best at different pH values, their optimum pH. Many enzymes work fastest in neutral conditions. Making the solution more acidic or alkaline will slow the reaction down. At extremes of pH the reaction will stop altogether.
- Some enzymes, such as those used in digestion, are adapted to work faster in unusual pH conditions. For example, stomach enzymes have an optimum pH of 2, which is very acidic.
What 3 ways can mutations be caused?
- Spontaneous
- Radiation
- Chemicals, such as tar from cigarette smoke
How to mutations work?
Genes can be switched on and off. In any one cell, only some of the full set of available genes are used. Different types of cells produce different ranges of proteins. This affects the functions they can carry out. For example, only pancreas cells switch on the gene for making the hormone insulin.
Mutations to genes can alter the production of certain proteins, or even prevent them being made by a cell.
Mutations can be helpful or harmful. What else an they be?
Having no effect.
Describe what happens to enzymes at extremes of pH and high temperatures.
What happens at extreme low tempratures?
Changing the shape of the active site of an enzyme will cause its reaction to slow down until the shape has changed so much, the substrate no longer fits. When this happens the reaction stops. At this point we say the enzyme is denatured.
Enzymes work slowly at low temperatures too. However, this is because the substrate molecules have less energy and move into the active site more slowly. This is not a permanent change.
What is Q10?
A measure of the rate of change of a reaction when the temperature is increased by 10 °C
Describe 3 life processes energy is needed for
- Protein synthesis
- Muscle contraction
- Control of body temperature in mammals
What is the difference between aerobic and Anaerobic respiration?
Anaerobic respiration does not need oxygen for it to happen.
How can respiration rate be measured (NOT detailed)
- Increased oxygen consumption
- Increased carbon dioxide production
What is the word equation for aerobic respiration
Glucose + oxygen → carbon dioxide + water
Muscles respire more during excersize than they do at rest. What 2 things must occur beacaue of this?
- Oxygen and glucose must be delivered to them more quickly
- Waste carbon dioxide must be removed more quickly
Give the word equation for anaerobic respiration
Glucose → lactic acid
why does anaerobic respiration hurt and why is it not as effective?
The waste product, lactic acid, builds up in the muscles causing pain and tiredness.
Anaerobic respiration releases much less energy per glucose molecule than aerobic respiration does.
What influences respiration rate and why?
The rate of respiration is influenced by changes in temperature and pH. This is because enzymes are involved in respiration, and their activity varies with temperature and pH.
What is metabolic rate and how can it be estimated?
Themetabolic 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.
It takes a while to recover from hard exercise, during which time you may still breathe heavily and have a higher heart rate than normal.Why?
- Hard exercise causes a lack of oxygen in cells
- Glucose is not broken down completely in anaerobic respiration
- Panting replaces oxygen, allowing aerobic respiration to happen
- The increased heart rate ensures that the blood carries lactic acid away to the liver.
What is ATP and where is it produced?
ATP is a substance that is used as the energy source for many processes in cells. ATP is produced as a result of respiration.
Give 3 advantages of being multicelluar
- The organism can be larger
- Cell differentiation (having different types of cells with different functions)
- The organisms can be more complex
Why do multicelluar organims need specialised organ systems? (3 reasons)
- Communication between cells, eg the nervous system and circulatory system
- Supplying the cells with nutrients, eg the digestive system
- Controlling exchanges with the environment, eg the respiratory system and excretory system
Name 3 things mitosis may be used for.
- Growth
- Repair to damaged tissue
- Replacement of worn out cells
- Asexual reproduction (which involves only one parent)
Describe breifly the four stages of mitosis and detail on the chromosomes.
Chromosomes:
- Line up along the centre of the cell
- Divide
- Copies then move to opposite poles (ends) of the cell
Name 3 sperm adaptations.
- A tail to move them towards an egg cell
- Many mitochondria to provide energy
- An acrosome (part of the tip of the head) that releases enzymes to digest the egg membrane
