SB1 - Key concepts in Biology Flashcards
What is a Eukaryotic cell?
A cell with a nucleus
Give some examples of Eukaryotic cells:
- Animal cells
- Plant cells
What is a Prokaryotic cell?
A cell which does not have a nucleus
—> DNA is free to roam around in the cell
Give some examples of Prokaryotic cells:
Bacteria
What sub-cellular structures do animal cells have?
- Nucleus
- Cell membrane
- Mitochondria
- Ribosomes
What sub-cellular structures do plant cells have?
- Nucleus
- Mitochondria
- Cell membrane
- Cell wall
- Vacuole
- Ribosomes
What sub-cellular structures do bacteria cells have?
- Chromosomal DNA
- Plasmid DNA
- Cell membrane
- Ribosomes
- Flagella
What is the Nucleus?
Contains genetic material which controls the cell’s activities
—> Including DNA
What are Ribosomes?
Tiny structures where protein synthesis occurs
Where are Ribosomes found?
Rough endoplasmic reticulum
What is Cytoplasm?
A jelly-like material that contains dissolved nutrients, salts and organelles
What occurs in the Cytoplasm?
Chemical reactions
What is the cell membrane?
A selectively permeable membrane surrounding the cell and controlling the entry and exit of materials
What is mitochondria?
Organelles that contains the enzymes for respiration & where most energy is released in respiration
What type of respiration occurs in mitochondria?
Aerobic
What is a Chloroplast?
Organelle that contains chlorophyll, which absorbs light energy for photosynthesis
—> Contains the enzymes needed for photosynthesis
What colour is chlorophyll?
Green
What is the role of the Cell wall?
To provide structure and protection to the cell
What are plant cell walls made out of?
Cellulose
What is a vacuole?
A space within the cytoplasm of plant cells that contains cell sap
—> Also improves cells rigidity
What is the flagella?
Long, thin ‘whip-like’ tails attached to bacteria
What’s the purpose of the flagella?
Allows bacteria to move
What are plasmids?
Small rings of DNA
What is the function of plasmids?
Codes for extra genes to those provided by chromosomal DNA
Function of chromosomal DNA?
Floats in the cytoplasm
Why does the chromosomal DNA float in the cytoplasm?
Bacterial cells have no nucleus
Cells specialise by going through which process?
Differentiation
What is Differentiation?
A process that involves the cell gaining new sub-cellular structures for it to be suited to its role
Give 3 examples of specialised cells in animals:
- Sperm cells
- Egg cells
- Ciliated epithelial cells
Give 3 examples of specialised cells in plants:
- Root hair cells
- Xylem cells
- Phloem cells
What are sperm cells?
Specialised to carry the male’s DNA to the ovum for successful reproduction
How are sperm cells adapted to aid swimming?
- Streamlined head & long tail
- Many mitochondria
How does lots of mitochondria aid sperm cells to swim?
Supplies the energy to allow the cell to move
—> Respiration occurs here
How are sperm cells adapted to fertilisation
- Acrosome
- Haploid nucleus
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
How does the haploid nucleus aid sperm cells to fertilise?
Contains 23 chromosomes
—> Joins up with egg cell to create a zygote
How many chromosomes does a normal human body cell have?
46
What is the slime coat on bacteria for?
Protection
Does all bacteria have slime coats?
No
Only some do
What are egg cells?
Specialised to accept a single sperm cell and develop into an embryo
How are egg cells adapted to aid the process of fertilisation?
Surrounded by a special membrane
How does the special membrane aid egg cells during fertilisation?
Special membrane can only accept one sperm cell, then becomes impermeable
How are egg cells adapted to aid the development of an embryo (after fertilisation)?
- Lots of mitochondria
- Large size & Cytoplasm
How does having lots of mitochondria aid egg cells during the development of an embryo?
Provides an energy source for the developing embryo
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
What are Ciliated epithelial cells?
Specialised to waft bacteria (trapped by mucus) to the stomach
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
Which cells produce mucus?
Goblet cells
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
How are root hair cells adapted to aid osmosis?
- Large surface area
- Permanent vacuole
How does having a large surface area aid root hair cells to carry out osmosis?
More water can be taken in
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
How are root hair cells adapted to aid active transport?
Lots of Mitochondria
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
What are Xylem cells?
Specialised to transport water and mineral ions up the plant from the roots to the shoots
How are Xylem cells adapted to aid transport of water & mineral ions?
- During formation, Lignin is deposited
- Lignin is deposited in spirals
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
How does Lignin being deposited in spirals aid Xylem cells to transport water?
Helps cells to withstand the pressure of the movement of water
What are Phloem cells?
Specialised to carry the products of photosynthesis (food) to all parts of the plants
Give some examples of substances transported in the phloem
- Sucrose
- Amino acids dissolved in water
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
What is a sieve tube dependant on?
The companion cells
What is translocation?
The transport of dissolved material within a plant
What does translocation require?
Energy
Describe the direction of transport in the xylem cells
Upwards from roots to leaves
Describe the direction of transport in the phloem
Upwards and downwards
What structures are formed when cell walls of each cell break down?
Sieve plates
What are sieve tubes?
Specialised for transport and have no nuclei
What is this?
Xylem tube
What is this?
Phloem tube
Describe the differences between the xylem and phloem tube
What is an enzyme?
A protein produced by living organisms that acts as a catalyst to speed up the rate of a reaction
What is a Biological catalyst?
A substance found in living organisms that speed up reactions
What is an example of a Biological catalyst?
An enzyme
What is the active site of an enzyme?
The space in the enzyme where the substate fits during an enzyme-catalysed reaction
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
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
When do enzymes only catalyse reactions?
When they bind to a substrate that has a complementary shape
What is Denaturation?
The permanent change in shape of an enzyme’s active site
—> Upon exposure to high temperatures or extremes of pH
What is the effects of enzymes denaturing?
Prevents the binding of a substrate
What is the optimum body temperature in humans?
37 degrees
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
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
What is the optimum pH for most enzymes?
7
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
What is substrate concentration?
Concentration of the substance binding to the enzyme
What happens when substrate concentrations increase?
The rate at which enzyme-substrate complexes are formed increases
What is the Saturation point?
When all the active sites of an enzyme are occupied
If you increase the substrate concentration above the saturation point what will happen?
Nothing
Give some examples of enzymes
- Amylase
- Catalase
- Starch Synthase
- DNA polymerase
Where is Amylase found?
Saliva and small intestine
What reaction is catalysed for the enzyme Amylase?
Breaking down starch to small sugars
e.g. Maltose
Where is Catalase found?
Most cells but especially liver cells
What reaction is catalysed for the enzyme Catalase?
Breaking down hydrogen peroxide made in many cell reactions to water & O2
Where is Starch synthase found?
Plants
What reaction is catalysed for the enzyme Starch synthase?
Synthesis of starch from glucose
Where is DNA polymerase found?
Nucleus
What reaction is catalysed for the enzyme DNA polymerase?
Synthesis of DNA from its monomers
What is synthesis?
Building larger molecules from smaller subunits
Give 2 examples of polymers in Biology
- Carbohydrates
- Proteins
Core practical - Effect of pH on Enzyme Activity
What colour is Iodine?
Dark orange
Core practical - Effect of pH on Enzyme Activity
What is iodine used for?
To check for the presence of starch in a solution
Core practical - Effect of pH on Enzyme Activity
What enzyme is used in this core practical?
Amylase
What does Amylase do?
Breaks down carbohydrates into simple sugars
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.
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
Core practical - Effect of pH on Enzyme Activity
What type of variable is temperature?
Control
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
Who discovered microscopes?
Robert Hooke
Which year was cells discovered using microscopes?
1665
What is a Light microscope?
A type of microscope that uses a series of lenses to magnify the visible light reflecting off a specimen
How many lenses does a light microscope have?
2
What are light microscopes used to view?
Tissues, cells and large sub-cellular structures
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.
Which decade was the electron microscopes discovered?
1930s
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
What are the types of electron microscopes?
- Scanning electron microscope
- Transmission electron microscope
What does Magnification mean?
The number of times bigger an image appears compared to the original object
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
What’s the order of the prefixes from largest to smallest?
Centi
Milli
Micro
Nano
Pico
How would you go from picometres to nanometres?
DIVIDE by 1000
How would you go from picometres to micrometres?
DIVIDE by 1,000,000
How do you convert between each prefix?
What is the eyepiece?
The part of microscope that we look through to view specimens
What is the Barrel?
The upper part of the microscope that can be moved up or down to focus the image
What is the Turret?
The part of the microscope that is rotated to change the magnification lens in use
What is the Stage?
The flat surface on which we place the specimen
How do we calculate magnification
measured size / actual size
How do we calculate total magnification
objective lens magnification x eyepiece lens magnification
Describe & explain how you would make a slide of some plant or animal tissue
- Take a thin layer of cells from your sample by either peeling them off or using a cotton bud
- Add a small amount of the correct chemical stain
- Apply the cells to your glass slide by placing them on or wiping the cotton bud against it
- Carefully lower a coverslip onto your slide, taking care to avoid air bubbles.
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.
How do you calculate rate for enzyme activity?
Rate = Change / Time
What is the purpose of Carbohydrases?
Convert carbohydrates into simple sugars
Where are Carbohydrases produced?
It is produced in the salivary glands, pancreas and small intestine
What is the purpose of Proteases?
Convert proteins into amino acids
What is the purpose of Lipases?
Convert lipids into fatty acids and glycerol
Where are Lipases produced?
In the pancreas and small intestine
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
Core practical: Investigating Macronutrients
What does Benedict’s solution test for?
Reducing sugars
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.
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
Core practical: Investigating Macronutrients
How do you test for Starch using Iodine solution?
Add iodine solution to the food sample
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
Core practical: Investigating Macronutrients
What does Biuret test test for?
Protein
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 )
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
Core practical: Investigating Macronutrients
What does Emulsion test test for?
Lipids
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
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
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
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
Describe how we measure calories in food
- Take a tube of 50ml cold water
- Record the starting temperature of the water
- Place the test tube at 45 degrees and hold a burning food sample just beneath it
- When the food is burned up, record the final temperature of the water
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
How are substances are transported into and out of cells?
- Diffusion
- Osmosis
- Active transport
What are some forms of passive transport?
- Osmosis
- Diffusion
What is Diffusion?
Where particles move from an area of high concentration to one of low concentration
What is Osmosis?
Movement is from a dilute solution to a more
concentrated solution, across a selectively permeable membrane
What is Active transport?
Used to move molecules against a concentration gradient
Where does the energy required in active transport come from?
ATP- The molecule produced in respiration
Core practical: Osmosis in potatoes
How would you measure percentage gain or loss?
- Cut potato into small discs of equal size
- Blot the potato disks gently with tissue paper to remove excess water
- Measure the initial mass of each disk
- Place the disks in sucrose solutions of different concentrations (1%, 2% etc)
- Blot with tissue paper again and record new mass
- Find difference in mass (end mass - start mass) and use the percentage change equation to calculate percentage gain or loss of mass.
Core practical: Osmosis in potatoes
What is the independent variable?
Concentration
Core practical: Osmosis in potatoes
What is the dependent variable?
Change in mass
Core practical: Osmosis in potatoes
What is the control variable?
Diameter of disks
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).
