B2 Revision Cards

BOTH Animal and Plant Cells -

Cell Membrane: Controls what enters and leaves the cell, for example oxygen, carbon dioxide and glucose.

Nucleus: Contains DNA, which instructs the building and working of the cell.

Cytoplasm: A jelly-like filling of the cell where reactions tend to take place.

Mitochondria: A tiny structure where respiration takes place and energy is released.

ONLY Plant Cells -

Chloroplasts: Where photosynthesis takes place.

Cell Wall: Made of cellulose, it is tough to support the cell's shape.

Central Vacuole: Contains cell sap, this keeps the plant cell rigid.

Cell Membrane: Controls what enters and leaves the cell.

Chromosomal DNA: A single loop in the cytoplasm, carries bacterial genes.

Plasmid DNA: Extra circles of DNA, contains additional genes.

Cell Wall: Made of different substances to the plant's cell wall, functions as protection.

Flagellum: A tail-like structure to help them move.

Light Microscopes: Use light to magnify objects, their greatest magnification is x2000.

Electron Microscope: Uses electrons to view an object, their greatest magnification is x10 million.

Magification of an Object =
Magnification of Eyepiece x Magnification of Objective

Nucleus: Contains chromosomes.

Chromosome: Contains a string of genes.

Gene: A short piece of DNA, which codes for specific proteins, for example eye colour.

DNA: A long, coiled molecule, which is two strands in a double helix shape.

Double Helix: Two strands joined by pairs of bases with weak hydrogen bonds.

Bases: Adenine, Thymine, Cytosine and Guanine.

ADENINE pairs with THYMINE

CYTOSINE pairs with GUANINE

AN EXAMPLE METHOD USING KIWI FRUIT -

1) The kiwi is mashed up and mixed with salty water and detergent. This is to break open the cells and to release the DNA from the Nuclei.

2) Protease enzyme is added to the filtered mixture, this is to break up proteins in cell membranes, and so more DNA is released.

3) Ice cold ethanol is poured into the mixture, this is to make the DNA separate from the liquid so it is easier to lift out.

MAURICE WILKINS and ROSALIND FRANKLIN studied DNA structure using X-rays.

FRANKLIN studied x-ray photographs of DNA to work out atom grouping.

JAMES WATSON and FRANCIS CRICK used other scientists data in order to interpret DNA structure. Franklin's photographs were the last clues they needed, eventually leading to them building the Double Helix Model.

Human Genome: The order of bases on all human chromosomes.

BENEFITS OF THIS KNOWLEDGE -

Identifying Faulty Genes:
This will help patients and family to prepare for the effects of the faulty gene. However, some would prefer not to know of their faulty genes due to stressing about it.

Gene Therapy:
This involves replacing faulty alleles with healthy ones, improving the patients quality of life. However, the faulty alleles could still be passed on to children if they are not replaced in the gametes.

A gene, for example Insulin, is cut out of a human chromosome using enzymes.

A DNA Plasmid is taken from a bacterium and cut open using enzymes.

They are mixed and then stuck together to make a new plasmid.

It is then put back into a bacterium, which has now been genetically modified to make human insulin.

GM Insulin -

Advantage: Quicker and cheaper to make, so more diabetics are treated. Disadvantage: Some react badly to it, so will require another form of Insulin.

GM Golden Rice -

Advantage: Contains beta-carotene, prevents illnesses caused by lack of Vitamin A. Disadvantage: More expensive, so poorer people cannot afford it.

Mitosis: Makes two identical cells - produces new body cells for growth, repair and asexual reproduction.

Diploid: Two sets of chromosomes, for example zygotes.

Haploid: One set of chromosomes, for example egg and sperm cells.

Parent Cell: The diploid cell that divides.

Daughter Cell: Genetically identical, the diploid cells that are formed.

The parent cell is diploid, so has two sets of chromosomes.

Before parent cell division, each chromosome is copied exactly.

Once the parent cell has divided into two, each daughter cell gets one copy of each chromosome.

They are therefore genetically identical.

Asexual Reproduction: The production of new organism without fertilisation, for example bacteria splitting, or plants making plantlets to grow on their own.

Fertilisation: When the male gamete (sperm) combines with a female gamete (egg) to produce a zygote.

Gametes: Haploid sex cells, sperm and eggs.

Zygotes: Diploid cell, a fertilised egg.

Meiosis: When a diploid cell divides to produce haploid gametes. This produces four, non-identical daughter cells.

1) The parent cell has two sets of chromosomes.

2) Each chromosome is copied exactly.

3) The parent cell splits into four. Each daughter cell gets a copy of one chromosome from each pair.

4) This means not all of them are identical, therefore meiosis results in variation.

1) The diploid nucleus is removed from an adult body cell.

2) The nucleus is removed from an egg cell.

3) The diploid nucleus is put into the empty egg cell, which is then stimulated using an electric pulse to start miotic division.

4) The formed embryo is then placed into the uterus of a surrogate mother, whom is different to the two donors.

Advantage: The offspring will inherit good features.

Disadvantage: Cloning may take many attempts, each attempt costing more money, therefore it is expensive.

Disadvantage: Offspring of cloning tend to have more health problems and die early.

Disadvantage: Genetic defects will be inherited.

Embryonic Stem Cells: Found in embryos, they contain few cells.

Adult Stem Cells: Found in differentiated tissue, such as bone and skin, they divide to replace damaged cells.

EMBRYONIC STEM CELLS -

Advantage: They are easy to extract, they will produce any cell type.

Disadvantage: The embryo is destroyed causing ethical issues, they are rejected without drugs, risk of producing cancer cells.

ADULT STEM CELL -

Advantage: No ethical issue caused, there is no rejection if taken from patient.

Disadvantage: They are difficult to find and extract, they produce only a few types of cells, risk of producing cancer cells.

Transcription: Takes place in the nucleus.

mRNA: Moves into the cytoplasm, Thymine is replaced with Uracil, so A pairs with U.

1) A section of DNA is unwound and the two strands separate.

2) Complementary bases, A+U and C+G, pair with the open bases on the DNA strand to make a complementary mRNA.

Translation: Takes place in cytoplasm when mRNA strand attaches to a ribosome.

1) Ribosome moves along the mRNA reading each codon/triplet of bases.

2) tRNA brings amino acids to the ribosome, the amino acid attached to the tRNA depends on the order of bases in the tRNA.

3) tRNA bases pair with the mRNA bases, and close together amino acids form a polypeptide, which is one piece of a protein.

Globular Proteins - enzymes, hormones, haemoglobin:
Control reactions,
they are transported in blood to target cells,
they carry oxygen in red blood cells.

Fibrous Proteins - keratin, collagen:
Tough nails to protect fingers and toes,
ligaments hold bones together,
tendons attach muscles to bones.

Mutation: Can change 1 or more DNA bases, which may change the amino acids added to chain during Translation.

A change in amino acid may -

1) Not change the shape or function of the protein.

2) Benefit the protein by improving the function.

3) Worsen the function, an example of this is the mutation that causes sickle cell disease.

Enzyme: Biological catalysts that control reactions in the body, they are specific for their substrate.

Enzyme Controlled Reactions Inside the Body: Join the substrate molecules together, for example DNA replication.

Enzyme Controlled Reactions Outside the Body: Break the substrate molecules into smaller molecules, for example the digestion of food.

Two different substrate molecules will insert into the active site, the shape of the active site matches the shape of the substrate molecules, therefore it holds them closely so they can form a bond.

The molecule produced does not fit the active site, so it is released from the enzyme.

Lower than Optimum Temperature: Causes molecules to move, fit and react more slowly.

Higher than Optimum Temperature: Active Site changes shape, not as tight, slower. Very high temperature causes the Active Site to break and enzymes to denature.

Optimum Temperature: Works at fastest rate.

Higher Concentration: Increases rate of reaction, until the point where all enzymes are busy, then it has no effect.

Lower or Higher than Optimum pH: Rate of reaction is slower.

Optimum pH: Works at fastest rate.

Respiration: Release of energy from organic molecules.

Energy: Used for growth and movement.

GLUCOSE + OXYGEN -> CARBON DIOXIDE + WATER

Diffusion: Net movement of particles from an area of higher concentration to an area of lower concentration.

Heart Rate: Take pulse at wrists, measured in beats per minute.

Breathing Rate: Count number of breaths in one minute.

Faster Heart Rate: Blood is pumped faster, so oxygen and glucose gets to cells faster and carbon dioxide is removed faster.

Faster Breathing Rate: Oxygen is taken into the body faster and carbon dioxide is released faster.

Stroke Volume: Volume of blood pumped in 1 heartbeat.

CARDIAC OUTPUT = STROKE VOLUME x HEART RATE

GLUCOSE -> LACTIC ACID (No Oxygen Involved)

Advantage: Releases energy for the muscles when the heart and lungs can't deliver oxygen fast enough.

Disadvantages: Releases less energy than aerobic respiration, lactic acid can build up in muscle and blood, and must be broken down.

EPOC (excess post-exercise oxygen consumption): Oxygen needed after exercise has ended, compared with the resting rate.

CARBON DIOXIDE + WATER -light energy-> GLUCOSE + OXYGEN

Leaf Adaption: Large surface area to capture as much light as possible.

Chlorophyll Adaption: In Chloroplasts, captures light energy needed for photosynthesis.

Stomata Adaption: Allows carbon dioxide to diffuse in, and oxygen and water to diffuse out of the leaf.

Rate of Photosynthesis: Measure rate at which oxygen is given off by using a piece of pondweed.

LOW Temperature: Investigate effects using warm and cold water baths.

DIM Light Intensity: Investigate effects using bright and dim lights.

LOW Carbon Dioxide Concentration: Investigate effects using different amounts of sodium hydrogen carbonate in the water.

Veins: Transport water and dissolved substances, contain xylem and phloem.

Xylem: Transports water from the roots to the plant.

Phloem: Glucose is converted to Sucrose and transported.

Transpiration: Evaporation of water from inside leaves out into the air, water moves up the plant from the roots.

Diffusion: Move down concentration gradient, no energy needed.

Active Transport: Move up concentration gradient, energy needed for substances to move.

Osmosis: Diffusion of water molecules.

Osmosis: Net movement of water molecules from a region of high concentration to low concentration through a partially permeable membrane.

Partially Permeable Membrane: Lets some molecules through but not others.

Root Hair Cell Adaption: Large surface area, so more water molecules cross the cell membrane at the same time.

Pitfall Trap: A container in a hole in the ground, with a lid stabilised above it with stones to shelter any insects from the sun.

Pooter: An inlet tube in a jar, with a mouthpiece covered with netting to inhale the animal through the inlet tube into the jar.

Quadrants: A square frame used to calculate the average area containing certain organisms.

Temperature: Measured with a temperature probe connected to a datalogger.

Light Intensity: Measured with a light probe connected to a datalogger.

pH of soil: Mix soil with distilled water, use universal indicator to measure pH.

Fossil: Preserved remains of an organism that lived thousands/millions of years ago.
Pentadactyl Limb: A long bone supporting carpal bones and phalanges - suggesting humans and whales share an ancestor in their evolution lines.

REASONS FOR GAPS IN THE FOSSIL RECORD -

1) Fossils only form in suitable conditions, for example not too acidic.

2) Soft tissue, such as muscle and leaves, tend to decay too fast to fossilise.

3) Many fossils are deeper in the ground than we can dig, and so haven't been discovered yet.

Growth: A permanent increase in size, measured in length and mass.

Percentile Chart: Show if a child is growing faster or slower than the average for their age.

RAISES FOR CONCERN -

1) If a baby has mass above the 95th percentile or below the 5th percentile, they may not be growing properly.

2) If a babies mass descreases by two or more percentiles in their first year, they may not be growing properly.

Plant Growth: Cell Divsion (behind the shoot tip) and Cell Elongation (further away from the shoot tip).

Animal Growth: Through ageing, body cells differentiate.

EMBRYO -> BIRTH -> YOUNG -> ADULT

Cell Division: Rapid for growth -> Slow for repair

Cell Differentiation: Not differentiated -> Most differentiated

Blood Plasma: Liquid part of the blood, carry blood cells through blood vessels, contain dissolved substances such as carbon dioxide.

White Blood Cells: Larger than red blood cells, have a nucleus, a part of the immune system. Some surround and destroy pathogens, some produce antibodies to destroy pathogens.

Platelets: Fragments of larger cells, cause the blood to clot which prevents pathogens entering the blood.

Red Blood Cells: Contain haemoglobin to carry oxygen. Biconcave shape for a larger surface area - oxygen diffuses easier. No nucleus means there's more space for haemoglobin to carry more oxygen.

Pulmonary Artery: Deoxygenated blood, from heart to lungs.

Pulmonary Vein: Oxygenated blood, from lungs to heart.

Aorta: Oxygenated blood, from heart to body.

Vena Cava: Deoxygenated blood, from body to heart.

Valves: Prevent blood backflow/blood flowing the wrong way.

Left Ventricle: Thicker than the right ventricle to push blood all round the body.

Left/Right Atrium: Holding chambers for the blood.

Circulatory System: Consists of the heart, blood vessels and blood.

Arteries: Carry blood away from the heart, all carry oxygenated blood EXCEPT the pulmonary arteries.

Veins: Carry blood towards the heart, all carry deoxygenated blood EXCEPT the pulmonary veins.

Capillaries: Exchange materials such as glucose, oxygen and carbon dioxide with body tissues.

Mouth: Food enters body, chewing breaks up food and mixes it with enzymes in saliva.

Oesophagus: Carries food from mouth to stomach using perastalsis - muscle contraction and relaxation to push the food along.

Liver: Produces bile to digest fats in small intestine.

Gall Bladder: Where liver bile is stored until needed.

Stomach: Acid and enzymes added, contents mixed by muscular wall churning.

Pancreas: Produces enzymes released into the small intestine.

Small Intestine: Food and Water molecules absorbed into blood.

Large Intestine: Faeces is formed.

Anus: Faeces is released out of the body.

Carbohydrases: Digest carbohydrates, for example Amylase digests starch to simple sugars.

Proteases: Digest Proteins to amino acids.

Lipases: Digest fats to fatty acid and glycerol.

Bile: Neutralises stomach acid so enzymes in the small intestine can work at Optimum pH. Emulsifies (breaks up) fats so there is a greater surface area for lipases to work on.

Capillary network carries absorbed molecules rapidly away - maintains steep concentration gradient for diffusion.

Increase surface area of the small intestine for diffusion of soluble products of digestion.

Surface formed from single layer of cells allow rapid diffusion.

Visking Tubing: Visking Tubing containing starch and amylase is place in a test tube containing some water, which is put in a beaker of 30 degree Celsius water.

The glucose will diffuse out of the bag containing the starch and amylase, and into the water.

The Visking Tubing is a model for the alimentary canal because, like the wall of the small intestine, small molecules can diffuse out of it but not larger molecules.

Probiotic Food: Contains good bacteria, for example Bifidobacteria.

Manufacturer Claim: Improves digestive and immune system. (little evidence).

Prebiotic Foods: Contain high levels of Oligasacharides.

Manufacturer Claim: Encourage beneficial bacteria growth in the alimentary canal and prevents diarrhoea. (increasing evidence).

Plant Stanol Esters: Reduce cholesterol absorption, reduce risk of heart disease. There is scientific evidence of it reduceing cholesterol levels, the effects on heart disease is still being tested.