B1-B4 AQA combined

• All things are made up of cells
• A prokaryote is a single celled organism that does not have a nucleus
• Eukaryotes are multicellular or unicellular organisms with a true nucleus
• in prokaryotic cells, the genetic information can be found in a sub cellular structure known as a plasmid
• in eukaryotic cells, the genetic information is enclosed in a subcellular structure known as a nucleus
• The nucleus contains genetic material that controls the activities of the cell
• cytoplasm is a gel like substance where most of the chemical reactions happen. It contains enzymes that control these chemical reactions.
• The cell membrane holds the cell together and controls what goes in and out
• The mitochondria is where most of the reactions for aerobic respiration take place respiration transfers energy that the cell needs to work
• ribosomes are where proteins are made in the cell
• A plant cell has a rigid cell wall made of cellulose. It supports the cell and strengthens it.
• A plant cell has a permanent vacuole containing cell sap and a weak solution of sugar and salts
• A plant cell has chloroplasts, this is where photosynthesis occurs which makes food for the plant
• plant cells contain a green substance called chlorophyll which absorbs the light needed for photosynthesis
• bacteria cells are prokaryotes, they don’t have a true nucleus. Instead they have a single circular strand of DNA that floats freely in the cytoplasm.
• bacteria cells have a cytoplasm, cell membrane and cell wall. they don’t have chloroplasts or mitochondria.
• differentiation is the process by which a cell changes to become specialised for its job.
• sperm cells are specialised for reproduction. It has a long tail and a streamlined head to help it swim to the egg. There are a lot of mitochondria in the cell to provide the energy needed. Also carries enzymes in its head to digest through the egg cell membrane.
• nerve cells are specialised for rapid signalling. The cells are long to cover more distance and have branched connections at their ends
• muscle cells are specialised for contraction. The cells are along so they have more space to contract and contain lots of mitochondria to generate the energy needed for contraction.
• muscle cells are specialised for contraction. The cells are long so they have space to contract and contain lots of mitochondria to generate the energy needed for contraction.
• root hair cells are specialised for absorbing water and minerals. They have a big surface area for absorbing water and mineral ions from the soil.
• phloem and xylem cells are specialised for transporting substances. xylem cells are hollow in the centre and phloem cells have very few sub cellular structures so that stuff can flow through them.
• chromosomes contain genetic information in the form of DNA molecules. A human cell has 23 pairs of chromosomes
• The cell cycle makes new cells for growth development and repair
• undifferentiated cells are called stem cells and they can divide to produce lots more undifferentiated cells
• embryonic stem cells can be used to replace faulty cells in sick people
• adults stem cells can be used to cure diseases. e.g stem cells can be transferred to the bone marrow to replace faulty blood cells
• some people are against stem cell research because they feel that human embryos shouldn’t be used for experiments since each one is a potential human life
• diffusion is the spreading out of particles from an area of higher concentration to an area of lower concentration
• Diffusion happens in both solutions and gases.
• osmosis is the movement of water molecules across a partially permeable membrane from a region of high water concentration to a region of lower water concentration
• root hairs take in minerals using active transport
• gas exchange happens in the lungs. The job of the lungs is to transfer oxygen to the blood and to remove waste carbon dioxide from it.
• Carbohydrases convert carbohydrates into simple sugars. Amalase breaks down starch into simple sugars
• proteases convert proteins into Amina acids. Proteases are made in the stomach the pancreas and the small intestine.
• lipases convert lipids into glycerol and fatty acids, they are made in the pancreas and the small intestine
• bile neutralises the stomach acids and emulsifies fats
• Communicable diseases can spread from person to person or between animals and people
• noncommunicable diseases cannot be spread between people or between animals they generally last for a long time and get worse slowly