B1

What is a eukaryotic cell and give example

Eukaryotic cells contain DNA in a nucleus. Plant and animal cells and protists are eukaryotic cells

Function of the part of the cells

Cell Membrane- Allows gases and water to diffuse freely in and out of the cell.
Nucleus- Contains DNA- genetic code for making enzymes and other proteins.
Cytoplasm- Where enzymes and other proteins are made. Location of anaerobic respiration
Ribosomes- where amino acids join together to make a protein
Mitochondria- contains enzymes for aerobic respiration

Function of special part of plant cells

Vacuole- filled with cell sap to help support the cell
Cell Wall- made from cellulose fibres. Strengthen cell and support plant
Chloroplast- contains chlorophyll which absorbs light for photosynthesis and enzymes needed for photosynthesis

Describe onion cell experiment

1. Carefully peel a very thin layer of cells from inside the onion
2. Gently place sample onto the slide
3. Stain specimen with iodine
4. Cover sample with a cover slip
5. Have a look at the cells and draw what you can see

What is bacteria

Single celled organisms
Extremely small
Classified by their shape

Parts unique to bacteria and their function

Flagella- tail like structure for movement
Pilli- to attach to structures and used in transfer of DNA
Capsule- prevents it from drying out
Plasmid- single stranded circular piece of DNA

Differences between eukaryotic cells and prokaryotic

Eukaryotic cells have a nucleus whilst prokaryotic don’t
Eukaryotic cells have membrane bound organelles but prokaryotic cells don’t

Define Magnification and Resolution

Magnification- How many times bigger an object is than the image in real life
Resolution- how close together 2 objects are but still be seen as separate objects. How clear something is

How to calculate magnification and image size

Magnification = eyepiece lens x objective lens
Image = actual image x magnification

Difference between light and electron microscopes

Electron microscopes use an electron beam instead of light.
Electron microscopes have a much higher resolution and magnification
But more expensive and can not be moved.
Specimen must be dead and could be damaged in preparation

Structure of DNA

Double helix shape with a backbone made of sugars and phosphates to hold the structure. Has complementary base pairs that carry the genetic code.

What are the base pairs in DNA

Adenine and Thymine (AT)
Guanine and Cytosine (GC)

What does a nucleotide consist of

Phosphate
Sugar
Nitrogenous base

Describe process of protein synthesis

DNA double helix is separated
Transcription- mRNA is made using DNA strand
mRNA leaves nucleus and enters cytoplasm then joins onto a ribosome
Translation- mRNA acts as a code for tRNA
Amino acids on neighbouring tRNA join together
Chain of amino acids called a poly-peptide
Poly-peptide chain folds to form a protein which is used in the cell or exported to the body

What are enzymes

Large protein molecules made of long chains of amino acids, folded and coiled into a specific shape.
They are biological catalysts (speed up a reaction without being used up)

What is optimum temperature of an enzyme and why is it bad to denature

Optimum temperature 37 degrees or it denatures. Change in shape of active site so substrate is no longer complementary and the reaction stops.

Equation for aerobic respiration

Oxygen + Glucose = carbon dioxide + water + ATP
6O² + C6H12O6 = 6CO² + 6H²O

Why do we need to respire? (4 reasons)

Protein synthesis
Digestion ( enzymes colliding into substrates)
Repairing of muscles and muscle contraction/relaxation
Regulating body temperature

Equation of Anaerobic respiration

Glucose = lactic acid + some ATP

Describe properties of aerobic respiration

Releases lots of energy (2900kJ)
Oxygen available
Happens all the time
Water and carbon dioxide waste products
Glucose broken down completely

Describe properties of Anaerobic respiration

Releases small amount of energy (120kJ)
Can occur for short periods only
Not enough oxygen available
Lactic acid waste product
Glucose broken down everyday

What is lactic acid

Waste product of anaerobic respiration and can cause fatigue and pain/cramps in the muscles when built up
Transported to liver where oxygen is used to break it down but this creates an oxygen debt

How to calculate oxygen debt

Oxygen debt = difference between oxygen demand and supply

Anaerobic respiration in Microbes

Glucose = Ethanol +CO² + “some” energy

Equation for photosynthesis

Carbon dioxide + water = Glucose + oxygen through use of light and chlorophyll
6CO² + 6H²O = C6H12O6 + 6O²

What is glucose used for in a plant

Glucose is converted to all the substances a plant needs

What substances does a plant need (5 things)

Sucrose- stored in fruit
Starch- food stores
Cellulose- to form cell walls
Glucose + Nitrogen = protein for growth/repair
Fats and oils- food store and growth

What is a light dependent reaction

Light energy splits water molecules into oxygen gas and H+ ions
H²O = H+O

What is a light independent reaction

Carbon dioxide gas combines with the hydrogen ions to make glucose
3CO²+12(H+) = C6H12O6

What are the limiting factors of photosynthesis

Temperature (enzymes denature)
Carbon dioxide concentration
Light intensity

How to calculate rate of photosynthesis and light intensity

Rate = 1/t where t is time
Light intensity = 1/Relative distance²

How do you test for different substances in food
(Glucose, Starch, Proteins, Lipids)

Glucose- Add 5cm³ of solution to test tube followed by 10 drops of Benedict’s solution. Place in water bath for 5 minutes. If glucose present, solution will turn orange yellow etc.

Starch- Take 5cm³ of food sample and add few drops of iodine solution. This turns solution a brown-orange colour but when you shake it, it will turn blue-black colour if it contains starch

Proteins- Add 2cm³ of sample to test tube followed by 2cm³ of Biuret solution. This turns it blue but when you shake it, it will turn purple if it contains protein

Lipids- Take food sample and add 2cm³ of ethanol then shake it vigorously then add equal volume of distilled water. If solution turns cloudy white colour then lipids are present