Biology 6 Flashcards
What is a catalyst ?
A substance which increases the speed of a reaction without being changed or used up in the reaction
What are enzymes ?
Catalysts produced by living things
How do enzymes catalyse reactions ?
They have specific shapes which catalyse their specific substances
What two things are needed for enzymes?
The right temperature and pH
What temperature do enzymes in the human body usually work at ?
37 degrees Celsius
What do digestive enzymes do ?
Break large molecules into smaller molecules
What does Amylase do ?
Convert starch into sugars
What does protease do ?
Convert proteins into amino acids
What does lipase do ?
Convert lipids into glycerol and fatty acids
Why are large molecules broken down ?
Because smaller molecules can pass easily through the digestive system
What does bile do and where is it produced ?
It is produced in the liver and stored in the gall bladder. It neutralizes stomach acids whilst emulsifying fats
True or false - respiration is breathing in and out
False
What is respiration ?
Respiration is the process of releasing energy from glucose, which goes in every cell
What is aerobic respiration ?
Respiring using oxygen
Why is aerobic respiration better than anaerobic respiration ?
Aerobic respiration is more efficient, so more energy is made
Give four examples of what respiration releases energy for ?
- to build larger molecules from smaller molecules
- allow muscles to contract
- to keep body temperature steady (animals)
- to build sugars, nitrates and other nutrients into amino acids (plants
Why does exercise make you breathe deeply ?
The muscle cells require oxygen for respiration. The energy produced is used to contract the muscles. By breathing deeper the demand for oxygen is met
Why does exercise increase the heart rate ?
To remove carbon dioxide from the muscle cell the blood has to flow faster, meaning the heart has to pump harder
What is stored glucose called ?
Glycogen
What is glycogen used for ?
When exercising the glycogen is converted back to glucose to supply enough energy
When does anaerobic respiration take place ?
When doing vigorous exercise and there isn’t enough oxygen
What is the by-product of anaerobic respiration ?
Lactic acid
What is bad about lactic acid ?
It builds up in the muscle which becomes painful. The muscles fatigue and stop contracting properly
What is an advantage of anaerobic respiration ?
You can use your muscles for longer
Why do you keep breathing heavily after exercising ?
When anaerobic respiration takes place you are left with an oxygen debt, the oxygen is used to ‘oxidise’ the lactic acids
Why are enzymes used in detergents ?
Proteases and lipids can break down animal an plant material. Therefore they can remove stains like food or blood
How can proteases be used in baby food ?
They make food easy to digest for babies as the enzymes break it down slightly
Glucose can be turned into fructose using what ?
Isomerase
Why is fructose used in slimming foods rather than glucose ?
It is sweeter, so less is needed
Why are enzymes used in industry ?
To speed up reactions rather than using high temperatures and pressures
What are the advantages of using enzymes in industry ?
- Specific, so they only catalyse the reaction you want
- Lower energy costs
- They can be used multiple times, for a long time
- Biodegradable and Eco friendly
What are the disadvantages of using enzymes in industry ?
- People can develop allergies
- They can denature
- Expensive
- Contamination can affect the reaction
What does DNA stand for ?
Deoxyribose nucleic acid
What structure does DNA have ?
Double helix
What does DNA contain and where is it found ?
All the information needed to form an organism and make it work. It is found in the nucleus of animal and plant cells in really long molecules called chromosomes
What are genes ?
A section of DNA that contains the information to make a specific protein
How are proteins made ?
20 amino acids are used, by stringing them together in a particular order
What are the exceptions to the rule that ‘everyone has unique DNA’ ?
Identical twins and clones
What is DNA fingerprinting ?
It is when you cut up DNA into small sections and then separating them, every genetic fingerprint has a unique pattern so you can tell people apart by comparing the DNA
How can genetic fingerprinting be used ?
Forensic science - DNA from crime scene can be compared by DNA from suspects
Paternity tests - to see if a man is the father of the child
How many copies of each chromosome is contained in body cells ?
Two - on from the mother and one from the father
What is mitosis ?
Mitosis is when a cell reproduces itself by splitting to form two identical offspring
Describe the process of mitosis
- Cell duplicates its genetic information
- Chromosomes line up and are split and divided equally
- membranes form around chromosomes, becoming the nuclei of the two new cells
- Lastly the cytoplasm divides
Can mitosis be used in asexual reproduction ?
Yes - some organisms reproduce by mitosis. The offspring have exactly the same genes as the parent so there is no variation
Why do gametes only half the usual number of chromosomes ?
This is so you can combine the sex cells from the mother and the sex cells from the father and still have the right number of chromosomes
How does sexual reproduction produce variation ?
It has a mixture of two sets of chromosomes, so it will inherit characteristics from both parents
What does meiosis produce ?
Meiosis produces cells which have half the normal number of chromosomes
Describe meiosis
- DNA duplicated
- After first division, chromosome pairs line up
- The pairs are pulled apart so each new cell only has one copy of each chromosome
- The arms of the chromosomes are pulled apart in the final split
- You are left with four gametes each with only a single set of chromosomes in it
Why is mitosis used ?
For growth or repair
Why is meiosis used ?
For sex cells
What are embryonic stem cells ?
Undifferentiated cells, they can develop into different types of cell depending on what instructions they’re given
Where can stem cells be found ?
Embryos, bone marrow
How do bone marrow transplants help sickle cell anaemia ?
The stem cells, in bone marrow, can differentiate into new blood cells to replace the faulty ones
What could be made with embryonic stem cells ?
Beating heart muscles for people with heart disease, insulin producing cells for people with diabetes, nerve cells for people paralyses by spinal injuries
Why do people believe embryonic stem cells should not be used ?
Because it is potential human life
What are the 23rd pair of chromosomes called ?
XX or XY, they are the chromosomes which determine whether you are male or female
What chromosomes do you have if you are male ?
X and Y, Y being the dominant allele
All women have two ??????Chromosomes.
X
What is the probability of having a boy ?
50:50
If you have four children, would you definitely have 2 boys and 2 girls ?
Not definitely - there is a 50:50 chance of having a boy or girl EACH TIME you have a child
Who was Gregor Mendel ?
An Austrian monk who trained in mathematics and natural history.
What did he notice ?
How characteristics of plants were passed on from one generation to the next
First Mendel crossed a tall plant with a dwarf plant, all of the pea plants were tall. Why is this and what does it tell us ?
It shows that the tall allele is dominant. The tall plant was TT and the dwarf plant was tt, so the four eventualities were Tt
What had Mendel shown ?
That the height characteristics in pea plants were determined by separately inherited “hereditary units” passed on from each parent
What else did Mendel discover about hereditary units ?
They can be dominant or recessive- if an individual has both the dominant and the recessive unit for a characteristic, the dominant characteristic will be expressed
What are hereditary units now known as ?
Genes
What are alleles ?
Different versions of the same gene
What represent alleles in genetic diagrams ?
Letters
What is it called when an organism has two alleles for a particular gene the same ?
Homozygous
If two alleles for the same gene are different, it’s _______
Heterozygous
I the gene I heterozygous, which allele determines the characteristic shown ?
The dominant allele
What is the opposite of a dominant allele ?
Recessive
What are dominant alleles represented as ?
Capital letters
What are recessive alleles represented as ?
Lower case letters
How is a recessive characteristic shown ?
Only when it is homozygous and both alleles are recessive
What does genotype mean ?
What alleles you have
What does phenotype mean ?
The actual characteristics
What is cystic fibrosis ?
A genetic disorder of the cell membranes
What are the symptoms of cystic fibrosis ?
The body produces a lot of mucus in the air passages and pancreas. This causes breathing problems
Is the cystic fibrosis allele recessive or dominant ?
Recessive - ‘f’
How does a child get cystic fibrosis ?
Both parents must carry the recessive gene at the very least, the parents don’t have to be sufferers but can be
What is polydactyly ?
A genetic disorder where a baby is born with extra fingers or toes
Is polydactyly a recessive or dominant allele ?
Dominant - ‘D’
What is embryo screening ?
When a cell’s genes are analysed, many genetic disorders can be found this way
Why are some people against embryo screening ?
- One day every parent may want to scan their embryo, to have the most desirable baby
- Rejected embryos are destroyed - they could have developed into humans
- it implies people with genetic disorders are undesirable
- It is expensive
What are the advantages of embryonic screening ?
- it will reduce suffering
- there are laws to stop it going too far
- during IVF, the embryos are already destroyed
- Treating disorders already costs the gouvernment a lot of money
What are fossils ?
The remains of organisms from many years ago, which are found in rocks
What are the three ways fossils form ?
- Gradual replacement by minerals
- Casts and impressions
- Preservation in places where no decay happens
What is the most common way fossils form ? How does this occur ?
Gradual replacement - shells and bones are buried, when they decay the space is filled with minerals which form a rock substance in the shape of the bone or shell
What process allows us to find fossils of footprints ?
Casts and impressions, it is when footprints are pressed in soft material like clay which later hardens leaving the impression
How do species become extinct ?
Environmental change, New predators, New disease, Competition, catastrophic event, speciation
What is speciation ?
The development of a new species.
When does speciation occur ?
When populations of the same species become so different they can no longer breed together to produce fertile offspring
How does isolation lead to speciation ?
Isolation is when species are seperated. This can happen due to a physical barrier like a flood o earthquake. If conditions are different characteristic will develop because of natural selection
What is natural selection ?
- Each population shows variation because they have a wide range of alleles
- Individuals with better characteristics for their environment stand a better chance o survival and are more likely to breed
- So the alleles that control the better characteristics are more likely to be passed onto the next generation
