B1- cell biology

• plant and animal cells are eukaryotic
• bacterial cells are prokaryotic
• prokaryotic cells are much smaller in comparison to eukaryotic
• the genetic material of a bacteria cell is a single DNA loop. there may be one or more small rings of DNA called plasmids
• the nucleus controls the activities of the cell and contains the genetic material in the form of chromosomes
• the cytoplasm is a gel-like substance where most of the chemical reactions occur
• cytoplasm contains enzymes which control the chemical reactions
• cell membrane holds the cell together and controls what goes in and out
• 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
• chloroplasts are where photosynthesis occurs which makes food for the plant
• chloroplasts contain a green substance called chlorophyll
• chlorophyll absorbs the light needed for photosynthesis
• plant and algal cells have a cell wall made of cellulose, which strengthens the cell
• permanent vacuole contains cell sap- a weak solution of sugar and salts
• sperm cells are specialised for reproduction
• the function of a sperm is to fertilise and egg cell to form a zygote (get the male DNA to the female DNA)
• sperm cells have a long tail and streamlined head to help it swim to the egg
• sperm cells have lots of mitochondria to provide the energy needed for respiration
• sperm cell head contains enzymes to digest through the egg cell membrane
• nerve cells are specialised for rapid signalling
• the function of a nerve cell is to carry electrical signals from one part of the body to another
• nerve cells are long to cover more distance
• nerve cells have branched connections at their ends to connect to other nerve cells and form a network throughout the body
• muscle cells are specialised for contraction
• the function of muscle cells is to contract quickly
• muscle cells are long so that they have space to contract
• muscle cells contain lots of mitochondria to generate energy for contraction by respiration
• root hair cells are specialised for absorbing water and minerals
• root hair cells are on the surface of plant roots and hold the plants in place as they grow
• root hair cells have a large surface area for absorbing water and mineral ions from the soil
• xylem cells transport water from the roots to other parts of the plant
• phloem cells transport food substances (mainly dissolved sugars) from the leaves to the rest of the plant
• phloem and xylem cells form phloem and xylem tubes
• xylem and phloem cells are long and joined end to end
• xylem cells are hollow in the centre so water can flow through them
• phloem cells contain very few subcellular structures so that food substances can flow through them
• cell differentiation is important because it allows the cell to carry out specific functions (specialised for its job)
• as an organism develops, cells differentiate to form different types of cells