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)