Introduction to the Cell · Introduction to the Cell • An adult human body has approx. 75...
Transcript of Introduction to the Cell · Introduction to the Cell • An adult human body has approx. 75...
Introduction Introduction Introduction Introduction
to the Cellto the Cellto the Cellto the Cell
• An adult human body has approx. 75 TRILLION cells!
• Cells in different tissues vary considerably in size and shape (and functions)
• We will focus on a “typical” cell
(unspecialized)
NUCLEUS
• membrane-bound organelle that contains most of the cell’s DNA– visible with light microscope– visible with light microscope
– enclosed by a nuclear envelope
– contains all of the information for cell to function
NUCLEAR ENVELOPE
• double membrane which encloses the nucleus– lipid bilayer membrane w/specific proteinsw/specific proteins
– is perforated by pores which regulate molecular traffic into and out of the nucleus
CHROMATIN• complex of DNA and proteins which make up chromosomes
CHROMOSOMES
• compacted, coiled up chromatin;
• long threadlike structures composed of chromatin and composed of chromatin and found in nucleus;
• visible under microscope;
• form as a cell prepares to divide
• human cells have: 46 (23 pairs)
NUCLEOLUS
• spherical region in the nucleus– visible when cell is NOT dividing– visible when cell is NOT dividing
– where ribosomes form
RIBOSOMES:• the sites of protein synthesis
– made in the nucleolus
– cells with high rates of protein
synthesis have large numbers of
nucleoli & ribosomes (e.g. human nucleoli & ribosomes (e.g. human
liver cells have millions)
– may be attached to the ER or
scattered throughout cytoplasm
ENDOPLASMIC RETICULUM (ER):
• extensive network of tubules and sacs
• may be “rough” (ribosomes) or “smooth” (no ribosomes)
• transports molecules within cell• transports molecules within cell
Smooth ER:
• synthesizes lipids, phospholipids,
steroids
• participates in carbohydrate • participates in carbohydrate
metabolism
• detoxifies drugs and
poisons
Rough ER:
• manufactures secretory proteins and
membranes
GOLGI APPARATUS:
• organelle made of stacked, flattened
membrane sacs
• finishes, sorts and ships many cell products• finishes, sorts and ships many cell products
• vesicles arrive from the ER and fuse with the Golgi membrane
LYSOSOMES• the “garbage disposals of the cell”
• contain powerful enzymes that break down nutrients or foreign particles
• recycle the cell’s own organic material;
• destroy cells• destroy cells
VESICLES / VACUOLES:
• membrane-bound sacs formed by the inward folding of the cell membrane
• contain liquid or solid material
• Golgi apparatus and ER also form vesicles
PEROXISOMES:• contain special
enzymes for specific
metabolic pathways,
including:
-synthesis of bile acids -synthesis of bile acids
(used to digest fats);
-detoxifying hydrogen
peroxide and alcohol;
MITOCHONDRIA:
• sites of cellular respiration (energy
from nutrients is released and from nutrients is released and
converted into ATP!
• the # in cells varies and is related to
the cell’s metabolic activity
• inner membrane is
convoluted and
contains enzymes
involved in cellular
respiration
• inner membranes many • inner membranes many
infoldings are called
cristae; they increase
the surface area for
cellular respiration
reactions to occurMitochondria in a human liver cell
MICROTUBULES & MICROFILAMENTS
• make up the cytoskeleton
• network of fibers throughout cytoplasmcytoplasm
• structural support to cell; maintain shape
• involved in cell motility (movement)
Microtubules:• straight, hollow rods made of protein
• can serve as “tracks” to guide organelle
movement;
YellowYellow: nucleus: nucleus
GreenGreen: microfilaments throughout cytoplasm: microfilaments throughout cytoplasm
movement;
• involved in separation of chromosomes in
cell division; make up CENTRIOLES
• responsible for beating of flagella & cilia
Cilia and Flagella:
► CILIA: fringe the surfaces of some epithelial (lining) cells
-tiny, hairlike structures
-beat in succession producing a wave of motion (e.g. sweep dust and of motion (e.g. sweep dust and debris out of respiratory tubes)
► FLAGELLA: longer; usually single structures
-move in wavelike motion to propel a cell