Key Concepts In Biology Flashcards
What is the function of cytoplasm?
- Contains dissolved nutrients and salts
- Where most chemical reactions take place
What is the function of the nucleus?
- Contains genetic material, including DNA
- This controls cellular activities
What is the function of the cell membrane?
- Permeable, allows some substances but not others
- Controls what enters and leaves the cell
What is the function of mitochondria?
- Contains the enzymes for respiration
- Where most energy is released, respiration
What is the function of ribosomes?
- Site of protein synthesis
What is the function of chloroplasts?
- Contains green pigment called chlorophyll which absorbs light energy for photosynthesis
- Contains the enzymes needed for photosynthesis
What is the function of the cell wall?
- Provides structure, support and protection
- Plant cell walls are made from cellulose
What is the function of the permanent vacuole?
- Filled with cell sap to provide support
What is the function of chromosomal DNA?
- Found loose in the cytoplasm, not contained in a nucleus
What is the function of plasmid DNA?
- Small closed circles of DNA
- Can move from one bacterium to another, giving variation
What is the function of the flagella?
- Rotate or move in a whip-like motion to move the cell
How is a sperm cells adapted to its function?
- Acrosome, contains enzymes to digest a way through the egg cell membrane
- Haploid nucleus, to fuse with egg nucleus
- Mid piece, lots of mitochondria to release energy to swim
- Tail, enables the cell to swim
How is an egg cells adapted to its function?
- Cytoplasm, contains nutrients for growing embryo
- Haploid nucleus, to fuse with sperm nucleus
- Cell membrane, changes after fertilisation by a single sperm so no more sperm can enter
How is a ciliated epithelial cell adapted to its function?
- Cilia, on the surface to move mucus containing dirt and bacteria away from the lungs
What is the inverse square rule for light intensity?
Light intensity 🐟 1/distance^2
How to you test for starch using chemical reagents?
- Add iodine solution
- Negative result will be orange
- Present will be blue/black
How do you test for reducing sugars using chemical reagents?
- Add equal volume of Benedict’s solution to a food solution and mix
- Heat the mixture in a 95°C water bath for a few minutes
- The colour of the reagent/negative result will be blue
- The colour if sugar is present will be green>orange>red depending on how much sugar is present
How do you test for proteins using chemical reagents?
- Add an equal volume of potassium hydroxide solution to the food solution and mix
- Add a few drops of copper sulfate solution and mix
- The colour if the reagent/negative result will be pale blue
- The colour if protein is present will be pale purple
How do you test for fats using chemical reagents?
- Add an equal volume of ethanol to the food solution and shake thoroughly
- Add water to the mixture
- The colour of the reagent/negative result will be clear
- The colour if fat is present will be cloudy
How have electron microscopes enabled scientists to develop their understanding of cells?
- Allow small subcellular structures to be observed in detail
- They could develop better explanations about how cell structure relate to its function
What is a milli-?
10^-3
/ 1000
What is a micro-?
10^-6
/ 1 000 000
What is a nano-?
10^-9
/ 1 000 000 000
What is a pico-?
10^-12
/ 1 000 000 000 000
What are the steps to using a light microscope?
- Collect a small specimen of cells with correct equipment
- Add a drop of water or stain to the centre of the slide
- Place your specimen on the drop of water or stain
- Lower a cover slip onto the specimen
- Start with the lowest magnification and work up at the higher
Why is the water or stain used?
Water - prevents the specimen from drying out
Stain – allows us to see otherwise colourless parts
Why is it cover slip used?
To minimise the chance of air bubbles which make it difficult to see the specimen
Why do you start with the lowest magnification and move to a higher one?
Lowest – allows us to find a specimen on the slide and focus
Higher – you don’t need to use the coarse focusing wheel
What are the rules for scientific drawings?
- Smooth lines
- No shading
- Lines to label, no arrows
- Keep the relative sizes of structures approximately correct
- For microscope, write magnification next to it
What are enzymes?
- Biological catalysts
- That speed up chemical reactions in the body
What is the active site of an enzyme?
The part that a specific substrate can attach or fit into
What are the steps of enzymes catalysing substrates?
- Substrate collides with active site of enzyme and becomes attached
- Enzyme catalyses breakdown of substrate
- Products released from active site
What is enzyme specificity?
Enzymes can only bind to a substrate with a complimentary shape
What factors affect the activity of enzymes?
- Temperature
- Substrate concentration
- pH
What happens when an enzyme is denatured?
The shape of its active site may change so the substrate will no longer fit into the enzymes
What effect does temperature have on enzyme activity?
- As temperature increases, molecules move quicker and collide more
- So more complexes form and rate of reaction increases
- At optimum temperature enzymes have the fastest rate
- Higher temperatures cause the active site to change shape so no more complexes can form, becomes denatured
What effect does pH have an enzyme activity?
- Have an optimum pH
- If the pH shifts from the optimum the active site will change shape and it will become denatured
How does substrate concentration affect enzyme activity?
- As concentration increases, there are more particles in the same volume
- So more collisions happen and more complexes form
- Rate of reaction increases until all active sites become full, it then plateaus
How do you calculate the rate of reaction of enzymes?
Amount of substrate used or amount of product formed
/
Time taken
How do you investigate the effect of pH on amylase activity?
- Set of heating apparatus
- Heat the water to 40° C and maintain
- Drop of iodine solution into each spot of spotting tile
- Add 2 cm³ of amylase solution to a tube
- Add 1 cm³ of a pH solution
- Add 2 cm³ of starch solution and place into water bath
- Every 20 seconds, place a drop of mixture on a fresh drop of iodine solution
- Stop testing when iodine solution stops changing colour
- Record time taken
- Repeat with different pH solutions
Which enzyme convert carbohydrates into simple sugars?
Carbohydrase enzymes
Which enzyme converts proteins into amino acids?
Protease enzymes
Which enzymes convert lipids into fatty acids and glycerol?
Lipase enzymes
Why do enzymes break larger molecules into smaller molecules?
The large molecules are too large to pass from the intestine into the blood
Why do some enzymes synthesise larger molecules from smaller molecules?
Large molecules are used for storage or to build structures
What is calorimetry?
- A way to measure the energy taken in and given out during a chemical reaction
- Used to measure the amount of calories in food
How would you measure the amount of energy in a sample of food?
- Record the initial temperature of a set volume of water in a boiling tube
- Set the food alight using a Bunsen flame then immediately place under the tube
- Measure the maximum temperature of the water
- Calculate the change in temperature
How would you calculate the energy in food?
Energy in food = Mass of water (g) x Temperature change of water (°C) x 4.2
How do you investigate osmosis using potatoes?
- Set up boiling tubes each with a different sucrose solution (0%, 20%, 40%, 100%) and label
- Cut potato into small equal-sized discs then remove excess water with tissue
- Measured initial mass of each disc
- Place in each of the solutions for 20min
- Remove the potato and dry with tissue then record the mass again
- Repeat the whole process with different discs of potato
How do you calculate the percentage change in mass?
Change in mass / Initial mass
x 100%
