cell structure and division

• eukaryotic cells are complex and include plant and animal cells but prokaryotic cells are smaller and simpler and example is bacteria
• animal cells contain: nucleus, cytoplasm, cell membrane, mitochondria, ribosomes, lysosome, nuclear envelope, golgi apparatus , smooth endoplasmic reticulum, rough endoplasmic reticulum and nucleolus
• plant cells contain: nucleus, cytoplasm, cell membrane, mitochondria, ribosomes, lysosome, nuclear envelope, golgi apparatus , smooth endoplasmic reticulum, rough endoplasmic reticulum, nucleolus as well as chloroplast, plasmodesma, vacuole and cell wall
• fungal cells are similar to plant cells but don't have chloroplasts and their cell wall is made out of chitin
• cell surface membrane

  description: it is mainly made of lipids and proteins

  function: regulate the movement of substances in and out of the cell and has receptor molecules which allow it to respond to chemicals
• nucleus

  description: surrounded by a nuclear envelope which contains many pores. it also contains chromosomes which are protein bound linear DNA and a nucleolus

  function: control cells activities. DNA contains instructions to make proteins and the pores allow substances to move between the nucleus and the cytoplasm and the nucleolus makes ribosomes
• mitochondrion

  description: usually oval sized, have a double membrane and the inner membrane is folded to create cristae and the inside is the matrix which contains enzymes involved in respiration

  function: the site of aerobic respiration where ATP is produced and they are found in large numbers of cells that are very active and require a lot if energy
• chloroplast

  description: a small flattened structure found in plant and algal cells and is surrounded by double membrane and has thylakoid membranes and these are stacked up to form grana and the grana are linked together by lamellae

  function: site of photosynthesis
• golgi apparatus

  description: a group of fluid filled membrane bound flattened sacs and vesicles are often seen at the edges of the sacs

  function: it processes and packages new lipids and proteins and also makes lysosomes
• golgi vesicles

  description: a small fluid filled sac in the cytoplasm and is surrounded by a membrane and produced by the golgi apparatus

  function: stores lipids and proteins made by the golgi apparatus and transports them out of the cell
• lysosome

  description: a round organelle surrounded by a membrane with no clear internal structure

  function: contains hydrolytic enzymes and these are separate from the cytoplasm and can be used to digest invading cells or to break down worn out components of cells
• ribosome

  description: a very small organelle that either floats free in the cytoplasm or is attached to the rough endoplasmic reticulum. it is made up of proteins and RNA and is not surrounded by a membrane

  function: the site where proteins are made
• rough endoplasmic reticulum

  description: a system of membranes enclosing a fluid filled space and the surface is covered with ribosomes

  function: folds and processes proteins that have been made at the ribosomes
• smooth endoplasmic reticulum

  description: similar to rough endoplasmic reticulum but with no ribosomes

  function: synthesises and processes lipids
• cell wall

  description: a rigid structure that surrounds cells in plants, algae and fungi. in plants and algae it is made up of cellulose but if fungi it is made up of chitin

  function: supports the cells and prevent them from changing shape
• cell vacuole

  description: a membrane bound organelle that is found in the cytoplasm of plant cells. it contains cell sap and the membrane surrounding it is called the tonoplast

  function: helps to maintain pressure inside the cell and keep the cell rigid this stops the plant from wilting. and is also involved in the isolation of unwanted chemicals inside the cell
• epithelial cells in the small intestine are specialised to absorb food efficiently

  • the walls of the small intestine have lots of villi and these increase the surface area for absorption
  • the epithelial cells on the surface of the villi have folds in the cell-surface membranes called microvilli and these help to increase the surface as well
  • have lots of mitochondria to provide energy for the transport of digested food molecules into the cell
• specialised cells are grouped together to form tissues
• a tissue is a group of cells working together to perform a particular function
• different tissues join together to form organs and different organs make up the organ system
• example of specialised cells to a organ system

  • epithelial cells make up the epithelial tissue
  • the epithelial tissue, muscular tissue and glandular tissue all work together to form the stomach which is an organ
  • the stomach is apart of the digestive system which is an organ system that is made up of all the organs involved in the digestion and absorption of food
• prokaryotic cells are smaller and a example cell is bacteria
• prokaryotic cell

  plasma membrane - mainly made up of lipids and proteins and controls the movement of substances in and out of the cell

  cell wall - supports and prevents it from changing shape and is made from murein which is a glycoprotein

  plasmids - small loops of DNA and contain genes for things like antibiotic resistance but they are not always present

  flagellum - it is a long hair like structure that allows for the cell to move not all prokaryotes have one

  • the DNA floats around in the cytoplasm and is known as circular DNA