Key Biology Concepts Flashcards
What is the function of the nucleus?
To contain the cell’s DNA and to control the cell’s functions
What is the function of the ribosome?
To synthesise proteins from amino acids using mRNA
What is the function of the cell membrane?
To control what substances go in and out of the cell
What is the function of the cell wall?
Made of cellulose, it protects the cell and gives it shape
What is the function of the chloroplasts?
To contain chlorophyll, a chemical to allow photosynthesis in the chloroplasts
What is the function of the large vacuole?
It contains a cell sap, a weak solution of sugar and salts. It maintains the internal pressure to support the cell.
What is the function of the mitochondria?
To perform respiration for the cell, which produces energy
What are the differences between prokaryotic and eukaryotic cells?
Eukaryotic cells are complex and include all plant and animal cells. They have a nucleus and are usually multicellular, making up a eukaryote
Prokaryotic cells have no nucleus but rather chromosomal DNA and are smaller and simpler e.g. bacteria. A prokaryote is a prokaryotic cell as it is unicellular
What are acrosomes and how do they help the sperm cell to function?
An acrosome is an organelle that forms over the head of the sperm cell. It contains digestive enzymes that break down the outer membrane of the ovum so that the sperm cell’s nucleus can fuse with that of the egg cell (fertilisation).
How does an egg cell membrane change after fertilisation?
Once one sperm cell has fertilised the egg cell, the egg cell’s plasma membrane rapidly depolarises, preventing other sperm from fusing with the egg cell and fertilising it
How is a ciliated epithelial cell adapted to its function?
It lines the surfaces of organs
Some have cilia on it which wag from side to side, which pulls away dust, mucus and bacteria.
It is flat so that cilia cells can interlock and cover surfaces completely.
How has the microscope developed over time?
Light microscopes were invented in the 1590s and pass light through the specimen, allowing us to see large parts of the cell e.g. the nucleus and chloroplasts.
Electron microscopes were invented in the 1930s and use electrons. They have a much higher resolution and magnification, allowing us to see more subcellular structures in greater detail
How is magnification calculated?
Magnification = Image size/ real size
What are millimetres, micrometres, nanometres and picometers in standard form and how do you convert from one to another?
Millimetres - x10-3m
Micrometres - x10-6m
Nanometres - x10-9m
Picometres - x10-12m
To go one bigger divide by 1000 and to go one smaller multiply by 1000
What is the lock and key hypothesis?
The hypothesis that one substrate can only fit into one enzyme, similar to how one key can only fit into one lock
What are enzymes?
Biological catalysts that speed up the rate of or lower the activation energy of reactions, reducing the need for high temperatures
What is the active site?
The place where enzymes and substrates meet
Why does temperature, pH and substrate concentration affect the rate of an enzyme reaction.
At certain amounts of the three, the enzyme will work most efficiently, but at extreme concentrations of the three, the enzyme will change its shape so it will no longer work: it is denatured.
What enzymes break down starch, proteins and lipids? What do they get broken into?
Starch: amylase -> maltose and other sugars
Proteins: protease -> amino acids
Lipids: lipase -> glycerol and fatty acids
What chemical reagents are used to test for proteins, reducing sugars, starch and fats?
Proteins: Biuret’s solution
Reducing sugars: Benedict’s solution
Starch: Iodine
Fats: Water and ethanol
How is a calorimeter used to measure the energy in foods?
Food is set alight and oxygen is provided to keep the fire going
The food is put under a boiling tube of water, which heats up water in it
After the fire goes out the change in water temperature is measured
This shows you how much energy is in foods
What factors affect the rate of diffusion?
The concentration gradient
Temperature
The distance particles must travel
Particle size
What is diffusion?
The net movement of particles from an area of high concentration to an area of low concentration until even distribution is reached
What are the differences between diffusion and active transport?
Diffusion happens from an area of high concentration to an area of low concentration down the concentration gradient. It is a passive process and does not require energy. Active transport happens from an area of low concentration to an area of high concentration. It is an active process and requires energy.
What is the function of the cytoplasm?
A gel like substance where most chemical reactions happen
What is the function of chloroplasts?
They contain chlorophyll and are where photosynthesis happens, which makes food for the plant
What are the parts of animal and plant cells?
Animal cells: nucleus, cytoplasm, cell membrane, mitochondria, ribosomes
Plant cells: all of the above plus cell wall, a large vacuole, chloroplasts
What are the parts of a bacterial cell?
Chromosomal DNA (one long circular chromosome)
Ribosomes
Cell membrane
Plasmid DNA (small loops of extra DNA, which give functions such as drug resistance)
Flagellum (a hair like structure that rotates to move the bacterium)
What are the adaptations of a sperm cell?
Long tail to swim
Lots of mitochondria in the middle section to provide energy
An acrosome
A haploid nucleus
What are the adaptations of the egg cell?
Nutrients in the cytoplasm to feed the embryo
A haploid nucleus
A membrane that changes structure after fertilisation to stop any more sperm getting in
How do you calculate total magnification?
Total magnification = eyepiece lens magnification x objective lens magnification
How do you view a specimen using a light microscope?
Take a thin slice of the specimen. Put a drop of water on a clean slide to secure in and put the specimen in place with tweezers. Add a stain to the specimen if it is transparent. Put a cover slip on. Clip the slide onto the stage. Select the lowest power objective lens and move the stage up. Move the stage down until it is in focus.
How do you create a scientific drawing of a specimen?
Use a sharp pencil Draw outlines of the main features Use clear, unbroken lines Do not shade Take up most of the space Label with straight lines that do not cross Include the magnification and scale
What is a substrate?
The molecule changed in the reaction using an enzyme
How does temperature affect the rate of reaction with enzymes?
At low temperatures the substances little energy so reactions are slow. As temperature increases, the reaction rate speeds up. However, after a point some of the bonds holding enzymes together break down, changing the shape of the active sight. The enzyme is denatured so no reactions can happen.
How does pH affect the rate of reaction with enzymes?
If the pH is too high or too low it interferes with the bonds holding the enzyme together, changing the shape of the active site and denaturing it. All enzymes have an optimum pH.
How does substrate concentration affect the rate of reaction with enzymes?
At low concentrations the enzyme is not likely to meet and react with substrate molecules, so reaction rate increases to a point, where all the active sites are full.
How can you investigate the effect of pH on enzyme activity?
Put a drop of iodine solution into every well of a spotting tile. Use a Bunsen burner to heat water in a beaker to 35 degrees. Add amylase solution and buffer solution with pH5 to a boiling tube and place it in the beaker. Wait, then add starch solution. Start a stopwatch and take a sample every 10 seconds and add it to a drop in the well. If starch is present it will change from brown/orange to blue/black; if it does not, the starch has broken down. Repeat with different pHs.
How do you calculate rate of reaction?
Rate = 1000 / time
What is the Benedict’s test?
Add Benedict’s reagent (blue) to a sample and heat it in a water bath to 75 degrees. It will form a coloured precipitate if reducing sugars are present.
As concentration increases the colour turns from:
Blue to green to yellow to orange to brick red
What is the test for starch?
Add iodine solution to the sample. If starch is present, it will change from brown/orange to blue/black
What is the test for lipids?
Shake the substance with ethanol for about a minute until it dissolves, then pour the solution into water. Lipids will precipitate out of the liquid and form a milky emulsion; the more lipid, the more noticeable the milky colour.
What is the test for proteins?
Biuret test:
Add a few drops of potassium hydroxide to make the solution alkaline. Add copper(II) sulphate (bright blue). Protein will turn the solution purple.
What is the equation for calculating energy in food?
Energy in food (J) = Mass of water (g) x temperature change (degrees C) x 4.2
What is osmosis?
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
What is active transport?
The movement of particles across a membrane against a concentration gradient using energy
How can you investigate osmosis in potatoes?
Prepare sucrose solutions of different concentrations ranging from pure water to very concentrated. Cut a potato into same sized pieces. Divide the cylinders into groups of three and measure the mass of each group. Place one group in each solution and wait. Remove the cylinders and pat dry with a paper towel. Weigh each group again and calculate the change in mass.
