B2 Flashcards
(169 cards)
1
Q
What does the mitochondria do?
A
They carry out most of the reactions for respiration which releases energy for the cell.
2
Q
What do the ribosomes do?
A
They make the proteins inside the cell.
3
Q
What features does an animal cell have? What are their functions?
A
Nucleus: contains genetic material that controls the activities of the cell
Cytoplasm: gel-like substance where most of the chemical reactions take place. It also contains enzymes that control the chemical reactions
Cell membrane: holds the cell together and controls what goes in and out of the cell
Mitochondria: reactions for respiration take place here, which releases energy for the cell in order for it to work properly
Ribosomes: Where proteins are made in the cell
4
Q
What are the features of a plant cell? What are their functions?
A
Nucleus: contains genetic material that controls the activities of the cell
Cell wall: made of cellulose which supports and strengthens the cell
Cell membrane: controls what goes in and out of the cell
Vacuole: contains cell sap (a weak solution of sugar and salts)
Mitochondria: reactions for respiration take place here which releases and provides energy to the cell in order for it to work.
Ribosomes: Where proteins are made in the cell
Chloroplasts: Contains green pigment called chlorophyll which carries out photosynthesis
5
Q
What are the features of a yeast cell?
A
Cytoplasm Cell membrane Cell wall Nucleus containing genetic material Yeast is a microorganism
6
Q
What are the features of a bacteria cell?
A
Cell membrane Cytoplasm No defined nucleus so the genetic material floats around in the cytoplasm Ribosomes Cell wall Some bacteria have a flagellum and pili
7
Q
What is diffusion?
A
The spreading out of particles from an area of high concentration to an area of low concentration
8
Q
How does the cell membrane allow diffusion to happen?
A
Small dissolved molecules can move in and out of the semi permeable membrane via diffusion. Bigger molecules cannot pass through the membrane.
9
Q
What substances can pass through the cell membrane?
A
Glucose
Oxygen
Amino acids
Water
10
Q
Which substances cannot pass through the cell membrane?
A
Starch and proteins
11
Q
How is a palisade leaf cell adapted for photosynthesis?
A
- Packed with chloroplasts and there are more near the top of the leaf to be closer to light
- Tall shape- larger surface area down the sides of the cell for absorbing carbon dioxide from the air to the leaf
- Thin shape- means that more palisade cells can be packed into the top of the leaf
12
Q
Why are palisade cells grouped together at the top of the leaf?
A
They are able to get more light in order to carry out photosynthesis. Therefore, the most photosynthesis happens at the top of the leaf.
13
Q
What is the function of a guard cell?
A
To allow gas exchange and control the amount of water loss within the leaf
14
Q
How is a guard cell adapted to its function?
A
- When the plant takes on lots of water, the guard cells fill up and become turgid. This causes the stomata to open so gases can be exchanged for photosynthesis.
- When the plant has little water, the guard cells become flaccid and the stomata closes. This prevents too much water from escaping.
- The thin outer wall and thick inner wall allows for the opening and closing of the stomata.
- They are also sensitive to light so they close the stomata at night to save water
15
Q
What is the function of a red blood cell?
A
To supply the body, muscles and cells with oxygen in order for them to carry out respiration and work.
16
Q
How is a red blood cell adapted to its function?
A
- They have a biconcave shape which gives them a larger surface area for absorbing oxygen. It also allows the cell to pass easily through the capillaries.
- They are filled with haemoglobin (a pigment that absorbs oxygen)
- They do not have a nucleus which means they are able to contain more haemoglobin. Therefore, they are able to absorb more oxygen
17
Q
What is the main function of an egg cell?
A
To carry the female DNA and nourish a developing embryo
18
Q
How has an egg cell adapted in order to carry out its function?
A
- It contains huge food reserves to feed the embryo
- Once a sperm enters the egg, the egg’s membrane immediately changes structure in order to stop any more sperm getting in. This ensures that the offspring ends up with the right amount of DNA
19
Q
What is the main function of a sperm cell?
A
To get the male DNA to the female DNA
20
Q
How has a sperm cell adapted to carry out its function?
A
- Has a long tail and streamlined head to help it swim to the egg
- It has a large amount of mitochondria inside it in order to be supplied with enough energy to get to the egg
- It also carries enzymes in their head to digest through the egg cell’s membrane
21
Q
How does one cell become an organ system?
A
- Groups of similar cells form a tissue
- Groups of different tissues form an organ
- Groups of similar organs form an organ system
22
Q
What is differentiation?
A
A process by which a cell changes to become specialised to a certain job.
23
Q
Does an animal cell have the ability to differentiate?
A
It is usually lost at an early stage. However plant cells don’t ever lose this ability.
24
Q
What are stem cells?
A
It’s where undifferentiated cells can be changed into different cells depending on the instructions they are given.
25
Where are stem cells found?
In early human embryos.
They can also be found in adults but only certain places like bone marrow. Also they aren't as versatile as embryonic cells as they can't turn into any type of cell.
26
Why are stem cells exciting to doctors and medical reshearchers?
Because the have the potential to turn into different cells.
27
When does differentiation occur?
During the development of multi-cellular organisms
28
What is present in the structure of a plant's leaves?
1. Mesophyll tissue
2. Xylem and Phloem
3. Epidermal tissue
29
What does the xylem and phloem do?
Transport water, mineral ions and sucrose around the plant
30
What does the mesophyll tissue do?
This is where most photosynthesis in the plant occurs
31
What does the epidermal tissue do?
Covers the whole plant
32
What is the equation for photosynthesis?
Carbon dioxide + Water ------------------> Glucose + Oxygen
| (sunlight and chlorophyll)
33
What is photosynthesis?
The process that produces glucose for the plant
34
Where does photosynthesis occur?
Inside the chloroplasts.
35
Why do the chloroplasts carry out photosynthesis?
They contain chlorophyll which absorbs sunlight and uses its energy to convert carbon dioxide and water into glucose and oxygen. The glucose is used and stored by the plant and the oxygen is released into the air.
36
What is the rate of photosynthesis affected by?
1. Light intensity
2. Volume of CO2
3. Temperature
37
What happens as light intensity increases?
- The rate of photosynthesis will steadily increase up to a certain point (optimum light intensity)
- After this point, the plant will need an increase in CO2 or temperature to increase further
38
How can you change the intensity of light? (Exam Question)
By moving a lamp closer or further way from the plant
39
What happens when the volume of carbon dioxide is increased?
- At first the rate of photosynthesis will increase
| - When the line on graph flattens out the volume of CO2 is not the limiting factor
40
What are the ways to control the amount of CO2? (Exam Question)
- Dissolving different amounts of sodium hydrogen carbonate in water.
41
What happens to the rate of photosynthesis when the temperature is increased and decreased?
1. Too low- the enzymes needed will work more slowly decreasing rate of phtosynthesis
2. Too high- the enzymes will become damaged and denature (happens at about 45 C)
42
What is the best way to control temperature?
Put the conical flask in a water bath at a set temperature
43
How can you artificially create ideal conditions for plant growing?
1. Use a greenhouse
2. Control the light intensity
3. Control the volume of CO2`
44
How does a greenhouse help create ideal conditions?
It traps the Sun's heat and makes sure that the temperature does not become the limiting factor
- In winter farmers can use a heater to keep temperature up
- In summer farmers can use shades or a form of ventilation to keep temperatures down
45
How does a farmer control the intensity of light to create ideal conditions?
They often supply artificial light after the Sun goes down to give plants more time to carry out photosynthesis (increases growth)
46
How does a farmer control the volume of carbon dioxide to create ideal conditions?
They use a paraffin burner to heat greenhouse. As it burns it creates CO2 as a by-product
47
What are the advantages of creating ideal conditions?
The plants will grow faster and a decent crop will be harvested more often which can be sold. More profit
48
What are the disadvantages of creating ideal conditions?
- It costs money
| - The conditions have to be kept exact
49
How do plant use glucose?
1. Respiration
2. Making cell walls
3. Making proteins
50
How does respiration use glucose?
- Respiration releases energy which enables plants to convert glucose into other useful substances
(they can use converted glucose for growth and building new cells, to produce some of the substances they need to gather minerals from soil)
51
How is glucose used in making cell walls?
- Glucose is converted into cellulose is used for making strong cell walls
52
How is glucose used in making proteins?
- Glucose is combined with nitrate ions to make amino acids
| - Amino acids are sued to make proteins
53
How is glucose stored?
1. In seeds
| 2. As starch
54
How is glucose stored as starch?
- Turned into starch and stored in roots, stem and leaves
- Starch is insoluble which is better for storing than glucose- Cells with lots of glucose in could draw in loads of water and swell up.
55
What does the distribution of organisms mean?
Where an organism is found?
56
What can affect the distribution of organisms?
- Temperature
- Availability of water
- Availability of oxygen and carbon dioxide
- Availability of nutrients
- Amount of light
- Availability of food
57
How do you work out the population size?
Mean number of organisms per metre squared x total area
58
What does a transect show you?
How organisms are distributed along a line
59
What is a quadrat?
A square frame, enclosing an area, that is used to compare the distribution of organisms in two areas (We used in when with Miss McKinney and we went measured daises)
60
What is an enzyme?
- Proteins which are made up of chains of amino acids
| - They make he chemical reactions in your body work
61
What do enzymes do?
- They speed up the useful chemical reactions in the body
| - The reduce the need for high temperatures
62
What produces enzymes?
All living organisms produces enzymes that act as biological catalysts.
63
How are the chains of amino acids structured?
They are folded into unique shapes, which enzymes need to do their job
64
What do the proteins also act as?
Structural components of tissues, hormones and antibodies
65
Why do enzymes only catalyse one specific reaction?
Because each enzyme has one unique shape that fits onto only one substance involved in the reaction
66
How does the temperature affect the rate of a reaction?
It changes the how fast the enzymes catalyses the reaction.
- If the temperature is too hot, the enzyme will change shape and denature
- At first the higher the temperature, the faster the rate of reaction until it reaches the optimum temperature
67
What is meant by the term 'optimum condition'?
The condition (temperature/pH) at which the enzyme is most active
68
What is the optimum temperature of enzymes in the human body?
37C
69
How does the pH affect enzymes?
- Too high/too low- the pH interferes with bonds holding enzyme together-causes enzyme to change shape and denature
70
What is the optimum pH for the human body
Usually pH 7
(not all though- pepsin is used to break down proteins in the stomach so it works best at pH 2-well suited to acidic conditions in stomach)
71
What do digestive enzymes do?
Break down bid molecules into smaller ones
72
What does amylase do?
Converts starch into sugars
73
Where is amylase made?
1. the salivary glands
2. the pancreas
3. the small intestine
74
What does protease do?
Converts proteins into amino acids
75
Where is protease made?
1. the stomach
2. the pancreas
3. the small intestine
76
What does lipase do?
Converts lipids into glycerol and fatty acids
77
Where is lipase made?
1. the pancreas
| 2. the small intestine
78
What does bile do?
Neutralises stomach acid and emulsifies fat
79
Where is bile produced, stored and released?
Produced in liver
Stored in gall bladder
Released in small intestine
80
Where is bile produced, stored and released?
Produced in liver
Stored in gall bladder
Released in small intestine
81
Why does bile need to neutralise the stomach acid?
The stomach is too acidic for enzymes to work in small intestine so, because bile is alkaline, it neutralises the acidic conditions to make them alkaline so the enzymes work better
82
How does bile emulsify fats?
It breaks down fat into tiny droplets which gives the fat a larger surface area fro lipase to work on. This makes digestion faster.
83
Why are some people against stem cell research?
It destroys a potential human life
| They feel that scientist should focus on developing other sources of stem cells
84
Why are some people for stem cell research?
Curing patients who already exist and are suffering are. Ore important then embryos
Embryos used for research are usually unwanted one from fertility clinics that would otherwise be destroyed
85
How many pairs of chromosomes are there in a human body cell?
22 matched pairs
| There is a 23rd pair that is labelled xx or xy which decides if your male or female
86
What Happens to the x and Y chromosomes when making sperm?
They are drawn apart by the first division in meiosis. So there is 50/50 chance of the sperm getting an x or a Y chromosome
87
What chromosomes do males and females have?
Females have the xx combination of chromosomes which develops female characteristics. And males have and xy combination which develops male characteristics
88
What is respiration?
The process of releasing energy from glucose, which happens in every cell.
89
What is aerobic respiration?
Respiration with oxygen
90
What is anaerobic respiration?
Respiration without oxygen
91
Where, in the cells, does most aerobic respiration take place?
In the mitochondria
92
What is the word equation for respiration?
Glucose + oxygen ------> Carbon dioxide + water + energy
93
What is the energy released by aerobic respiration used for?
1. to build up larger molecules from smaller ones
2. to allow muscles to contract (allows movement)
3. to keep body temperature (in mammals and birds)
4. In plants- to build sugar, nitrates and nutrients into amino acids, which are then built into proteins
94
During exercise, what happens to the body and respiration rates?
1. The body adapts so muscles get more oxygen and more glucose to provide the body with more energy
2. The muscle cells use oxygen to release energy from glucose which is used to allow movement and muscle contractions
3. The blood flows at a faster rate to supply working muscles with more oxygen and glucose and to remove carbon dioxide.
4. This is why breathing rate increases and makes you breath deeply- to maintain oxygen supply under demands of exercise
5. This is why your heart rate increases because the heart and blood is pumps faster
6. Therefore, respiration should increase during exercise
95
What is glycogen?
Stored glucose from food.
96
When is glycogen used?
During exercise.
97
Where is glycogen stored?
Mainly in the liver but each muscle has its own store
98
What is glycogen used for?
Muscles use glucose rapidly during exercise so the glycogen stores are converted back into glucose to provide the body with more energy.
99
What is the word equation for anaerobic respiration?
Glucose -----> energy + lactic acid
100
What are the disadvantages of anaerobic respiration?
1. It does not release as much energy as aerobic respiration
2. It causes the build up of lactic acid which is painful
3. The lactic acid also causes muscle fatigue so muscles stop contracting as efficiently
101
What is the advantage of anaerobic respiration?
1. You can keep using muscles for a while longer
102
What is oxygen debt?
It is caused by anaerobic respiration and it is where you have to replace the oxygen that muscles were not able to have during exercise
103
How do you replace the oxygen lost during exercise?
1. You breathe hard after exercise to get more oxygen into the blood
2. Blood flows through muscles and removes lactic acid by oxidation
3. Pulse and breathing rate stay high to decrease high levels of carbon dioxide and lactic acid
104
What uses do enzymes have?
1. Used in biological detergents and washing powders:
- mainly protease and lipases
- ideal for removing stain like food and blood because they usually break down animal and plant matter
- more effective
2. used to change foods
- proteins in baby foods are pre-digested using protease to make it easier for baby to digest
- carbohydrases used to turn starch syrup into sugar syrup
- glucose syrup into fructose syrup using isomerase enzyme
105
What are the advantages of using enzymes in industry?
1. enzymes are specific-only catalyse wanted reaction
2. work at lower temperatures-lowers cost because it saves energy
3. they work for a long time
4. they are biodegradable so less environmental pollution
106
What are the disadvantages of using enzymes in industry?
1. people develop allergies to enzymes
2. can be denatured by small increase in temperature
3. susceptible to poisons and changes in pH
4. Conditions have to be tightly controlled
5. expensive to produce
6. contamination of enzyme with other substances can affect the reaction
107
What does DNA stand for?
Deoxyribonucleic Acid
108
Where is DNA found?
In the nucleus of animal and plant cells, in the chromosomes
109
What does DNA contain?
All the instructions to put an organism together and make it work
110
What is a gene?
One section of DNA
111
What does a gene contain?
The instructions to make specific proteins
112
How do cells make proteins?
By stringing amino acids together in a particular order
113
What do genes do?
Tell cells what order to put amino acids in
114
What does DNA determine?
What proteins a cell produces and what type of cell it will be.
115
What is DNA fingerprinting?
The cutting up of a person's DNA into small sections and separating them.
116
When can DNA fingerprinting be used?
1. Forensic Science: DNA taken from a crime scene and compared to DNA sample taken from a suspect
2. Paternity Testing: to see if a man is the father of a particular child
117
What is the disadvantage of using DNA fingerprinting?
- False positives can occur if errors are made in the procedure or when the data is misinterpreted
118
What is mitosis?
When a cell reproduces by splitting in two and creating two identical offspring
119
Describe the process of mitosis.
1. DNA inside cell duplicates and copies to from X-shaped chromosomes.
2. The chromosomes line up in the centre of the cell and cell fibres pull them apart to opposite sides of the cell
3. Membranes form around sets of chromosomes. These become the nuclei of the two new cells
4. Lastly, the cytoplasm divides and two new cells containing the exact same DNA as the parent cell are produced
120
What does mitosis do?
It makes new cells for growth and repair
121
When is mitosis used?
During asexual reproduction. The offspring have exactly the same genes as the parents so there is no variation.
122
What is meiosis?
When four new cells are produced and have half the normal number of chromosomes of a normal cell. It also involves two divisions instead of one.
123
Describe the process of meiosis.
1. Before cell divides it duplicates its DNA
2. In the first division, the chromosome pairs line up in the centre of the cell. The pairs are then pulled apart so each cell only has one copy of each chromosome.
3. In the second division, the chromosomes line up again in the centre of the cell. The arms of the chromosomes get pulled apart by the cell fibres
4. After the second division, four gametes are produced with a single set of chromosomes in each cell
124
Where does meiosis happen?
Only in the reproductive systems
125
When is meiosis used?
In sexual reproduction:
- two gametes (egg cell and sperm) combine o form offspring
- the two gametes contain only 23 chromosomes each
- the offspring will inherit characteristics from both parents (variation) because it will have a combination of both chromosomes.
126
What are stem cells?
A cell that has the potential to turn into other types of cells, unlike any other type of cell.
127
Who was Gregor Mendel?
- Known as the Founder of Genetics
| - An Austrian monk who trained in mathematics and natural history at the University of Vienna
128
What did Mendel do?
- He recorded how the characteristics in plants were passed on from one generation to another using pea plants
- His results were published in 1866 and they became the foundation for modern genetics- the significance of his work was not realised until after his death.
129
What did Mendel notice?
1. That one dwarf plant and one tall plant's offspring would all be tall
2. Two tall plant's offspring would be tall apart from one who would be a dwarf plant.
130
What conclusions did Mendel reach?
1. Characteristics in plants are caused by genes
2. Genes are passed on from both parents
3. Genes can be dominant or recessive. If an individual has both a dominant and recessive gene then the dominant one will be shown
131
What does a genetic diagram do?
Shows the possible genes of offspring
132
What is an allele?
Different versions of the same gene
133
How many alleles does an allele have?
One but all other cells have two
134
What is a homozygous allele?
A gene that has two alleles that are the same (two dominant or two recessive alleles)
135
What is a heterozygous allele?
A gene that has two alleles that are different (one dominant allele and one recessive allele)
136
What is a phenotype?
An actual characteristic
137
What is a genotype?
The alleles you have
138
What is cystic fibrosis?
A genetic disorder of the cell membranes where the body produces mucus in the air passages and pancreas
139
What is the cause of cystic fibrosis?
A recessive allele
140
How can a child inherit the disease?
Both parents must be carriers or sufferers of the disease. People with one copy of the disease will not inherit it (Ff). There is a 1 in 4 chance that the child will inherit the disease if both parents are carriers
141
What is polydactyly?
A genetic disorder that causes babies to be born with extra digits
142
What is the cause of polydactyly?
A dominant allele so it can be inherited if just one parent carries the defective allele. There is a 50% chance of the child having the disorder if one person has the dominant gene (Dd or DD)
143
What is IVF?
- When embryos are fertilised in a lab and then implanted back into the mother's womb
- More than one egg is usually fertilised in order to increase success rate
144
What does IVF stand for?
In vitro fertilisation
145
What is genetic screening?
- When a cell is removed from an embryo and its genes are analysed.
146
Why do genetic screenings happen?
- In order to detect genetic disorders. The good alleles will be implanted into the womb and the bad ones (if any) will be destroyed.
147
Why are people against genetic screening?
1. The rejected and destroyed embryos could have been a human life
2. It creates prejudice because it suggests that those with genetic problems are unwanted
3. The screening itself is expensive
4. The parents may be able to choose embryos depending on certain desirable characteristics in the future
148
Why are people for genetic screening?
1. It stops people suffering
2. There are laws to stop it going too far- parents are not allowed to choose gender of baby etc.
3. During IVF embryos are destroyed anyway
4. Treating disorders is also really expensive
149
What are fossils?
Remains of organisms (plants and animals) from many years ago
150
How do fossils form in rock?
1. Gradual Replacement
2. Casts and Impressions
3. Preservation
151
What is the process of gradual replacement?
- Hard materials (teeth, bones, shells) do not decay easily and last a long time when buried
- They are eventually replaced by minerals as they decay- forms rock-like substance in shape of original part of organism
- The surrounding sediment also turns into rock but fossil stays visible
152
What is the process of casts and impressions?
- When an organism is buried in soft material such as clay.
- The soft material hardens around it and organism decays which leaves a cast of the organism
- Footprints can be pressed into soft materials-leaves impression when hardened
- Animal burrows and plant roots can be preserved in casts
153
What is the process of preservation?
- In places where there is no oxygen or moisture decay microbes cannot survive so decay will not occur
- In glaciers, it is too cold for decay microbes so decay will not occur
- Peat bogs are too acidic for decay microbes so decay will not occur
- All of this means that the organism will not decay and will be preserved
154
What are the causes of extinction?
1. Environment changes too quickly (destruction of habitat)
2. New predator kills them
3. New disease kills them
4. Cannot compete with other species for food
5. Catastrophic event occurs and kills them all
6. A new species develops
155
What is speciation?
The development of a new species
156
What is a species?
A group of similar organisms that can reproduce to give fertile offspring
157
When does speciation occur?
Occurs when populations of same species become so different that they can no longer breed together and produce fertile offspring.
158
How does isolation lead to speciation?
- can occur because of a physical barrier
- the conditions on one side of the barrier become slightly different to the other side
- this means that one population will have different common characteristics compared to other population due to natural selection
- Eventually, the populations will have changed so much that they cannot breed together to produce fertile offspring
- The two populations will have become different species
159
How does natural selection lead to speciation?
- some individuals in a population will be better adapted to an environment because of variation within the species
- Therefore, they will have a better chance of survival and so are more likely to breed successfully
- The beneficial characteristics will then be passed on to their offspring so on
- Therefore, the populations of the same species will eventually become different because certain organisms will be adapted to a different environment
160
Describe the process of natural selection.
- Individuals within a species show variation in their characteristics
- Individual characteristics that are better adapted to the environment are more likely to survive and reproduce
- The beneficial characteristics will then be passed on to the individual's offspring
161
Describe Jean-Baptiste Lamarck's theory of evolution.
He believed that:
- a characteristic that is used more and more by an organism will become bigger and stronger and one that is not used will disappear eventually
- any characteristic that is improved by an organism will b passed on to their offspring
162
What is the equation for photosynthesis?
Carbon dioxide + Water ------------------> Glucose + Oxygen
| (sunlight and chlorophyll)
163
What happens to the rate of photosynthesis when the temperature is increased and decreased?
1. Too low- the enzymes needed will work more slowly decreasing rate of phtosynthesis
2. Too high- the enzymes will become damaged and denature (happens at about 45 C)
164
What are the disadvantages of creating ideal conditions?
- It costs money
| - The conditions have to be kept exact
165
How is glucose used in making proteins?
- Glucose is combined with nitrate ions to make amino acids
| - Amino acids are sued to make proteins
166
How is glucose stored in seeds?
- It is turned into lipids for storing in seeds
| - Seeds also store starch
167
How is glucose stored as starch?
- Turned into starch and stored in roots, stem and leaves
- Starch is insoluble which is better for storing than glucose- Cells with lots of glucose in could draw in loads of water and swell up.
168
What is a quadrat?
A square frame, enclosing an area, that is used to compare the distribution of organisms in two areas (We used in when with Miss McKinney and we went measured daises)
169
Why do enzymes only catalyse one specific reaction?
Because each enzyme has one unique shape that fits onto only one substance involved in the reaction
