B1- cell biology

• Cells can either be prokaryotic or eukaryotic
• Eukaryotes are organisms made up of eukaryotic cells
• prokaryotes are organisms made out of prokaryotic cells
• nucleus - contains genetic material that controls the activities of the cell
• mitochondria - where most of the reactions for aerobic respiration take place and respiration transfers energy the cell needs to work
• cytoplasm -where most of the chemical reactions take place and contains enzymes that control these reactions
• cell membrane - holds the cell together and control what goes in and out
• ribosomes - where protein synthesis happens (where proteins are made)
• cell wall - made of cellulose and supports and strengthens the cell
• permanent vacuole - contains cell sap, a weak solution of sugars and salts
• chloroplasts - where photosynthesis occurs and contains chlorophyll which absorbs light for photosynthesis
• bacteria are prokaryotes
• bacterial cells don't have a true nucleus, instead they have a singular strand of DNA that floats in the cytoplasm
• bacterial cells may also contain plasmids which are one or more small rings of DNA
• Bacteria don‘t have chloroplasts or mitochondria
• light microscopes - use light to form an image of the specimen allowing us to see individual cells and larger sub cellular structures
• electron microscope - uses electrons instead of light and have a higher magnification and resolution than light microscopes
• magnification= image size / real size
• cell differentiation - the process by which a cell changes to become specialised for its job
• Chromosomes - coiled up lengths of DNA molecules, which carry genes, found in the nucleus and are in pairs in body cells
• cell cycle - a series of stages that a cell goes through to divide and produce two new cells
• before a cell divides it does 3 things

  1. Grows in size
  2. increases the amount of subcellular structures
  3. duplicates its DNA
• in the cell cycle, more time is taken for growth and DNA replication than mitosis
• mitosis - the process of cell division that results in two genetically identical daughter cells
• mitosis:

  1. the cell’s DNA is doubled and there are 2 copies of each chromosome
  2. the chromosomes line up in the middle and are then pulled apart to each end of the cell
  3. the cytoplasms and cell membranes divide
  4. two genetically identical daughter cells are formed
• Mitosis allows multicellular organisms to grow or replace cells that have been damaged
• sperm cell: specialised for reproduction, has a long tail and a streamlined head for swimming to the egg
• nerve cell - specialised for rapid signalling, long to cover a large distance, and branched to form a network of connections
• xylem cells- specialised for transporting substances, made of dead cells and are hollow
• phloem cells- specialised for transporting substances, have fewer subcellular structures
• muscle cells- specialised for contraction, long so there’s space to contract and lots of mitochondria for energy
• root hair cell - specialised for absorbing water and minerals, large surface area
• stem cells - undifferentiated cells that can divide to produce more stem cells and can then differentiate into many other cell types
• adult bone marrow stem cells can differentiate into many types of cell like blood cells
• human embryo can differentiate into any kind of human cell
• plant meristem can differentiate into any kind of plant cell
• stem cell uses in medicine:

  1. could produce nerve cells to treat paralysis
  2. could produce insulin producing cells for diabetes type 1
  3. therapeutic cloning- embryo could be made with same genes as patient and stem cells used from the embryo won’t be rejected by patient
• stem cell uses in plants:

  1. produce clones of whole plants quick and cheap e.g. to grow more plants of a rare species or desired features
• risk of stem cells - can get a virus in the lab and spread it to the patient and other people
• diffusion - the spreading out of particles from an area of high concentration to an area of low concentration through a partially permeable membrane