The building blocks of cells Biology Unit 2 – Topic 1

Chromosomal DNA is a giant loop of DNA containing most of the genetic material.Bacteria

Plasmid DNA comes in small loops and carries extra genetic information.Bacteria

The flagella, if there is one, is on the outside of the bacteria cell. These are long, whip-like structures to move the bacteria along.Bacteria

The cell wall does a similar job to a plant cell wall but it is different. It is more flexible and it is not made from cellulose.Bacteria

Chloroplasts contain the green pigment called chlorophyll. This absorbs light energy for photosynthesis. Plant cell only

The large vacuole is a space in the cytoplasm that is filled with cell sap. This helps to support the plant by keeping the cells rigid. Plant cell only

The cell wall is made of cellulose to support the cell and to keep its shape. Plant cell only

The cell membrane controls the movements of substances like oxygen, carbon dioxide and glucose into and out of the cell. Plant and animal cell

Mitochondria are very small organelles in which respiration occurs. Plant and animal cell

The cytoplasm is where many of the chemical reactions that take place. Plant and animal cell

The nucleus contains the DNA. It controls all the activities of the cell. Plant and animal cell

The best light microscopes can magnify specimens more than 1500 times. Light microscope

These microscopes use a beam of electrons to magnify the specimen up to 2 million times. This lets us see very clear and detailed structures inside cells. Electron microscope

A gene is a section of a molecule of DNA. It codes for a specific protein.Gene

A DNA molecule is two strands coiled together to form a double helix.DNA

The two strands are linked (like rungs on a ladder) by a series of base pairs joined together by weak hydrogen bonds.DNA

Adenine (A) pairs with thymine (T) (so the pointy letters pair together) Cytosine (C) pairs with guanine (G) (and the curly letters pair together) DNA Base Pairs

The order of bases in a section of DNA decides the order of amino acids in the protein DNA Base Pairs

This is where scientists remove a gene from one organism and insert it into the DNA of another organism. Genetic engineering

Golden rice plants are normal rice plants with 2 extra genes inserted so that they make beta-carotene in the grains. This is required in humans to make Vitamin A Advantages Genetic engineering

The gene for human insulin is inserted into bacterial plasmid DNA. The genetically modified (GM) bacteria can then make insulin. This is used by people with Type 1 diabetes. Advantages Genetic engineering

Scientists have added genes to some plants to make them herbicide resistant (weed-killer resistant). This will reduce the amount of crop spraying needed because the farmer can use one large dose of the herbicide rather than lots of smaller doses. Advantages Genetic engineering

Most nuclei contain 2 copies of each chromosome. This makes the diploid cells.Mitosis

Human diploid cells contain two sets of 23 chromosomes. Body cells (all cells except sperm and egg cells) are diploid.Mitosis

Body cells divide to make more body cells or to replace damaged cells by mitosis.Mitosis

Mitosis occurs during growth, repair and asexual reproduction.Mitosis

Mitosis produces 2 daughter cells, each with identical sets of chromosomes in the nucleus to the parent cell.Mitosis

Mitosis results in the formation of two genetically identical diploid body cells.Mitosis

At fertilization, haploid gametes combine to form a diploid zygote.Fertilisation

A zygote is a fertilized egg cell.Zygote

Meiosis is needed to produce haploid gametes.Meiosis

Meiosis makes four haploid daughter cells, each with half the number of chromosomes. This results in genetically different haploid gametes.Meiosis

Me1osis for 1 set of chromosomes. Mi2osis for 2 sets of chromosomes. Mitosis or Meiosis

Each chromosome in a pair contains the same genes but may have different versions of those genes called alleles.Alleles

Clones are examples of asexual reproduction that are genetically identical copies of each other.Clones

Stem cells in the embryo can differentiate into all other types of cells, but that cells lose this ability as the animal matures. Stem cells

Proteins are made from amino acids.Proteins

Different proteins have different numbers of amino acids arranged in different orders. This makes different shaped molecules that have different functions or jobs.Proteins

Enzymes are proteins.Proteins

Gene mutations change the DNA base sequence and so can change the protein. Gene mutations

Gene mutations can harmful, have no effect or be beneficial to the organism. Eg. Some mutations in bacteria make them resistant to antibiotics. Gene mutations

Enzymes are Biological catalysts.Enzymes

Enzymes catalyse chemical reactions occurring inside and outside living cells.Enzymes

Enzymes catalyse: DNA replication Protein synthesis DigestionEnzymes

The molecules that enzymes work on are called substrate molecules.Enzymes

Enzymes are very specific and will only work with a particular substrate or a small group of substances.Enzymes

Enzymes are affected by: Temperature Substrate concentration pHEnzymes

Changing the pH or temperature will change the shape of the active site in the enzyme. Too much change may break the chemical bonds in an enzyme.Enzymes

Too many changes in the enzyme will destroy the active site so the enzyme will not work. The enzyme has been denatured.Denatured

The model of how enzymes work is called the Lock and key hypothesis.Enzymes

Organisms and energy Biology Unit 2 – Topic 2

Respiration is a process used by all living organisms that releases the energy in organic molecules Respiration

Glucose and oxygen diffuses from capillaries into respiring cells. Respiration

Carbon dioxide diffuses from respiring cells into capillaries. Respiration

Diffusion is the movement of particles from an area of higher concentration to an area of lower concentration. Diffusion

Aerobic respiration uses Oxygen to release energy from glucose. Aerobic respiration

Glucose + oxygen carbon dioxide +water The energy from the glucose is released for use in the cell. Aerobic respiration

Exercise can cause a change in heart and breathing rates. Exercise

During exercise the muscles use up oxygen and glucose quickly, so the breathing rate increases to get more oxygen and the heart beats faster to pump more blood with more oxygen and glucose to these cells. Exercise

The cardiac output is the volume of blood circulated by the heart in a given time. Amount of blood

Cardiac output = stroke volume x heart rate Amount of blood

Cardiac output Stroke volume Heart rate

Sometimes, when we carry out vigorous exercise we cannot supply enough oxygen to the muscle cells so we start to respire anaerobically. Anaerobic respiration

Anaerobic respiration breaks down glucose and releases energy without any oxygen. Anaerobic respiration

Glucose lactic acid The energy from the glucose is released for use in the cell. Anaerobic Respiration

Anaerobic respiration releases less energy than aerobic respiration.

Lactic acid produced by anaerobic respiration exercise may cause muscle cramps. Lactic acid

After exercise increased oxygen is required to break down the Lactic acid into carbon dioxide and water. This need for extra oxygen after exercise is called Excess post-exercise oxygen consumption. (EPOC) Lactic acid

A leaf is adapted for photosynthesis. Large surface area Chlorophyll in chloroplasts to absorb light Stomata for gas exchange (carbon dioxide, oxygen and water) Photosynthesis

Plants absorb light energy to make glucose. Carbon dioxide + water glucose + oxygen Photosynthesis

For photosynthesis to happen there must be enough carbon dioxide, water, a suitable temperature and light to give the energy for the reactions. The one that is in the shortest supply is called the limiting factor. Rate of photosynthesis

Roots do more than just anchor a plant to the ground. They take up water and dissolved nitrate and other mineral ions from the soil. Water transport

Root hair cells have long tin extensions that reach into the nearby soil. This gives them a bigger surface area for the water and mineral ions to enter. Root hair cells

Water enters the root hair cells by osmosis. Here, water moves across a partially permeable membrane. Water transport

Osmosis is the movement of water molecules from an area of higher concentration of water to an area of lower concentration of water through a partially permeable membrane. Osmosis

This is the evaporation of water vapour from the surface of a plant. Transpiration

The loss of water from a leaf pulls water and dissolved mineral salts up through the xylem from the roots. This process is called transpiration. Transpiration

Roots can absorb nitrates and other mineral ions dissolved in soil water even if the concentration is higher in the plant than in the soil water. Absorbing particles against a concentration gradient is called active transport. The energy for this comes from repiration. Active transport

Xylem vessels transport water and dissolved mineral salts up a plant. Water Xylem W X Xylem vessels

The glucose made in the leaves by photosynthesis is converted to sucrose and carried to other parts of the plant by the phloem tissue. Phloem vessels

A pooter is used to suck small invertebrates into a tube. Sampling techniques

A sweep net is used to drag through long grass to catch any organisms. Similarly, a pond net could be used for aquatic habitats. Sampling techniques

A pitfall trap is a jar which small animals fall into and are trapped. Sampling techniques

A quadrat is a square frame placed at random place on the ground and the plants in that area counted. Sampling techniques

Environmental factors which could be measured include: Temperature Light intensity pH Sampling techniques

Common systems B2 – Topic 3

Fossils are the preserved traces or remains of organisms that lived thousands or millions of years ago.Fossils

This is the collection of fossils identified from different periods of time that can be interpreted to form a hypothesis about the evolution of life on Earth. Fossil record

There are gaps because: 1) fossils do not always form. 2) soft tissue decays 3) many fossils are yet to be found. Gaps in the Fossil record

When organisms grow they get bigger. The easiest way to observe growth is to measure an increase in size, length or mass.Growth

These charts or graphs are used to compare a certain characteristic (e.g. mass) against the total population. Percentile charts

Growth in an organism involves two processes. 1)Cell division where one cell divides to form two identical cells. 2)The cell gets longer by elongation. Plant growth

Plants grow all the time. As the plant stem or root continues to grow the older meristem cells start to become specialised – they differentiate. Plant development

Animals stop growing when they become adults. In an animal, cells that can differentiate to form a number of different types of specialised cells are called stem cells. Animal development

Red blood cells White blood cells Plasma Platelets Parts of the blood

A red blood cell has the shape of a biconcave disc. This increases the surface area for diffusion. Red blood cells contain the red pigment haemoglobin. Red blood cells have no nucleus. Parts of the blood

White blood cells are part of the body’s defences against disease. Some white blood cells make antibodies. Other white blood cells surround and destroy any foreign cells like bacteria that get into the body. White blood cells have a nucleus. Parts of the blood

Plasma is a yellow liquid. It transports dissolved substances, such as carbon dioxide, food substances and hormones. Parts of the blood

Platelets are tiny fragments of cells (and so do not have a nucleus). They are important in making your blood clot if you cut or damage your blood vessels. The clot dries out and forms a scab which stops micro- organisms like bacteria getting into the body. Parts of the blood

A group of the same specialised cells form a tissue. e.g. muscle tissue is made from muscle cells. Cells, tissues, organs and systems

An organ contains several different tissues working together to carry out a particular job. The heart is an organ that pumps blood to the lungs and around the body. Cells, tissues, organs and systems

Groups of organs that work together are called organ systems. e.g. the heart and blood vessels make an organ system called the circulatory system. Cells, tissues, organs and systems

Groups of organs that work together are called organ systems. e.g. the heart and blood vessels make an organ system called the circulatory system. Cells, tissues, organs and systems

The heart is an organ that pumps blood around the body. There are 4 major blood vessels associated with the heart. The heart

The pulmonary artery takes deoxygenated blood to the lungs to get oxygen. The pulmonary vein takes oxygenated blood back from the lungs to the heart. The heart

The aorta carries oxygenated blood around the body. The vena cava carries deoxygenated blood back to the heart where it is pumped back to the lungs. The heart

The left atrium and ventricle pump oxygenated blood. The heart

The right atrium and ventricle pump deoxygenated blood. The heart

Veins and the heart have valves to prevent backflow – to stop the blood going the wrong way. The heart

The muscle wall of the left ventricle is thicker than the right ventricle because it has to pump blood all around the body rather than just to the lungs. The heart

Arteries transport blood away from the heart. Arteries have strong, thick walls to withstand the blood at high pressure.

The heart Veins transport blood to the heart. Veins are wide because the blood flows relatively slowly under low pressure.

The heart Capillaries exchange materials with tissues by diffusion so they have very thin walls.

The digestive system Food is broken down in the organ system called the digestive system.

The digestive system In the mouth, teeth break up the food into small pieces. This increases the surface area for digestive enzymes to work on – like amylase.

The digestive system The oesophagus is a muscular tube between the mouth and stomach. Muscles contract in waves to push the food down it – this is called peristalsis.

The digestive system The stomach is a bag that makes Hydrochloric acid and some enzymes like pepsin to break down proteins. It churns the food up.

The digestive system The small intestine is a long tube where most of the large insoluble food molecules are broken down into smaller soluble molecules. There are lots of enzymes. Food is again moved by muscles in peristalsis.

The digestive system The surface area of the small intestine is greatly increases by having lots of finger like projections called villi which contain capillaries.

The digestive system Water diffuses back into the blood in the large intestine leaving the waste material called faeces behind.

The digestive system The pancreas make digestive enzymes and releases them into the first part of the small intestine.

The digestive system Digested food absorbed by the small intestine is taken in the blood plasma to the liver. Here some of the molecules are broken down even more. Some are built up into larger molecules. The liver also makes bile which helps in the digestion of fats.

The digestive system – Higher paper The gall bladder is a small organ that stores the bile made by the liver. It releases the bile into the small intestine when it is needed.

The digestive system

Enzymes Carbohydrases are digestive enzymes that break down carbohydrates into sugars. Amylase breaks down starch into sugar.

Enzymes Proteases are enzymes that break down proteins into amino acids. Pepsin is an enzyme that breaks down proteins in the stomach.

Enzymes Lipases are enzymes that break down fat molecules into fatty acids and glycerol.

Bile – Higher paper Bile breaks down large globules of fat and oil into tiny droplets forming an emulsion. The smaller droplets have a larger surface area which lets the lipase enzymes break down the fat molecules quicker. Bile is also slightly alkaline and so will neutralise the Hydrochloric acid from the stomach.

Probiotics Probiotics contain live bacteria which maybe helpful to the digestive system. These bacteria are usually Lactobacillus and Bifidibacteria. They are found in yoghurts or yoghurt drinks.

Prebiotics Prebiotics are substances that the body can’t digest. They act as food for the probiotic bacteria. Tomatoes, bananas, onions and asparagus all contain oligosaccharides, a common form of prebiotic.

Plant stanol esters Plant stanol esters are oily substances found in plants. These can stop the small intestine absorbing cholesterol so lowering the level of cholesterol in the blood. Plant stanols are now used in many yoghurt, drinks and spreads.