Cell specialisation & organisation

• cell specialisation - cell with certain features that allow them to carry out a particular function
• tissue - a collection of differentiated similar cells that work together to carry out a particular functions
• organ - group of tissues that are adapted to carry out a particular function
• organ systems - a group of organs working together to carry out a particular function
• examples of cells:

  • Erythrocytes
  • Neutrophils
  • Sperm cells
  • Palisade cells
  • Root hair cell
  • Guard cell
• examples of tissues:

  • Epithelium
  • Cartilage
  • Muscle
  • Xylem
  • Phloem
  • Epidermis
• Examples of organs:

  • heart
  • lungs
  • stomach
  • pancreas
  • leaf
• examples of organ systems:

  • respiratory system
  • cardiovascular system
  • digestive system
• Squamous epithelium: animal tissue

  • provides a one cell thick lining for many organs including the lungs
  • gases can diffuse quickly
  • made up of a single layer of squamous epithelium cells
• ciliated epithelium: animal tissue

  • lines organs such as the trachea that sweeps mucus away from the lungs
  • tissue is made up of ciliated epithelium cells and goblet cells
  • goblet cell release mucus to trap pathogens
  • cilia move in rhythmic manner
• cartilage: animal tissue

  • connective tissue
  • prevents bones rubbing
  • contains fibres of elastin and collagen
  • composed of chondrocyte cells embedded in an extracellular matrix
• muscle: animal tissue

  • made up of muscle fibres
  • these fibres contract and relax in order to create movement

  types of muscle tissue:

  cardiac

  skeletal

  smooth
• xylem: plant tissues

  • responsible for the transport of water and minerals within plants
  • made of dead xylem vessel cells which have no end walls or organisms
  • walls strengthened with a waterproof material called lignin
• Phloem: plant tissue

  • responsible for the transport of sugars and amino acids within plants
  • made of up sieve tube elements and companion cells
  • sieve tubes separated by sieve plates
• Epidermis: plant tissue

  • single layer of closely packed cells covering the surface of plants
  • covered by a waxy waterproof cuticle to reduce water loss
  • stomata are present in epidermis
• erythrocytes: animal cell

  • red blood cells, transport oxygen around the body
  • flattened biconcave shape, which increases their SA:V
  • no nucleus or organelles, increases space for haemoglobin
  • flexible, can squeeze through narrow capillaries
• neutrophils: animal cell

  • white blood cell, defends against pathogens
  • multi-lobed nucleus, allows cell to deform, so they can squeeze through small gaps
  • flexible cell membrane, allows cell to engulf pathogens
  • contains lysosomes that contains digestive enzymes which break down engulfed pathogens
• sperm cells: animal cell

  • male gametes
  • deliver genetic information to female gamete, the ovum
  • flagellum (tail), allows cell to swim to the egg
  • mitochondria, supply energy for movement
  • acrosome on the head contain digestive enzymes, which digest the protective layers around the ovum leading to fertilisation
• Palisade cells: animal cells

  • carry out photosynthesis in the mesophyll
  • chlorophyll, absorb light for photosynthesis
  • thin cell walls, increasing the rate of carbon dioxide diffusion
  • tall thin shape, so palisade cells can closely pack together
  • large vacuole to maintain turgor pressure
• root hair cell: plant cell

  • absorb water and mineral ions from the soil
  • root hair structures, increase surface area
  • thin, permeable cell wall allows entry of water and minerals
  • mitochondria, provide energy for active transport
• guard cell: plant cell

  • control the opening and closing of the stomata, allow carbon dioxide in and reduce water loss
  • come in pairs to form a small gap between stoma
  • change shape when light is present, guard cell absorb water to become turgid
  • change shape when lose water, guard cells shrink to prevent water loss
  • thin outer walls and thick inner walls, allows the cells to bend when they are turgid to open stomata
• stem cells - genetically identical unspecialised cells that carry a full set of genetic information, and are capable of dividing to become genetically identical new cells, which can then differentiate to become specialised into any of the different cell types found in organisms.
• Stems cell features:

  • can divide by mitosis to produce more undifferentiated cells
  • can differentiate into specialised cells
• types of stem cells:

  • potency
  • totipotent
  • pluripotent
  • multipotent
• potency - ability to differentiate into different cell types
• totipotent - can differentiate into any type of cell and go on to form who organisms
• pluripotent - can differentiate into most cell types, but cannot form whole organisms
• multipotent - these can differentiate into a few different cell types
• embryonic stem cells:

  • Found in the early stages of embryo development where they can differentiate into cells to form a foetus.
  • In the first few divisions of the embryo, the stem cells are totipotent.
  • After about 7 days, blastocyst stage these stem cells become pluripotent.
• cord stem cells:

  • obtained from the umbilical cord after birth
  • easy to collect
  • can be stored for a time for use in later life
  • multi-potent
• adult stem cells:

  • Found in some adult tissues where they can replace faulty cells.
  • Stem cells are multi-potent or unipotent. 
  • Stem cells from the bone marrow replace worn out erythrocytes,(red blood cells) and neutrophils (white blood cells). 
• Plant stem cells:

  • Found in the meristematic tissue or meristems at the tips of the shoots and roots of plants.
  • Stem cells are pluripotent.
  • Meristematic tissue is also found between phloem and xylem tissues in an area known as the vascular cambium.
  • These stem cells differentiate into cells of the xylem and phloem.  
• undifferentiated = not adapted to any particular function
• stem cells division problem:

  • if there is an uncontrolled division then they form masses of cells called tumours, which can lead to development of cancer
• stem cells can provide treatment from diseases:

  • parkinsons disease
  • alzheimers disease
  • type 1 diabetes
  • heart disease
• stems cells can be used for:

  • testing new drugs
  • studying development of organisms
  • identify causes of disorder