chapter 2 cells. comparing cells cells differ in size and shape depending on their function –ex:...
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Chapter 2
Cells
Comparing Cells
• Cells differ in size and shape depending on their function– Ex: nerve cell needs to
communicate between places, so it is a long cell
– Ex: a muscle cell can contract and change it’s shape
• Two cell types:• Prokaryotic – lack membrane-
bound internal structures• Eukayrotic – contain
membrane-bound internal structures
Cell Organization
Cell wall– Tough, rigid outer coverings that
protect the cell and give it shape– Made of cellulose– Only in plants, algae, fungi and
most bacteria– “frame of a house”
• Cell Membrane– A protective layer around all cells– Inside the cell wall, if it is present– Allows food and gasses into the
cell and waste products out of the cell
– “the bouncer”
Cell Structures
• Cytoplasm– A gelatin-like substance
inside the cell membrane– Medium for things to move
about in the cell
• Cytoskeleton– Scaffolding-like structure in
cytoplasm which helps cell keep its shape
• Organelles– Membrane bound structures
inside eukaryotic cells that helps the cell perform life processes
Cell Structures
• Nucleus– Organelle that directs
all cell activities – Contains instructions
for everything a cell does (within the DNA)
– “foreperson”
Cell Structures• Chloroplasts
– Organelles in plants and a few bacteria that help the organism make food
– Photosynthesis occurs here
• Mitochondria – Organelles in all eukaryotes
that release the energy from food and turn it into something the organism can use
– “powerhouse”
Cell Structures
• Ribosomes– Organelles that make proteins– Produced in the nucleus
• Endoplasmic Reticulum (ER)– Series of folded membranes from
the nucleus to the cell membrane– Moves materials around in a cell
• Two types of ER– Rough – ribosomes are attached– Smooth – no ribosomes attached
• Material movement and lipid processing
Cell Structures
• Golgi Bodies– Sort proteins and other cellular
substances and package them into membrane-bound structures called vesicles
– “post office”
• Vacuoles– Organelles that serve as
temporary storage for materials• Can be water, waste products,
food, etc.
– Vacuoles make up most of the volume of plant cells
Cell Structures
• Lysosomes– Organelles that
contain digestive chemicals that help break down food molecules, cell wastes, and worn-out cell parts
– “recycler”
From Cell to Organism
• Cell• Tissues
– Groups of similar cells working together on one job
• Ex: muscle tissue, nervous tissue
• Organ– Different types of tissues
working together • Ex: muscle, brain
From Cell to Organism
• Organ System– A group of organs working
together on a particular function• Ex: muscular system, nervous
system
• Organism – All of organ systems working
together to create a particular organism
Review Questions
1. Explain the important role of the nucleus in the life of a cell.
2. Compare and contrast the energy processing organelles.
3. Why are digestive enzymes in a cell enclosed in a membrane-bound organelle?
4. How are cells, tissues, organs and organ systems related?
5. How is the cell of a one-celled organism different from the cells in many-celled organisms?
6. What are some differences between plant and animal cell?
7. List 3 organelles and give their functions.
Early Microscopes
• Dutch reading glass maker put two lenses at ends of a tube (1500s)– Larger image
• Antonie van Leeuwenhoek (Dutch fabric merchant)– First simple microscope (p.
50 in book)
– Could magnify up to 270 times
Modern Microscopes
• Use lenses to bend light• A simple microscope has one lens
while a compound microscope (what we have here) has mulitple lenses – Ex: one lens at 10x – 10 times bigger
• Two lenses at 10x – 100 times bigger
• Stereomicroscopes have two eyepieces, which create a three-dimensional image
Electron Microscopes• Use a magnetic field inside a
vacuum to bend electronic beams– Scanning Electron
Microscope (SEM) bounce electrons off the sample to create a 3-D image
– Transmission Electron Microscope (TEM) send electrons through a sample to see internally
• Either way, electons then end up on a screen to produce an image (kind of like older TVs)
Cell Theory
• 1665, Robert Hooke looked at cork under a microscope– Made of little boxes he
named cells
• 1830s, Matthias Schleiden studied plant parts– Concluded all plants
are made of cells
Cell Theory
• Theodor Schwann looked at animal cells– Concluded all animals are
made up of cells
• Rudolf Virchow– Said that cells come from other
cells that already exist
Cell Theory
• All organisms are made up of one or more cells
• The cell is the basic unit of organization in organisms
• All cells come from pre-existing cells
Review Questions
1. Explain why the invention of the microscope was important in the study of cells.
2. What is stated in the cell theory?3. What is the difference between a simple
microscope and a compound microscope?4. What was Virchow’s contribution to the cell
theory?5. How do electron microscopes work?6. Why would it be better to look at living cells
rather than dead cells?
Cell Processes
• Passive Transport – the movement of substances through a cell membrane without the use of energy– Diffusion or Osmosis
• Active Transport – the movement of substances through the cell membrane using energy
• Endocytosis & Exocytosis – vesicles transport large materials into (endocytosis) and out of (exocytosis) the cell
Cell Processes• Photosynthesis
– The process plants and other organisms use to convert sunlight energy into chemical energy or sugars to be used as food
• Respiration– The process in which chemical
reactions break down food molecules into simpler substances and release stored energy
• Fermentation– Cells that do not have enough
oxygen for respiration use this process to release some of the stored energy in glucose molecules
Cell Processes
• Cell Division – process where one cell splits into two cells
• Mitosis – process in which the nucleus divides to form two identical nuclei– Four stages: Prophase, Metaphase, Anaphase, Telophase– Happens during growth of organism or during asexual
reproduction
• Meiosis – process in which the nucleus divides to form cells with half the genetic material of the original– Eight Stages: Prophase I, Metaphase I, Anaphase I, Telophase
I, Prophase II, Metaphase II, Anaphase II, Telophase II– Happens when an organism produces gametes (sex cells) for
sexual reproduction
Review Questions
1. What is active transport?
2. What are the two main types of passive transport?
3. How do cells get large materials out?
4. What is photosynthesis?
5. What is respiration?
6. What is mitosis and when does it happen?
7. What is meiosis and when does it happen?
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