SB1-Key Concepts in Biology Flashcards
How do you work out a microscopes magnification?
Multiple the magnification of its lenses together
How do electron microscopes work?
Beams of electrons pass through a specimen to build up an image
Which type of microscopes have better resolution and magnification?
Electron
How many millimetres are in a metre?
1000
How many micrometres (μm) are in a metre?
1000000
How many nanometres (nm) are in a metre?
1000000000
How many picometres (pm) are in a metre?
1000000000000
What is an electron microscopes max resolution and magnification?
Resolution- 0.0000002
Magnification- x2000000
What is a light microscopes max resolution and magnification?
Resolution- 0.0001
Magnification- x1500
What is a eukaryotic cell?
A cell with a nucleus
What does the cell membrane do?
Controls what enters and leaves the cell
Separates one cell from another
What occurs in the mitochondria?
Aerobic respiration
Where are ribosomes?
Cyptoplasm
What do ribosomes do?
Make new proteins for the cell
What is the cyptoplasm?
Jelly-like substance where most of the cells activities occur
What does the nucleus contain?
Chromosomes which contain DNA
What does the nucleus do?
It controls the cell and it’s activities
What is the the cell wall?
It is made of cellulose and supports and protects the cell
What are chloroplasts?
They contain chlorophyll which traps energy transferred from the sun which is used for photosynthesis
What does the permanent vacuole do?
It stores cell sap and helps keep the cell firm and rigid
What sub-cellular structures do plant cells have that animal cells do not?
Cell wall
Chloroplasts
Permanent vacuole
What sub-cellular structure do animal cells have that plant cells do not?
Mitochondria
What are the steps you would take to use a microscope?
Collect a thin specimen
Add stain to the centre of a microscope slide
Place the specimen on the stain
Use a toothpick to lower a coverslip on the specimen
Examine with the microscope- start with the lowest magnification and work up to higher magnifications
What does it mean for a cell to be specialised?
They have a specific function/job which they are adapted for
How are the cells that line the small intestine specialised for their functions?
They have membranes with tiny foods (microvilli) which increase the surface area of the cell which increases the speed of absorption
How are enzymes adapted?
Having a lot of ribosomes as they are proteins
How are the walls of the small intestine adapted?
They have muscles to squeeze food along which require a lot of energy so have many mitochondria
What are diploid cells?
Cells with two sets of chromosomes
What are haploid cells
Cells with one set of chromosomes
How many types of chromosomes are there?
23
How does an egg cell stop other sperm cells entering after fertilisation?
The cell membrane becomes hard
What does the egg cell have a lot of and why?
The cytoplasm has lots of nutrients to provide energy and raw materials for the embryos development
What allows the sperm cell to swim?
It’s tail waving side to side
What type of shape does a sperm cell have?
Streamlined shape
What is the acrosome?
A vacuole in the tip of a sperm cells head which contain enzymes that break down the substances in the egg cells jelly coat, allowing the sperm cell to burrow inside
How are oviduct cells adapted?
They have hair-like cilia which wave from side to side to sweet substances along
What does prokaryotic mean?
Cells without a nucleus, chromosomes, mitochondria or chloroplasts
What do prokaryotic cells have instead of chromosomes?
One large loop of chromosomal DNA in the cyptoplasm
What sub-cellular structures do most bacteria cells have?
Flagellum/flagella
Slime coat- protection
Flexible cell wall
Cyptoplasm
Chromosomal DNA
How do bacteria get substances for energy, growth or development?
Release digestive enzymes into their environment and then absorb the digested food into their cells
How do humans get substances for energy, growth or development?
Digestive enzymes turn large food molecules into smaller subunits which are small enough to be absorbed by the small intestine
What is synthesis
Building larger molecules from smaller subunits
What are polymers?
Small molecules (monomers) joined in a long chain
What are catalysts?
A substance that speeds up a chemical reaction but are unchanged by the reactioj
What are enzymes?
A group of proteins that speed up breakdown (eg digestion) and synthesis reactions in living organisms
What type of catalysts are enzymes?
Biological catalysts
What does amylase speed up the breakdown of?
Starch to small sugars
What does catalase speed up the breakdown of?
Hydrogen peroxide into water and oxygen
What does iodine solution test for?
Starch
What transformation does iodine solution go through when in contact with starch?
Yellow/orange ~> blue/black
What does Benedict’s solution test for?
Reducing sugars
How do you test for reducing sugars?
Mix a food solution with an equal volume of Benedict’s solution
Place in a hot water bath for a few minutes
What transformation does iodine solution go through when in contact with reducing sugars?
Blue~> green/orange/red
This may form a precipitate
What does green Benedict’s solution show?
Very little reducing sugar
What does blue Benedict’s solution show?
No reducing sugar
What does orange Benedict’s solution show?
More reducing sugar
What does red Benedict’s solution show?
Lots of reducing sugar
What transformation happens in the biuret test if proteins are present?
Pale blue ~> purple
What does the biuret test test for?
Proteins
How do you perform the biuret test?
Potassium hydroxide is mixed with a solution of the food
Two drops of copper sulfate solution are added
What happens when ethanol comes into contact with lipids?
Fats and oils dissolved in the ethanol float to the surface, forming a cloudy emulsion
How do you perform the ethanol emulsion test?
Mix the food with ethanol and shake
Pour this mixture into water and shake again
Leave to stand
What does the ethanol emulsion test test for?
Fats and oils (lipids)
What can you use to measure the amount of energy in a food?
Burn it in a calorimeter
What forms a protein?
A chain of amino acids
What forms proteins 3D shape?
Folding of the chain
What is an active site?
Where the substrate of the enzyme fits at the start of a reaction. Different enzymes have different active sites which is why every enzyme can only work with one specific substrate- the one that fits the active site
What is denatured enzyme?
An enzyme that will no longer catalyse the reaction as it’s active site has changes shape too mich
What causes an enzyme to denature?
Changes in pH or temperature which affect how the protein folds up
Why does an increase in temperature increase the rate of reaction and then drop it?
As the temperature increases molecules move faster which increases the chance of substrate molecules bumping into enzyme molecules and slotting into the active site
However if the temperature gets too high it will cause the enzyme to denature as it will change the shape of the active site
What is the optimum temperature?
The temperature at which an enzyme works fastest
What is diffusion?
Movement of gas and liquid particles from an area of high to low concentration down the concentration gradient
What is a concentration gradient?
The difference between an area of high concentration and an area of low concentration
What does an increase in the difference between two concentrations do?
It makes the concentration gradient steeper and so diffusion faster
What does diffusion allow?
Small molecules (like oxygen) to move in and out of cells
What is a semi-permeable membrane?
A membrane that allows some molecules through it and not others
What is osmosis?
Diffusion of water molecules across a semi-permeable membrane from an area of high to low concentration following the concentration gradient
What can osmosis cause?
Tissues to gain or lose mass
What is the formula for percentage change in mass?
Percentage change in mass = [(Final mass- initial mass) / initial mass ] x 100
What is active transport?
Transportation of molecules against a concentration gradient
Where is active transport carried out?
By transport proteins in cell membrane
What does active transport require and why?
Energy
Why do osmosis and diffusion not require energy?
They are passive processes
How does active transport occur?
Transport proteins capture certain molecules and carry them across the cell membrane
What process do roots use to take water from the soil?
Osmosis
