Chapter 6/7: Cell and Cell Membranes Flashcards
(164 cards)
1
Q
Cell Fractionation
A
- Useful technique for studying cell structure and function
- Takes cells apart and separates major organelles
- Centrifuge: instrument used which spins test tubes holding mixtures of disrupter cells at increasing speeds
- Each speed causes a fraction of the cells components to settle to the bottom of the tube
- Lower speeds: pellet consists of larger components
- Higher speeds: pellet consists of smaller components
- Enables researchers to prepare specific cell components in bulk and identify their functions
2
Q
Both Prokaryotic and Eukaryotic
A
- All bounded by a selective barrier= plasma membrane
- Inside all cells is a semifluid, jelly like substance =cytosol
- All cells contain chromosomes which carry genes in the form of DNA
- All cells have ribosomes which are tiny complexes that make proteins according to instructions from the genes
3
Q
Eukaryotic Cell
A
- Most of the DNA is in an organelle called the nucleus, which is bounded by a double membrane
- Much larger than prokaryotic cells
- The cells compartments provide diff local environments that facilitate specific metabolic functions
- Eukaryotes are able to be bigger because of compartmentalization, they ave parts inside them that are small, allows them specialization and increase in SA.
4
Q
Prokaryotic Cell
A
- DNA is concentrated in a region that is not membrane enclosed, called the nucleoid region
- Lack membrane-bound organelles
- Prokaryotic Cells evolved before Eukaryotic Cells
5
Q
Cytoplasm
A
- interior of either type of cell
- within the cytosol are a variety of organelles of specialize form and function
- In eukaryotic cells: the term refers only to the region between the nucleus and the plasma membrane
6
Q
Plasma Membrane
A
- Functions as a selective barrier that allows passage of enough oxygen, nutrients, and wastes to service the entire cell
- Only a limited amount of substance can cross per second
7
Q
Volume to SA Ratio
A
- As a cell increases in size, its volume grows proportionally more that its surface area
- a smaller object has a great ratio of surface area to volume
- Larger organisms have more cells
- A high ratio of SA to volume is especially important in cells that exchange a lot of material with their surroundings
- Microvilli: increase SA without an increase in volume
8
Q
Cell
A
Simplest collection of matter that can be alive
9
Q
Biological Membranes
A
- basic fabric feature is a double layer of phospholipids and other lipids, embedded in this lipid bilayer or attached to its surfaces are diverse proteins
- lipids and proteins
10
Q
Nucleus
A
- Contains most of the genes in the eukaryotic cell
- Contains DNA
- directs protein synthesis by synthesizing messenger RNA according to instructions provided by the DNA
- The mRNA is then transported to the auto plasm via the nuclear pores.
- Once an mRNA molecule reaches the cytoplasm, the ribosomes translate the mRNA’s genetic message into the primary structure of a specific polypeptide
11
Q
Nuclear Envelope
A
Encloses the nucleus, separating its contents from the cytoplasm
-A double membrane-each a lipid bilayer with associated proteins
12
Q
Pore Complex
A
- Intricate protein structure
- Lines each pore and plays an important role in the cell by regulating the entry and exit of proteins and RNA’s
13
Q
Nuclear Lamina
A
-The nuclear side of the envelope is lined by the nuclear lamina, a netlike array of protein filaments that maintains the shape of the nucleus by mechanically supporting the nuclear envelope
14
Q
Nuclear Matrix
A
- A framework of protein fibers extending throughout the nuclear interior
- May help organize the genetic material so it functions efficiently
15
Q
Chromosomes
A
- Within the nucleus, DNA is organized into discrete units called chromosomes
- Structures that carry the genetic information, each chromosome contains one long DNA molecule associated with many proteins
16
Q
Chromatin
A
- The complex of DNA and proteins making up chromosomes
- As a cell prepares to divide, the chromosomes coil further, becoming thick enough to be distinguished as separate structures.
17
Q
Nucleolus
A
- Prominent structure within the non dividing nucleus, which appears through the electron microscope as a mass of densely stained granules and fibers adjoining part of the chromatin
- proteins imported from the cytoplasm are assembled with rRNA into large and small subunits of ribosomes
- subunits then exit the nucleus through the nuclear pores to the cytoplasm, where a large and small subunit can assemble into a ribosome
18
Q
Ribosomal RNA
A
-rRNA is synthesized from instructions in the DNA
19
Q
Ribosomes
A
- Complexes made of ribosomal RNA and protein, are the cellular components that carry out protein synthesis
- Cells that have high rates of protein synthesis, have particularly large numbers of ribosomes
- Free Ribosomes: suspended in cytosol
- Bound Ribosomes: attached to the outside of the endoplasmic reticulum or nuclear envelope (EX: lysosomes or cells that specialize in protein secretion frequently have a high proportion of bound ribosomes
20
Q
Endomembrane System
A
- Regulates protein traffic and performs metabolic functions in the cell
- INCLUDES: the nuclear envelope, endoplasmic reticulum, the Golgi apparatus, lysosomes, vesicles and vacuoles, and the plasma membrane
- Carries out a variety, like synthesis of proteins, transport proteins into membranes and organelles or out of the cell, metabolism and movement of lipids and detoxification of poisons.
21
Q
Vesicles
A
- Sacs made of membrane
- related either through direct physical continuity or by the transfer of membrane segments as tiny vessels
- may be modified
22
Q
Endoplasmic Reticulum
A
- An extensive network of membranes that it accounts for more than half the total membrane in many eukaryotic cells
- cisternae: consists of a network of membranous tubules and sacs
- Separates the internal compartment of the ER called the ER lumen cavity or cisternal space from the cytosol
- Rough ER and Smooth ER
- Rough ER: ribosomes (mRNA and make proteins)
- Smooth ER: Make lipids, make steroids, detoxifies, responsible for metabolism of carbs, regulates calcium ion concentration
23
Q
Passive Transport
A
-Requires no cell energy
24
Q
Diffusion
A
-The movement of molecules from an area of high concentration of those molecules to an area of lower concentration
25
Concentration Gradient
-A metaphorical "downhill" from high concentration to low concentration
26
Dynamic Equilibrium
-A balance
27
Active Transport
- Uses energy to move molecules either into or out of the cell
- Uses energy in the form of ATP
28
Hypertonic
- Experiences a net loss of water
- contains high concentration of solutes than the cell and therefore a lower concentration of water
- Water will flow out of the cell from the region of higher water concentration to the region of lower concentration
29
Hypotonic
- Experiences a net gain of water
- Contains lower concentration of solutes than the cell and therefore a higher concentration of water
- Water will flow into the cell from the region of higher water concentration to the region of lower concentration
30
Isotonic
- It will experience neither a net gain or loss of water
- Contains equal concentration of solutes as the cell and therefor an equal concentration of water
- Water will flow equally into and out of the cell
31
Plasmolysis
- The shrinking of the cytoplasm of a plant cell in response to diffusion of water out of the cell and into a hypertonic solution surrounding the cell
- During plasmolysis, the cell membrane pulls away from the cell wall.
32
Cell Membrane
- Regulates what comes into and out of the cell
- Has a hydrophilic( -) and hydrophobic head (+)
- Heads face the water, tails face away from the water
- All cells that we have, have a cell membrane
- All the membrane inside of a cell is moving around, if it ever stops moving, then it doesn't function as the membrane
- A membrane is made up of phospholipids and proteins
33
Amphipathic Cell
-A molecule that is both hydrophilic and hydrophobic
34
Phospholipid
- Keeps water on either side
| - Inside a cell membrane
35
Proteins
- Give proteins their specific characteristics
- Allows material in and connects to the out
- Within the membrane, regulate transport, allow things that are large and uncharged
- Allows big things and things that have a charge to cross
36
Cytoplasm
Inside the membrane
37
Extracellular Fluid
Outside the membrane
38
Glycoprotein
- has protein on inside
- Sugar attached to it
- Antibodies
39
Cell Membrane Fluidity
- float back and forth
- unsaturated lipid tail
- cholesterol
40
Materials That Can Enter/Leave Cell
- Oxygen (diffusion)
- CO2
- Things that are uncharged can go through the cell
41
Water
- Water enters and leaves the cell by proteins
- Allows material into and out of the cell
- Water can't go through the membrane because it is non polar through the inside
42
Aquaporins
-protein will allow water to move through
43
Selective Permeability
- Cells only allow certain things in and certain things out
| - Can regulate this and does this by using the cell membrane
44
Cell Walls
- Only plant cells have cell walls
- provide structure
- aid in plant cells= more structure
- Cell walls are made of cellulose, additional selection and rigidity
- Plants-cellulose/membrane
- Bacteria-cell wall/capsule/cellmembrane/peptidoglycin
- Fungi-cell wall-chitin
45
Fluid Cell Membrane
- Made up of a number of things
- Fluid because everything is moving
- Phospholipids float
- In flux
- If not flowing then material won't go through
46
Cholesterol In Membrane
- Connects phospholipids together
- Keeps phospholipids from drifting off
- It keeps together and at the same time keeps apart
47
Glycolipids
- Made up of fats and sugars
| - Important for signaling
48
Fat
- Phospholipids are fat
- Mostly made up of carbon and hydrogen
- Has head with charge
49
Substances That Move Through The Membrane
- Small and not charged molecules
| - Examples: O2 and CO2
50
Cell Size
- Cells are small because the material moves in through a cell through diffusion. The distance between material has to move is small
- Cells aren't infinitely small because the DNA has to be able to fit, everything has to be able to fit
51
Cytoskeleton
-It is a lattice made up of a number of difference macromolecules, organelles fit inside the lattice, motor proteins walk
52
Central
- Cytoskeleton
| - Only in animal cells, 9+2, replicate, makes spindle fibers, chromosomes-separating, sets up formation
53
Lysosomes
-The suicide sac, digestive enzymes, contained within membrane and breakdown
54
Cytosol
-fluid, dissolved material with solutes
55
Compartmentalization
- Parts within parts, specialization, and surface area
| - Example: Endoplasmic Reticulum which allows multiple jobs and increase in surface area
56
Mitochondria
- Make ATP
| - Used to be bacteria cells on own, use them now for compartmentalization
57
Organelle
- Tiny organ, and part of the cell
| - Allows for specialization
58
Microtubules
-Compressional support in the cytoplasm
59
Microfilaments
-Tensional support in the cytoplasm
60
Osmoregulation
- The general term for the processes by which animals control solute concentrations and balance water gain and loss
- Balances the uptake and loss of water and solutes
61
Excretion
-The process that rids the body of nitrogenous metabolites and other metabolic waste products
62
Osmolarity
--Whenever two solutions separated by the membrane differ in osmotic pressure
-(total solute concentration expressed as molarity, that is, moles of solute per liter of solution)
-milliOsmoles per liter (mOsm/L)
-
63
Isoosmotic
-Two solutions separated by a selectively permeable membrane have the same osmolarity
64
Hyperosmotic
-Two solutions differ in osmolarity, the one with greater concentration of solutes
65
Hypoosmotic
-Less concentration of solutes
66
***Water flows by osmosis from a hypo osmotic solution to a hyperosmotic one***
...
67
Osmoconformer
- To be isosmotic with its surroundings
- All are marine animals
- Internal osmolarity is the same as that of its environment, there is no tendency to lose or gain water
- Live in water that has a stable composition and hence have a constant internal osmolarity
68
Osmoregulator
- To control internal osmolarity independent of that of its environment
- Enables animals to live in environments that are uninhabitable for osmoconformers
- Must discharge excess water
- Must take in water to offset osmotic loss
- allows
69
Stenohaline
--Osmoconformers and Osmoregulatory cannot tolerate substantial changes in external osmolarity
70
Euryhaline
- these animals, can survive large fluctuations in external osmolarity
- include barnacles and mussels which are continually covered and uncovered by ocean tides
71
Marine Animals
- Osmoconformers
- Osmolarity is the same as that of seawater
- No substantial challenges in water balance
72
Freshwater Animals
--Must be in hyperosmotic because animal cells cannot tolerate salt concentrations as low as that of lake or river water
73
Desiccation
- Extreme dehydration
| - Fatal for most animals
74
Anhydrobiosis
- "life without water"
| - animals ever a dormant state when their habitats dry up
75
Energetics of Osmoregulation
- Needs energy
- must expend energy to maintain the osmotic gradients that cause water to move in or out
- Use active transport to manipulate solute concentrations in their body fluids
- Body fluids of most animals that live in fresh water have lower solute concentrations than the body fluids of their closes relatives that live in seawater
- Minimizing the osmotic difference between body fluids and the surrounding environment decreases the energy the animal expends for osmoregulation
76
Transport Epithelia
- part os osmoregulation
- osmoregulation and metabolic waste disposal rely on transport epithelia
- One or more layers of epithelial cells specialized for moving particular solutes in controlled amounts in specific directions
- Arranged into complex tubular networks with extensive surface area
77
Osmoregulation
-ultimate function is to control solute concentrations in cells, but most animals do this indirectly by managing the solute content of an internal body fluid that bathes the cells
78
Circulatory System
-link exchange surfaces with cells throughout the body
79
Hypotonic (OSMOSIS ONLY)
- Water goes from high to low
- water enters cell (to the inside)
- Animal Cell will burst or lyse (cytolysis)
- Plant-Turgid (best environment)
- High water potential outside of the cell
- Increase turgor pressure inside the cell
80
Isotonic (OSMOSIS ONLY)
- Water enters and leaves is equal
- Animal cell: size will remain the same (perfect environment)
- Plant Cell: flaccid
- Water potential is equal
- No turgor pressure
- No movement of H2O
81
Hypertonic
- Water leaves the cell
- Animal Cell-will shrink crenate or shrivel
- Plant Cell: dies or flaccid or plasmolysis
- High water potential inside the cell
- Turgor pressure will decrease in the cell
82
Tight Junctions
- Tight connections between the membranes of adjacent cells.
- They're so tight that there is no space between them.
- Seal off body cavities and prevent leaks.
83
Gap Junctions
-Protein complexes that form channels in membranes and allow communication between the cytoplasm of adjacent animal cells or the transfer of small molecules and ions
84
Desmosomes
- Hold adjacent animal cells tightly to each other
- Consist of a pain of discs associated with the plasma membrane of adjacent cells, plus the intracellular protein filaments that cross the small space between them.
- Intermediate filaments within the cells are also attached to the discs
85
Cell Junctions
- When cells come in close contact with each other, they develop specialized intercellular junctions that involve their plasma membranes.
- These structures may allow neighboring cells to form strong connections with each other, prevent passage of materials, establish rapid communication between adjacent cells.
86
Exocytosis
-A cell ejects waste products or specific secretion products, such as hormones, by the fusion of a vesicle with the plasma membrane
87
Dialysis
-The diffusion of solutes across a selectively permeable membrane
88
Bulk Flow
- Other substances move by bulk flow
| - One way movement of fluids brought about by pressure
89
Types of Endocytosis
- Pinocytosis: the cell ingests liquids "cell drinking"
- Phagocytosis: the cell takes in solids "cell-eating"
- Receptor Mediated Endocytosis: involves cell surface receptors that are covered in clear thin coated pit. (A king of protein)
- When a particle, or ligand, binds to one of these receptors, the ligand is brought into the cell by the invagination or folding in of the cell membrane
- A vesicle then forms around the incoming ligand and carries it into the cell's interior.
90
Endocytosis
- When a particle that wants to enter a cell are too large, the cell uses a portion of the cell membrane to engulf the substance.
- The cell membrane forms a pocket, pinches in, and eventually forms either a vacuole or vesicle
91
Active Transport
- Some proteins in the plasma membrane are powered by ATP
- Active Transport: movement against the natural flow
- From a region of lower concentration to a region of higher concentration
- Needs Energy
- Sodium Potassium Pump: example of active transport
- Ushers out sodium ions (Na+) and brings in (K+) potassium ions across the cell membrane. These pumps depend on ATP to get ions across that would otherwise remain in regions of higher concentration.
92
Facilitated Transport
- Solutes: dissolved substances, rely on proteins embedded in plasma membrane
- Channel Proteins: help liquid-insoluble substances get in or out
- The proteins pick up the substance from one side of the membrane and carry it across to the other which is called facilitated diffusion or facilitated transport
- The flow of the substance is down the concentration gradient, doesn't require energy
93
Osmosis
-Special kind of diffusion that involves the movement of water
94
Diffusion
- Some substances move across a membrane by simple diffusion
- if there is a high concentration of a substance outside of the cell and low concentration inside the cell, the substance will move into the cell
- the substance moves down the concentration gradient
- "goes with the natural flow"
- called passive transport
- simple diffusion does not require energy
95
Rule of Water
-Although water molecules are polar, they can rapidly cross a lipid bilayer (rate at about 3 billion water molecules per second) through aquaporins, which are integral membrane proteins that regulate the flow of water
96
Cell Membrane (Work)
- For a cell to maintain internal environment, it has to be selective in the materials it allows to cross its membrane
- Lipid-soluble substances cross membrane without any resistance
- "like dissolves like"
- Lipid Membrane: Open door for lipids
- If hydrophilic= won't let in
97
Ability of Molecules To Move Across A Cell
- Semipermeability of the plasma membrane
| - The size and charge of particles that want to get through
98
Animal Cell Characteristics
- Cell Wall NO
- Plasma Membrane YES
- Organelles YES
- Nucleus YES
- Centrioles YES
- Ribosomes YES
99
Plant Cell Characteristics
- Cell Wall YES
- Plasma Membrane YES
- Organelles YES
- Nucleus YES
- Centrioles NO
- Ribosomes YES
100
Prokaryote Characteristics
- Cell Wall YES
- Plasma Membrane YES
- Organelles NO
- Nucleus NO
- Centrioles NO
- Ribosomes YES
101
Chitin
- In fungi, the cell wall is usually made of chitin which is a modified polysaccharide
- Principle component of an arthropods skeleton
102
Plant Cells
- Cell Wall: have a protective outer covering made of glucose, rigid layer just outside the plasma membrane that provides support for the cell. Found in plants, protists, fungi, bacteria
- Chloroplasts: organelles involved in photosynthesis, contain chlorophyll which is green
- Large Vacuole: most of the cytoplasm is vacuole, contains the cell sap
- NO centrioles
103
Cytosol
- Fluid within cell, metabolism of cell
- The shape of a cell is determined by a network of fibers called the cytoskeleton
- Microtubules and Microfilaments
104
Microfilaments (Cytoskeleton)
- important for movement
- Thin, rod like shaped structures are composed of the protein actin, they are involved in cell mobility and playa central role in muscle contraction
105
Paramecium
- covered in cilia
| - Rythmic beating of cilia enables it to motor about in waterways, ponds, microscope slides
106
Euglena
-Have cilia and flagella
107
Cilia and Flagella
- Threadlike structures best known for their locomotive properties in single celled organisms
- Beating motion of C and F structures propels these organisms through their watery environments
108
Microtubules (Cytoskeleton)
- Centrioles: help chromosomes separate during cell division
- Microtubules: made up of protein tubular, participate in cellular division and movement
- Small fibers are an integral part of 3 structures: centrioles cilia and flagella
109
Peroxisomes
- Organelles that detoxify various substances producing hydrogen peroxide as byproduct.
- Contain enzymes that break down (H2O2) into oxygen and water
- Common in liver and kidney
110
Vacuoles
- Food, water, waste storage
| - Fluid filled sacs that store water, food, waste, salts, and pigments
111
Centrioles
- Small, paired, cylindrical structures that are found within microtubule organizing centers
- Most active during cell division
- Centrioles produce microtubules which pull the replicated chromosomes apart and move them to opposite ends of the cell
- ONLY IN ANIMAL CELLS
112
Lysosomes
- Digest, suicide organelle, breaks down, recycling, explode, digest damaged organelles
- Small membrane bound structures
- Carry digestive enzymes which they use to break down old, worn out organelles, debris or large ingested particles
- Makeup the cells clean up crew helping keep cytoplasm clear
- Contain hydrolytic enzymes that only function at acidic PH.
113
Mitochondria
- Power house of the cell
- Aid in cell respiration
- Makes ATP
- Power stations responsible for converting the energy from organic molecules into useful energy for the cell
- The entry molecule in the cell is ATP
- The inner mitochondrial membrane forms folds known as cristae. Most of the ATP is done on the cristae.
114
Vesicles
- Transport
- Move out of a Cell
- Package of final product from golgi, gets packaged in little sacs, which carry the products to the plasma membrane
115
Golgi Apparatus
- Part of the endomembrane system
- CIS: Receiving
- Trans: Shipping
- Modify and package and ship proteins
- Participate in the processing of proteins
- Modify, process, ship and sort products
- Production of Lysosomes
116
Nuclear Pores
-Regulate what leaves and enters the cell
117
Endoplasmic Reticulum
- RER: synthesize proteins (polypeptides) [ribosomes]
- SER: detoxifies synthesis of lips and carbs[no ribosomes]
- Continuous channel that extends into many regions of the cytoplasm
- proteins generated in the rough ER are trafficked to or across the plasma membrane
- SER: makes lipids, hormones, steroids, breaks down toxic chemicals
118
Ribosomes
- Sites of protein synthesis
- Manufacture all the proteins required by the cell or secreted by the cell
- Round structures composed of 2 sub units
- The structure is composed of RNA and proteins
- Can either be free floating in the cell or bound to another structure called the endoplasmic reticulum
119
Nucleolus
-Where rRNA is made and ribosomes are assembled
120
Nucleus
- Contains nucleolus
- DNA--->Chromosomes
- Largest organelle
- Control center of the cell
- Directs what goes on in the cell
- Responsible for cells ability to reproduce
- Home of DNA---> organizes into large structures called chromosomes
- Nucleolus which is where Rona is made and ribosomes are assembled
121
Carbohydrate Side Chains
- Attached to the surface of some proteins
- Found only on the outer surface of the plasma membrane
- Cholesterol molecules are also found in the phospholipid bilayer because they help stabilize membrane fluidity in animal cells.
122
Recognition and Adhesion Proteins
-Some proteins such as glycoprotein are exposed on the extracellular surface and play a role in cell recognition and adhesion
123
Channel Proteins
-Form channels that selectively allow the passage of certain ions or molecules
124
Transport Proteins
-Proteins form pumps that use ATP to actively transport solutes across the membrane
125
Receptor Proteins
-Serve a docking sites for proteins of the extracellular matrix or hormones
126
Adhesion Proteins
-Some membrane proteins form junctions between adjacent cells
127
Fluid Mosaic Model
Arrangement of phospholipids and proteins
128
Transmembrane Proteins
Some integral proteins do not extend all the way through the membrane
129
Integral Proteins
- Proteins firmly bounded to plasma membrane
- Amphipathic proteins means their hydrophilic regions extend out of the cell or into the cytoplasm, while their hydrophobic regions interact with the tails of the membrane phospholipids.
130
Peripheral Proteins
- Some of these proteins are loosely associated with the lipid bilayer.
- Located on the inner or outer surface of the membrane
131
Plasma Membrane
- Outer envelope
- Complex Double-layered structure made up o phospholipids and proteins
- hydrophobic fatty acids tails face inward and hydrophilic phosphate heads face outward
- regulates the movement into and out of the cell
- Semi-Permeable , only small hydrophobic molecules can pass through it
- Many proteins associated with the cell membrane
132
Flagella
-Long projections used for motility (movement)
133
Prokaryotes
- Smaller than eukaryotic cells
- Lacks nucleus and membrane bound organelles
- nucleoid region-DNA
- plasma membrane
- cell wall
- ribosomes
- flagella
134
Cell
- All living things are composed of cells
- The cell is the life basic unit of structure and function
- Smallest unit of living material that can carry out all the activities necessary for life
135
Cytoskeleton
- Structure inside the cell
- "Bridge support"
- Microtubules: compressional Suport
- Microfilaments: Tensional Support
136
BOTH EUK AND PRO
- DNA
- Cell Membranes
- Ribosomes
- Cytosol
137
Temperature Affecting Membrane
-A membrane remains fluid as temperature decreases until the phospholipids settle into a closely packed arrangement and the membrane solidifies
138
Cholestoral
-Steroid, wedged between phospholipid molecules in the plasma membranes of animal cels
-High Temps: cholesterol makes the membrane less fluid by restraining phospholipid movement
-Lowers the temp required for the membrane to solidify
-
139
Cell-Cell Recognition
A cell's ability to distinguish one type of neighboring cell from another, crucial to the functioning of an organism.
-Important in the sorting of cells into tissues and organs in an animal
-
140
***Hydrophobic interior of the membrane impedes direct passage through the membrane of ions and polar molecules***
-Polar molecules cross very slowly
-Charged atom or molecule is less likely to penetrate the hydrophobic interior
-
141
Aquaporin
- Channel proteins which greatly facilitate the passage of water molecules through the membrane
- Makes it faster
142
Carrier Proteins
-Transport proteins, hold onto their passengers and change shape so that they shuttle across the membrane
143
Passive Transport
-Diffusion of a substance across a membrane with no energy investment
-molecules have thermal energy due to constant motion
-Will diffuse from where it is more concentrated to where it is less concentrated
-
144
*****Water diffuses across the membrane from the region of high free water potential (lower solute concentration) to that of lower free water concentration (higher solute concentration) until the solute concentrations on both sides are nearly equal*****
---
145
Tonicity (ONLY applies to Osmosis)
- The ability of the surrounding solution to cause a cell to gain or lose water
- Isotonic: same, the volume of an animal cell stays stable (perfect environment)
- Hypertonic: "more", way more solute than in the cell, the cell will lose water, shrivel and die
- Hypotonic: "less", low solute, water will rush in, water will enter the cell faster than it leaves, the cell will swell and lyse or burst like an overfilled abloom
146
Osmoregulation
The control of solute concentrations and water balance
147
Contractile Vacuole
An organelle that functions as a Blige pump to force water out of the cell as fast as it enters by osmosis (hypotonic)
148
Cell Wall
* ****HYPOTONIC is ideal for plants*****
- helps maintain the cells water balance, it exerts a back pressure of the cell, called turgor pressure that opposes further water uptake
149
Turgid
The cell is very firm, which a HEALTHY STATE for plans (hypotonic)
150
Flaccid
- When a plants cells and surrounding are isotonic, there is no net tendency for water to enter, cels become limp (not strong) NOT IDEAL
- If a cell is n a hypertonic env., it will lose water to its surrounding and shrink, as the plant cell shrivels, its plasma membrane pulls away from the cell wall
151
Plasmolysis
- Causes the plant to wilt and can lead to plant death
- Walled cells of bacteria and fungi also plasmolyze in hypertonic environments rupture!
- VERY BAD
152
Active Transport
- Must use a protein
- To pump a solute across a membrane against its gradient requires work, the cell must get energy, the transport proteins are all carrier proteins which enables a cell to maintain internal concentrations of small solutes that differ from concentrations in its environment
- ATP supplies energy
- Transfers its terminal phosphate group directly to transport proteins
153
Sodium Potassium Pump
- Transport System
- Exchanges NA+ for K+ across the plasma membrane of animal cells
- NA+ goes out, K+ goes in, changing the charge of the cell
154
Ions
- passive transport
- an ion diffuses not simply down its concentration gradient but down its electrochemical gradient
- Some membrane proteins that actively transport ions contribute to the membrane potential=sodium potassium pump
- With each crank of the pump, there is a net transfer of one positive charge from the cytoplasm to the extracellular fluid=a process that stores energy as voltage
155
Electrogenic Pump
Transport protein that generates voltage across a membrane
156
Proton Pump
- Main electrogenic pump of plants, fungi, and bacteria which actively transports protons out of the cell
- Electrogenic pumps help store energy that can be used for cellular work
- An important use of protein gradients in the cell is for ATP synthesis during cellular respiration, another is a type of membrane traffic called cotransport
157
ATP
Phosphate and ADP
| -yields greatest amount of energy
158
ADP
ATP broken down into smaller parts
159
Cotransport
-A transport protein can couple the downhill diffusion of the solute to the uphill transport of a second substance against its own concentration gradient
160
Bulk Transport
-Occurs by exo and eno cytosis
******Water and small solutes enter and leave the cell by diffusing through the lipid bilayer of the plasma membrane or by being pumped or moved across the membrane by transport proteins
-Large molecules like proteins and polysaccharides generally require energy a lot because they cross the membrane in BULK
-
161
Human Cells
-Use receptor mediated endocytosis to take in cholesterol for membrane synthesis and the synthesis of other steroids
162
LDL's (Low Density Lipoproteins)
-Cholestorol travels in the blood in particles called LDL's, which is each a complex of lipids and proteins, they bind to LDL receptors on plasma membranes and then enter the cells of endocytosis
163
Freshwater Fish
Osmosis water gain
-gain water and salt ions, uptake of salt ions by gills, excretion of salt ions and large amounts of water in flute urine of kidneys
164
Marine Fish
Osmosis water loss
-gain water and salt ions from water and food, excretion from gills and kidneys
high to low
