B3 Flashcards
What do plant cells have the animal cells don’t?
Chloroplasts, cell wall and a vacuole.
What does the nucleus contain?
DNA in the form of chromosomes.
What does a cell membrane do?
Keeps cell together and controls what goes in and out.
What happens in the ribosome?
Proteins are synthesised.
What happens in the cytoplasm?
Chemical reactions.
What happens in the mitochondria?
The reactions involved with respiration take place.
What happens in the chloroplasts?
Photosynthesis.
What does the cell wall do?
Supports the cell.
What does the vacuole contain?
Cell sap.
What do bacteria have instead of a nucleus?
A single circular strand of DNA that floats freely in the cytoplasm.
What are chromosomes?
Long molecules of coiled up DNA.
What is the structure of DNA?
A double helix.
What are the short sections of DNA called?
Genes.
What connects the two strands of DNA together?
Bases.
What are the four different bases?
A, C, G and T.
Which bases pair up with which?
A and T, C and G.
Who built the first DNA model and when?
Watson and Crick in 1953.
What does DNA control the production of?
Proteins in the cells.
What is a section of of DNA that codes for a protein called?
A gene.
What decides the order of amino acids in a protein?
The order of bases.
What codes for the amino acid?
A sequence of three bases.
How does the code get from the DNA to the ribosome?
The mRNA carry it.
Why do different cells have different functions?
Because they all make different proteins.
Why do cells only make certain proteins?
Only some of the full set of genes is used in a cell.
Example: In a muscle cell, which genes would be switched on?
The genes that code for the muscle.
What is the function of enzymes?
To control cell reactions.
What is the purpose of carrier molecules?
To transport smaller molecules e.g. haemoglobin.
What is the purpose of structural proteins?
To provide strength to cells and other structures - they are very strong.
Why do reactions in cells need to be carefully controlled?
In order to get the right amounts of substances and keep the organism working properly.
What do enzymes act as?
Biological catalysts.
What is the benefit of enzymes as catalysts?
They aren’t changed and also don’t get used up.
What is unique about each enzyme?
Their shape.
What are the two main parts of an enzyme?
The substrate molecule and the active site.
How is each enzyme unique?
The substrate and active site will be unique and so they will only be able to fit into each other.
What affects enzyme activity?
Temperature and pH.
What can happen if their is high/low pH’s and high temperatures?
The enzyme can denature meaning it cannot fit together anymore and cannot work.
How do mutations occur?
Either spontaneously or as a result of radiation/chemicals.
What can mutations cause?
Production of different proteins, general harm and can occasionally have an advantage.
What do gene mutations do?
Prevent the production of the protein that is usually made.
What does respiration do?
Releases energy from food which is trapped in a molecule called ATP.
What is the balanced symbol equation for aerobic respiration?
C6H12O6 + 6O2 –> 6CO2 + 6H2O
What does aerobic respiration involve the use of?
Oxygen
Why does anaerobic respiration happen?
When the muscles do not receive sufficient oxygen.
What is the word equation for anaerobic respiration?
glucose –> lactic acid (+energy)
What is bad about lactic acid?
It builds up in the muscles and causes pain.
What is the name for the build up of lactic acid?
The oxygen debt.
How can the respiration rate be measured?
Measuring how much oxygen is used up or the rate at which carbon dioxide is made.
What is the formula for respiratory quotient?
RQ = carbon dioide produced / oxyen used.
What is the metabolic rate?
The sum of all the reactions that are occurring in the body.
What are the advantages of being multicellular?
It allows an organism to become larger and more complex. It also allows different cells to different jobs (cell differentiation).
What does a multicellular organism need to be able to do?
Allow communication between all cells, supply all cells and control exchange of things such as heat and gases.
What is mitosis?
The process that produces new cells for growth.
What are the cells that are made by mitosis?
Genetically identical.
What happens before cells divide?
They are replicated.
What are diploid cells?
Cells with two copied of each chromosome.
What is meiosis?
The cell division that produces gametes (sex cells).
What are haploid cells?
Cells that contain only one chromosome from each pair.
What is the liquid part of the blood called?
Plasma.
What does plasma carry around the body?
Dissolved food, carbon dioxide, hormones, proteins and waste.
What do red blood cells carry?
Oxygen.
How are red blood cells adapted?
Very small, shaped like biconcave discs so larger surface area, contain haemoglobin and don’t have a nucleus.
What do haemoglobin react with and what is formed?
They react with oxygen in the lungs, forming oxyhaemoglobin.
What does the biconcave shape of the red blood cell provide?
A larger surface area to volume ratio to exchange oxygen quicker.
What are the three types of blood vessel?
Arteries (blood away from heart), veins (blood back to heart) and capillaries (link arteries to veins).
How are arteries adapted?
Have a thick muscular and elastic wall.
How are veins adapted?
Have large lumen and valves to prevent the flow going backwards.
How are capillaries adapted?
Have permeable walls so substances can be transferred.
What do the left and right atria do?
Receive blood from the veins.
What do the left and right ventricles do?
Pump blood out into arteries.
What do the semilunar, tricuspid and bicuspid valves do?
Prevent the backflow of blood.
What are the pulmonary veins and vena cava?
The main veins carrying blood back to the heart.
Which ventricle has a thicker muscle and why?
The left one as it has to pump blood all over the body, rather than just to the lungs.
What is the double circulatory system?
Where the blood is pumped to the lungs and returns to the heart to be pumped to the body.
How are bacterial cells different from plant and animal cells?
They lack a ‘true’ nucleus, mitochondria and chloroplasts.
Where is DNA found in a bacterial cell?
In the cytoplasm as a single circular strand or chromosome.
What is the best way to measure growth?
Using dry mass, however this requires killing the organism.
What makes stem cells unique from other types of cell?
They stay undifferentiated, meaning they can develop into different types of cells.
How can stem cells be obtained?
From embryos and can potentially be used to treat some medical conditions.
Why do some people think using stem cells is wrong?
Because the embryos are destroyed.
What are the differences between plant and animal growth?
Animals grow to a certain size while plants keep growing, plant cell division only happens in areas called meristems, plants gain height by cells enlarging rather than dividing, most animal cells lose the ability to differentiate at an early age.
What is the problem with selective breeding?
Can lead to inbreeding.
What can inbreeding lead to?
Reduced variety of alleles in the population (gene pool) causing an increased risk of harmful recessive characteristics showing up in offspring and a reduction in variation, so populations cannot adapt to change easily.
What is an advantage of genetic engineering?
Organisms with desired features can be produced very quickly.
What is a risk of genetic engineering?
Inserted genes may have unexpected harmful side effects.
What are the ethical issues involved with genetic engineering?
Some people are concerned about long-term side effects, or others think it’s morally wrong, despite any benefits.
What are the four steps for carrying out genetic engineering?
- The desired characteristics are selected.
- The genes responsible are identified and removed (isolation).
- The genes are inserted into other organisms.
- The organisms are allowed to reproduce (replication).
What is gene therapy?
The process of using genetic engineering to change a person’s genes and cure certain disorders.
What is the process of nuclear transfer?
Removing the nucleus from a body cell and placing it into an egg cell that has had its nucleus removed.
Why might animals be cloned?
- mass-produce animals with desirable characteristics
- produce animals that have been genetically engineered to provide human products
- produce human embryos to supply stem cells for therapy.
What is an ethical issue of cloning humans?
Some people think they will not be ‘true individuals’.
What are the specific steps of nuclear transfer?
- Donor egg has nucleus removed
- Egg nucleus replaced with other nucleus
- Embryo implanted into surrogate mother
- Embryo grows into clone.
What are the advantages of cloning plants?
-Growers can be sure of the characteristics of each plant since all the plants will be genetically identical. lt is also possible to mass-produce plants t hat may be difficult to grow from seed.
What are the disadvantages of cloning plants?
-If the plants become susceptible to disease or to change in the environmental conditions, then all the plants will be affected. There is a lack of genetic variation in the plants.
What is the process plants can be cloned by?
Tissue culture.
What are the steps of tissue culture?
- A plant is selected that has certain characteristics.
- A large number of small pieces of tissue are then cut from the plant.
- The small pieces of tissue are grown in test tubes or dishes containing a growth medium.
- Aseptic technique is used at all stages to stop any microbes infecting the plants.
Why is it easier to clone plants than animals?
Many plant cells retain the ability to differentiate, whereas animal cells often lose this ability at an early age.
