Animal & Plant Cells

Cell micrograph practice: https://quizlet.com/au/561328048/organelle-micrographs-flash-cards/?i=5hlgmi&x=1jqt

The cell - the unit of life:

• the basic structural and functional unit of all known living organisms

• organisms can be classified as unicellular (eg bacteria) or multicellular (eg animal)

• humans contain about 10 trillion cells

• most plant and animal cells are between 1 and 100 micrometers (μm) and are only visible under a microscope

Cell structures: common to plant and animal cells

1. Cell Membrane - a cell’s protective coat

   • the outer lining of the cell is called the plasma membrane

   • it is a selective barrier (semi-permeable)

   • double layered

2. Cytoskeleton - a cell’s skeleton

   • structure to help cells maintain their shape and internal organization

   • provides mechanical support that enables cells to carry out essential functions like division and movement

   • acts to organize and maintain the cell’s shape

   • anchors organelles in place

   • moves parts of the cell in growth and motility

3. Cytoplasm - A cell’s inner space

   • large fluid-filled space called the cytoplasm

   • contains dissolved nutrients

   • helps break down waste products

   • moves material around the cell

Cell Organelles: common to plant and animal cells

1. Nucleus - the cell’s brain

   • houses the cell’s DNA

   • can be thought of as the “brain” of the cell - controls all cell activities with genetic information

   • surrounded by a membrane called the nuclear envelope/membrane

   • within is a dark spot called the nucleolus

   • surrounding the nucleolus is the DNA, which when viewed under the microscope is called chromatin (genetic material)

   • roughly spherical, often in the centre of the cell

2. Endoplasmic Reticulum (ER) - the cell’s subway system

   • organelle that forms an interconnected network

   • classified into two types:

     • rough endoplasmic reticulum (RER)

     • smooth endoplasmic reticulum (SER)

   • the RER is studded with ribosomes

   • the SER is a smooth network without the ribosomes

   • 3d network of branching tubes and pockets (fluid filled)

   • extends through cytoplasm from nuclear membrane to cell membrane

3. Ribosome - the protein production machine

   • makes the 1000s of different proteins a cell needs to make

   • a larger number of ribosomes (sometimes 100s or 1000s) can be found throughout a cell

   • ribosomes are either bound to the ER or float in the cytoplasm

4. Mitochondria - the power generators

   • plays a critical role in generating energy in the cell

   • food that is eaten is broken down into simple molecules like glucose

   • these are delivered to the mitochondria where they are further broken down to produce energy for the cell

   • this energy is stored in a molecule called ATP (adenosine triphosphate)

   • contain enzymes that help to convert the stored energy into easily useable form (cellular respiration)

5. Golgi apparatus - the cell’s packaging plant

   • composed of stacks of structures known as cisternae (singular: cisterna)

   • packages proteins inside the cell before they are sent to their destination

   • collect and process materials to be removed from the cell

   • it is particularly important in the processing of proteins for secretion

     • eg. insulin, oxytocin, gastrin

6. Vesicle - the cell’s closet

   • function varies a lot according to the type of cell (eg. move molecules, secrete substances, digest materials, regulate pressure in the cell)

   • vesicles are bubbles within a cell

   • made of the same material as the cell membrane

   • range in size from very small to nearly the size of the entire cell

   • there are different kinds of vesicles; named after what is inside them

     • Vacuole - a vesicle that mostly contains water. Very large in plant cells

       • single layer of membrane enlosing fluid in a sack

     • Lysosome - a vesicle that contains special chemicals for breaking down substances

7. Centrioles

   • appear as short, cylindrical structures and always come in pairs

   • they are usually located near the nucleus

   • play an important role in mitosis; the process by which a cell reproduces

Organelles in plant cells only:

• Cell wall

  • rigid but porous wall surrounding plasma membrane (made of cellulose & lignin)

  • Provides support for the cell and protection from injury

  • Static/protected, gives structure to leaves/roots/stems

  • Fun facts: cellulose may hold together long after the plant dies (eg paper) & our digestive systems can’t digest cellulose

• Plastids

  • make and store needed compounds

  • Double membrane (one from original bacteria, one from cell)

  • Fun fact; plastics and mitochondria started as bacteria

  • Chloroplasts:

    • Most important plastids

    • Convert light energy/sunlight (CO2, H20, energy) into glucose and oxygen: photosynthesis; allows plant to make its own food but still relies on mitochondria to metabolize

    • Contain chlorophyll which gives leaves their green colour

• Central vacuole

  • Plant cells usually have one large vacuole that takes up most of the space in the cell

  • Become full of water, resulting turgor pressure keeps cells plump; keeps stem cells+ leaf firm

    • If water level drops, vacuoles lose turgid pressure & become soft/limpy/droopy until water is replaced

  • Export stuff the cell doesn’t need (waste)

  • In summary: water + turgor pressure to reinforce plant, contain/store water, export