Organization of the Organism (1.6-1.7)

Cell Structure and Organization

• %%All living organisms are made of cells%%
• %%Cell%%: The basic structural unit of life
• Although cells carry out different functions, animal and plant cells both have common features:
  • Cell membrane
  • Cytoplasm
  • Nucleus
  • Endoplasmic reticulum
  • Mitochondria
  • Ribosomes
  • Golgi Body
  • Lysosomes

Functions of Cellular structures

• Cell wall: makes up the outer most structure in the plant cell, is made of cellulose and is dead

  • Fully permeable meaning that the cell wall allows substances in and out of the cell
  • Gives the cell its shape and structure

• Cell membrane: located in the inner cell wall of a plant cell and in the outermost structure in an animal cell

  • Semi-permeable meaning that the cell membrane allows some/specific substances in and out of the cell

• Cytoplasm: jelly like fluid inside the cell made of water and dissolves substances eg. glucose & salt

  • Site of all metabolic (chemical) reactions

• Nucleus: Contains genetic material of the cell in chromosomes which controls cell functions & the center of the cell

  • Determines quality and quantity of proteins made by the cell

• Chloroplasts: Site of photosynthesis and contains a green pigment (chlorophyll)

  • Chlorophyl absorbs light energy and converts it into chemical energy by photosynthesis

  @@6H2O + 6CO2 → C6H12O6 + O6@@

• Mitochondria: Made up of a double membrane: inner and outer

  • Inner has many folding to increase the surface area for enzyme reactions
  • Site of aerobic respiration and release energy
  • Nicknamed the “Powerhouse” of the cell

• Rough of Endoplasmic Reticulum (ER): Membranous outgrowth of outer nuclear membranes and has ribosomes attached to its surface

  • Site of synthesis and transport of protein

• Ribosome: The smallest cell of organelles present in the cytoplasm

  • Either free or attached to rough ER
  • Site of protein synthesis

• Vacuole: While large and permanent, it is centrally located in a plant cell but is small and temporary in animal cells.

  • Contains cell sap which is a solution of nutrients and salts
  • Provides turgor pressure to the plant cell and helps maintain its shape

• Vesicle: Sac like structures containing secretory substances eg. enzymes in the cytoplasm

Specialized Cells

• Large organisms are multicellular
• Different types of cells have particular structures to help them carry out specific functions, and so they become %%specialized%%

Root Hair Cells

• Absorb nutrients from soil by osmosis, absorbs minerals by active uptake/transport, and fixes the plant in the soil

• Adaptations:

  • Have finger like outgrowth to @@increase the surface area for more absorption@@
  • Have extended vacuole and cytoplasm for @@easier absorption@@
  • Have more mitochondria to provide energy for @@active uptake/transport@@

  

Xylem Vessels

• They are found in vascular bundles, transporting water and minerals from the roots to the stem and leaves

• Provide mechanical support to the stem and leaves

• Adaptations:

  • Do not have a nucleus or cytoplasm to @@make space for bulk transport of water and minerals@@

  • Cells are dead and hollow and connected from end to end to @@form a long continuous tube@@

  • Cell wall is strengthened with lignin (hard substance) which @@gives mechanical support@@

    

Specialized Animal Cells

Red Blood Cells

• Transport oxygen from lungs to the rest of the body as well as transport CO2 from the body to the lungs

• Adaptations:

  • Have red pigment (hemoglobin) which @@binds with oxygen to allow transport@@
  • Don’t have a nucleus because of its biconcave shape, but their shape enables the cells’ increased surface area to @@carry more oxygen@@
  • Are spongy/flexible to squeeze into capillaries

  

Ciliated Epithelial Cells

• Goblet cells secrete mucus which @@trap the dust particles from the inhaled air@@

• Cilia of the cells beat and push the trapped dust and air towards the throat (outside)

  

Muscle Cells

• Contracts and relaxes which brings about movement; structures can be brought closer
• Adaptations:
  • Made of myofibrils which have the ability to contract and relax
  • Have protein fiber which can @@shorten the cell when energy is present@@

Nerve Cells

• Sensory Nerve Cell: conducts message from sense organ to the central nervous system

• Motor Nerve Cell: carries message from central nervous system to the effector

• Adaptations

  • Have extensions and branches so that it @@communicates with other nerve cells and glands@@
  • The Axon (extension of the cytoplasm away from cell body to carry impulse long distances) is covered with fatty sheath which @@insulates the cell and speeds up the nerve impulse@@

  

Egg Cells

• Female Gamete: responsible for reproduction in females

• Adaptations:

  • A lot of cytoplasm that contains a lot of nutrients for the @@growth of the early embryo@@
  • Haploid nucleus contains @@genetic material for fertilizations@@
  • Cell membrane @@modifies after fertilization so that only one sperm cell can penetrate@@

  

Sperm Cells

• Male Gamete: responsible for reproduction in males

• Adaptations:

  • Head contains haploid nucleus
  • @@Acrosome in head contains digestive enzymes to breakdown jelly coat around egg cell so sperm can penetrate egg cell@@
  • Many mitochondria to provide energy so sperm can ==travel long distances==
  • Flagellum allows sperm to travel

  

Levels of Organization

• Cell: Basic structural and functional unit of life

• Tissue: A group of identical cells which work together to perform a specific function

• Organ: Many tissues which work together to perform a specific function

• Organism: A group of organ systems which coordinate with each other to create an effective functioning of the body

• %%Cell → Tissue→ Organ → Organ System → Organism%%

  

Size of Specimens

• Size of a structure or an organism

• Magnification = Measured length / Actual length

  • Magnification has no units so is represented as eg. x100
  • The image size is usually given in centimeters (cm) or millimeters (mm) so make sure to @@convert both the actual size and image size units to be the same to get the correct magnification@@
  • 1cm = 10mm
  • 1mm = 1000μm (micrometer)