Cell notes Flashcards
Plasma membrane-
cell membrane
cell membrane Structure:
thin outer membrane. Called a lipid bilayer- double layer of lipids
Purpose:
cell membrane
Separates metabolic activities inside the cell from random events outside cell. Still allows materials in and out
Nucleus
membrane bound sac in eukaryotic cells that contains DNA
Nucleoid
region in prokaryotic cells that contains
DNA that is not enclosed in a membrane
Cytoplasm
Everything in between the plasma membrane and the region of DNA. Contains a semi-fluid matrix (called the cytosol) and
structural components with specific jobs (organelles)
Why can’t cells grow infinitely large?
surface to vol ratio
surface-to-volume ratio
if a cell expands in diameter during growth,
then its volume will increase faster than its surface area
why can’t a cell live if the cell gets too big and vol increases faster than surface area?
The inward flow of nutrients and outward flow of wastes
will not be fast enough to keep up with the metabolic activity of the cell, and it’ll be hard to move materials thru cytoplasm
compound light microscope structure
two or more sets of glass lenses bend waves of light
passing thru a specimen
compound light microscope ability
Views objects that are thin enough for light to
pass through them
electron microscope structure
Structure: use magnetic lenses to
bend and defract beams of electrons
Transmission electron microscope:
electrons pass through a
specimen and are used to make images of its internal details
Scanning electron microscope:
a beam of electrons pass back
and forth across a surface of a specimen with a thin metal coating
Two domains of prokaryotic cells:
Bacteria and Archaea
Size of prokaryotic cell
not much wider than a micrometer, no more than a few micrometers long
Cell wall permeability prokaryotic
permeable to dissolved substances
Flagella:
movable structure that helps move prokaryotic cells through
fluid habitats
characteristics cytoplasm–prokaryotic
contains many ribosomes, DNA is concentrated in a
nucleoid region, some have plasmids
plasmids
small circles of DNA (separate from main DNA)
advantages of partitioning the cell interior into many organelles:
Outer membrane encloses a microenvironment for cell
activities, allowing each organelle to do its own job. Specialized organelles interact, keeping a whole cell functioning as it should.
DNA in the nucleus
contains the instructions for encoding proteins
functions of nucleus DNA
- Prevents the DNA from getting
tangled with the cytoplasm, Can control what moves in and out of the nucleus from the cytoplasm
Nuclear envelope-
Consists of double membrane system in which two lipid
bilayers are pressed against each other
Nucleolus
produces ribosomes
ribosomes
get info from RNA about DNA and make proteins
Chromosomes stages
Chromatin + chromosomes
Chromatin
all of a cell’s DNA and its associated proteins
chromosomes
a specific section of a double-stranded DNA
molecule and its associated proteins
- Endomembrane System
ER, Golgi bodies, vesicles
- Endoplasmic reticulum:
Flattened channel that starts at nuclear envelope and folds back on its own repeatedly
Rough ER
Has many ribosomes attached to its
outer surface. Allows polypeptide chains that are produced by
ribosomes to enter where they can be modified by enzymes
where is rough ER abundant
Abundant in cells such as: pancreas, or any cells that make and secrete a lot of proteins
Smooth ER:
Ribosome free; Makes lipids that become part of cell membrane, helps
break down fatty acids and toxins
Golgi Bodies
Attaches sugar side chains to proteins and lipids received from ER. Package finished products into vesicles. Membrane channel folds back on itself (like stacked pancakes)
Vesicles
tiny sacs that bud from the ER, Golgi bodies, and plasma
membrane.
Lysosomes
vesicles that bud from Golgi bodies and take part in intracellular digestion. They store enzymes
Peroxisomes
hold enzymes that digest fatty acids, amino acids, and hydrogen peroxide
Mitochondria
where ATP is formed through aerobic respiration. has a double-membrane system, allowing for two separate compartments.
Where are mitochondria found?
eukaryotic cells
Mitochondria are like bacteria in that they-
1- Have their own DNA and divide on their own
2- Have ribosomes
Plastids
organelles that function in
photosynthesis or storage in plants
chloroplasts
plastid Function-photosynthesis
Oval or disk shaped
Two outer membranes enclose stroma
stroma
semifluid interior, contains the thylakoid
membrane
thylakoid membrane
membrane in stroma that is folded into
granum
granum
(plural, grana). flattened disks–folded shape of thylakoid membrane
Chlorophyll
most abundant
photosynthetic pigment. Chloroplasts are also like bacteria: have DNA, replicate
on their own, may have evolved by endosymbiosis
Chromoplasts
plastid–have no chlorophylls, have an abundance of
carotenoids
Amyloplasts
plastid–pigment free, store starches in plants
Central vacuole:
Stores fluid (amino acids, sugars, ions, toxic wastes) o During growth, it expands and increases pressure against the cell wall o Takes up 50 to 90 % of the cell’s interior
cell wall: eukaryotic
Cell wall:
Protects and physically supports the cell
Porous, allows water and solutes to easily move to and from the plasma membrane
primary cell wall
not every time. Composed of pectin, glue-like polysaccharides, and cellulose
Secondary cell wall:
Composed of lignin
Function: waterproof and stronger, reinforces cell shape
matrixes
instead of cell walls, animals have these between them, made of cell secretions
and materials absorbed by surroundings (such as cartridge)
Cell Junctions
allows cell to sends or receives signals or materials to
other cells or
to recognize and glue itself to cells of the same type
plant cell junctions
plasmodesmata
plasmodesmata
channels in plant cells that
connect the cytoplasm of neighboring cells
animal cell junctions
tight, adhering, gap junctions
tight junctions
links cells of most body tissues, seals
neighboring cells together so
substances cannot leak between them
desmosomes
adhering junctions
adhering junctions
occur in organs
subjected to
continuous stretching
Gap junctions-
cytoplasm of certain adjacent cells
connect directly to allow for
the flow of substances
Cytoskeleton
organized system of protein filaments that extends
between nucleus and plasma membrane.
Microtubules-
Keeps organelles or cell structures in place or moves them to new locations
Examples of microtubule poisons: colchicine, taxol (used
to stop the spread of certain tumors)
Where do microtubules grow from?
centrosomes
How does a cell act on microtubules?
Cell can cap the microtubules to stabilize them or leave them uncapped so they’ll break apart.
Structure: Microfilaments-
thinnest of cytoskeletal elements, two helically
coiled polypeptide chains of
actin, Found in the cell cortex
Microfilaments-function
1- Reinforce the cell’s shape
2- Reconfigure the cell surface (example, pinches a cell
down the middle during cell division)
3- Anchor membrane proteins and are components of muscle contraction
4- Allow for cytoplasmic streaming
Intermediate filaments:
Structure: between microtubules and microfilaments in
size
Function: strengthen and maintain the
shape of cells or cell parts
pseudopods
false feet found in marcophages and amoebas. Temporary, irregular lobes bulge out from cell and help
move the cell for engulfing prey
motor protein cell movement
Tracks= microtubules and microfilaments
o Train engines= motor proteins- kinesins, dyneins, myosins
Myosin moves structures along microfilaments or slide
one microfilament over another.
ways cells move
cilia, flagella, false feet, motor proteins
flagella
motile structure, longer and not as
abundant as cilia
cilia
motile structure, many are found one one cell
bottom of cilia/flagella
basal body
Where do cilia and flagella arise from?
Both arise from a centriole found in an area called a
centrosome.
cilia or flagella beating
Both beat by a sliding mechanism using dynein arms and ATP. The arms grab the microtubule pairs in front of them and tilt in a short, downward stroke- bends them
cilia and flagella structures
Both cilia and flagella have a structure of 9 + 2 array.
Nine pairs of microtubules form a ring around a central pair, always stabilized by protein spokes
Microtubules structure
Structure: hollow cylinders of tubulin monomers
primary cell wall function
Cements neighboring cells together. Cells with primary
cell wall can still
enlarge, divide, change shape
