Science Biology Flashcards
How do you work out the maginification of a microscope
Multiply the magnification of the two leses.
Example:
x5 eyepiece lens + x10 objective lens = x50
How do you work out an image’s magnification?
Size of image
______________
Real size
What is a microscope’s resolution?
The smallest distance between two points that can still be seen as two points.
What are the advantages of using an electron microscope over a light microscope?
An electron microscope can magnify an image up to x2,000,000 times, while light microscopes can only magnify up to x1,500 times.
What are the disadvantages of using an electron microscope over a light microscope?
An electron microscope cannot be used on living cells, because the beams of electrons kill the cells. The light from a light microscope does not, and can therefore be used on living cells.
What are the disadvantages of using an electron microscope over a light microscope?
An electron microscope cannot be used on living cells, because the beams of electrons kill the cells. The light from a light microscope does not, and can therefore be used on living cells.
List all 4 measurement units after centimetres (cm).
Millimetres (mm)
Micrometres (μm)
Nanometres (nm)
Picometres (pm)
Check Biology book page 3.
What is a eukaryotic cell? Examples of eukaryotic cells? (4)
A cell with a nucleus.
Examples:
Main:
1. Animal
2. Plants
Extra:
3. Fungi
4. Protists
What does a human white blood cell consist of? (6)
- Cell membrane
- Cytoplasm
- Mitochondrion
- Nucleus
- Red blood cells
- Ribosomes
What does a plant cell consist of? (6)
- Nucleus
- Cell wall
- Cytoplasm
- Cell membrane
- Chloroplasts
- Vacuole
Explain the role of each part.
Parts: Cell membrane, Cytoplasm, Mitochondrion, Nucleus, Red blood cells, Ribosomes, Cell wall, Chloroplasts, Vacuole.
Cell membrane: Very thin bag - controls what enters and leaves, and separates one cell from another.
Cytoplasm: Contains watery jelly - where most of the cell’s activities occur.
Mitochondrion: Jelly-bean shaped structures - where aerobic respiration occurs.
Nucleus: Controls the cell and its activities. Inside it are chromosomes which contain DNA.
Red blood cells: Contains protein called hemoglobin which carries oxygen from the lungs to all parts of the body.
Ribosomes: Make protein.
Cell wall: Made of cellulose - supports and protects the cell.
Chloroplasts: Contain chlorophyll which traps energy transferred from the sun. Energy is used for photosynthesis.
Vacuole: Large and permanent sac - stores cell sap and helps to keep the cell firm and rigid.
Check Biology book page 4 and 5.
What is the field of view? (FOV)
Circular area you see in light microscopes. If we know its diameter, we can estimate sizes.
What are scale bars?
Shown on micrographs and used to estimate sizes. Tells us how big a section of a picture is.
Check Biology book page 5.
What are specialised cells?
Cells that have a specific function.
What are human gametes?
The egg cell and sperm cell.
What is the difference between diploid and haploid cells?
Diploid cells have two sets of chromosomes and haploid cells only have one.
What does an egg cell consist of? (4)
1.Cell membrane
2.Cytoplasm
3.Jelly coat
4.Haploid nucleus
What do the cell membrane, cytoplasm and jelly coat do?
Cell membrane: Fuses with the sperm cell membrane. Becomes hard after fertilisation to stop other sperm cells entering.
Cytoplasm: Packed with nutrients. Supply fertilised egg cell with energy and raw materials for growth and development of the embryo.
Jelly coat: Protects the egg cell. Also hardens after fertilisation, to ensure that only one sperm cell enters the egg cell.
What does a sperm cell consist of? (6)
- Acrosome
- Mitochondria
- Tail
- Nucleus
- Cell surface membrane
- Streamlined shape
Explain the functions of the acrosome, mitochondria and tail?
Acrosome: Is a small vacuole in the tip of the head. Contains enzymes that break down substances in the egg cell’s jelly coat. This allows the sperm cell to burrow inside.
Mitochondria: A large number of mitochondria are arranged in a spiral around the top of the tail, to release lots of energy to power the tail.
Tail: Waves from side to side to allow the sperm cell to swim.
Where does fertilisation occur?
In the oviducts.
How are egg cells transported?
By cells in the lining of the oviduct. They are adapted for this function by having hair-like cilia. Cilia are covered in cell membrane and contain strands of a substance that can contract and cause wavy movement, to sweep substances along.
What are cells that line structures in the body called?
Epithelial cells. These cells with cilia are called ciliated epithelial cells.
What can we use to make bacteria show more in a microscope?
Stains.
What are bacteria cells?
Bacteria are prokaryotic, meaning their cells do not have nuclei or chromosomes. Instead, cytoplasm contains one large loop of chromosomal DNA which controls most of the cell’s activities.
What are plasmids?
Smaller loops of DNA. Plasmid DNA controls a few of the cell’s activities.
What are two things prokaryotic cells don’t have?
Mitochondria and chloroplasts.
What do bacteria consist of usually? (7)
- Flagellum
- Slime coat
- Flexible cell wall
- Cell membrane
- Cytoplasm
- Plasmids
- Chromosomal DNA
Explain the functions of the flagellum, slime coat, flexible cell wall and cytoplasm.
Flagellum: Used for movement. Is not covered in membrane and not all bacteria have them. Some have many flagella.
Slime coat: For protection - not all bacteria have this.
Flexible cell wall: For support - not made out of cellulose.
Cytoplasm: Contains ribosomes.
What is synthesis?
Building larger molecules from smaller subunits.
What are polymers?
Made up of many similar small molecules (monomers), joined in a chain.
What are do protein, starch and lipid molecules turn into after digestion?
Protein molecule → Amino acids
Starch molecule → Glucose molecules
Lipid molecule → Fatty acids
Check Biology book page 12.
What is a catalyst?
A substance that increases the rate of a chemical reaction without itself undergoing any permanent chemical change. In living organisms, catalysts that speed up breakdown (e.g. digestion) and synthesis reactions are called enzymes.
What are enzymes?
Biological catalysts that increase the rate of reactions.
What are substrates and products?
The substances that enzymes work on are called substrates, and the substances that are produced are called products.
Examples of enzymes, where they are found and what they do.
Amylase: Found in saliva and small intestine - break down starch to small sugars such as maltose.
Catalase: Found in most cells, but especially liver cells - break down hydrogen peroxide made in many cell reactions to water and oxygen.
Starch synthase: Found in plants - catalyse the synthesis of starch from glucose.
DNA polymerase: Found in nucleus - catalyse the synthesis of DNA from its monomers.
Check Biology book page 13.
How do you test for starch?
Using iodine solution. The solution turns yellow-orange → blue-black.v
How do you test for reducing sugars (glucose, fructose)?
Using Benedict’s solution. The solution is added to a food solution and is placed in a warm water bath. Turns blue (no sugar) → green (very little sugar) → orange (more sugar) → red (lots of sugar). May form precipitate (solid at the bottom of the beaker).v
How do you test for protein?
Using biuret test. Potassium hydroxide is mixed with food solution. Then 2 drops of copper sulfate solution are added. Turns blue → purple.
How do you test for fats and oils (lipids)?
Using ethanol emulsion test. Food solution is mixed with ethanol and shaken. Some of the mixture is poured into water and shaken again. Fats and oils dissolved in the ethanol float to the surface, forming a cloudy emulsion.
How do we measure the amount of energy in a food?
By burning it in a calorimeter.
How is a product molecule made? (3 steps)
1.Two different substrate molecules go into the active site of an enzyme.
- The active site holds the substrate molecules tightly in the right position for bonds to form and make a product molecule.
- The product molecule is a slightly different shape to the substrate molecules, so it no longer fits tightly in the active site and is released.
To separate a product molecule, it is the same process but the opposite order.
Check Biology page 19.
Why can’t substrates fit in all active sites?
Different substrates have different 3D shapes, and different enzymes have active sites of different shapes. This explains why active sites can only work with specific substrates that fit the active site.
What does a food energy test consist of? (6)
- Thermometer
- Stirrer
- Clamp
- Calorimeter
- Water
- Burning food
Check Biology page 15.
How can the change in PH affect the enzyme?
It changes the shape of the active site. if it changes too much the substrate will no longer fit neatly in it. if the active site changes shape too much , the enzyme will no longer catalyse the reaction. We say that the enzyme has been DENATURED
How does temperature affect an enzyme’s performance positively?
As temperature increases, molecules move faster. Higher speeds increase the chance of substrate molecules bumping into enzyme molecules and slotting into the active site.
How does temperature affect an enzyme’s performance negatively?
When the temperature gets too high, the shapes of the enzyme molecule starts to change. The higher the temperature, the more the change. This makes it more difficult for the substrate molecule to fit into the active site.
What is the temperature or pH that an enzyme works the best at called?
Optimum temperature or optimum pH.
What is a concentration gradient?
A difference between 2 concentrations. The bigger the difference between concentrations, the steeper the concentration gradient and the faster diffusion occurs.
Check Biology page 24.
What is diffusion?
The random movement and spreading of particles. There is an overall division of particles from regions of high concentration to regions of lower concentration.
What is a partially permeable or semi-permeable membrane?
A membrane that allows some molecules through it and not others.
What is osmosis?
The diffusion of small molecules of a solvent through a semi-permeable membrane. The overall movement of solvent molecules will stop when the concentration of solutes is the same on both sides of a membrane.
Which type of processes are osmosis and diffusion?
They are passive processes, so they don’t require an input of energy.
How do you find the percentage change in mass?
(Final mass - initial mass)
__________________________ x100
Initial mass
What is active transport?
Transporting molecules against a concentration gradient or transporting molecules that are too big to diffuse through the cell membrane.