GCSE Biology: Flashcards
1
Q
What are the two types of cells?
A
Prokaryote and Eukryote.
2
Q
What is a eukaryote?
A
Complex.
Animal and plant cells.
3
Q
What is a prokaryote?
A
Smaller and simple bacteria.
4
Q
What are different parts of the cell called?
A
Subcellular structures.
5
Q
Name the structures in a animal cell:
A
Nucleus, Cytoplasm, Cell Membrane, Mitochondria, and Ribosomes.
6
Q
What is a Nucleus?
A
Genetic material and control cell activity.
7
Q
What is a Cytoplasm?
A
Gel substance, chemical reactions happen and has enzymes that control reactions.
8
Q
What is a Cell Membrane?
A
Holds cells together and controls what goes in and out.
9
Q
What is a Mitochondria?
A
Reactions for aerobic respiration take place and transfers energy.
10
Q
What is Ribosomes?
A
Proteins are made.
11
Q
Name the structures in a plant cell:
A
Cell wall, Permanent vacuole and Chloroplasts.
12
Q
What is a Cell wall?
A
Made of cellulose and supports the cell.
13
Q
What is a Permanent vacuole?
A
Has cell sap and a weak solution of sugar and salts.
14
Q
What is Chloroplasts?
A
Photosynthesis occurs.
15
Q
What is Chlorophyll?
A
Green substance that absorbs the light needed for photosynthesis.
[ In a Chloroplasts. ]
16
Q
In a bacterial cell what cells aren’t included?
A
Chloroplasts or mitochondria.
17
Q
What kind of nucleus does a bacterial cell have?
A
A single circular strand of DNA that floats freely in the cytoplasm.
18
Q
Name the cells that might be in a bacterial cell:
A
Cytoplasm, Cell Membrane and a Cell Wall.
19
Q
What are Plasmids?
A
Small rings of DNA that might be in bacterial cells.
20
Q
Why are microscopes important?
A
To study cells that can’t be seen by the human eyes. Also, developed over years of technology and improved.
21
Q
What is a Light Microscope?
A
The light and lenses to form an image of a specimen and magnify it.
22
Q
Why do you use Standard Form in Science?
A
Because of the tiny objects which could be very big or small numbers with a lot of zeros so. Using standard form is useful and manageable.
23
Q
What is an Electron Microscope?
A
Using electrons instead of light to form an image, a higher magnification and a higher resolution. See the internal structures of mitochondria and chloroplasts.
24
Q
What is the formula of Magnification?
A
Magnification= Image size ÷ Real size
25
A specimen is 50um wide. Calculate the width of the specimen under a magnification of x100. [In mm]
Image size= Magnification x real size
Image size= 100 x 50
=5000um
=5mm [um= 1000÷ =mm]
26
Which mircroscopes do you look at a specimen?
A light microscope.
27
How do you prepare a slide to view an onion cell?
1. Add a drop of water on a clean slide.
2. Cut up the onion and seperate them into layers. Use tweezers to peel off some epidermal tissues from the bottom of one of the layers.
3. Place the epidermal tissue into the water on the slide.
4. Add a drop of iodine solution [Stain] to highlight objects.
5. Then put a cover slip upright on the slide next to the water droplet. Carefully, tilt and lower it so it covers the specimen.
28
While you prepare your slide what do you try not to do?
Get any air bubbles under the slide because they'll obstruct your view on your specimen.
29
Name the six things that a light microscope has:
Eyepiece, Coarse adjustment knob, Fine adjustment knob, High and Low power objective lenses, Stage and Light.
30
How do you use a light microscope?
1. Clip the slide you've prepared onto the stage.
2. Select the lowest-powered objective lens.
3. Use the cosarse adjustment knob.
4. Look at the eyepiece then move the stage downwards until the image is roughly in focus.
5. Adjust the fine adjustment knob when you get a clear image.
6. [If you need to see the slide with greater magnification swap to a higher-powered objective lens.]
31
When drawing your observations what do you need to use?
A pencil with a sharp point and at least half a page with clear unbroken lines.
32
When drawing your observations what do you not do?
No colouring or shading.
33
When drawing your observations what do need to include?
A title, write down the magnification that it was observed under, label important features and using straight uncrossed lines.
34
What is an Enzyme?
Proteins that help speed up metabolism, or the chemical reactions in our bodies.
35
Name 2 facts about cells:
Cells don't look the same and have different structures to suit their different functions.
36
What is the definition of Differentiation?
The process of a cell changes to become specialised for its job.
37
What happens when cells changes?
They develop different subcellular structures and turn into different types of cells. This allows them to carry specific functions.
38
Where does differenation mostly occur?
As an organism develops.
39
Explain the differentiation in most animal cells:
Lost at an early stage after they become specialised.
40
Explain the differentiation in most plant cells:
They don't ever lose this ability of being lost at an early stage.
41
The cells that differentiate in mature animals are mainly used for?
Repairing and replacing cells such as skin or blood cells.
42
Name the scientific word for this phrase;
'Undifferentiated cells'...
Stem Cells.
43
What is the function of a Sperm Cell?
Is to get the male DNA to the female DNA.
44
What does a sperm cell looks like?
It has a long tail and a streamlined head to help it swim to the egg.
45
Name two facts about a Sperm Cell:
1. Lots of mitochondria in the cell to provide the energy needed.
2. Carries enzymes in its head to digest through the egg cell memberane.
46
What is the Sperm Cell spicialised for?
Reproduction.
47
What is the function of a Nerve Cell?
Carry electrical signals from one part of the body to another.
48
Describe what a Nerve Cell looks like:
The cells are long [to cover up distance] and have branched connections at their ends to connect to other nerve cells to form a network throughout the body.
49
What is a Nerve Cell specialised for?
Rapid Signalling.
50
What is the function of a Muscle Cell?
To contract quickly.
51
Describe what a Muscle Cell looks like:
These cells are long [for space to contract] contain lots of mitochondria to generate energy needed.
52
What is a Muscle Cell specialised for?
Contraction.
53
Describe what a Root Hair Cell looks like?
On surface of plant roots which grow into long 'hairs' out into the soil.
54
Why does a plant need a big surface area?
For absorbing water and mineral ions from the soil.
55
What is a Root Hair Cell specialised for?
For absorbing water and minerals.
56
What is the funtion of Phloem and Xylem Cells?
Form Phloem and Xylem tubes which transport substances such as food and water around plants.
57
How are the Phloem and Xylem tubes formed?
The cells are long joined end to end.
58
Name a fact about Xylem cells:
Hollow in the centre.
59
Name a fact about Phloem cells:
Very few subcellular structures so that stuff can flow through them.
60
What are Phloem and Xylem cells specialised for?
Transporting Subtances.
61
What happens to cells in the human body when we grow in order to surrive?
The cells divide and DNA.
62
What does Chromosomes contain?
DNA
63
In your body most cells have what in it?
A nucleus that conntains genetic material in form of chromosomes.
64
What do Chromosomes look like?
Coiled up with lenghts of DNA molecules.
65
What does each Chromosomes carry?
A large number of genes. Different genes control the development of different characteristics.
66
Give an example of a characteristics:
Hair colour.
67
In Body Cells there are two copies of Chromosomes from whom?
One of the organism's "mother" and one from its "father".
68
In a human cell how many pairs of Chromosomes are there?
23 pairs of Chromosomes.
69
What does a Cell Cycle do?
Makes new cells for growth, development and repair.
70
What happens in Body Cells in multicellular organism?
They divide to produce new cells as part of a series of stages called The Cell Cycle.
71
What is the definition of Mitosis?
The stage of the cell cycle when the cell divides.
72
In multicellular organisms what do they use?
They use Mitosis to grow or repalce cells that have been damaged.
73
What happens at the end of the Cell Cycle results?
Two new cells identical to the original cell with the same number of Chromosomes.
74
What are the two main stages of the Cell Cycle:
Growth and DNA Replication.
Mitosis.
75
In Growth and DNA Replication what happens in a cell that's not dividing?
The DNA is all spread out in long strings.
76
In Growth and DNA Replication what happens before the cell divides?
The cell has to grow and increase the amount of subcellular structures such as mitochondria and ribosomes.
77
In Growth and DNA Replication when its DNA duplicates what is formed?
The DNA is copied and forms X-shaped chromosomes. Each 'arm' of the chromosome is an exact duplicate of the other.
78
In a X-shaped chromosome what does each 'arm' represent?
The left arm has the same DNA.
The right arm has chromosomes.
79
What happens next once the DNA has been copied?
The chromosomes line up at the centre of the cell and cell fibres pull them apart. The two arms of each chromosome goes to opposite ends of the cell.
80
What happens next when chromosomes go to the opposite ends of the cell?
Membranes form around each of the sets of chromosomes. These become nuclei of the two new cells [the nucleus has divided].
81
Finally what happens next once the nucleus has been divided?
The cytoplasm and cell membrane divide. The cell has now produced two new daughter cells. The daughter cells contain exactly the same DNA [they're identical].
82
The daughters DNA is also identical to whom?
The parents cell.
83
Whats the type of simple cell division that can reproduce Prokaryotic Cells?
Binary Fission.
84
In binary fission, the cell...
Splits into two.
85
What is the method of Binary Fission?
What is the circumstance of each of the daughter cell having one copy of the circular DNA?
1. Circular DNA and plasmid(s) replicate.
2. Cell gets bigger. The circular DNA strands move to opposite "poles" (ends) of the cell.
3.Cytoplasm begins to divide. New cell walls begin to form.
4. Cytoplasm divides. Two daughter cells are produced. Each daughter cell has 1 copy of the circular DNA.
86
What is the circumstance of each of the daughter cell having one copy of the circular DNA?
Can have a variable number of copies of the plasmid(s).
87
How long does bacteria divide and why?
Very quickly by the right conditions.
88
Give an example of a condition that can make a bacteria divide quickly:
Warm environement.
89
What happens when the conditions become infavourable to a bacteria?
Stop dividing and eventually die.
90
What is Mean Division Time?
A method of how many times a bacteria cell has divided in a certain amount of time and the number of cells it has been produced in that time.
91
Bacteria (and some other microganisms) are grown in a "Culture Medium". What does a Culture Medium contain for the need to grow?
Carbohydrates.
Minerals.
Proteins.
Vitamins.
92
The Culture Medium used can be a...
Nutrient broth solution.
Solid agar jelly.
93
Bacteria grown on agar "plates" will form visible...
Colonies on the surface of the jelly or spread out to give an evening covering of bacteria.
94
To make an agar plate what gets poured into the shallow round plastic?
Hot agar jelly.
95
What are the "plates" called when testing Culture Medium?
Petri Dishes.
96
Name the correct scientific term of "wire loops" in a Petri Dish:
Inoculating Loops.
97
When the jelly's cooled and set, what can the inoculating loops be used for?
Transfer microorganisims to the cluture medium.
Alternatively, a sertile dropping pipette and spreader can be used to get an even covering of bacteria.
98
In Labs at School cultures of microorganisms aren't kept above 25*c. Why?
Harmful pathogens are more likely to grow.
99
What kind of conditions does the Cultures Medium grow a lot faster at higher temperatures?
Industrial conditions.
100
After the evening covering of bacteria what does the microorganisims do?
Multiply.
101
(Investigate the effect of antibiotics on bacterial growth:)
Step 1-Preparation:
Place paper discs soaked in different types or concentrations of antibiotics on an agar plate with an even covering of bacteria.
102
Why is an even covering of bacteria important in the peperation step?
An even covering ensures consistent results by providing a uniform environment for the antibitics to act upon.
103
(Investigate the effect of antibiotics on bacterial growth:)
Step 2-Diffusion:
Antibiotics will diffuse into the agar around the paper discs, creating areas where bacteria may have died.
104
What happens during the diffusion step?
Antibiotics diffuse into the agar from the paper discs, potentially killing or inhibiting bacteria around the discs.
105
(Investigate the effect of antibiotics on bacterial growth:)
Step 3-Control Setup:
Use a control disc soaked in sertile water instead of an antibiotic to ensure the results are due to the antibiotic.
106
Why is a control disc used in the experiment?
To ensure any observed effects on bacterial growth are due to the antibiotic and not other variables.
107
(Investigate the effect of antibiotics on bacterial growth:)
Step 4-Incubation:
Leave the plate for 48 hours at 25*C.
108
What are the conditions for the incubation step?
Incubuate the plate for 48 hours at 25*C to allow sufficient time for bacterial growth and antibiotic action.
109
(Investigate the effect of antibiotics on bacterial growth:)
Step 5-Observation:
Measure the inhibition zone (clear area) to determine the antibiotic's effectiveness. Larger inhibition zones indicate more effective antibiotics.
110
What does the inhibition zone represent?
The clear area around the disc where the bacteria have not grown, indicating the effectiveness of the antibiotic.
111
How do you measure the effectiveness of an antibiotic?
By measuring the size of the inhibition zone around the paper disc.
Larger inhibition zones indicate more effective antibiotics.
112
What does a larger inhibition zone indicate?
The antibiotic is more effective at inhibiting bacterial grwoth.
113
What is the purpose of using a control in the antibiotic effectiveness test?
The control disk (soaked in sertile water) ensures that the observed effects on bacterial growth are due to the antibiotic and not other factors.
114
What are the potential consequences of contamination by unwanted microorganisms in mircobiology experiments?
Contamination can skew experimental results and lead to the growth of harmful pathogens which could affect the accuracy and safety of the experiment.
115
Describe the process for preparing petri dishes and culture medium to ensure they are uncontaminated before use.
Petri dishes and culture medium must be sterilized, typically by heating them to a high temperature to kill any existing microorganisms that might be present.
116
What is the recommended method for sterilizing an inoculating loop before transfering bacteria to the culture medium?
The inoculating loop should be sterilized by passing it through a hot flame to eliminate any potential contaminants.
117
Explain why is it necessary to lightly tape the lid of a petri dish after inoculating it with bacteria.
Taping the lid helps to secure it and prevnt unwanted microorganisms, from entering the dish. Thereby reducing the risk of contamination.
118
What is the reason for sstoring petri dishes upside down after inoculation?
Prevents condensation droplets from falling onto the agar surface, which can otherwise cause contamination and effect the growth of the bacteria.
119
(Culturing Microorganisms:)
Purpose of comparing inhibition zones:
It's important because of the effectiveness of antibiotics.
120
(Culturing Microorganisms:)
Methods for comparison:
By eye vs calculating the area.
121
(Culturing Microorganisms:)
Formula for the calculation:
Area = PieR*2
122
(Culturing Microorganisms:)
Application to bacterial colonies:
Area = PieR*2
But to measure the diameter first.
123
What is the process called when a cell changes to become specialized for its job?
Differentation.
124
What are stem cells?
Undifferenetiated cells that can divide to produce more undifferenetiated cells and can differentiate into different types of cells.
125
Where are stem cells found in the early stages of human development?
In early human embryos.
126
Why are stem cells from embryos exciting to doctors and medical researchers?
Because they have the potential to turn into any kind of cell at all.
127
Can adult stem cells differentiate into any type of cell?
No they only turn into certain types of cells.
Like blood cells.
128
Where are adult stem cells typically found?
In certain places like bone marrow.
129
How are stem cells from embryos and bone marrow be used in the lab?
They can be grown to produce clones (genetically identical cells) and made to differentiate into specialised cells for use in medicine or research.
130
What is one way adult stem cells are currently used in medicine?
Adult stem cells from a healthy person's bone marrow can be used to replace faulty blood cells in patients.
131
How might embryonic stem cells benefit people with diseases?
Embryonic stem cells could potentially replace damaged cells, such as creating insulin-producing cells for diabetics or nerve cells for those with spinal cord injuries.
132
What is therapeutic cloning and how does it reduce the risk of stem cell rejection?
Therapeutic cloning involves creating an embryo with the same genetic makeup as the patient.
So stem cells from this embryo match the patients genes and are less likely to be rejected.
133
What is a major risk associated with stem cell therapy?
Stem cells grown in the lab could become contaminated with viruses which might be trnsferred to the patient and potentially worsen their condition.
134
Why are some people against stem cell research?
They believe that human embryos shouldn't be used for experiments since each one is a potential human life.
135
What do supporters of stem cell research argue is more important than the rights of embryos?
Curing existing patients who are suffering.
136
What is a common arguement in favour of using embryos for stem cell research?
The embryos used are often unwanted ones from fertility clinics that would otherwise be destroyed.
137
What do campaigners for the rights of embryos want scientists to focus on?
Developing other sources of stem cells to avoid using embryos.
138
What is the stance of stem cell research in some countries?
How does the UK approach it?
Stem cell research is banned in some countries.
It's allowed in the UK under strict guidelines.
139
Where are the stem cells found in plants?
Stem cells in plants are found in the meristems, which are parts of the plant where growth occurs.
140
What is the significance of cells in the meristem tissues throughout a plant's life?
Cells in the meristem can diiferentiate into any of plant cell.
141
How can plant stem cells be used in relation to cloning?
Plant stem cells can be used to produce clones (identiacal copies) of whole plants quickyly and cheaply.
142
What is one way plant stem cells can help with conservation?
They can be used to grow more plants of rare species to prevent them from being wiped out.
143
How can plant stem cells be beneficial for agriculture?
Plant stem cells can be used to grow crops of identical plants with desired features, such as disease resistance for farmers.
144
What is diffusion in simple terms?
The movement of particles from areas of high concentration to areas of low concentration.
145
How is diffusion defined scientifically?
The spreading out of parcticles from an area of higher concentration to an area of lower concentration.
146
In which states of mater does diffusion occur and why?
Happens in both solutions and gasses because the particles in thses substances are free to move about randomly.
147
What is the simplest type of diffusion?
When different gasses diffuse through each other.
148
How does the concentration gradient affect the rate of diffusion?
The bigger the concentration gradient the faster the diffusion rate.
149
How does the temperature affect the rate of diffusion?
A higher temperature increases the diffusion rate because particles have more energy and move around faster.
150
What is the role of cell membranes in relation to diffusion?
Cell membranes hold the cell together and allow substances to move in and out.
151
How do dissolved substances move in and out of cells?
Dissolved substances move in and out of cells by diffsion.
152
What types of molecules can diffuse through cell membranes?
Only very small molecules like oxygen, glucose, amino acids and water can diffuse through cell membranes.
153
Why can't large molecules diffuse through cell membranes?
Large molecules like starch and proteins can't fit through the membrane.
154
How do particles flow through a cell membrane during diffusion?
Particles flow from an area of higher concentration to an area of lower concentration.
155
Why is there a net movement of particles through a cell membrane?
There is a net movement from the side with more particles to the side with fewer because particles move randomly in both directions.
156
How does the surface area of the membrane affect the diffusion rate?
The larger the surface area of the membrane the faster the diffusion rate because the more particles can pass through at once.
157
What is osmosis?
Osmosis is the movement of water molecules across a partially permeable membrane from higher to lower water concentration.
158
What is a partially permeable membrane?
It has very small holes that allow only tiny molecules like water to pass through not bigger molecules like sucrose.
159
How do water molecules move during osmosis?
Water molecules move both ways through the membrane but there is a net flow from higher to lower water concentration.
160
Why does water move into the region with fewer water molecules?
To dilute the stronger sugar solution and even up the cncentration on both sides.
161
How is osmosis related to diffusion?
Osmosis is a type of diffusion involving the passive movement of water from higher to lower concentration.
162
(Practicle Osmosis Part:)
What is the independant variable in the osmosis experiment with potato cylinders?
The concentration of the sugar solution.
163
(Practicle Osmosis Part:)
What is the dependent variable in the osmosis experiment with potato cylinders?
The mass of the potato cylinders.
164
(Practicle Osmosis Part:)
Hoe do you determine if a potato cylinder has gained or lost water in the experiment?
By measuring the change in mass before and after immersion in the sugar solution.
165
(Practicle Osmosis Part:)
What must be kept constant to ensure a fair test in the osmosis experiment?
Volume of solution, teperature, time, type of sugar used and other variables.
166
(Practicle Osmosis Part:)
What is one potential error in the osmosis experiment related to measuring the mass of the potato cylinders?
Excess water not being removed leading to a higher mass measurement.
167
How can you minimize errors from water evaporation in the osomosis experiment?
By repeating the experiment and calculating the mean percentage change in mass for each concentration.
168
What is active transport?
Substances are absorbed against a concentration gradient from a lower to a higher concentration.
169
What role do root hairs play in plant roots?
Absorb mineral and water from the soil.
170
How do root hairs increase the efficiency of absorption in plants?
Growing into the soil and increasing the surface area available for absorning water and mineral ions.
171
Why do plants need to absorb mineral ions?
Mineral ions are necessary for healthy plant growth.
172
Why can't root hair cells rely on diffusion to absorb minerals from the soil?
Concentration of minerals is usually higher in the root hair cells than in the surrounding soil making diffusion ineffective.
173
Why can't minerals naturally move into root hiars by diffusion?
Beacuse diffusion would cause minerals to move out of root hairs not into them.
174
What process allows root hairs to absorb minerals against a concentration gradient?
Active transport.
175
Why is active transport essential for plant growth?
To absorb minerals from a very dilute solution which is necessary for its growth.
176
What energy source does active transport require?
Energy from respiration.
177
In which other processes within the human body does active transport occur?
In the absorption of glucose from the gut and kidney tubules.
178
What is the purpose of active transport in the gut?
Transport nutrients into the blood when the concentration of nutrients in the gut is lower than in the blood.
179
When do glucose and amino acids diffuse naturally into the blood?
When their concentration is higher in the gut than in the blood.
180
What happens when the concentration gradient of nutrients in the gut is lower than in the blood?
Active transport is used to move nutrients against the concentration gradient.
181
What process is used in both plant roots and the gut to transport nutrients?
Active transport.
182
Why is active transport necessary for glucose absorption in the gut?
To be absorbed in the bloodstream even when its concentration in the blood is higher than in the gut.
183
Where is glucose transported after being absorbed into the bloodstream?
To cells its used for respiration.
184
What does a ratio show when comparing surface area to volume?
It shows the compassion between surface area and volume.
185
How do you calculate the surface area of a cuboid?
Add the areas of all six faces.
186
How is the volume of a cuboid determined?
Multiply length, width and height.H
187
How is the surface area to volume ratio of a cuboid calculated?
Divide the surface area by the volume.
188
How does the surface area to volume ratio differ between a smaller and a larger object?
Smaller objects have a higher surface area to volume ratio.
189
How do single-celled organisms exchange gases and substances?
They diffuse directly across the cell membrane.
190
Why do multicellular organisms need exchange surfaces?
They have a smaller surface area compared to thier volume so diffusion alone isn't enough.
191
How are exchange surfaces adapted for efficiency?
Large surface area.
Thin membrane.
Often ventilated.
Well supplied with blood vessels.
192
Why is a thin membrane important for exchange surfaces?
It ensures a short distance for substances to diffuse.
193
What is the primary job of the lungs?
Transfer oxygen to the blood and remove carbon dioxide.
194
Where does gas exchange occur in the lungs?
In the alveoli.
195
How are alveoli specialized for gas exchange?
They have a large surface area, thin walls and a good blood supply.
196
Why is a large surface area important for alveoli?
It maximizes the diffusion of oxygen and carbon dioxide.
197
What is the approximate surface area of the alveoli in humans?
About 75m^2.
198
What are the tiny projections that cover the inside of the small intestine called?
Villi.W
199
What is the main function of the villi in the small intestine?
They increase the surface area to speed up the absorption of digested food into the blood.
200
What are two features of the villi that aid in the quick absorption of nutrients?
Single layer of surface cells and a very good blood supply.
201
What is the role of the network of capillaries within a villus?
They help in the absorption and transport of nutrients into the bloodstream.
202
Which muscle layers are present below the villi in the small intestine?
Circular muscle and longitudinal muscle.
203
How does carbon dioxide enter the leaf for photosynthesis?
Carbon dioxide diffuses into the air spaces within the leaf, then into the cells where photosynthesis occurs.
204
What part of the leaf acts as an exchange surface allowing gases to diffuse in and out?
The underside of the leaf acts as an exchange surface with stomata allowing gases to diffuse in and out.
205
What gases diffuse out of the leaf through the stomata?
Oxygen (produced during photosynthesis) and water vapour diffuse out through the stomata.
206
What role do guard cells play in the leaf?
Control the opening and closing of stomata preventing excessive water loss that could cause the plant to wilt.
207
How does the shape of the leaf enhance gas exchange?
The flattened shape of the leaf increases the area of the exchange surface making gas exchange more effective.
208
What is the function of the air spaces inside the leaf?
Air spacess inside the leaf increase the surface area for gas exchange allowing more carbon dioxide to enter the cells.
209
Why does water vapour diffuse out of the leaf?
Higher concentration inside the leaf than in the air outside.
210
Whatis the main function of gills in fish?
Gills are the gas exchange surface in fish. Allowing oxygen to diffuse from water into the blood into water.
211
How does water enter and exit a fish during gas exchange?
Water enters through the fish's mouth and passes out through the gills.
212
What structures in the gills increase the surface area for gas exchange?
The gill filaments and lamellae increase the surface area for gas exchange.
213
What is the function of lamellae in fish gills?
Lamellae increase the surface area of the gills and contain lots of blood capillaries to speed up diffusion.
214
Why do lamellae have a thin surface layer of cells?
Minimize the distance that gases have to diffuse improving the efficiency of gas exchnge.
215
How is a large concentration gradient maintained between water and blood in fish gills?
Blood flows through the lamellae in one direction while water flows over in the opposite direction.
216
Why is the concentration of oxygen higher in water than in the blood of fish?
Oxygen diffuses from the water into the blood.
217
What are the basic building blocks of all living organisms?
Cells are the basic building blocks of all living organisms.
218
What is the function of specialised cells in an organism?
Specialised cells carry out a particular function.
219
What is the process called when cells become specialised for a specific job?
Differentiation.
220
When does differentiation occur in multicellular organisms?
During the development of a multicellular organism.
221
How are tissues, organs and organ systems related in multicellular organisms?
Specialised cells form tissues, which form organs and organs form organ systems.
222
Why do large multicellular organisms need different systems inside them?
They need different systems for exchanging and transporting materials.
223
What is a tissue?
Group of similar cells that work together to carry out a particular function potentially including more than one type of cell.
224
What are three types of tissues found in mammals like humans?
Muscular tissue.
Glandular tissue.
Epithelial tissue.
225
What is the function of muscular tissue?
Contracts (shortens) to move whatever it's attached to.
226
What does glandular tissue do?
Makes and secretes chemicals like enzymes and horomones.
227
Where can epithelial tissue be found and what is it's role?
Covers some parts of the body such as the inside of the gut.
228
What is an organ?
Group of different tissues that work together to prform a certain function.
229
What are the three types of tissues found in the stomach?
Muscular tissue.
Glandular tissue.
Epithelial tissue.
230
What does mucular tissue do in the stomach?
It moves the stomach wall to churn up the food.
231
What is the role of glandular tissue in the stomach?
It produces digestive juices that help digest food.
232
What does epithelial tissue do in the stomach?
It covers the outside and inside of the stomach.
233
What is an organ system?
Group of orgns working together to perform a particular function.
234
What is the function of the digestive system in humans and other mammals?
Break down and absorb food.
235
Which organs in the digestive system produce digesyive juices?
The glands such as the pancreas and salivary glands.
236
What is the role of the stomach and small intestine in the digestive system?
Digest food.
237
What is the function of the liver in the digestive system?
Produces bile.
238
What is the function of the small intestine in the digestive system?
Absorbs soluble food molecules.
239
What role does the large intestine play in the digestive system?
Absorbs water from undigested food leaving feces.
240
What role do enzymes play in the body?
Enzymes act as catalysts speeding up chemical reactions in the body.
241
Why do chemical reactions in living things need to be carefully controlled?
Ensure the right amount of substances is produced.
242
What is one way to speed up a chemical reaction and why is it not ideal for living organisms?
Raising the temperature. Speeds up both useful and unwanted reactions and can damage cells if the temperature is too high.
243
How do enzymes benefit living organisms in terms of reaction speed and temperature?
Enzymes speed up useful chemical reactions without the need for high temperatures.
244
What is a catalyst?
Substance that increases the speed of a reaction without being changed or used up in the reaction.
245
What are enzymes made of and why is their shape important?
Enzymes are large proteins made of chains of amino acids and their unique shapes are necessary for them to function.
246
What do enzymes do to help catalyze reactions?
Enzymes have special shapes that allow them to catalyze specific reactions.
247
What kinds of processes do chemical reactions usually involve?
Substances being split apart or joined together.
248
What is the active site of an enzyme?
Unique part of the enzyme that fits onto the substrate involved in the reaction.
249
What is the relationship between an enzyme and its substrate?
Subtrate must fit into the enzymes active site for the reaction to be catalyzed.
250
Why do enzymes usually only catalyse one specific reaction?
Beacuse their active site is shaped to fit only ome specific substrate.
251
What is the "lock and key" model of enzyme action?
A model where the enzyme's active site fits perfectly with the substrate similar to how a key fits into a lock.
252
How does the "induced fit" model differ from the "lock and key" model?
"Induced ft" model the active site changes more slightly tp fit the substrate more tightly when it binds.
253
What factors affect the rate of an enzyme catalyzed reaction?
Temperature and pH.
254
How does increasing temperature initially affect the rate of an enzyme catalyzed reaction?
Increases the rate of the reaction.
255
What happens to an enzyme if the temperature gets too high?
Enzyme becomes denatured as the bonds holding it together break changing the shape of the active site.
256
What is the term used when an enzyme loses its function due to high temperture?
Denaturation.
257
What is the optimum temperture for an enzyme?
Temperature at which the enzyme works best.
258
How does pH affect enzyme activity?
If the pH is too high or too low it interferes with the bonds holding the enzyme together denaturing together.
(Denaturing the enzyme)
259
What is the optimum pH for most enzymes?
Neutral pH 7 but it can vary.
(Eg pepsin works best at pH 2)
260
Why does the enzyme pepsin work best at pH 2?
Well suited to the acidic conditiond of the stomach where it breaks down proteins.
261
What does the enzyme amylase break down and into what substance?
Breaks down starch into maltose.
262
How can you detct the presence of starch in a solution?
By adding iodine solution which will change from browny-orange to blue-black if starch is present.
263
What is the purpose of placing iodine solution in each well of a spotting tile during the experiment?
Test for the presence of starch at different intervals.
264
Why is it important to maintain the water at 35*C during the experiment?
The enzyme amylase functions at a constant temperature which is necessary for a fair test.
265
How long should you wait after placing the boiling tube in the water bath before adding starch solution?
Five minutes.
266
What is the purpose of using continuous sampling with a dropping pipette every 30 seconds during the experiment?
The amylase has completely broken down the starch indicated by the iodine solution remaining browny-orange.
267
How do you investigate the effect of pH on amylase activity in this experiment?
Repeating the experiment with buffer solutions of different pH values and measuring the time taken for starch to be broken down.
268
What variables must be controlled to ensure a fair test when investigating how pH affects amylase activity?
Concentration and volume of the amylase solution must be controlled.
269
What is the general formula to calculate the rate of reaction?
Rate=1000 divided by time
(Time in seconds)
270
How can you calculate the rate of reaction whne given the time for amylase to break down at pH 6 in 90 seconds?
1000/90
=11s-1
(To 2 significant figures)
271
How do you calculate the rate of reaction when an experiment measures how much something changes over time?
Divide the amount that it has changed by the time taken.
272
During an experiment with catalase 24cm*3 of oxygen was released in 50 seconds. What is the rate of reaction in cm*3/s?
24cm*3 / 50s= 0.48 cm*3/s
273
Where are digestive enzymes produced and where do they act?
Digetsive enzymes are produced by cells and released into the gut to mix with food.
274
Why do digestive enzymes break down large molecules?
Too big to pass through the walls of the digestive system.
275
Name three large molecules:
Starch.
Proteins.
Fats.
276
What do digestive enzymes break large molecules down into?
Digetsive enzymes break large molecules into smaller molecules. Like:
Sugar (glucose and maltose), amino acids, glycerol and fatty acids.
277
Why is it important that digestive enzymes break down large molecules into smaller ones?
Pass through the walls of the digestive system and be absorbed into the bloodstram.
278
What is the function of amylase?
Amylase is a carbohydrase that breaks down starch into maltose and other simple sugars.
279
Where is amylase produced in the body?
Salivary glands.
Pancreas.
Small intestine.
280
What is the role of the protease enzymes?
Convert proteins into amino acids.
281
In which part of the body are protease enzymes made?
Stomach (AS pepsin)
Pancreas.
Small Intestine.
282
What do lipase enzymes do?
Convert lipids into glycerol and fatty acids.
283
Where are lipase enzymes produced?
Pancreas.
Small Intestine.
284
What is the role of bile in digestion?
Neutralizes stomach acid and emulsifies fat.
285
Where is bile produced and stored?
Produced in the liver.
Stored in the gallbladder.
286
How does bile help enzymes in the small intestine?
Neutralizes the acidic pH from the stomach making conditions alkaline which is optimal for enzymes in the small intestine.
287
How does bile affect the digestion of fats?
Emulsifies fats breaking them into tiny droplets which increases the surface area dor lipase to act on speeding up fat digestion.
288
What catalyzes the breakdown of food?
Enzymes.
289
Where are digestive enzymes produced in the body?
In specialised cells in glands and in the gut lining.
290
Do different enzymes catalyze the breakdown of different food molecules?
Yes.
291
What enzyme is produced by the salivary glands?
Amylase.
292
What are the three main functions of the stomach in digestion?
Pummels food with muscular walls produces the protease. Enzyme pepsin. Hydrochloric acid.
293
Why does the stomach produce hydrochloric acid?
Kill bacteria.
Provide the right pH (pH 2) for the protease enzyme to work.
294
What is the function of the liver in digestion?
Produces bile which neutralizes stomach acid and emulsifies fats.
295
Where is bile stored before it is released into the small intestine?
Gall bladder.
296
What is the function of the large intestine?
Absorbs excess water from food.
297
Which organ produces protease, amylase and lipase enzymes?
Where are these enzymes released?
Pancreas produce those enzymes.
The small intestine is what they're released to.
298
What happens in the small intestine during digestion?
Produces protease amylase and lipase enxymes to complete digestion.
Absorbed into the blood too.
299
Where are feces stored before they are excreted?
Rectrum.
300
What is the first step in preparing a food sample for testing?
Break up the food using a pestle and motar.
301
After breaking up the food where should the ground up food be transferred?
Transfer the ground up food to a beaker.
302
What should be added to the beaker containing the ground up food?
Add some distilled water.
303
What is the purpose of stirring the food and water mixture with a glass rod?
Dissolve some of the food.
304
How do you remove solid bits from the food mixture before testing?
Filter the solution using a funnel lined with filter paper.
305
What test is used to identity reducing sugars in food like biscuits, cereal and bread?
The Benedicts Test.
306
How much of the prepared food sample should be transferred to the test tube for the Bennedicts Test?
5cm*3.
307
What temperature should the water bath be set to for the Benecdict's Test?
75*C.
308
How much Benedict's solution should be added to the test tube containing the food sample?
About 10 drops.
309
How long should the test tube be left in the water bath during the Benedict's Test?
5 minutes.
310
What colour change indicates the presence of reducing sugars in the Benedict's Test?
Solution changes from blue to green, yellow or brick red depending on the amount of sugar.
311
How do you test for starch in a food sample?
. Add iodine solution to the sample.
When the starch becomes present the solution changes from browny-orange to black/blue-black.
312
What is the Biuret Test used for?
Checks for proteins.
313
How is the Biuret Test done by?
. Add Biuret solution to the sample.
. Gently shake.
. If proteins are present the solution turns from blue to purple.
314
How do you test for Lipids using Sudan III stain solution?
. Add Sudan III stain solution to the sample.
When the lipids are present:
Mixture seperates into two layers.
Top layer turns bright red.
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