SB1 - Key concepts in Biology Flashcards
1
Q
What is a Eukaryotic cell?
A
A cell with a nucleus
2
Q
Give some examples of Eukaryotic cells:
A
- Animal cells
- Plant cells
3
Q
What is a Prokaryotic cell?
A
A cell which does not have a nucleus
—> DNA is free to roam around in the cell
4
Q
Give some examples of Prokaryotic cells:
A
Bacteria
5
Q
What sub-cellular structures do animal cells have?
A
- Nucleus
- Cell membrane
- Mitochondria
- Ribosomes
6
Q
What sub-cellular structures do plant cells have?
A
- Nucleus
- Mitochondria
- Cell membrane
- Cell wall
- Vacuole
- Ribosomes
7
Q
What sub-cellular structures do bacteria cells have?
A
- Chromosomal DNA
- Plasmid DNA
- Cell membrane
- Ribosomes
- Flagella
8
Q
What is the Nucleus?
A
Contains genetic material which controls the cell’s activities
—> Including DNA
9
Q
What are Ribosomes?
A
Tiny structures where protein synthesis occurs
10
Q
Where are Ribosomes found?
A
Rough endoplasmic reticulum
11
Q
What is Cytoplasm?
A
A jelly-like material that contains dissolved nutrients, salts and organelles
12
Q
What occurs in the Cytoplasm?
A
Chemical reactions
13
Q
What is the cell membrane?
A
A selectively permeable membrane surrounding the cell and controlling the entry and exit of materials
14
Q
What is mitochondria?
A
Organelles that contains the enzymes for respiration & where most energy is released in respiration
15
Q
What type of respiration occurs in mitochondria?
A
Aerobic
16
Q
What is a Chloroplast?
A
Organelle that contains chlorophyll, which absorbs light energy for photosynthesis
—> Contains the enzymes needed for photosynthesis
17
Q
What colour is chlorophyll?
A
Green
18
Q
What is the role of the Cell wall?
A
To provide structure and protection to the cell
19
Q
What are plant cell walls made out of?
A
Cellulose
20
Q
What is a vacuole?
A
A space within the cytoplasm of plant cells that contains cell sap
—> Also improves cells rigidity
21
Q
What is the flagella?
A
Long, thin ‘whip-like’ tails attached to bacteria
22
Q
What’s the purpose of the flagella?
A
Allows bacteria to move
23
Q
What are plasmids?
A
Small rings of DNA
24
Q
What is the function of plasmids?
A
Codes for extra genes to those provided by chromosomal DNA
25
Function of **chromosomal DNA**?
Floats in the cytoplasm
26
Why does the *chromosomal DNA* float in the *cytoplasm*?
Bacterial cells have no nucleus
27
Cells specialise by going through which process?
Differentiation
28
What is **Differentiation**?
A process that involves the cell gaining new sub-cellular structures for it to be suited to its role
29
Give 3 examples of *specialised cells* in **animals**:
* Sperm cells
* Egg cells
* Ciliated epithelial cells
30
Give 3 examples of *specialised cells* in **plants**:
* Root hair cells
* Xylem cells
* Phloem cells
31
What are **sperm cells**?
Specialised to carry the male’s DNA to the ovum for successful reproduction
32
How are **sperm cells** adapted to aid swimming?
* Streamlined head & long tail
* Many mitochondria
33
How does *lots of mitochondria* aid *sperm cells* to **swim**?
Supplies the energy to allow the cell to move
---> Respiration occurs here
34
How are **sperm cells** adapted to fertilisation
* Acrosome
* Haploid nucleus
35
How does the *acrosome* aid *sperm cells* to **fertilise**?
Acrosome contains **digestive enzymes** which break down
the outer layers of membrane of the egg cell
36
How does the *haploid nucleus* aid *sperm cells* to **fertilise**?
Contains 23 chromosomes
---> Joins up with egg cell to create a zygote
37
How many *chromosomes* does a normal human body cell have?
46
38
What is the **slime coat** on bacteria for?
Protection
39
Does all **bacteria** have slime coats?
No
| Only some do
40
What are **egg cells**?
Specialised to accept a single sperm cell and develop into an embryo
41
How are **egg cells** adapted to aid the process of fertilisation?
Surrounded by a special membrane
42
How does the *special membrane* aid *egg cells* during **fertilisation**?
Special membrane can only accept one sperm cell, then becomes impermeable
43
How are **egg cells** adapted to aid the development of an embryo (after fertilisation)?
* Lots of mitochondria
* Large size & Cytoplasm
44
How does having *lots of mitochondria* aid *egg cells* during the development of an **embryo**?
Provides an energy source for the developing embryo
45
How does having a *large size and cytoplasm* aid *egg cells* during the development of an **embryo**?
Allows quick, repeated division as the embryo grows
46
What are **Ciliated epithelial cells**?
Specialised to waft bacteria (trapped by mucus) to the stomach
47
How does having **cilia** aid *Ciliated epithelial cells* to *protect our body against illnesses*?
Cilia wafts bacteria trapped by sticky mucus down to the stomach, killed by the stomach acid
48
Which cells produce *mucus*?
Goblet cells
49
What are **Root hair cells**?
Specialised to take up water by osmosis and mineral ions by active transport from the soil as they are found in the tips of roots
50
How are **root hair cells** adapted to aid **osmosis**?
* Large surface area
* Permanent vacuole
51
How does having a **large surface area** aid *root hair cells* to carry out *osmosis*?
More water can be taken in
52
How does having a **permanent vacuole** aid *root hair cells* to carry out *osmosis*?
Affects the speed of movement of water from the soil to the cell
53
How are **root hair cells** adapted to aid **active transport**?
Lots of Mitochondria
54
How does having **mitochondria** aid *root hair cells* to carry out *active transport*?
Provides energy from respiration
---> To carry out active transport of mineral ions to root hair cells
55
What are **Xylem cells**?
Specialised to transport water and mineral ions up the plant from the roots to the shoots
56
How are **Xylem cells** adapted to aid **transport of water & mineral ions**?
* During formation, Lignin is deposited
* Lignin is deposited in spirals
57
How does **Lignin being deposited (during formation)** aid *Xylem cells* to *transport of water & mineral ions*?
Causes cells to die
---> Becomes hollow and are joined end-to-end to form a continuous tube
---> Water & mineral ions can move through
58
How does **Lignin being deposited in spirals** aid *Xylem cells* to *transport water*?
Helps cells to withstand the pressure of the movement of water
59
What are **Phloem cells**?
Specialised to carry the products of photosynthesis (food) to all parts of the plants
60
Give some examples of *substances transported* in the *phloem*
* Sucrose
* Amino acids dissolved in water
61
How is energy *supplied* to the phloem cells if there aren't any *sub-cellular structures*?
Its supplied by the mitochondria of the companion cells
62
What is a **sieve tube** dependant on?
The companion cells
63
What is **translocation**?
The transport of dissolved material within a plant
64
What does **translocation** require?
Energy
65
Describe the direction of transport in the **xylem cells**
Upwards from roots to leaves
66
Describe the direction of transport in the **phloem**
Upwards and downwards
67
What *structures* are formed when cell walls of each cell break down?
Sieve plates
68
What are **sieve tubes**?
Specialised for transport and have no nuclei
69
What is this?
Xylem tube
70
What is this?
Phloem tube
71
Describe the **differences** between the **xylem and phloem** tube
72
What is an **enzyme**?
A protein produced by living organisms that acts as a catalyst to speed up the rate of a reaction
73
What is a **Biological catalyst**?
A substance found in living organisms that speed up reactions
74
What is an example of a **Biological catalyst**?
An enzyme
75
What is the **active site** of an **enzyme**?
The space in the enzyme where the substate fits during an enzyme-catalysed reaction
76
What is the **lock and key hypothesis**?
A theory that described how substrates must be the correct shape to fit the active site of an enzyme
77
What is **enzyme specificity**?
Ability of enzyme to catalyse only a particular reaction/ set of reactions
---> In which a specific substrate fits the active site of the enzyme
78
When do *enzymes* only catalyse reactions?
When they bind to a substrate that has a **complementary shape**
79
What is **Denaturation**?
The permanent change in shape of an enzyme's active site
---> Upon exposure to high temperatures or extremes of pH
80
What is the *effects* of enzymes denaturing?
Prevents the binding of a substrate
81
What is the **optimum body temperature** in humans?
37 degrees
82
Explain what happens to the *enzyme* in this graph:
1) Rate increases w/ an increase in a temperature up to the optimum
2) Above this temp rate of reaction decreases & eventually stops. Enzyme denatures
83
Explain what happens to an **enzyme** when the temperature becomes *too hot*
The bonds that hold the enzyme will begin to break
---> Changes shape of active site
---> Enzyme is said to be denatured
84
What is the **optimum pH** for most enzymes?
7
85
Explain what happens to the **enzyme** if the pH is *too high or low*
The forces that hold the amino acid chains that make up the protein will be affected
---> Changes shape of active site
---> Enzyme is said to be denatured
86
What is **substrate concentration**?
Concentration of the substance binding to the enzyme
87
What happens when *substrate concentrations increase*?
The rate at which **enzyme-substrate complexes** are formed increases
88
What is the **Saturation point**?
When all the active sites of an enzyme are occupied
89
If you increase the substrate concentration above the **saturation point** what will happen?
Nothing
90
Give some examples of **enzymes**
* Amylase
* Catalase
* Starch Synthase
* DNA polymerase
91
Where is **Amylase** found?
Saliva and small intestine
92
What *reaction is catalysed* for the enzyme **Amylase**?
Breaking down **starch** to **small sugars**
| e.g. Maltose
93
Where is **Catalase** found?
Most cells but especially liver cells
94
What *reaction is catalysed* for the enzyme **Catalase**?
Breaking down **hydrogen peroxide** made in many cell reactions to **water & O2**
95
Where is **Starch synthase** found?
Plants
96
What *reaction is catalysed* for the enzyme **Starch synthase**?
Synthesis of **starch** from **glucose**
97
Where is **DNA polymerase** found?
Nucleus
98
What *reaction is catalysed* for the enzyme **DNA polymerase**?
Synthesis of **DNA** from its **monomers**
99
What is **synthesis**?
Building larger molecules from smaller subunits
100
Give 2 examples of **polymers** in Biology
* Carbohydrates
* Proteins
101
# Core practical - Effect of pH on Enzyme Activity
What *colour* is **Iodine**?
Dark orange
102
# Core practical - Effect of pH on Enzyme Activity
What is **iodine** used for?
To check for the presence of **starch** in a solution
103
# Core practical - Effect of pH on Enzyme Activity
What **enzyme** is used in this core practical?
Amylase
104
What does **Amylase** do?
Breaks down carbohydrates into simple sugars
105
Describe the steps you would take to find the **optimum pH** of **Amylase**?
1) Place one drop of Iodine solution into each depression of a well tray
2) Measure 2cm^3 of amylase solution in a tube
3) Add 1cm^3 of a solution with a particular pH into the tube
4) Add 2cm^3 of starch solution to the tube & place it carefully into the water bath. Start the stop clock and stir the mixture
5) Every 20 secs, take a small amount of mixture & place 1 drop of it into the iodine solution. Stop testing when iodine solution stops changing colour.
106
# Core practical - Effect of pH on Enzyme Activity
Why do we use a **bunsen burner and a water beaker** during the experiment?
To keep the solution at a relatively constant temperature throughout the reaction
107
# Core practical - Effect of pH on Enzyme Activity
What type of variable is **temperature**?
Control
108
# Core practical - Effect of pH on Enzyme Activity
What results do we expect to see?
The optimal pH of amylase will be == pH of reaction that is completed in the shortest time
| Should be around pH 7.0
109
Who discovered microscopes?
Robert Hooke
110
Which year was *cells* discovered using microscopes?
1665
111
What is a **Light microscope**?
A type of microscope that uses a series of lenses to magnify the visible light reflecting off a specimen
112
How many *lenses* does a **light microscope** have?
2
113
What are **light microscopes** used to view?
Tissues, cells and large sub-cellular structures
114
How do you use a **light microscope**?
1) Place the slide on the stage and look through the eyepiece lens
2) Turn the focus wheel to obtain a clear image
3) Start with the lowest objective lens magnification
4) Increase the magnification of the objective lens and refocus.
115
Which decade was the *electron* microscopes discovered?
1930s
116
What is an **Electron microscope**?
A type of microscope that uses a beam of electrons, focused using magnets, to produce an image of a specimen
117
What are the *types* of **electron microscopes**?
* Scanning electron microscope
* Transmission electron microscope
118
What does **Magnification** mean?
The number of times bigger an image appears compared to the original object
119
What did the *invention* of **electron microscopes** allow us to do?
* To see cell structures and organelles with more clarity and detail than in the past
* Increased our understanding of the role of sub-cellular structures
120
What's the order of the *prefixes* from **largest to smallest**?
Centi
Milli
Micro
Nano
Pico
121
How would you go from **picometres** to **nanometres**?
DIVIDE by 1000
122
How would you go from **picometres** to **micrometres**?
DIVIDE by 1,000,000
123
How do you convert between each *prefix*?
124
What is the **eyepiece**?
The part of microscope that we look through to view specimens
125
What is the **Barrel**?
The upper part of the microscope that can be moved up or down to focus the image
126
What is the **Turret**?
The part of the microscope that is rotated to change the magnification lens in use
127
What is the **Stage**?
The flat surface on which we place the specimen
128
How do we *calculate* **magnification**
measured size / actual size
129
How do we *calculate* **total magnification**
objective lens magnification x eyepiece lens magnification
130
Describe & explain how you would *make a slide* of some **plant or animal tissue**
1. Take a thin layer of cells from your sample by either peeling them off or using a cotton bud
2. Add a small amount of the correct chemical stain
3. Apply the cells to your glass slide by placing them on or wiping the cotton bud against it
4. Carefully lower a coverslip onto your slide, taking care to avoid air bubbles.
131
Why would you add a **stain** to a *slide*?
Chemical stains are used to make some parts of the specimen more visible when you look at them through the microscope.
132
How do you *calculate* **rate for enzyme activity**?
Rate = Change / Time
133
What is the *purpose* of **Carbohydrases**?
Convert carbohydrates into simple sugars
134
Where are **Carbohydrases** produced?
It is produced in the salivary glands, pancreas and small intestine
135
What is the *purpose* of **Proteases**?
Convert proteins into amino acids
136
What is the *purpose* of **Lipases**?
Convert lipids into fatty acids and glycerol
137
Where are **Lipases** produced?
In the pancreas and small intestine
138
Explain the importance of enzymes as biological catalysts in the synthesis of carbohydrates, proteins and lipids and their breakdown into sugars, amino acids and fatty acids and glycerol
Enzymes play a crucial role in digestion by breaking down the large, complex molecules in our food into smaller, simpler molecules that can be absorbed by our bodies
139
# Core practical: Investigating Macronutrients
What does **Benedict's solution** test for?
Reducing sugars
140
# Core practical: Investigating Macronutrients
How do you test for **Reducing sugars** using *Benedict's solution*?
1) Add 2cm^3 of the sample solution and 2cm^3 of blue
Benedict’s solution to a test tube
2) Place in a boiling water bath for 5 minutes (until there is no further change in colour)
3) Presence of reducing sugar is indicated by a colour change to reddish-brown.
141
# Core practical: Investigating Macronutrients
If **reducing sugars** are present in the **Benedict's solution**, what will it be indicated by?
Presence of reducing sugar is indicated by a colour change to reddish-brown
142
# Core practical: Investigating Macronutrients
How do you test for **Starch** using *Iodine solution*?
Add iodine solution to the food sample
143
# Core practical: Investigating Macronutrients
If **starch** is present in the **Iodine solution test**, what will it be indicated by?
The colour will change from orange to blue-black
144
# Core practical: Investigating Macronutrients
What does **Biuret test** test for?
Protein
145
# Core practical: Investigating Macronutrients
How do you test for **Protein** using the *Biuret test*?
1) Add 1cm 3 of 40% potassium hydroxide to the food sample, and then add the same amount of 1% copper sulphate
2) Shake well and observe colour change if protein is
present ( blue -> violet )
146
# Core practical: Investigating Macronutrients
If **proteins** are present in a **Biuret test**, what will it be indicated by?
Solution will turn from blue to violet
147
# Core practical: Investigating Macronutrients
What does **Emulsion test** test for?
Lipids
148
# Core practical: Investigating Macronutrients
How do you test for **Lipids** using the *Emulsion test*?
1) Add 2cm 3 ethanol to food sample and shake
thoroughly
2) Add 2cm 3 deionised water and shake thoroughly
149
# Core practical: Investigating Macronutrients
If **lipids** are present in an **Emulsion test**, what will it be indicated by?
If lipids are present, this will be indicated by the formation of a white emulsion layer at the top of the sample
150
# Core practical: Investigating Macronutrients
How could we improve the **Investigating
Macronutrients practical**?
By using a control - to know what a positive and negative result looks like
151
What is **Calorimetry**?
A way to measure the energy taken in and given out during a chemical reaction
---> We can use this to measure the amount of calories in food
152
Describe how we **measure calories** in **food**
1. Take a tube of 50ml cold water
2. Record the starting temperature of the water
3. Place the test tube at 45 degrees and hold a burning food sample just beneath it
4. When the food is burned up, record the final temperature of the water
153
How do we *calculate* **energy transferred**?
| And what are the units?
Energy transferred = mass of water x 4.2 x temperature increase
| Mass of water = grams, Energy transferred = joules
154
How are substances are *transported* into and out of **cells**?
* Diffusion
* Osmosis
* Active transport
155
What are some forms of **passive transport**?
* Osmosis
* Diffusion
156
What is **Diffusion**?
Where particles move from an area of high concentration to one of low concentration
157
What is **Osmosis**?
Movement is from a dilute solution to a more
concentrated solution, across a selectively permeable membrane
158
What is **Active transport**?
Used to move molecules against a concentration gradient
159
Where does the energy required in **active transport** come from?
ATP- The molecule produced in respiration
160
# Core practical: Osmosis in potatoes
How would you **measure percentage gain or loss**?
1. Cut potato into small discs of equal size
2. Blot the potato disks gently with tissue paper to remove excess water
3. Measure the initial mass of each disk
4. Place the disks in sucrose solutions of different concentrations (1%, 2% etc)
5. Blot with tissue paper again and record new mass
6. Find difference in mass (end mass - start mass) and use the percentage change equation to calculate percentage gain or loss of mass.
161
# Core practical: Osmosis in potatoes
What is the **independent variable**?
Concentration
162
# Core practical: Osmosis in potatoes
What is the **dependent variable**?
Change in mass
163
# Core practical: Osmosis in potatoes
What is the **control variable**?
Diameter of disks
164
# Core practical: Osmosis in potatoes
Explain what is *happening* in this experiment?
Water is moving by osmosis from a more dilute solution (in the potato) to a more concentrated solution (the sucrose solution) across a selectively permeable membrane (the cell membranes of all the potato cells holding water).
