Key Concepts In Biology Flashcards
1
Q
What are the two main types of cells?
A
Cells can be either eukaryotic or prokaryotic.
2
Q
What are eukaryotic cells?
A
Eukaryotic cells are complex and include all animal and plant cells.
3
Q
What are prokaryotic cells?
A
Prokaryotic cells are smaller and simpler, e.g. bacteria.
4
Q
What is a eukaryote?
A
Eukaryotes are organisms that are made up of eukaryotic cells.
5
Q
What is a prokaryote?
A
A prokaryote is a prokaryotic cell (it’s a single-celled organism).
6
Q
What are subcellular structures?
A
The different parts of a cell are called subcellular structures, also known as organelles.
7
Q
What are the main subcellular structures in animal cells?
A
1) Nucleus, 2) Cytoplasm, 3) Cell membrane, 4) Mitochondria, 5) Ribosomes.
8
Q
What is the function of the nucleus?
A
The nucleus contains genetic material that controls the activities of the cell.
9
Q
What is the function of the cytoplasm?
A
The cytoplasm is a gel-like substance where most of the chemical reactions happen.
10
Q
What is the function of the cell membrane?
A
The cell membrane holds the cell together and controls what goes in and out.
11
Q
What is the function of mitochondria?
A
Mitochondria are where most of the reactions for respiration take place.
12
Q
What is the function of ribosomes?
A
Ribosomes are involved in translation of genetic material in the synthesis of proteins.
13
Q
What additional structures do plant cells have compared to animal cells?
A
Plant cells usually have a rigid cell wall, a large vacuole, and chloroplasts.
14
Q
What is the function of the rigid cell wall?
A
The rigid cell wall, made of cellulose, supports and strengthens the cell.
15
Q
What is the function of the large vacuole?
A
The large vacuole contains cell sap and maintains internal pressure to support the cell.
16
Q
What is the function of chloroplasts?
A
Chloroplasts are where photosynthesis occurs, making food for the plant.
17
Q
What are the main subcellular structures in bacterial cells?
A
1) Chromosomal DNA, 2) Ribosomes, 3) Cell membrane, 4) Plasmid DNA, 5) Flagellum.
18
Q
What is the function of chromosomal DNA in bacterial cells?
A
Chromosomal DNA controls the cell’s activities and replication.
19
Q
What is plasmid DNA?
A
Plasmid DNA consists of small loops of extra DNA that aren’t part of the chromosome.
20
Q
What is the function of the flagellum?
A
The flagellum is a long, hair-like structure that helps the bacterium move.
21
Q
A
22
Q
What are specialised cells?
A
Cells that have a structure which makes them adapted to their function.
23
Q
What is the function of egg cells?
A
To carry the female DNA and to nourish the developing embryo in the early stages.
24
Q
How are egg cells adapted to their function?
A
1) They contain nutrients in the cytoplasm to feed the embryo.
2) They have a haploid nucleus.
3) Their membrane changes structure after fertilisation to prevent more sperm from entering.
25
What is the function of sperm cells?
To transport the male's DNA to the female's egg.
26
How are sperm cells adapted to their function?
1) They have a long tail to swim to the egg.
2) They contain lots of mitochondria for energy.
3) They have an acrosome that stores enzymes to digest the egg cell membrane.
4) They have a haploid nucleus.
27
What are ciliated epithelial cells specialised for?
Moving substances along the surface of the tissue.
28
How do ciliated epithelial cells move substances?
The cilia beat to move substances in one direction.
29
Where can ciliated epithelial cells be found?
In the lining of the airways, helping to move mucus up to the throat.
30
31
What is the purpose of microscopes?
Microscopes are used to discover and study cells by magnifying images and increasing resolution.
32
What does resolution mean in microscopy?
Resolution refers to how well a microscope distinguishes between two points that are close together.
33
When were light microscopes invented?
Light microscopes were invented in the 1590s.
34
How do light microscopes work?
They work by passing light through the specimen, allowing us to see structures like nuclei and chloroplasts.
35
What are electron microscopes and when were they invented?
Electron microscopes were invented in the 1930s and use electrons rather than light for higher magnification and resolution.
36
What can electron microscopes reveal?
They can reveal much smaller details, such as the internal structure of mitochondria and chloroplasts.
37
What is the first step in viewing a specimen using a light microscope?
Take a thin slice of the specimen to allow light to pass through.
38
How do you secure a specimen on a slide?
Put one drop of water in the middle of a clean slide and place the specimen on it.
39
What should you do if your specimen is transparent?
Add a drop of stain to make the specimen easier to see.
40
What is the purpose of a cover slip?
A cover slip is used to protect the specimen and prevent air bubbles.
41
What is the first adjustment to make when using a light microscope?
Select the lowest-powered objective lens.
42
How do you focus on the specimen?
Use the coarse adjustment knob to move the stage up and then the fine adjustment knob for a clear image.
43
What is the field of view (FOV)?
The field of view is the circular area visible when looking through the microscope.
44
How do you calculate the new FOV when changing lenses?
If you swap to a lens that is 10 times more powerful, divide your previous FOV by 10.
45
What are the steps to make a scientific drawing of a specimen?
Draw outlines with clear lines, ensure it takes up half the space, and label features with straight lines.
46
What should you include in your scientific drawing?
Include labels for important features and the magnification used.
47
What is the importance of measuring your field of view?
Measuring your field of view allows you to estimate the size of your specimen.
48
49
What is magnification?
Magnification is how many times bigger the image is.
50
How do you calculate total magnification?
Total magnification = eyepiece lens magnification x objective lens magnification.
51
What is the total magnification if eyepiece lens magnification is x 10 and objective lens magnification is x 40?
The total magnification would be 10 × 40 = × 400.
52
How can you find magnification if you know the image size and real size?
Magnification = image size / real size.
53
What should you ensure when measuring image size and real size?
Both measurements should have the same units.
54
How can you rearrange the magnification formula?
You can rearrange using a formula triangle.
55
What is a method to estimate magnification?
Round the numbers to 1 significant figure and divide.
56
What is standard form?
Standard form is a way to express very big or small numbers more manageably.
57
How do you convert 0.017 into standard form?
0.017 can be written as 1.7 x 10^-2.
58
What does a positive power of 10 indicate?
It indicates the decimal point has moved to the left.
59
What does a negative power of 10 indicate?
It indicates the decimal point has moved to the right.
60
How can you express 0.0007 m in different units?
0.0007 m could be written as 0.7 mm.
61
What is the standard form of a millimetre (mm)?
Millimetre (mm) is × 10^-3 m.
62
What is the standard form of a micrometre (um)?
Micrometre (um) is × 10^-6 m.
63
What is the standard form of a nanometre (nm)?
Nanometre (nm) is × 10^-9 m.
64
What is the standard form of a picometre (pm)?
Picometre (pm) is × 10^-12 m.
65
How do you calculate the width of an image under magnification?
Image size = magnification x real size.
66
If a specimen is 5 × 10^-6 m wide and viewed under a magnification of × 100, what is the image size?
Image size = 100 × (5 × 10^-6 m) = 5 × 10^-4 m.
67
How can you enter standard form numbers into a scientific calculator?
Use the 'EXP' or the 'x10*' button.
68
What is the real width of a cheek cell if the image is 2.4 mm wide under x 40 magnification?
The real width of the cheek cell is calculated as follows: real size = image size / magnification.
69
70
What are enzymes?
Enzymes are catalysts produced by living things that increase the speed of chemical reactions without being changed or used up.
71
Why do living things produce enzymes?
Living things produce enzymes to speed up useful chemical reactions in the body without requiring high temperatures.
72
What is a substrate?
A substrate is the molecule that is changed in a chemical reaction.
73
What is an active site?
The active site is the part of the enzyme where it joins to its substrate to catalyse the reaction.
74
What does high specificity mean in relation to enzymes?
High specificity means that enzymes usually only work with one substrate.
75
What is the 'lock and key' mechanism?
The 'lock and key' mechanism describes how the substrate fits into the enzyme's active site, similar to how a key fits into a lock.
76
How does temperature affect enzyme activity?
Increasing temperature generally increases the rate of an enzyme-catalysed reaction, but if it gets too hot, the enzyme can become denatured.
77
What is denaturation?
Denaturation occurs when the shape of the enzyme's active site changes, preventing the substrate from fitting.
78
What is optimum temperature?
Optimum temperature is the temperature at which an enzyme is most active.
79
How does pH affect enzyme activity?
pH affects enzymes by interfering with the bonds holding the enzyme together; extreme pH levels can denature the enzyme.
80
What is the optimum pH for most enzymes?
The optimum pH for most enzymes is often neutral pH 7, but some, like pepsin, work best at acidic pH 2.
81
How does substrate concentration affect the rate of reaction?
Higher substrate concentration increases the rate of reaction until all active sites are full; beyond that point, adding more substrate makes no difference.
82
83
What does the enzyme amylase catalyse?
The breakdown of starch to maltose.
84
How can you detect starch?
Using iodine solution, which changes from browny-orange to blue-black in the presence of starch.
85
What is the first step in investigating pH's effect on amylase activity?
Put a drop of iodine solution into every well of a spotting tile.
86
What temperature should the water be heated to for the experiment?
35 °C.
87
What should you use to add amylase and buffer solution to the boiling tube?
A syringe.
88
How often should you sample the mixture during the experiment?
Every 10 seconds.
89
What indicates that starch is no longer present?
When the iodine solution remains browny-orange.
90
What should you do to ensure a fair test?
Control any variables such as concentration and volume of amylase solution.
91
How do you calculate the rate of reaction?
Rate = change ÷ time.
92
What is the formula for calculating rate using time?
Rate = 1000 ÷ time.
93
What are the units for rate of reaction?
s⁻¹.
94
What does the enzyme catalase break down?
Hydrogen peroxide into water and oxygen.
95
How do you calculate the rate of reaction for catalase?
Rate = change ÷ time = 24 cm³ ÷ 50 s = 0.48 cm³ s⁻¹.
96
What other factors can affect the rate of amylase activity?
Temperature.
97
What was the rate of reaction at pH 4 after 2 minutes if 36 cm³ of product was released?
Rate = 36 cm³ ÷ 120 s = 0.3 cm³ s⁻¹.
98
99
What role do enzymes play in organisms?
Enzymes help break down big molecules into smaller ones and build small molecules back up into bigger ones.
100
What are examples of big molecules that need to be broken down?
Proteins, lipids, and some carbohydrates.
101
Why is it important for organisms to break down big molecules?
To use the smaller components for growth and other life processes.
102
What are lipids?
Lipids are fats and oils.
103
How do digestive enzymes function?
They break down large food molecules into smaller, soluble molecules that can be absorbed into the bloodstream.
104
What do carbohydrases do?
Carbohydrases convert carbohydrates into simple sugars.
105
Give an example of a carbohydrase.
Amylase, which breaks down starch into maltose and other sugars.
106
What do proteases do?
Proteases convert proteins into amino acids.
107
What do lipases do?
Lipases convert lipids into glycerol and fatty acids.
108
What happens to the pH when lipids are broken down?
The fatty acids lower the pH of the solution they are in.
109
What is the process of synthesizing carbohydrates?
Carbohydrates are synthesized by joining together simple sugars.
110
What enzyme synthesizes glycogen?
Glycogen synthase joins together chains of glucose molecules to make glycogen.
111
How are proteins synthesized?
Proteins are made by joining amino acids together.
112
What is the role of enzymes in the synthesis of lipids?
Enzymes are involved in synthesizing lipids from fatty acids and glycerol.
113
What are the smaller components that make up carbohydrates?
Simple sugars.
114
What are the smaller components that make up proteins?
Amino acids.
115
116
How can you test for reducing sugars?
Add Benedict's reagent (which is blue) to a sample and heat it in a water bath set to 75 °C. A positive test will form a coloured precipitate. The colour changes from blue to green, yellow, orange, or brick red depending on the concentration of reducing sugar.
117
What indicates the presence of starch in a sample?
If starch is present, the sample changes from browny-orange to a dark, blue-black colour when iodine solution is added.
118
How do you test for lipids?
Shake the test substance with ethanol for about a minute, then pour the solution into water. If lipids are present, they will precipitate out and form a milky emulsion.
119
What does a purple colour indicate in the Biuret test?
A purple colour indicates the presence of protein after adding potassium hydroxide and copper(II) sulfate solution.
120
What does a blue solution indicate in the Biuret test?
A blue solution indicates no protein is present.
121
What is an emulsion?
An emulsion is when one liquid doesn't dissolve in another, forming little droplets.
122
123
What is the posh name for burning food to see how much energy it contains?
Calorimetry.
124
What materials do you need for the calorimetry experiment?
A dry food, water, and a flame.
125
What type of food works best for the calorimetry experiment?
Dry foods like dried beans or pasta.
126
What is the first step in the calorimetry experiment?
Weigh a small amount of the food and skewer it on a mounted needle.
127
What should you do with the water before burning the food?
Add a set volume of water to a boiling tube and measure its temperature.
128
What should you do after setting fire to the food?
Hold the burning food under the boiling tube until it goes out, then relight and repeat.
129
How do you calculate the energy in the food?
Use the formula: Energy in Food (in J) = Temperature change x 4.2 x Mass of water (in g).
130
Why is it important to insulate the boiling tube?
To minimize energy loss to the environment.
131
How do you calculate energy per gram of food?
Energy per gram of food (in J/g) = Energy in food (in J) ÷ Mass of food (in g).
132
What was the energy in popcorn if the temperature increased by 28.6 °C?
2402.4 J.
133
What was the energy in bread if the temperature increased by 38.7 °C?
3250.8 J.
134
Which food has more energy per unit mass, popcorn or bread?
The bread has more energy per unit mass.
135
What do food scientists use to measure the energy content of food accurately?
Calorimeters.
136
Why is it important to record the increase in temperature quickly after burning the food?
To ensure accurate measurement of the energy transferred.
137
138
What is diffusion?
Diffusion is the gradual movement of particles from areas of higher concentration to areas of lower concentration.
## Footnote
It is the net movement of particles down a concentration gradient.
139
What types of molecules can diffuse through cell membranes?
Only very small molecules, such as glucose, amino acids, water, and oxygen, can diffuse through cell membranes.
## Footnote
Big molecules like starch and proteins cannot fit through the membrane.
140
What is osmosis?
Osmosis is the net movement of water molecules across a partially permeable membrane from a region of higher water concentration to a region of lower water concentration.
## Footnote
It can also be described as the movement from lower solute concentration to higher solute concentration.
141
What is a partially permeable membrane?
A partially permeable membrane has very small holes that allow tiny molecules, like water, to pass through while blocking larger molecules, such as sucrose.
142
How does water move during osmosis?
Water molecules move both ways through the membrane, but there is a net flow into the region with fewer water molecules.
## Footnote
This results in the solute solution becoming more dilute.
143
What is active transport?
Active transport is the movement of particles across a membrane against a concentration gradient, from an area of lower concentration to an area of higher concentration, using energy from respiration.
144
How does active transport differ from diffusion?
Active transport requires energy and moves particles up a concentration gradient, whereas diffusion is a passive process that moves particles down a concentration gradient.
145
Give an example of active transport in the digestive system.
When there is a lower concentration of nutrients in the gut than in the blood, active transport allows nutrients to be taken into the blood despite the concentration gradient being the wrong way.
146
What happens to a sodium ion during diffusion?
A sodium ion moves from inside a nerve cell, where there is a low sodium ion concentration, to outside the cell, where the concentration is higher.
## Footnote
This process is known as diffusion.
147
148
What is the purpose of the osmosis experiment?
To see the effect of different water concentrations on potato cylinders placed in sucrose solutions.
149
What is the relationship between sucrose concentration and water concentration?
The higher the concentration of the sucrose solution, the lower the water concentration.
150
What is the first step in the osmosis experiment?
Prepare sucrose solutions of different concentrations ranging from pure water to a very concentrated sucrose solution.
151
How should the potato cylinders be prepared for the experiment?
Use a cork borer to cut the potato into pieces about 1 cm in diameter from the same potato.
152
What should be done with the potato cylinders before placing them in the solutions?
Divide the cylinders into groups of three and measure the mass of each group using a mass balance.
153
How long should the potato cylinders be left in the sucrose solution?
Leave the cylinders in the solution for at least 40 minutes.
154
What should be done after removing the potato cylinders from the solution?
Pat dry gently with a paper towel to remove excess water for accurate mass measurement.
155
What is the only variable that should change in the osmosis experiment?
The sucrose solution concentration.
156
How do you calculate the percentage change in mass?
Use the formula: percentage change = (final mass - initial mass) / initial mass × 100.
157
What does a positive percentage change in mass indicate?
It indicates that the potato cylinders gained mass.
158
What does a negative percentage change in mass indicate?
It indicates that the potato cylinders lost mass.
159
What happens at the points where the graph crosses the x-axis?
The water concentration of the sucrose solutions is isotonic with the fluid inside the cylinders.
160
What happens to the potato cylinders in a concentrated salt solution?
The mass of the potato will decrease as water is drawn out by osmosis.
161
Can different solutes be used in this experiment?
Yes, the experiment can be conducted with different solutes, such as salt.
