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Cell Review
Cells
The Cell Theory
• All living things are made of one or more
CELLS.
• Cells are the basic unit of structure and
function in an organism.
• New cells are produced from existing cells.
2 types of cells
• Prokaryotes
– Cells without a nucleus
or organelles
surrounded by
membranes
• Eukaryotes
– Cells with a nucleus and
organelles surrounded
by membranes.
Prokaryotes
• Single celled organism
• Has DNA that is circular floating all around in
the cytoplasm
• Only has ribosomes and no other membrane
bound organelles
• Most common = bacteria
– Some can make their own food, most get food
from other sources
Eukaryotes
• There can be singled celled eukaryotes as well
as multicellular
• Highly organized
• More complex than prokaryotes
Cell membrane (plasma membrane)
• Made mainly of phospholipids (2 layers) and
proteins
Outside
of cell
Proteins
Carbohydrate
chains
Cell
membrane
Inside
of cell
(cytoplasm)
Protein
channel
Lipid bilayer
Cell membrane
made of:
• Phospholipids have
3 kinds of proteinshydrophobic tails made • channel-provides a path
of lipids and hydrophilic
for materials to move in
heads.
and out
• marker- used for
recognition
• receptor- receive signals
Cell membrane
• Acts as a boundary
• Controls what enters and leaves cell
• Fluid (fluid mosaic model)
– Molecules in cell membranes are constantly
moving and changing (ex. cholesterol and
carbohydrates)
Nucleus
• LARGEST organelle in animal cells
• Surrounded by nuclear envelope
• Contains nuclear pores = openings that allow
molecules to move in and out of nucleus
• Contains genetic material (DNA)
• Control center of the cell
Nucleolus
• Dark spot in nucleus
• Assembles RNA and also ribosomes
Cytoskeleton
• Helps cell maintain shape
• Help move organelles around
• Made of proteins
– Microfilaments
– Microtubules
Centrioles
• Made of microtubules
• Only seen in animal cells during cell division
• Function: Guide chromosomes during PMAT
Mitochondria
•
•
•
•
•
“Powerplant of cell”
Site of cellular respiration
Burns glucose to release energy
Stores energy as ATP
Surrounded by double membrane
– Inner membrane = cristae
Ribosomes
• Can be free in cytoplasm or attached to rough
ER
• Made of rRNA
• Function: assembles proteins
• Called the site of protein synthesis
Endoplasmic reticulum
(internal network of membranes)
• Rough ER
– Attached ribosomes
make proteins which are
modified and
transported to Golgi for
export
• Smooth ER
– Makes membrane lipids
(steroids)
– Regulates calcium in
muscles
– Breaks down toxins in
liver
Golgi Apparatus
• Looks like a “stack of pancakes”
• Made of membranes
• Modify, sort, and package substances from ER
for storage or export out of cell
Lysosomes
• Sac containing digestive
enzymes
• Digests food molecules
and unwanted cells/cell
parts
• Plays a role in apoptosis
“programed cell death”
– Cell suicide for the good
of the organism
Movement
• Pseudopodia = “false feet” help amoebas with
movement and eating (phagocytosis)
• Cilia = many and short
microtubules (little hairs)
– Move cells
– Move substances past cells
• Flagella = few and long
microtubules (like a tail)
– Move cells
What’s special about plant cells?
•
•
•
•
Cell wall
HUGE central vacuole
Chloroplasts
No centrioles!!
Cell wall
• Found outside the cell membrane
• Provides support and protection
• Made of Cellulose (carbohydrate) makes plant
sturdy
• Bacteria have cell walls made of peptidoglycan
instead
• Cell walls of fungi are made
of chitin
Vacuoles
• Storage space for: proteins, carbohydrates,
water, waste
• Contractile vacuoles control excess water in a
paramecium (homeostasis)
• Huge in plant cells, small animal cells, not in
bacteria
Chloroplast
• Surrounded by double membrane
• Thylakoids = membrane sacs inside
• Contains chlorophyll where photosynthesis
happens
• Found photosynthetic cells (plants, some
bacteria and protozoans)
Molecule Movement and Cells
• Passive Transport = does not require energy by
the cell
• Active transport = requires energy!
Passive transport
• No energy required
• Move due to gradient
– Differences in concentration, pressure, charge
• Move to equalize gradient (equilibrium)
– High concentration moves toward low
concentration
• 3 Types
– Diffusion, osmosis, facilitated diffusion
Diffusion
• Molecules move to equalize concentration
Osmosis
• Special form of diffusion
• Fluid flows from lower solute concentration
• Always involves movement of water
– Into cell
– Out of cell
Hypotonic = solutes in cell more than
outside, fluid will flow into cell
Isotonic = solutes equal inside and out
of cell
Hypertonic = solutes greater outside
cell, fluid will flow out of cell
Facilitated Diffusion
• Channels (are specific) help molecule or ions
enter or leave the cell
• Channels usually are transport proteins
Active transport
• Molecular movement
• Requires energy (against gradient)
• Example: sodium-potassium pump
Endocytosis
• Phagocytosis – cell
eating
• Pinocytosis – cell
drinking
Exocytosis
• Reverse of endocytosis
• Cell discharge material
Cellular reproduction
• 5 ways
– 1. Fission
– 2. Budding
– 3. Vegetative propagation
– 4. Mitosis
– 5. Meiosis
Binary Fission
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•
•
•
Prokaryotes (bacteria)
Asexual reproduction
Cell makes copy of DNA and grows in size
Membrane will divide and two new cells
formed
Budding
• Asexual reproduction
• Hydra bud to form new hydra
• Yeast cells undergo budding
Vegetative propagation
• Asexual reproduction in plants
• Runners will grow off from the parent plant
and root to form a new identical plant.