1
Q
What is inside all cells
A
- Proteins
- Nucleic acids
- Carbohydrates
- Plasma membrane
- Ribosomes
- Chromosome(s)
- Cytoplasm
2
Q
Proteins
A
Proteins—perform most of the cell’s functions
3
Q
Nucleic acids
A
Nucleic acids—store, transmit, and process
information
4
Q
Carbohydrates
A
Carbohydrates—provide chemical energy, carbon,
support, and identity
5
Q
Plasma membrane
A
Plasma membrane—serves as a selectively
permeable membrane barrier (lipids)
6
Q
Ribosomes
A
Ribosomes—sites of protein synthesis
7
Q
Chromosome(s)
A
Chromosome(s)—structures made of nucleic acids
that serve to transmit hereditary information
8
Q
Cytoplasm
A
Cytoplasm—internal cellular fluid (cytosol)
9
Q
Types of cells
A
Cells are divided into two fundamental types based on
morphology:
- Eukaryotes have membrane-bound nucleus
- Prokaryotes lack membrane-bound nucleus
10
Q
three domains
A
- Bacteria—prokaryotic
- Archaea—prokaryotic
- Eukarya—eukaryotic
11
Q
Light Microscopes
A
use a beam of light to focus in
a specimen
12
Q
Electron Microscopes
A
use a bean of electrons
focused on a specimen instead of light
13
Q
Two main types of electron microscopes
A
Scanning Electron Microscope (SEM): view surface of specimen
provide 3-D exterior views
Transmission Electron Microscope (TEM):
view ultrastructure of specimen (how it is put together) can show fine detail within cells
14
Q
Magnification
A
the ratio of an objects image to its actual size
15
Q
Resolution
A
the measure of the clarity of an image; the
minimum distance two points can be separated and still
be distinguished as two points.
16
Q
What is the resolving power of light and electron microscopes?
A
The resolving power of a light microscope is approximately 200 nanometers, while that of an electron microscope is about 2 nanometers.
This significant difference allows electron microscopes to visualize much smaller structures than light microscopes.
17
Q
What can be imaged with a light microscope and an electron microscope?
A
Live or fixed specimens can be imaged with a light microscope, but only fixed specimens can be imaged with an electron microscope.
Light microscopes allow observation of living cells, while electron microscopes provide higher resolution images of fixed samples.
18
Q
What are the differences between a light microscope and an electron microscope?
A
Light microscopes use visible light for illumination. Electron microscopes use a beam of electrons.
Specimen preparation for light microscopes takes minutes to hours, while for electron microscopes it can take days.
Light microscopes can image live or dead specimens, whereas electron microscopes can only image dead or dried specimens.
Light microscopes have a resolving power of about 0.25 to 0.3 micrometers, while electron microscopes have a resolving power about 250 times higher.
Light microscopes can magnify objects from 500X to 1500X, while electron microscopes can magnify from 100,000X to 300,000X.
Images produced by light microscopes are colored, while those from electron microscopes are black and white.
Specimens for light microscopes are stained with colored dyes, while those for electron microscopes are coated with heavy metals to reflect electrons.
These differences highlight the unique capabilities and limitations of each type of microscope in biological research.
19
Q
Cells have four common components
A
1) An enclosing plasma membrane which separates the cell’s interior from the environment
4) Cytoplasm made of cytosol in which other components of
the cell are found
3) DNA – the genetic material of the cell
4) Ribosomes which synthesize proteins
20
Q
Prokaryotic cells
A
Contain at least one chromosome
Many protein-synthesizing ribosomes
phospholipid components differ in bacteria and archaea
cytoplasm
21
Q
How do phospholipid components differ between bacterial and archaeal cells?
A
Bacterial phospholipids consist of fatty acids bound to glycerol.
Archaeal phospholipids use branched isoprenoid chains bound to glycerol.
These differences contribute to the distinct membrane structures and functions in these two domains of life.
22
Q
What are prokaryotic cells similar to?
A
Prokaryotic cells are believed to be similar to the first cells that existed on Earth.
These cells are characterized by their simplicity and lack of a nucleus.
23
Q
What is the structure of prokaryotic DNA and plasmids?
A
Prokaryotic DNA typically consists of a single, circular chromosome that contains a large DNA molecule associated with proteins, which provide structural support. (supercoiled)
Additionally, prokaryotic cells may contain plasmids, which are smaller, circular DNA molecules that can carry additional genetic information
Plasmids often play a role in antibiotic resistance and other traits that can be beneficial for survival.
24
Q
What is the structure of ribosomes in Prokaryotes
A
Macromolecular machines
– Have large and small subunit
– Consist of RNA molecules and protein
– Used for protein synthesis
– Ribosomes in bacteria and archaea similar in size
and function
Primary structure of RNA and protein components
different
25
CYTOSKELETON STRUCTURES in prokaryotes
In bacteria, cytoskeleton essential for ____ _______
Bacteria and Archaea contain long, thin protein filaments in cytoplasm
Protein filaments form basis of cytoskeleton
Maintains cell shape
In bacteria, cytoskeleton essential for cell division
26
Cell wall
Cell wall forms protective “exoskeleton"
Most prokaryotes have cell wall:
– Composed of tough, fibrous layer
– Surrounds plasma membrane
– Protects shape and rigidity of cell
27
do eukaryotes have cell walls
it depends on the type of eukaryote
Plants, Fungi, and Algae:
They have a rigid cell wall outside their plasma membrane to provide structural support
Animal cells lack a cell wall. Instead, they are supported by something called the extracellular matrix (ECM)
28
polysaccharide peptidoglycan
In bacteria:
– Primary structural component of cell wall is
polysaccharide peptidoglycan
– Some have outer membrane made of glycolipids
29
Glycolipids
Glycolipids are membrane molecules made of lipids with attached sugars that help form and protect the bacterial outer membrane (some bacteria. not all)
30
internal photosynthetic
membranes
Many prokaryotes have internal photosynthetic membranes
Convert energy in sunlight to chemical energy
Some photosynthetic bacteria have extra membrane structures inside them. They are folds of the plasma membrane. This increases surface area
31
bacteria: Membrane-bound compartments
scientists later discovered that some bacteria have simple membrane compartments inside them.
Store calcium ions
Hold magnetite crystals to serve as a compass
Concentrate enzymes for building organic
compounds
32
External Structures found on primarily bacterial surfaces
Flagella—long filaments that rotate to propel cell
Fimbriae—needlelike projections that promote
attachment to other cells or surfaces
33
why are prokaryotic cells smaller than Eukaryotic cells
Prokaryotes are usually 1–5 µm
Eukaryotes are usually 10–100 µm
A small size gives them a high surface area to volume ratio, making exchange of materials efficient.
They cannot grow large like eukaryotes because they lack internal transport organelles.
34
Surface area–to–volume ratio
As cells get bigger, volume increases faster than
surface area → therefore, as a cell increases in size,
its surface area-to volume ratio decreases: less
effiicient!
35
The types of Eukaryotes
are they unicellular or multicellular
Protists, fungi, plants, and animals are eukaryotes
Eukaryotes can be unicellular or multicellular depending on the group.
Protists → mostly unicellular
Fungi → mostly multicellular but some unicellular
Plants → multicellular
Animals → multicellular
36
Are prokaryotic cells unicellular or multicellular
unicellular
37
Compartmentalization offers several advantages
1. Separation of incompatible chemical reactions
2. Increasing efficiency of chemical reactions
3. Increases membrane surface area to volume ratio in
the cell - allows for larger cells
38
Eukaryotic cell parts list
Nucleus (Nucleolus
ribosomes
Endoplasmic reticulum
Golgi apparatus
vesicles
lysosomes
vacuole (central vacuole in plants)
Mitochondria
chloroplasts
Cytoskeleton
39
The Nucleus parts in Eukaryotic cells
The Nucleus—Large, highly organized membrane
bound compartment. Stores and transmit information
Surrounded by double-membrane nuclear envelope
Studded with pore-like openings
Inside surface is linked to the nuclear lamina:
– Lattice-like sheet of fibrous proteins
– Provides structural support to help maintain nucleus shape
Nucleoplasm: aqueous fluid that fills the nucleus (separated from the cytoplasm)
The Nucleolus -
- Location where ribosomal RNA is synthesized, and
ribosome subunits are assembled (Not membrane bound)
Chromosomes -
- Units of DNA that carry the genetic information
- Made of chromatin: a complex of DNA and proteins
40
nuclear envelope in eukaryotic cells
The double membrane surrounding the nucleus is called the nuclear envelope
Studded with pore-like openings
Made of two phospholipid bilayers
41
Ribosomes
Ribosomes are complex molecular machines that
manufacture proteins (site of protein synthesis)
Lack a membrane
Some ribosomes are free in the cytosol
Some are attached to endoplasmic reticulum
42
Endoplasmic reticulum
Endoplasmic reticulum—extensive membrane-enclosed
factory
– Continuous with nuclear envelope
Two regions, distinct in structure and function:
– Rough endoplasmic reticulum (rough ER)
– Smooth endoplasmic reticulum (smooth ER)
43
Rough endoplasmic reticulum physical appearance and function
Studded with ribosomes:
* Dark, knobby looking structures
* Consists of flats membranous sacs called cisternae
Synthesizes proteins that will be:
- Shipped to another organelle
- Inserted into plasma membrane
- Secreted to the cell exterior
Proteins made on RER may:
– Carry messages to other cells
– Frequently are glycoproteins
– Act as membrane transporters or pumps
– Catalyze reactions (To speed up a chemical reaction)
44
Lumen
As proteins are manufactured on RER, they move to the
lumen:
– Lumen—inside of any sac-like structure (i.e. cisternae)
In RER lumen, proteins are folded and processed
45
Smooth ER
-- Lacks ribosomes
– Consists of membranous tubule-like structures
– Contains enzymes that catalyze reactions involving
lipids
-- Break down lipids and other molecules that are
poisonous (detoxification)
Instead of flattened sacs like rough ER, the smooth ER looks more like a network of smooth tubes made of membrane.
Smooth ER → lipid synthesis (makes phospholipids)
46
Golgi apparatus
Most proteins that leave RER must pass
through Golgi apparatus
Formed by series of stacked, flat, membranous sacs called cisternae
added to lipids and protein – start of production of glycoprotein and
glycolipids
47
Golgi apparatus (cis and trans)
The Golgi apparatus is the cell’s processing and shipping center
Cis face:
Faces the ER
Receives transport vesicles from the rough ER
This is the “receiving” side
Proteins and lipids enter the Golgi here
Trans face:
Faces the plasma membrane
This is the “shipping” side
Vesicles leave from here to go to:
Plasma membrane
Lysosomes
Secretion outside the cell
48
Vescicle
Membranous vesicles carry materials to and from
organelle
49
cisternal maturation model
The cisternae themselves move
A new cisterna forms at the cis face. Vesicles from the ER fuse together. They create a new Golgi sac at the cis side.
That cisterna gradually moves inward Instead of the protein moving forward between stationary sacs, the entire cisterna shifts position
50
Lysosomes
Recycling centers found only in animal cells
Contain approximately 40 different enzymes
Enzymes specialized for hydrolyzing different
macromolecules
51
acid hydrolases
Digestive enzymes inside lysosomes are called acid
hydrolases:
– Work best at pH 5.0
– Proton pumps in membrane maintain low internal pH
Example: acid hydrolases:
* Synthesized in ER
* Processed in Golgi apparatus
* Shipped to lysosomes
52
endomembrane system
Collectively, lysosomes, Golgi apparatus, and ER make up
the endomembrane system
Center for producing, processing, and transporting
proteins, carbohydrates and lipids
Secretory pathway:
Rough ER → Golgi → vesicles → plasma membrane → outside the cell
53
Vacuole
Central Vacuole
Tonoplast
prominent organelle found in cells of plants, fungi, and other eukaryotes
Some digest and recycle macromolecules
- Substitutes for lysosome found in animals (animals cells have little vacuoles)
Central Vacuole — in plants cells, takes up large volume
of the inside of the plant cell
Tonoplast: membrane that surrounds the plant central
vacuole
It is part of the plant’s endomembrane system
54
Peroxisomes
What they are:
Small, round, membrane bound organelles
Found in all eukaryotic cells (plants and animals)
How they form:
Vesicles bud off from the ER
These empty vesicles import specific enzymes from the cytosol
Once loaded with enzymes, they become functional peroxisomes
Peroxisomes are membrane bound organelles in eukaryotic cells that carry out oxidation reactions (a chemical reaction where a molecule loses electrons.) break down fatty acids, and detoxify hydrogen peroxide using catalase
55
Mitochondria
Mitochondria supplies ATP to cells
Prone to fusion and fission means the organelle can frequently join together or split apart to adjust to the cell’s needs
Site of Cellular Respiration
Have two membranes
* Outer membrane: defines organelle’s surface
* Inner membrane: folded into series of sac-like cristae
* Mitochondrial matrix—solution enclosed within inner membrane
* Intermediate space: space between the outer and
inner membranes
Powerhouse of the cell
increase surface area
Mitochondria have their own mitochondrial DNA. Grow and divide independently of cell division. Manufacture their own ribosomes (makes them prokaryotic)
56
chloroplasts parts list
Like mitochondria, chloroplasts contain their own DNA and
manufacture their own ribosomes
Chloroplasts grow and divide independently of cell
division
Most plant and algal cells have chloroplasts, where photosynthesis takes place
A chloroplast has three membranes total:
Outer membrane/Inner membrane:
These form the outer boundary of the chloroplast. Between them is a small gap called the intermembrane space.
Inside those two membranes is the stroma.
Stroma
Fluid filled space
Now inside the stroma are thylakoids
Thylakoid membrane:
Flattened sac like structures
Contains chlorophyll
This is where the light reactions happen
Thylakoids are stacked on top of each other.
A stack is called a granum.
Multiple stacks are called grana
57
Endosymbiosis theory
Proposes that mitochondria and chloroplast were once
free-living bacteria
– Bacteria were engulfed by ancestor of modern
eukaryotes but were not destroyed
– Mutually beneficial relationship evolved
58
Cytoskeleton
Extensive system of protein fibers
– Gives cells shape and structural stability
– Transports materials within cell
– Organizes all organelles and other cellular structures
into a cohesive whole
3 types :
1. Microfilaments
2. Microtubules
3. Intermediate filaments
59
Fungi, algae, and plants have ____ outer cell wall in
addition to plasma membrane
Cells of animals ____ a cell wall:
– Supported by ________
Fungi, algae, and plants have stiff outer cell wall in
addition to plasma membrane
Cells of animals lack a cell wall:
– Supported by extracellular matrix (ECM)
– Diffuse mixture of secreted proteins and
polysaccharides
60
Cell fractionation and its steps
This is a lab method used to break open cells and separate their parts
First step: Cell lysis
The cell is broken open so the organelles come out
Second step: Centrifugation
The broken cell mixture is placed in a machine called a centrifuge. The centrifuge spins very fast. Heavier and larger parts sink to the bottom first.
Smaller and lighter parts stay higher up. (This separates cell parts based on size and density)
Ultracentrifuge
This is a very powerful centrifuge. It spins extremely fast and can separate very tiny cell particles.
61
Differential centrifugation and fluorescent tags
Centrifugation to separate cell parts
Fluorescent tags to label and track specific molecules inside cells
62
Nucleolus
Nucleolus functions as site of ribosome assembly
* Ribosomal RNA binds proteins to form ribosomes
* Messenger RNA (mRNA) carries information to synthesize proteins
ALL PROTEINS ARE MADE IN THE CYTOPLASM
63
Structure and function of nuclear envelope
--Separates nucleus from rest of the cell
- Perforated with openings called nuclear pore complexes
- Connects inside of nucleus with cytosol
- Consists of about 30 different proteins
64
describe what enters the nucleus
The nucleus imports materials it needs to carry out its jobs
Those jobs are mainly:
Nucleoside triphosphates:
Copying DNA
Making RNA
Assembling ribosomal subunits
Example: ATP, GTP, CTP, UTP, dATP, etc.
But here’s the key clarification:
The nucleus does NOT make proteins.
Proteins are made in the cytoplasm by ribosomes.
Then certain proteins are transported into the nucleus to help it function
65
how do molecules enter the nucleus
Nuclear Localization Signal (NLS)
Nuclear Export Signal (NES)
Import of large molecules into the nucleus is selective
Nuclear pores:
These are protein channels in the nuclear envelope.
They act like security gates.
Small molecules can pass freely.
Large molecules need permission
Nuclear Localization Signal (NLS):
Some proteins are meant to work inside the nucleus.
Those proteins contain a special amino acid sequence called an NLS.
If a protein has an NLS:
It is recognized by transport proteins.
It is guided through the nuclear pore.
It enters the nucleus.
Without an NLS, large proteins cannot enter.
Nuclear Export Signal (NES)
Some proteins need to leave the nucleus. If they contain an NES:
They are recognized for export.
They are transported out through the nuclear pore.
Some proteins have BOTH NLS and NES.
66
Pulse–Chase experiment
What the scientists proved was this:
Proteins that are meant to be secreted do NOT randomly move around the cell.
They follow a specific, ordered pathway called the secretory pathway.
Using the pulse–chase experiment, they saw:
Right after the pulse → radioactive proteins were in the rough ER.
A little later → they appeared in the Golgi.
Later → they appeared in secretory vesicles.
Finally → they were detected outside the cell
67
signal hypothesis
The signal hypothesis states that proteins destined for the endomembrane system contain an N-terminal ER signal sequence that directs the growing polypeptide to the rough ER
68
steps of how PROTEINS ENTER THE ENDOMEMBRANE
SYSTEM
Step 1: Ribosome synthesizes ER signal sequence
* Step 2: ER signal sequence binds to signal recognition
particle (SRP)
* Step 3: Ribosome + signal sequence + SRP move to RER
membrane and bind to SRP receptor
* Step 4: SRP is released—protein synthesis continues
through channel called translocon
* Step 5: Growing protein is fed into ER lumen—ER signal
sequence is removed
69
process of glycosylation and how glycoproteins are made
Proteins enter the ER while they are being made.
They fold into their 3D shape.
An initial carbohydrate chain is added to the protein.
At this stage:
A short sugar chain is attached.
The protein becomes a glycoprotein.
This is the start of glycosylation.
Then the protein is sent to the Golgi.
70
how do proteins move from ER to Golgi
Proteins are transported in vesicles
Pulse–Chase experiment showed proteins in small,
membrane-bound structures:
* Bud off from ER
* Move to cis face of Golgi apparatus
71
describing how the Golgi actually works
New cisternae form at the cis face
Vesicles from the ER fuse together.
They form a new cisterna at the cis side (the receiving side).
Old cisternae break off from the trans face
As a cisterna moves forward and matures, it eventually becomes the trans cisterna.
Then it breaks apart into vesicles that ship proteins out.
72
Cisternal Maturation Model
Cisternal Maturation Model
The cisternae themselves move forward and mature.
Instead of proteins hopping between stationary sacs,
the entire sac carrying the proteins changes identity as it moves.
Different cisternae contain different enzymes
Each stage of the Golgi has specific enzymes.
73
How do the rough ER and Golgi apparatus function together?
The rough ER and Golgi apparatus function like an assembly line. The rough ER synthesizes proteins, and the Golgi modifies, sorts, and packages them for their final destination.
74
What happens to proteins after they leave the Golgi apparatus
Proteins leave the Golgi with a molecular tag that determines where they will go in the cell
75
How are proteins destined for lysosomes identified?
Lysosome-bound proteins receive a phosphate group attached to a mannose sugar, forming mannose-6-phosphate (M-6-P).
76
Where are M-6-P tagged proteins recognized?
They are recognized by receptor proteins in the membrane of the trans-Golgi cisternae.
The receptor pulls the tagged protein from the trans-Golgi lumen into a transport vesicle that will deliver it to the lysosome.
77
What happens after proteins are modified in the Golgi?
Cargo complexes form cargo-filled vesicles that package proteins into specific types of transport vesicles.
78
How are proteins sorted into the correct vesicles?
Proteins are placed into particular transport vesicles based on molecular signals or tags.
Each type of transport vesicle has its own tag that ensures it reaches the correct destination in the cell.
79
What happens if a transport vesicle is bound for the plasma membrane?
The vesicle moves to the plasma membrane and releases its contents outside the cell.
80
What is exocytosis
Exocytosis is a form of bulk transport in which a vesicle fuses (joins together and becomes one) with the plasma membrane and secretes (releases something out) macromolecules such as proteins or polysaccharides outside the cell.
81
What types of molecules are commonly secreted by exocytosis?
Large molecules like proteins, polysaccharides, and other large particles
82
What is the role of the lysosome in the cell?
The lysosome digests large molecules so their smaller building blocks can be reused by the cell
83
Why must large molecules be digested before reuse?
Large molecules cannot be directly reused. They must be broken down into monomers (small units like amino acids or sugars) before the cell can use them again
84
How does bulk transport contribute to protein recycling?
Bulk transport brings large materials into the cell inside vesicles, which eventually fuse with lysosomes for digestion and recycling.
85
What are two pathways that bring materials into the cell for lysosomal digestion?
Two pathways occur through endocytosis
86
What are the two types of endocytosis that end in the lysosome?
receptor-mediated endocytosis:
The cell brings in specific molecules.
Molecules bind to receptors on the cell surface.
The membrane pinches in and forms a vesicle containing those specific molecules.
Phagocytosis
The cell engulfs large particles.
Examples include bacteria, debris, or large food particles.
The membrane surrounds the material and forms a large vesicle.
(drinking)
Pinocytosis is non specific uptake of extracellular fluid into small vesicles.
87
autophagy
Autophagy is the process by which a cell digests and recycles its own components using lysosomes.
Why is this important?
Removes damaged organelles
Prevents buildup of waste
Recycles nutrients during starvation
Helps maintain cell health
88
Endocytosis vs Autophagy
Endocytosis = bringing things in from outside
Autophagy = recycling things from inside
89
Roles of the Cytoskeleton
Mechanical and Structural Support: maintain cell shape
Motility: cell movement and movement within the cell
Regulation of Biochemical Processes: helps convey information from outside of cell to the inside
90
Three major types of cytoskeletal elements
1. Actin filaments
(microfilaments):
-- Smallest cytoskeletal elements
* Fibrous structures made of globular proteins subunits (actin)
Maintain cell shape
– Change cell shape
– Muscle contraction
2. Intermediate filaments
Medium sized fibers.
Stronger and more stable than actin.
Functions:
Provide mechanical strength
Resist pulling forces
Help maintain cell structure
Anchor organelles
Form part of the nuclear lamina (supports the nucleus)
3. Microtubules
Largest cytoskeletal fibers.
Made of tubulin protein.
They are hollow tubes.
Functions:
Maintain cell shape
Act as tracks for motor proteins (like highways)
Move vesicles and organelles
Form mitotic spindle during cell division
Form cilia and flagella
Actin → movement and contraction
Intermediate filaments → strength and support
Microtubules → transport and cell division
91
ACTIN FILAMENT STRUCTURE
Two distinct ends of an actin filament are referred to as
plus and minus ends
- Structural difference results in:
- Different rates of assembling new actin subunits
- Plus (+) end grows faster than minus (-) end
92
Are actin filaments involved only in maintaining cell shape?
No. Actin filaments are also involved in cell movement.
helps with muscle contraction
93
Which motor protein works with actin filaments
Myosin
94
How does myosin produce movement?
Myosin uses ATP to change shape and generate force, allowing movement to occur.
95
What are pseudopodia?
Pseudopodia are temporary extensions of the plasma membrane formed by the polymerization of actin microfilaments.
96
What are intermediate filaments made of?
They are made of fibrous proteins that coil together to form strong, cable-like structures.
Help maintain structure
Anchor the nucleus
Provide mechanical strength
Form the nuclear lamina
97
Do all intermediate filaments have the same structure?
No. They vary in size and structure depending on the specific protein involved.
98
What is the most familiar type of intermediate filament protein?
Keratin (found in hair and nails.)
99
What is one main function of intermediate filaments?
They help maintain cell shape.
100
How do intermediate filaments support organelles?
They anchor (means to hold something firmly) the nucleus and other organelles in place.
101
What structure of the nucleus is made of intermediate filaments?
The nuclear lamina
102
Microtubules
They are the largest cytoskeletal element
Motor proteins like kinesin and dynein walk on them
They move vesicles and organelles
They form the mitotic spindle
They make up cilia and flagella
helps with cell division
103
kinesin and dynein
motor proteins that walk on microtubules, but they move in opposite directions
Microtubules have polarity.
They have:
A plus (+) end
A minus (−) end
Motor proteins move along these ends using ATP.
Kinesin
Moves toward the plus (+) end of the microtubule
Usually moves cargo from the center of the cell toward the cell membrane
Think: outward transport
Dynein
Moves toward the minus (−) end of the microtubule
Usually moves cargo from the cell membrane toward the center of the cell
Think: inward transport
Kinesin = “k” for “keep going outward”
Dynein = drives things back inward
104
In which direction do microtubules grow?
Their plus (+) ends grow outward from the MTOC
105
What is the MTOC called in animal cells?
In animal cells, the MTOC is called the centrosome.
106
What is one of the most important functions of microtubules?
Microtubules play a key role in separating chromosomes during mitosis and meiosis.
107
centrosome
The centrosome is the microtubule organizing center in animal cells
108
How do vesicles move inside the cell?
Vesicles move along filamentous tracks made of cytoskeletal elements
109
What are flagella
Flagella are long, hairlike projections from the cell surface that help cells move
110
What are prokaryotic flagella made of?
They are made of a single helical rod composed of the protein flagellin in bacteria, or other similar proteins in archaea.
111
How do eukaryotic flagella move differently from prokaryotic flagella?
Eukaryotic flagella move by whipping back and forth, rather than rotating.
112
Are prokaryotic flagella surrounded by a plasma membrane?
No. Prokaryotic flagella are not surrounded by a plasma membrane.
113
Are eukaryotic flagella surrounded by a plasma membrane?
Yes. Eukaryotic flagella are enclosed by the plasma membrane.
114
what are eukaryotic flagella made of
eukaryotic flagella and cilia are made of microtubules.
115
Eukaryotic flagella
Short, hairlike projection found in some eukaryotic cells
116
What are the two main types of membrane proteins?
Integral proteins and peripheral proteins
117
What are integral proteins?
Integral proteins are embedded within the phospholipid bilayer and often span the entire membrane.
118
What are peripheral proteins
Peripheral proteins are loosely attached to the surface of the membrane, either on the inside or outside.
119
What is one major function of membrane proteins?
They regulate transport of substances into and out of the cell.
120
Why is transport regulation important?
It allows the cell to maintain an internal environment that is different from the external environment.
121
How do membrane proteins interact with the cytoskeleton?
Some membrane proteins attach to cytoskeletal elements on the inside of the membrane to help maintain cell shape and stability
122
How do membrane proteins interact with structures outside the cell?
Some membrane proteins attach to extracellular structures, helping with support, communication, and cell recognition.
123
Extracellular membrane (ECM)
- Helps define cell shape
- Attaches it to other cells
- Acts as a first defense
124
Do most plant cells have a cell wall?
Yes, most plant cells are surrounded by a cell wall
125
What is the primary cell wall?
The primary cell wall is the flexible outer layer secreted by new plant cells.
126
What is the primary cell wall made of?
It is made mainly of the polysaccharide cellulose.
127
How is cellulose arranged in the primary cell wall?
Cellulose forms long strands that bundle together into cable-like structures called microfibrils.
128
What is the function of pectin in the cell wall?
What is the function of pectin in the cell wall?
129
How does the primary cell wall help the cell when water enters by osmosis?
It counteracts turgor pressure, preventing the cell from bursting.
130
What is turgor pressure
Turgor pressure is the internal pressure created when water enters the plant cell and pushes against the cell wall
