Flashcards in B3 Deck (131):
Where do fundamental processes of life take place?
What do all cells contain?
Cytoplasm, a cell membrane, a nucleus and mitochondria.
Where do chemical reactions within a cell take place?
In the cytoplasm.
What is the purpose of a cell membrane?
Allowing movement in and out of the cell.
What is the purpose of the nucleus?
It contains the genetic information and controls the cell's actions.
Where does respiration take place?
Inside mitochondria, which supplies energy for the cell.
Name three cell types that have a high energy requirement, and as such have large numbers of mitochondria.
Muscle cells, liver cells and sperm cells.
Name a structure in a cell which is too small to see with a light microscope
Where are ribosomes located?
In the cytoplasm.
What are the site of protein synthesis?
What are inside the nucleus of every cell?
What do chromosomes carry?
genetic information in the form of genes
What is a gene?
A region of chromosome that carries information about, and controls, a particular inherited characteristic.
What does the order/sequence of the bases provide?
The genetic code that controls cell activity.
How are genetic instructions carried?
By genes on chromosomes
What are chromosomes?
Long coiled molecules of DNA
How many pairs of chromosomes does the human body have in its cells
What does DNA control?
The production of proteins
What does the genetic code control?
Cell activity and some characteristics of the organism
What is the shape of the DNA molecules?
Double helixes (spirals)
What is complementary base pairing?
A always bonds with T, C always bonds with G
Where are proteins made?
In the cytoplasm
In a protein chain, what does a group of three bases represent?
One amino acid
What does the sequence of bases in a gene represent?
The order in which the cell should assemble amino acids to make the protein
What are proteins made of?
Long chains of amino acids
How does DNA control cell function?
By controlling the production of proteins, some of which are enzymes
What are enzymes?
Proteins that act as biological catalysts
What do enzymes do?
Speed up chemical reactions, including those that take place in living cells
What does the fact that enzymes are 'highly specific' mean?
Each enzyme only speeds up on particular reaction
How can enzyme activity, and therefore rate of reaction, be affected?
By a change in temperature or pH
How can the fact that enzymes are 'highly specific' be explained?
Every enzyme has an active site that only a specific reactant can fit into, like a key in a lock
How can the fact that enzyme activity can be affected by changes in temperature/be explained?
When enzymes get exposed to high temperatures/extreme pH, the bonds holding the protein's shape breaks, and so the shape of the enzyme's active site is denatured
What does it mean when a protein is 'denatured'?
It is changed irreversibly
What do temperatures above the 'optimum' do to enzymes?
Damage them irreversibly, decreasing or stopping enzyme activity
What are mutations?
Changes to genes
How can the rate of mutation be increased?
By environmental factors such as radiation or chemicals
What do mutations do?
They change the basic sequence of DNA. This alters the proteins shape and function, or prevents the production of the protein that the gene normally codes for.
How is energy needed for all life processes in plants and animals provided?
What is aerobic respiration, and which cells does it take place in?
The release of energy from glucose in the presence of oxygen. It takes place in all cells.
What happens when exercising in terms of respiration?
Muscles require more energy so respiration must go faster to release more energy.
Why does breathing and pulse rate increase when exercising?
To deliver oxygen and glucose to muscles more quickly and remove carbon dioxide from muscles quickly
What is the recovery rate?
How quickly the heart rate returns to resting after exercise.
Glucose + Oxygen ->
Carbon Dioxide and Water
What does aerobic respiration require?
What is the rate of oxygen consumption?
An estimate of metabolic rate
What type of reaction is respiration, and what does that mean?
An enzyme-controlled reaction, meaning that its rate is influenced by pH or temperature
What is ATP?
Adenosine triphosphate (ATP) is considered by biologists to be the energy currency of life. It is the high-energy molecule that stores the energy we need to do just about everything we do. It is present in the cytoplasm and nucleoplasm of every cell, and essentially all the physiological mechanisms that require energy for operation obtain it directly from the stored ATP
What does respiration result in the production of?
When does anaerobic respiration occur?
when the muscles are working so hard that the lungs and circulatory system can't deliver enough oxygen to break down all the available glucose through aerobic respiration
What does anaerobic respiration do?
It quickly releases a small amount of energy through the incomplete breakdown of glucose, so much less energy is released than in aerobic respiration.
How much energy, approximately, is released in anaerobic respiration in comparison to aerobic respiration?
About a twelfth of the energy released in aerobic respiration is released in anaerobic respiration.
In which form of respiration is Lactic acid produced?
What is the effect of lactic acid being produced in anaerobic respiration?
It is relatively toxic to the cells, and when it builds up in the muscles it can cause a sensation of fatigue in the muscles and painful cramps.
Immediately after anaerobic exercise, why does deep breathing continue?
So that oxygen is taken in to break down the lactic acid (producing carbon dioxide, water and more energy)
Immediately after anaerobic exercise, why does the heart rate stay high?
So it pumps blood quickly through the muscles to remove the lactic acid and transport it to the liver to be broken down.
Two words that describe multi-cell organisms.
Large + complex
Name three advantages of being multicellular
Allowing organisms to be larger, allowing for cell differentiation, and allowing organisms to be complex
What does becoming multicellular require the development of specialised organ systems for?
Communication between cells, supplying the cells with nutrients, controlling exchanges with the environment
In mammals, are most cells diploid or haploid?
What are diploid cells?
Cells which contain two sets of matching chromosomes
What are haploid cells?
Cells which contain only one set of chromosomes.
What are gametes?
Sex cells: eggs and sperm. They are specialised haploid cells.
At fertilisation, what do gametes combine to form?
A diploid zygote.
Describe the cellular process of fertilisation
Gametes combine together to create a diploid zygote, and the genes on the chromosomes combine, controlling the zygote's characteristics.
How are new cells for growth produced?
In which process are the new cells genetically identical, mitosis or meiosis?
What is mitosis needed for?
The replacement of worn out cells, repair to damaged tissue, and asexual reproduction.
Explain the process of mitosis
Before cells divide, the DNA copies itself, meaning that the new cell will have a copy of all the chromosomes. Because there are no other parents involved and the DNA is copied, these cells are genetically identical. Mitosis happens as follows: The DNA helix starts to unzip. The Bases are added to form a new strand. A new DNA molecule is formed.
Explain complementary base pairing
In a parent cell with two chromosomes, each chromosome replicates itself. the chromosomes line up along the centre of the cell, divide and then the copies move to opposite poles. Each 'daughter' cell has the same number of chromosomes, and contains the same genes as, the parent cell.
What is Meiosis?
A type of cell division which occurs in the testes and ovaries. The cells in these organs divide to produce gametes for sexual reproduction. The chromosome number is halved and each cell is genetically different. Meiosis introduces genetical variation.
What are the four components of blood?
platelets, plasma, white blood cells and red blood cells.
What do platelets do?
They clump together when a blood vessel becomes damaged in order to produce a clot.
What does Plasma do?
It transports several substances around the body, including foods like glucose, water, hormones, antibodies and waste products.
What do White Blood Cells do?
They protect the body against disease.
What do Red Blood Cells do?
They transport oxygen from the lungs to the tissues. They're small and flexible so that they can pass through narrow blood vessels, and don't have a nucleus so that they can be packed with haemoglobin. When the cells reach the lungs, oxygen diffuses from the lungs into the blood. The haemoglobin molecules in the red blood cells bind with the oxygen to form oxyhaemoglobin. The blood is then pumped around the body to the tissues, where the reverse reaction takes place. Oxygen is released which diffuses into cells.
Explain the purpose of the shape of Red Blood Cells.
The small size and biconcave shape of red blood cells gives them a large surface area to volume ratio for absorbing oxygen.
Do arteries transport blood away from the heart or towards it?
Away from it.
Do veins transport blood away from the heart or towards it?
What type of circulatory system do mammals have, and what are the advantages of it?
A double circulatory system, which means that the blood is pumped to the body at a higher pressure than it is pumped t the lungs, This provides a much greater rate of flow to the body tissues.
What are the special adaptations that arteries have to cope with their function?
Arteries have to cope with a high pressure of blood so they have a thick wall made of elastic muscle fibres.
What are the special adaptations that veins have to cope with their function?
Veins have a lumen which is much bigger compared to the thickness of the walls. They have halves to prevent the backflow of blood.
What are the special adaptations that capillaries have to cope with their function?
capillaries are the only blood vessels that have thin permeable walls, to allow the exchange of substances between cells and the blood.
What are the four main chambers of the heart?
The left and right ventricles, and the left and right atria.
Ventricles contract to pump blood out of the heart. The right ventricle pumps blood a short distance to the lungs. The left ventricle is more muscular because it pumps blood under higher pressure around the body, whereas the right ventricle only pumps blood to the lungs and back.
What do atria do?
Atria receive blood coming back to the heart through the veins.
What do semilunar, tricuspid and bicuspid valves do?
They make sure that the blood flows in the right direction.
What is the equation for aerobic respiration?
C6H12O6 + 6O2 → 6CO2 + 6H2O
In which organs does meiosis occur?
The testes and the ovaries.
What do both plant and animal cells contain, and what do plant cells contain that animal cells don't?
Both plant and animal cells contain a nucleus, cell membrane and cytoplasm. Plant cells also contain chloroplasts, a cellulose cell wall to provide support and a vacuole which contains cell sap and helps to provide support.
What is the method to see the parts of a plant cell?
Use tweezers to peel a thin layer of skin tissue from an onion, place the onion tissue onto a microscope slide, add a drop of iodine to the tissue and carefully cover the slide with a coverslip. Look at the onion cell through the microscope at x100 magnification.
Describe bacterial cells.
Bacterial cells are smaller and simpler than plant and animal cells. Bacterial cells lack a true nucleus, mitochondria and chloroplasts. Plant cells keep their DNa inside the nucleus, but bacterial cells have it floating as circular strands.
Describe growth in animals.
Animals grow by increasing the number of cells. The cells specialise or differentiate into different types of cell at an early stage to form tissues and organs. Animal cells lose the ability to differentiate at an early stage.
Describe growth in plants.
Growth is measured as an increase in height or mass. It involves both cell division and cell differentiation. Given the right conditions, many plants can grow continuously. All parts of an animal are involved in growth, whereas plants grow at specific parts of the plant. Plant cell division is mainly restricted to areas called meristems at the roots and tips. Cell enlargement is the main method by which plants gain height. Unlike animal cells, plant cells retain the ability to differentiate or specialise throughout their lives, whereas animals lose this ability at an early stage.
What are the three different ways to measure growth?
Length/height, wet mass, dry mass.
What are the pros/cons of measuring growth with length/height?
It's easy and rapid measurement, but an increase in mass might occur with no increase in length/height.
What are the pros/cons of measuring growth with wet mass?
It's not destructive and is relatively easy to measure, but water content of living tissue can be very variable and may give a distorted view overall.
What are the pros/cons of measuring growth with dry mass?
It's the most accurate method, but it is destructive as the removal of water kills the organism.
What are stem cells?
Stem cells are undifferentiated animal cells, which can specialise and develop into different types of cells, tissues and organs.
Where can stem cells be obtained from?
What is stem cell research, and what are the oppositions to it?
Stem cell research is research that scientists carry out on stem cells obtained from embryonic tissue, because they believe that they could potentially be used to treat medical conditions which presently have no cure. For research, scientists need to obtain large numbers of embryos to grow the stem cells in the laboratory. At present, unused embryos from IVF treatments are used. Some people think it's a good thing; embryos left over from IVF would otherwise be destroyed and the potential to cure disease is important. However, others think it's wrong to experiment on embryos, and that human life is so sacred that 'Playing God' is wrong.
Why do embryonic stem cells have a much wider use than adult stem cells?
Because embryonic stem cells can become any type of body cell, whereas adult stem cells are limited to differentiate into the cell types from their tissue of origin.
What are the steps to selective breeding?
Decide which characteristics are important
Choose parents that show these characteristics
Select the best offspring from parents to breed the next generation
Repeat the process continuously
What is selective breeding?
Selective breeding is when animals or plants with favourable characteristics are selected and deliberately crossbred to produce offspring with the desired characteristics. These offspring can then also be selected and bred until the desired result is achieved.
What are the problems with selective breeding?
It can lead to inbreeding, and intensive selective breeding reduces the gene pool, and the number of different alleles in the population decreases so there is less variation. Lack of variation can lead to an accumulation of harmful recessive characteristics.
What is genetic engineering?
The process of artificially transferring genes from one organism to another.
Give two reasons why genetic engineering may be carried out and give an example.
To increase crop resistance to frost damage, disease or herbicides: e.g. soya plants are genetically modified by inserting a gene that makes them resistant to a herbicide so, so the plants can grow better without competition from weeds. To increase the quality of food: e.g. people who eat a diet mainly of rice may become deficient in Vitamin A. The genes responsible for producing beta-carotene, which the body converts to Vitamin A, can be transferred from carrots to rice plants so that the people can get Vitamin A from the rice. To produce a required substance: e.g. the gene for human insulin can be inserted into bacteria to make insulin on a large scale to treat diabetes.
What is the main advantage of genetic engineering, and what is the main disadvantage?
Advantage: It allows organisms with new features to be produced rapidly. Disadvantage: The inserted genes may have unexpected harmful effects.
What are the benefits of genetic engineering?
Producing disease-resistant crops and higher yields which could feed more of the world's population, creating crops that will grow in poor or dry soil to feed people in poor areas, and potentially replacing faulty genes to reduce certain diseases,
What are the concerns about genetic engineering?
GM plants may cross-breed with wild plants and release their new genes into the environment, Gm foods may not be safe to eat in the long term, it could lead to the genetic makeup of children being modified or engineered, unborns with genetic faults could be aborted, and insurances could genetically screen applicants and refuse to insure those with an increased risk of illness.
What are the steps for genetic engineering?
The gene for a desired characteristic is selected.
The gene is isolated and removed using an enzyme which cuts through the DNA strands in precise places.
The selected gene is inserted into the genome of another organism.
When the organism replicates, the gene replicates making the new protein.
What is gene therapy?
Changing a person's genes in an attempt to cure genetic disorders.
Describe Gene Therapy, and why it is controversial.
Gene therapy can involve body cells or gametes. Gene therapy involving gametes is very controversial because the genetic changes that are made don't just affect the individual being treated but affect all future generations as those are the genes passed on to offspring.
What does asexual reproduction do?
It produces identical copies.
Give three examples of plant asexual reproduction.
Spider plants, strawberry plants and potato plants.
Describe the process of growing plants from cuttings.
1-A plant is selected
2-Cuttings are taken
3-The cutting is placed in soil in a damp atmosphere
4-New genetically identical plants develop.
Are plants grown from cuttings or tissue culture clones?
Yes, because they are genetically identical.
What are the parts of a plant that cuttings of can grow into new plants?
Stem, leaf, or root.
What are the advantages of commercially cloning plants?
The cloned plants will be genetically identical to the parent, so the characteristics will be known, and it is possible to mass-produce plants that may be difficult to grow from seeds.
What are the disadvantages of commercially cloning plants?
Any susceptibility to disease, or sensitivity to environmental conditions will affect all the plants, and the reduction in genetic variation reduces the potential for further selective breeding.
Describe the process of growing plants through tissue culture.
1-A parent plant is selected with the desired characteristics
2-A lot of small pieces of tissue is scraped off into beakers that contain nutrients and hormones.
3-Lots of genetically identical plantlets will grwo.
Why is it important that cloning by tissue culture is done aseptically (without the presence of bacteria)?
To avoid the new plants rotting
Why is cloning plants easier than cloning animals?
Many older plants are still able to differentiate/specialise, whereas animal cells lose this ability.
What is cloning?
An example of asexual reproduction which produces genetically identical copies. Identical twins are naturally occurring clones.
What cloning technique is used commonly in cattle breeding?
Name three uses of cloning.
1-It's possible to clone human embryos in the same way that animals are cloned. This technique could be used to provide stem cells for medical purposes.
2-The mass production of animals with desirable characteristics
3-Producing animals that have been genetically engineered to provide human products.
Name some of the major ethical dilemmas about cloning humans.
1-The cloning process is very unreliable- the majority of cloned embryos don't survive.
2-Cloned animals seem to have a limited life span and die early.
3-The effect of cloning on a human's mental and emotional development isn't known.
4-Religious views say that cloning humans is wrong
5-Using human embryos and tampering with them is controversial.
Describe the method used to produce a cloned sheep (Dolly).
1-The nucleus from an egg cell of a female sheep was removed. The nucleus was taken from an udder cell of the sheep to be cloned.
2-The nucleus from the udder cell was then inserted into an empty egg cell, which was then given an electric shock to make it divide like a fertilised egg.
3-The resulting embryo was placed into the uterus of a surrogate mother sheep.
4-The embryo developed into a foetus and was born as normal. The offspring produced (Dolly) was a clone of the sheep which the nucleus came from.
What are the benefits associated with cloning animals?
-Genetically identical cloned animals will all have the same characteristics
-The sex of an animal and timing of birth can be controlled
-Top-quality bulls and cows can be kept for egg and sperm donation, whilst other animals can be used to carry and give birth to the young.
What are the risks associated with cloning animals?
-Cloning reduces genetic variation.
-Cloned animals are identical copies, so are genetically the same. This means that there is potential for one disease wiping them all out.
-Welfare concerns; cloned animals may not be as healthy or live as long as 'normal' animals.
Describe the 'animal organ donor' solution to the shortage of human organ donors for transplants.
An animal would be genetically engineered so its organs wouldn't be rejected by the human body. The animal could then be cloned to produce a ready supply of identical donor organs.