Cell Biology Unit 3 Flashcards
1
Q
Cell Theory
A
All living things are composed of cells and all cells come from other cells
2
Q
Light Microscopes (LM)
A
- Earliest type of microscope
- Visible light passes through a sample
- Then through glass lenses
Objective lens
Ocular lens - Lenses bend the light so that the image of the specimen is magnified
- Image is projected into your eye or into a camera
3
Q
Magnification
A
The increase in an object’s image size compared with its actual size
- This is the ability to distinguish two nearby objects as being separated from each other
- Example: What look like one star in the sky to the naked eye may prove to be two stars very close when seen through a telescope
4
Q
Resolution
A
The measure of the clarity of an image
5
Q
Electron Microscope (EM)
A
- Came into use in the 1950s and allowed biology to take a huge leap forward
- Focuses beams of electrons (instead of light) through a specimen sample
- Electromagnets are used to bend the electron path and magnify the image
The same way lenses are used in LM - EM images are always black and white, colour is added later to highlight or clarify cellular structures
6
Q
Transmission EM (TEM)
A
- Electron beam is passed through a very thin section of a specimen
- Stains containing heavy metals are used to coat certain types of cellular structures
- Electrons will be scattered by the more dense stained parts
- The scattered electrons are detected, and an image is produced
7
Q
Scanning EM (SEM)
A
- Allows scientists to study the detailed architecture if a cell
- The sample is usually coated with a thin film of gold
- An electron beam excites the gold atoms
- The electrons are scattered and then detected by a device that projects the resulting image onto a video screen
- Makes the image look 3D
8
Q
Microscope Problems
A
- Electron Microscopy
o Cannot be used to look at live samples
o Preparing a specimen kills the organisms
o Scientists must use a light microscope to look at living cells - Light Microscopy
o Many parts of a cell are too small to be seen with a light microscope
o To see in great detail, an electron microscope must be used
9
Q
Minimum
A
Large enough to store enough DNA, proteins, and structures to survive and reproduce
10
Q
Maximum
A
- Maximum: influenced by geometry
o Must have enough surface area to service the full cell volume
o Needs to have flow of oxygen and nutrients and wastes
o If the cell is too large, the oxygen, waste, and nutrients will bottleneck at the membrane and the cell will be able to handle the molecular traffic
11
Q
Surface-to-Volume Ratio
A
- A large cell has more surface area than a small cell but has lower surface-to-volume ratio
- Some cells in your body can still be very large
o Example: Nerve cells that run all the way from your spine to your foot
These cells can be over a metre long
They are so thin that you still need a microscope to see them
Being so thin allows them a high enough surface-to-volume ratio to function well
12
Q
Prokaryotic Cells
A
These were the first cells to evolve and lived for 1.5 billion years before eukaryotic cells evolved
Small and simple structure
No internal membrane-bound structures
13
Q
Eukaryotic Cells
A
Evolved from prokaryotic cells about 1.8 billion years ago
o Includes all higher life forms such as plants, animals, and fungi
o Larger, more complex cells
14
Q
Structures Common to All Life
A
- Plasma membrane: Membrane that surrounds the cell
- Ribosomes: Machinery for protein synthesis
- Cytosol: Aqueous solution that fills the cells
- DNA: one or more chromosomes
- Cytoplasm: The entire contents of the inside of the cells, excluding the interior of the nucleus
15
Q
Plasma Membrane
A
The flexible boundary between the living cell and its surrounding environment
Also referred to as the cell membrane
16
Q
Phospholipids
A
Hydrophobic tail with a negatively charged hydrophilic head
- Forms a two-layer sheet called a phospholipid bilayer
- Hydrophilic head face outward
o In contact with aqueous solution both inside and outside of the cell - Hydrophobic tails point inwards
o Shielded from water
17
Q
Membrane Proteins
A
Proteins that are embedded in the lipid bilayer
18
Q
Plasma Membrane (Cell Membrane)
A
Regulates the flow of material in and out of the function of the cells
19
Q
What can pass through the cell membrane?
A
Small non-polar molecules pass directly through the membrane
20
Q
Channel Proteins
A
Forms a tunnel through the membrane that shields molecules as they pass through the hydrophobic layer
21
Q
Nucleiod
A
Region of the cell where the chromosome is coiled
Nucleiod = ‘nucleus-like region
22
Q
Cell wall
A
Rigid, chemically complex shell surrounding the plasma
o Protects the cell
o Maintains the cells shape
23
Q
Capsule
A
Sticky outer coat around the cell wall
o Helps glue the cells to surfaces or to other cells
o Only some prokaryotes have a capsule
24
Q
Flagella
A
Long projection that propels a cell through its environment
o Only some prokaryotes have flagella
25
Organelles
- Organelles: “Little organs”
o Membrane-bound structures that perform specific tasks
o A cell may contain many copies of each organelle
o The proportion of different organelles depends on the specialized function of the cell
26
Cellular Metabolism
The chemical activities of the cell
27
Organelles only found in animal cells
- Lysosomes and centrosomes
- Flagella and cilia
o Sometimes found in animal cells very rare in plant cells
28
Organelles found only in plant cells
- Rigid cell walls
o This cell wall is different than what it seen in prokaryotes
o Made mostly of the polysaccharide
Plasmodesma: Cytoplasmic channels that link adjacent cells together
Chloroplasts: Location of photosynthesis
- Large central vacuole that stores large amounts of water and various chemicals
29
The Nucleus
- Contains the cells genetic instructions (DNA)
- Control the cells activities by directing protein synthesis
30
DNA Organization
- DNA is organized into chromosomes
o The DNA associates with many proteins
o The proteins help coil the long strands of DNA to form a chromosome
o A human cell has 46 separate chromosomes
31
Chromatin
The complex of protein and DNA
32
Nuclear Envelope
Double membrane enclosing the nucleus
o Each of the two membranes is separate phospholipid bilayer
o Proteins are associated with nuclear envelope
o Control the flow of materials in associated with nuclear envelope
o Control the flow of materials in and out of the nucleus
o Pore proteins regulate the flow of large molecules and connect the nucleus to the endoplasmic reticulum
33
Nucleolus
The site where a specialized RNA molecule called ribosomal RNA (rRNA) is synthesized
- Proteins made in the cytoplasm are brought into the nucleus to be assembled with rRNA to make ribosomes
34
Ribosomes
The cellular components that use instructions from the nucleus to build protein
- A cell may contain millions of ribosomes
35
Non-Membranous Organelle
Not contained inside a membrane
36
Location of Ribosomes
- Free ribosomes are suspended in the cytosol
- Bound ribosomes are attached to the outside of the endoplasmic reticulum and nucleus
- both types are structurally identical and can function in either location
37
Free Ribosomes
o Proteins made here generally function in the cytosol
o Example: Enzymes that break down sugar for use in cellular respiration
38
Bound ribosomes
- Make proteins that will be exported from the cell
- Ribosomes interact with mRNA to build a protein
39
Endomembrane System
- Internal membranes are involved in most cellular functions
o Synthesis, storage, distribution, and export of molecules
40
Vesicle
Sac made of membrane
- Nuclear envelope, endoplasmic reticulum, Golgi apparatus, lysosomes, vesicles, vacuoles, plasma membrane
41
Endoplasmic Reticulum (ER)
An extensive network of flattened sacs and tubules that functions as a major manufacturing site in the cells
42
Smooth Endoplasmic Reticulum (SER)
- The smooth ER and its enzymes are responsible for many functions
o Synthesis of lipids (oil, phospholipids, steroids)
o Storage of calcium ions
o Detoxification
43
Rough Endoplasmic Reticulum (RER)
- Proteins produced by ribosomes attached to the rough ER are often excreted from the cell
o These are called secretory proteins
o Examples: Cells in the pancreas secrete insulin which is produced by ribosomes on the rough ER
- The rough ER synthesizes new membrane fragments
44
Secretory Proteins
1. A polypeptide produced by a bound ribosome enters the rough ER
2. Short sugar chains may be attached to the polypeptide to make a glycoprotein
3. The glycoprotein is packaged in a transport vesicle
4. The vesicle buds off from the ER membrane to be passed to the golgi apparatus for further processing
45
Golgi apparatus
- Stack of flattened sacs
- A cell may contain hundreds of this organelle
- Cells that are more active in protein excretion will have higher concentrations of golgi apparatuses
- After leaving the ER, transport vesicles travel to the golgi apparatus
- This apparatus acts as a warehouse and processing station for molecules produced by the ER
- Each flattened sac is not connected to the other ones around it
- After processing, products will be transported to the plasma membrane
46
Processing in the Golgi apparatus
1. One side of the sac serves as a docking station for a transport vesicle
2. The vesicle fuses with a golgi sac, adding its membrane and its contents to the sac
3. Products are modified as they travel through the stack from one sac to the next
4. The last sac acts as the shipping side of the golgi apparatus. Here the final products are dispatched in vesicles that bud off and travel to other sites in the cell
47
Processing in the Golgi apparatus
1. One side of the sac serves as a docking station for a transport vesicle
2. The vesicle fuses with a golgi sac, adding its membrane and its contents to the sac
3. Products are modified as they travel through the stack from one sac to the next
4. The last sac acts as the shipping side of the golgi apparatus. Here the final products are dispatched in vesicles that bud off and travel to other sites in the cell
48
Lysosomes
Membrane-enclosed sac of digestive enzymes
48
Lysosomes
Membrane-enclosed sac of digestive enzymes
49
Lysosomal Diseases
Diseases where lysosomal enzymes are missing
50
Vacuoles
- Large vesicles with a variety of functions
o Food vacuoles as food particles are engulfed by the cell
o Contractile vacuoles
o In plant seeds vacuoles store reserve of proteins for starting growth
51
Peroxisomes
- Metabolic, membrane-bound compartment that does not originate in the endomembrane system
- How they are related to other organelles is unknown
- Functions
o Break down fatty acids to use as a cellular fuel
o Detoxification of harmful compounds in your liver
51
Peroxisomes
- Metabolic, membrane-bound compartment that does not originate in the endomembrane system
- How they are related to other organelles is unknown
- Functions
o Break down fatty acids to use as a cellular fuel
o Detoxification of harmful compounds in your liver
52
Inter-membrane space
o Region in between the inner and outer membranes
53
Mitochondrial matrix
o Region inside the inner membrane
o Contains mitochondrial DNA, ribosomes and enzymes that catalyze some reactions of cellular respiration
54
Chloroplast
- Converts solar energy to chemical energy (photosynthesis)
- Similar in structure to the mitochondria
o 2 membranes (inner and outer) separated by a thin intermembranous space
- Inside the inner membrane is a thick fluid called stroma
o Contains chloroplast DNA, ribosomes, and enzymes
o Similar to the mitochondrial matrix
55
Thylakoids
- Thylakoids are suspended in the stroma
o Network of interconnected membranous sacs
o Thylakoids are often stacked like poker chips
o Each stack is called a granum
- The space inside the thylakoid is called the thylakoid space
- Chlorophyll is embedded in the thylakoid membranes to trap solar energy
56
Endosymbiont theory
Mitochondria and chloroplasts were once small prokaryotes that began living inside larger cells
57
Mitochondria
- Carries out cellular respiration in all eukaryotic cells
o Use O2 and release CO2 to transform the chemical energy of food into ATP
- Enclosed by two membranes
58
Cytoskeleton
Networks of protein fibers extending
throughout the cells
59
Microtubules
Straight hollow tubes composed of globular proteins
called tubulins
* Tubulin proteins consist of two subunits
* Microtubules grow longer by the addition of tubulin
proteins
* Can be disassembled and the tubulin proteins
reused elsewhere
In animal cells microtubules grow out of a region
called the centrosome
60
Intermediate Filaments
* Found in the cells of most animals
* Made of fibrous proteins that supercoil into
cables
* Function
* Reinforce cells shape and anchor some organelles that should not move
* Example: The nucleus sits in a cage made of intermediate
filaments
* Often a permanent fixture in the cell
* Outer layer of your skin is made of dead cells
packed full of intermediate filaments
61
Microfilaments
Also called actin filaments
* Rods composed of globular proteins called actin
* Arranged as a twisted double chain
* Form a network inside the plasma membrane to help
support the cell shape
* Important in animal cells because they do not have a cell wall
* Involved in cell movement
62
Cilia
Short, numerous
appendages protruding from
the cell
63
Flagella
Long tail-like appendage on cells
* Typically a cell will only have one or at most a
few flagella
* Functions to propel a cell using an undulating
whip-like motion
* Commonly found on animal sperm cells
* Commonly found on motile prokaryotic cells
64
Extracellular Matrix
* Holds cells together in
tissues
* Protects and supports the
plasma membrane
* Relays signals that affect
gene expression
* Directs the movement of
embryonic cells
65
Integrins
The extracellular matrix is bound to
the membrane by membrane
proteins called integrins
66
Tight Junctions
Plasma membranes of adjacent cells are knit tightly together
* Prevents fluid leakage between layers of cells
such as in the digestive system
67
Anchoring junctions
Intermediate filaments fasten cells together into strong
sheets
* Tissues susceptible to stretching and
mechanical stress such as skin and muscle
68
Gap Junctions
Channels or pores that allow the flow of small molecules from one cell to another
* Signal proteins move between heart cells to
coordinate contraction
69
Fluid mosaic model
Diverse protein molecules suspended in a fluid phospholipid bilayer
* This structure describes the plasma
membrane
70
Selectively Permeability
Some substances can cross the plasma
membrane more easily than others
71
Diffusion
The tendency for particles of any substance to spread out into the available space
* Molecules have thermal energy due to their constant movement. This results in diffusion
* Molecules will diffuse through air and water and across membranes
72
Passive Transport
Diffusion across a membrane with no
energy investment
73
What Substances can easily diffuse through a cell membrane
Small non-polar molecules
* This is the only way O2 enters the cells and CO2 exits the cell
Ions and polar molecules
can diffuse freely using simple transport proteins
* They cannot pass directly through the phospholipid bilayer
* They must still move down their concentration gradient
74
Osmosis
Diffusion of water across a membrane
* Water will pass through the membrane until the concentration of a solute is equal on both sides
* This occurs when a solute cannot pass through the membrane
75
Tonicity
The ability of a surrounding solution to cause a cell to gain or lose water
* Depends on the concentration of solutes in the environment compared to the concentration of solutes in the cell
76
Isotonic
Equal concentration of solutes
77
Hypotonic
Lower concentration of solutes
78
Hypertonic
Higher concentration of solutes
79
Osmoregulation
The control of water balance
* Prevention of excessive uptake or loss of water, and regulation of the solute concentrations in the body
80
Facilitated diffusion
Diffusion through the membrane with the help of transport proteins
Passive transport through a transport protein
* Does not require energy
* Solutes move along their concentration gradient
* Sugars, amino acids, ions, water
81
Channel protein
Provides a simple channel for a molecule to pass through
82
Carrier Protein
Solute binds the protein, causing it to change shape. The solute is released on the opposite side of the membrane.
83
Aquaporin
Allows the passage of water
* Slow diffusion of water directly through the membrane is adequate most of the time, if faster diffusion is required aquaporin is necessary
84
Active transport
A cell expends energy to move a solute against its
concentration gradient
* Solute will move from an area of low concentration to an area of high
concentration
* ATP supplies the energy
85
Exocytosis
fusion of secretory vesicles with the plasma membrane
86
Endocytosis
The process by which large molecules and fluids are
taken up by the cell
87
Phagocytosis
“cellular eating”
88
Pseudopodia
Extensions of the membrane that engulf a particle
89
Receptor Proteins
are embedded in the membrane in an area that is lined by coat proteins
90
Energy
The capacity to cause change, especially to do work
91
Kinetic Energy
The energy of motion
* Moving objects perform work by transferring motion to other matter
92
Thermal Energy
Kinetic energy associated with the random motion
of atoms or molecules
* Thermal energy transferred from one object to another is called heat
93
Light Energy
Kinetic energy harnessed for photosynthesis
94
Potential Energy
Energy that matter possesses based on its location or structure
95
Chemical energy
potential energy available for release in a chemical
reaction
* This is transformed to power the work in a cell
96
ATP
* Adenosine triphosphate (ATP)
* Energy carrying molecule
* Organic molecule called adenosine bound to a triphosphate
* Triphosphate: Chain of three phosphate groups
* The phosphate groups are all negatively charged
97
Hydrolysis
The addition of water
98
Exergonic Reaction
Reaction that releases energy
99
Endergonic reactions
Reactions that require an input of energy
100
Phosphorylation
The phosphate group broken off of ATP is
transferred to another molecule
101
Chemical work
Phosphorylation of reactants provides the energy required for endergonic reactions to form the products
102
Transport work
ATP drives the active transport of solutes across a
membrane against their concentration gradients
103
Mechanical work
Phosphorylation by ATP allows a protein to move
104
Activation barrier
Energy barrier that must be overcome for any
chemical reaction to begin
105
Activation energy
Energy required to contort or weaken bonds so that they
can break and new bonds can be formed
106
Substrate
The reactant that an enzyme acts on
107
Active site
The region of the enzyme that a substrate fits into
* Typically a pocket or groove on the surface of the enzyme
108
Catalytic Cycle
A reaction that proceeds with the help of an enzyme
* The enzyme is the catalyst
109
Induced fit
Active site may change shape to hold the substrate more tightly
110
Denaturation
The protein unfolds so that its shape is changed
111
Cofactors
non protein molecules that aid enzymes
112
Coenzyme
cofactor that is organic
* Example: Vitamins
113
Inhibitor
A chemical that interferes with an enzyme’s activity
114
Competitive Inhibitor
Chemical compound that resembles an enzyme’s normal substrate
115
Non-competitive inhibitor
Inhibitor that binds to a spot on the enzyme outside of the active site
116
Feedback inhibition
If a cell is producing more product than it needs,
the product itself may become an inhibitor
