intro to cells
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Intro to Cells. Eukaryotes vs Prokaryotes Plasma Membrane. Two Basic Cell Types. All cells contain organelles Small, specialized structures Has a specific function in the cell Prokaryotes Do not contain any membrane-bound organelles Most unicellular organisms Example: bacteria - PowerPoint PPT PresentationTRANSCRIPT
INTRO TO CELLSEukaryotes vs Prokaryotes
Plasma Membrane
Two Basic Cell Types All cells contain organelles
Small, specialized structures Has a specific function in the cell
Prokaryotes Do not contain any membrane-bound organelles Most unicellular organisms Example: bacteria
Eukaryotes Contain membrane-bound organelles Most multicellular oranisms Example: humans Note: amoebas, algae and yeast are unicellular but
eukaryotes
Prokaryotes vs. Eukaryotes
Eukaryotic cells are generally 1- 100 time bigger than prokaryotes
CELL ORGANELLES
Animal Cell
Cell Organelles Organelle= “little
organ” Found only inside
eukaryotic cells Everything in a
cell except the nucleus is cytoplasm Clear, gelatinous
fluid inside the cell
Plasma Membrane Boundary of the cell Made of a phospholipid bilayer
Cytoskeleton Acts as skeleton
and muscle Provides shape
and structure Helps move
organelles around the cell
Made of three types of filaments
Nucleus Control center of the
cell Contains chromatin,
strands of genetic material (DNA) that condense to make chromosomes
Surrounded by a double membrane
Usually the easiest organelle to see under a microscope
Usually one per cell
Nucleolus Inside the nucleus Makes ribosomes
Ribosome Site of protein
synthesis Found attached to
rough ER or floating free in cytoplasm
Produced in a part of the nucleus called the nucleolus
That looks familiar…what is a polypeptide?
Endoplasmic Reticulum A.k.a. “ER” Connected to
nuclear membrane
Highway of the cell
Rough ER: studded with ribosomes; it makes proteins
Smooth ER: no ribosomes; it makes lipids
Golgi Apparatus Looks like a stack
of plates Stores, modifies
and packages proteins
Molecules transported to and from the Golgi by means of vesicles
Lysosomes Garbage disposal
of the cell Contain digestive
enzymes that break down wastes
Which organelles do lysosomes work
with?
Mitochondria “Powerhouse of
the cell” Cellular
respiration occurs here to release energy for the cell to use
Bound by a double membrane
Has its own strand of DNA
Which type of cell do you think has the most mitochondria present?
Cell Wall Found in plant
and bacterial cells Rigid, protective
barrier Located outside of
the cell membrane
Made of cellulose (fiber)
Chloroplast Found only in
plant cells Contains the
green pigment chlorophyll
Site of food (glucose) production
Bound by a double membrane
Vacuoles Large central
vacuole usually in plant cells
Many smaller vacuoles in animal cells
Storage container for water, food, enzymes, wastes, pigments, etc.
Centriole Aids in cell division Usually found only in
animal cells Made of microtubules
Where else have we talked about
microtubules?
Quick Review Which organelle is the control center of the cell?
Nucleus Which organelle holds the cell together?
Cell membrane Which organelles are not found in animal cells?
Cell wall, central vacuole, chloroplasts Which organelle helps plant cells make food?
Chloroplasts What does E.R. stand for?
Endoplasmic reticulum
A MORE IN DEPTH LOOK AT THE PLASMA MEMBRANE
Plasma Membrane Flexible boundary between the cell and
its environment Allows a steady supply of nutrients (ie:
glucose, amino acids, lipids) to come into the cell no matter what the external conditions are
Plasma Membrane maintains homeostasis
Too much of any nutrient can be harmful to the cell If levels become too high the excess is
removed through the plasma membrane Maintains cells balance (homeostasis)
The Plasma Membrane is Selectively Permeable
Selective permeability: a process in which a membrane allows some molecules to pass through while keeping others out Similar to a window screen (lets fresh air in
but keeps most insects out) Water is allowed to freely enter but other
particles such as sodium and calcium ions must be allowed into the cell only at certain times
Structure of Plasma Membrane Recall: Lipids are
large molecules composed of Glycerol + 3 fatty
acids If a phosphate group
replaces a fatty acid then a phospholipid is formed. Glycerol + 2 fatty
acids + phosphate group
Polar Head
(includes
phosphate groupNonpolar
tail (fatty acids)
Phospolipid Molecule
Plasma membrane is composed of a phospholipid bilayer
Has 2 layers of phospholipids back to back
Create a Drawing Drawing must be similar to drawing on
page 177 and must include: A title Labeled parts Colored On back of drawing:
Facts about the phospholipid bilayer All bold faced words (include definitions) Additional Facts should include information you
think is important? (at least 8 facts in addition to bold faced words)
Important Facts 2 fatty acid tails – nonpolar (hydrophobic)
Avoids water Head containing phosphate group – polar
(hydrophilic) Allows the cell membrane to interact with its
watery environment Water molecules will not easily move
through the barrieer because they are stopped by the water insoluble layer of fatty acid tails.
More important facts… Fluid Mosaic Model
Model of plasma membrane – describes the plasma membrane as a phospholipid bilayer with embedded proteins
Phospholipids move within the membrane just like water molecules move with currents in a lake
Proteins also move (like boats with their decks above water and hulls below)
Proteins create a “mosaic” or pattern
More facts… Other components of the membrane:
Cholesterol Helps to stabilize the phospholipids by
preventing fatty acid tails from sticking together Transport proteins
Span the entire membrane Help form the selectively permeable membrane
that regulates which molecules enter and which molecules leave
Move needed substances and waste through the plasma membrane