Chapter 3 - Cellular level (Pt1) Flashcards
Describe the parts, and their function, of an animal cell. Discuss the importance of the plasma membrane and transport of material across the plasma membrane
1
Q
What is the basic structural and functional unit of the body?
A
Cells
2
Q
How many cells are in the average adult human body?
A
More than 100 trillion cells.
3
Q
What is the scientific study of cells called?
A
Cell biology or cytology.
4
Q
What are the three main parts of a cell?
A
Plasma membrane, cytoplasm, and nucleus.
5
Q
What role do cells play in the human body?
A
They carry out functions that help maintain homeostasis.
6
Q
what 3 parts can the cell be subdivided into?
A
Plasma (cell) membrane
Cytoplasm: Cytosol and organelles
Nucleus: chromosomes and genes
7
Q
What is the plasma membrane?
A
The plasma membrane is the cell’s flexible outer layer that separates the internal and external environments.
8
Q
What role does the plasma membrane play in a cell?
A
The plasma membrane regulates material flow and plays a role in cell communication and maintaining cellular conditions.
Recall: regulation, communication, maintenance.
9
Q
What is selective permeability in relation to the plasma membrane?
A
Selective permeability is the ability of the plasma membrane to control what goes in and out of the cell.
10
Q
Where is the cytoplasm located in a cell?
A
The cytoplasm is located between the plasma membrane and the nucleus.
11
Q
What is cytosol?
A
Cytosol is the fluid part of the cytoplasm that contains water, solutes, and particles.
12
Q
What are organelles?
A
Organelles are specialized structures within the cytoplasm, such as the cytoskeleton, ribosomes, endoplasmic reticulum, and mitochondria, each with distinct functions.
13
Q
What is the function of the nucleus in a cell?
A
The nucleus is the control center of the cell, housing most of its DNA.
14
Q
What do chromosomes in the nucleus contain?
A
Chromosomes contain DNA molecules associated with proteins, where genes are located to govern cell structure and function.
15
Q
What is the plasma membrane also known as?
A
The plasma membrane is also called the plasmalemma.
16
Q
What is the difference between cytoplasm and cytosol?
A
Cytoplasm includes the entire region between the plasma membrane and the nucleus, encompassing cytosol, organelles, and other inclusions. Cytosol is the fluid component of the cytoplasm.
17
Q
What is cytosol composed of?
A
Cytosol is composed mainly of water, dissolved solutes, and suspended particles.
18
Q
What is selective permeability?
A
Selective permeability is the plasma membrane’s ability to regulate which substances can enter or exit the cell, allowing some molecules or ions through while restricting others.
19
Q
What is an electrochemical gradient?
A
An electrochemical gradient is the combination of a chemical gradient (difference in solute concentration) and an electrical gradient (difference in charge), which drives ion movement across the membrane.
20
Q
What is the chemical gradient?
A
The chemical gradient refers to the difference in solute concentration across the membrane, causing diffusion from areas of high concentration to low concentration.
21
Q
What is the electrical gradient?
A
The electrical gradient refers to the difference in electrical charge across the membrane, where ions move toward areas of opposite charge.
22
Q
What is the fluid mosaic model?
A
The fluid mosaic model describes the plasma membrane as a dynamic, flexible structure made of lipids with embedded proteins that float freely or are anchored.
23
Q
What are the three main components of the plasma membrane’s lipid bilayer?
A
The plasma membrane’s lipid bilayer consists of phospholipids (75%), cholesterol (20%), and glycolipids (5%).
24
Q
What is the function of cholesterol in the plasma membrane?
A
Cholesterol strengthens the membrane and modulates its fluidity.
25
What is the role of glycolipids in the plasma membrane?
Glycolipids are involved in cell recognition and communication.
26
Why is the plasma membrane described as a fluid structure?
The plasma membrane is fluid because the lipids and many proteins can rotate and move sideways within their layer of the bilayer.
27
what is the flexible yet sturdy barrier that surrounds and contains the cytoplasm of the cell
The Plasma Membrane
28
What are the two main categories of membrane proteins?
Membrane proteins are categorized as integral proteins and peripheral proteins.
29
What are integral proteins?
Integral proteins are embedded within the lipid bilayer, with many spanning the entire membrane, known as transmembrane proteins.
30
What is the lipid bilayer?
The lipid bilayer is the fundamental structure of a cell's plasma membrane, consisting of two layers of lipid molecules.
31
How do some integral proteins attach to the lipid bilayer?
Some integral proteins attach to one side of the bilayer through covalent bonds with fatty acids.
32
What is a covalent bond?
A covalent bond is a type of chemical bond where two atoms share one or more pairs of electrons.
33
What does it mean for integral proteins to be amphipathic?
Amphipathic proteins have both hydrophilic (water-attracting) and hydrophobic (water-repelling) regions, allowing them to interact with the lipid bilayer.
34
What are peripheral proteins?
Peripheral proteins are not embedded in the lipid bilayer; they attach to the polar heads of lipids or to integral proteins on the membrane's surface.
35
What are glycoproteins?
Many integral proteins are glycoproteins, which have carbohydrate chains (oligosaccharides) extending into the extracellular fluid.
36
Why are membranes considered fluid structures?
Because the lipids and many proteins can rotate and move sideways within their layer of the bilayer.
37
What are membrane proteins and how are they categorized?
Membrane proteins are categorized by their association with the membrane: integral proteins and peripheral proteins.
38
What are integral proteins?
Proteins embedded in the lipid bilayer, often spanning the entire membrane (transmembrane proteins).
39
What is the lipid bilayer?
The fundamental structure of a cell's plasma membrane, consisting of two layers of lipid molecules.
40
How can some integral proteins attach to the bilayer?
Through covalent bonds with fatty acids.
41
What is a covalent bond?
A chemical bond where two atoms share one or more pairs of electrons.
42
How are peripheral proteins associated with the membrane?
They attach to polar lipid heads or integral proteins on the membrane's surface.
43
What are glycoproteins?
Integral proteins with carbohydrate chains extending into the extracellular fluid.
44
What is the glycocalyx?
A sugary coat formed by carbohydrate chains that helps in cell recognition, adhesion, and protection.
45
How does the glycocalyx benefit cells?
It attracts fluids to aid cell movement, prevents drying out, and is crucial for immune responses.
46
What is the function of ion channels in membrane proteins?
Ion channels allow specific ions, such as potassium, to move in and out of the cell, usually being selective for one type of ion.
47
How do carrier proteins function in the cell membrane?
Carrier proteins transport ions or molecules across the membrane by acting as carriers, specific to the substances they move. Example: sodium/potassium pump.
48
What role do receptors play in membrane proteins?
Receptors bind specific molecules (ligands), like hormones, to initiate cellular responses. Example: insulin binding or antidiuretic hormone.
49
How do membrane proteins function as enzymes?
They act as enzymes by speeding up chemical reactions on the cell's surface. Example: lactase enzyme breaking down lactose.
50
What is the role of linkers in membrane proteins?
Linkers connect cells or internal structures to the membrane, providing stability and structural support.
51
What are cell-identity markers?
Glycoproteins and glycolipids that serve as identifiers, helping recognize similar cells or detect foreign cells (e.g., blood type matching).
52
What functions do peripheral proteins have?
They support the membrane, assist in linking proteins, and participate in cellular activities like moving materials, altering cell shape, and connecting cells.
53
What do membrane proteins reflect in a cell?
Membrane proteins largely reflect the functions a cell can perform.
54
what type of bonds link amino acids together?
hydrogen bonds
55
How do membrane lipids and proteins move?
They are mobile within their own half of the bilayer.
56
What role does cholesterol play in the membrane?
Cholesterol stabilizes the membrane and reduces its fluidity.
57
What characterizes the fluid nature of cell membranes?
Cell membranes are not static; their lipids and some proteins move and rotate rapidly within their layer, with lipids swapping places millions of times per second.
58
How do double bonds affect membrane fluidity?
Double bonds in fatty acid tails create "kinks," preventing tight packing and increasing fluidity.
59
Describe cholesterol's role in membrane fluidity.
Cholesterol stabilizes membranes. At normal temperatures, it makes membranes stronger and less fluid; at low temperatures, it helps maintain fluidity.
60
Why is membrane fluidity important for cell function?
It allows protein assembly, membrane adjustments during cell movement, growth, division, and helps the membrane self-seal if punctured.
61
Why do lipids and proteins usually stay in their own layer?
They typically stay in their own layer because moving across involves crossing a challenging hydrophobic core, preserving membrane structure and function.
62
What overall benefits does membrane fluidity provide?
It supports various cellular activities while ensuring stability and self-repair capabilities.
63
What does it mean for plasma membranes to be selectively permeable?
They allow some substances to pass through while blocking others.
64
Which substances can always pass through the lipid bilayer?
Oxygen, carbon dioxide, and steroids.
65
How permeable is the membrane to water and urea?
It is somewhat permeable to both water and urea.
66
What substances are never permeable to the lipid bilayer?
Ions (e.g., sodium) and large molecules like glucose and amino acids.
67
How do transmembrane proteins affect membrane permeability?
They act as channels or transporters, increasing the membrane's permeability.
68
Which molecules can pass through the lipid bilayer easily?
Nonpolar molecules like oxygen, carbon dioxide, and steroids, as they are lipid-soluble.
69
How do water and urea pass through the membrane?
They are moderately permeable, often passing through temporary gaps in the lipid tails.
70
Which substances are typically impermeable to the bilayer?
Ions and large polar molecules like glucose cannot pass without assistance.
71
What role do transmembrane proteins play?
They act as channels or carriers to help ions and large molecules cross the membrane.
72
How do large molecules cross the membrane?
Macromolecules like proteins require processes like endocytosis and exocytosis to cross.
73
How does the plasma membrane structure support selective entry and exit?
It allows substances to pass based on their properties and often requires specific proteins for assistance.
74
What is a concentration gradient?
It's the difference in the concentration of a chemical between one side of the plasma membrane and the other.
75
What is an electrical gradient?
It's the difference in ion concentration between one side of the plasma membrane and the other.
76
What is an electrochemical gradient?
It's the combination of both the concentration gradient and the electrical gradient.
77
Why is the cell membrane selectively permeable?
It controls what enters and exits the cell, creating different concentrations of substances inside and outside.
78
What is an electrochemical gradient?
It combines the concentration and electrical gradients, determining ion movement from high to low concentration and opposite charges.
79
Why are concentration and electrical gradients important for cells?
They help control substance movement for nutrient uptake and waste removal.
80
Hydrophobic and Hydrophilic Regions - How do these regions govern lipid arrangement?
Hydrophilic heads face outward towards water, and hydrophobic tails face inward, forming a bilayer barrier.
81
Does the presence of proteins in a membrane determine its functions?
True: Proteins define membrane capabilities such as substance transport, signal reception, and enzymatic activity.
82
What contributes to an electrochemical gradient?
Concentration gradient (solute differences) and electrical gradient (charge differences), both driving ion movement across the membrane.
83
Why is transport across the plasma membrane vital?
It helps import necessary substances, export waste, and maintain cellular homeostasis, essential for cell survival and communication.
84
What are the two main types of membrane transport?
Passive transport and active transport.
85
What characterizes passive transport?
It does not require energy; substances move down their concentration or electrical gradients.
86
What is simple diffusion?
Movement of small or nonpolar molecules across the phospholipid bilayer without protein assistance.
87
What factors affect the rate of simple diffusion?
Concentration gradient, temperature, and membrane permeability.
88
What is facilitated diffusion?
Transport of larger or polar molecules across the membrane with help from specific proteins, like channels or carriers.
89
What makes facilitated diffusion specific?
It relies on specific transport proteins and is regulated by their availability.
90
What is active transport?
Movement of substances against their concentration gradients, requiring energy, typically from ATP.
91
Describe primary active transport.
Direct use of ATP to transport molecules. Example: The sodium-potassium pump (Na⁺/K⁺ ATPase).
92
What is the role of the sodium-potassium pump?
It maintains electrochemical gradients by pumping 3 Na⁺ out and 2 K⁺ into the cell, crucial for nerve impulses and muscle contraction.
93
What is vesicular transport?
Movement of substances via vesicles, such as endocytosis (into the cell) and exocytosis (out of the cell).
94
What are passive transport processes?
They require no cellular energy. Substances move from high to low concentration using their kinetic energy.
95
What is simple diffusion?
Direct movement of molecules through the membrane without energy.
96
Which molecules move via simple diffusion?
Gases (O₂, CO₂, N₂), fats, and small neutral molecules.
97
Why is simple diffusion important?
It's crucial for gas exchange, nutrient absorption, and waste removal.
98
What is facilitated diffusion?
Movement of substances across the membrane with the help of proteins.
99
What are the types of proteins in facilitated diffusion?
Channels (like tunnels) and carriers (like ferry boats).
100
What kind of substances use facilitated diffusion?
Polar or charged substances.
101
What is osmosis?
The movement of water across membranes to balance solute levels.
102
What are active transport processes?
They require cellular energy, usually ATP, to move substances against their concentration gradient, from low to high.
103
What is an example of active transport?
Transport mechanisms like pumps that use ATP.
104
What is primary active transport?
Direct use of ATP to move molecules across a membrane, using energy from ATP hydrolysis to pump against concentration gradients.
105
Why is transport across the plasma membrane essential?
It allows the import of materials for metabolism and the export of waste and products, essential for cell life.
106
What are the two main types of transport across cell membranes?
Passive transport and active transport.
107
What are examples of passive transport?
Simple diffusion and facilitated diffusion.
108
Which molecules are involved in simple diffusion?
Oxygen, carbon dioxide, nitrogen (gases), fats (fatty acids, steroids, vitamins A, D, E, K), small neutral molecules (water, urea, alcohols).
109
Why is simple diffusion important?
It facilitates gas exchange, nutrient absorption, and waste removal.
110
What substances use facilitated diffusion?
Polar or charged substances that can't pass on their own.
111
What proteins are involved?
Channels (tunnels) and carriers (ferry boats).
112
What is osmosis?
Passive diffusion of water across a selectively permeable membrane, moving from higher to lower water concentration.
113
What characterizes active transport?
It requires energy (ATP) to move substances against their concentration gradient, from low to high concentration.
114
What are endocytosis and exocytosis? (Vesicular Transport)
Endocytosis brings materials into the cell using vesicles, while exocytosis expels materials out of the cell.
115
What is diffusion in the context of solutions? Can you give an everyday example of diffusion?
Movement of particles from high to low concentration, spreading out to reach equilibrium.
Dye spreading evenly in water until the color is uniform.
116
Why do cells use passive and active transport?
Passive transport saves energy and manages gradients, while active transport gives precise control over cell composition and responses.
117
Diffusion is influenced by:
Steepness of the concentration gradient
Temperature
Mass of diffusing substance
Surface area
Diffusion distance
hint: "Some Tigers Make Swift Dashes"
118
Does simple diffusion require ATP?
No, simple diffusion is a passive process and does not require cellular energy (ATP).
119
Q: How do molecules move in terms of concentration during simple diffusion?
A: Molecules move from an area of higher concentration to an area of lower concentration until equilibrium is reached.
120
Q: What types of molecules can pass through the cell membrane via simple diffusion?
A: Nonpolar and hydrophobic molecules (e.g., O₂, CO₂, N₂, lipids) and small uncharged polar molecules (e.g., water, urea).
121
Q: Why can nonpolar and hydrophobic molecules easily pass through the lipid bilayer?
A: They dissolve in the nonpolar interior of the membrane.
122
Q: What role does simple diffusion play in gas exchange?
A: It allows oxygen to move from the lungs into the blood and cells, and carbon dioxide to exit cells into the blood and out through the lungs.
123
Q: How does the steepness of the concentration gradient affect diffusion?
A: A steeper gradient results in a faster rate of diffusion.
124
Q: How does temperature influence diffusion?
A: Higher temperatures increase kinetic energy and diffusion rate, while lower temperatures decrease both.
125
Q: How does the mass of diffusing substances affect their diffusion rate?
A: Lighter molecules diffuse faster than heavier ones.
126
Q: What effect does surface area have on diffusion?
A: A larger surface area allows more molecules to diffuse simultaneously, increasing the rate.
127
Q: How does diffusion distance affect the rate of diffusion?
A: Shorter distances result in quicker diffusion, while longer distances slow it down.
128
Q: What is facilitated diffusion?
A: Facilitated diffusion is a type of passive transport where transmembrane proteins help transport solutes that are too polar or charged across the lipid bilayer.
129
Q: What role do transmembrane proteins play in facilitated diffusion?
A: They assist solutes in crossing the cell membrane, bypassing the lipid bilayer.
130
Q: What are the two main types of facilitated diffusion?
A: Channel-mediated facilitated diffusion and carrier-mediated facilitated diffusion.
131
Q: What characterizes channel-mediated facilitated diffusion?
A: It involves membrane channels, most of which are ion channels.
132
Q: What happens in carrier-mediated facilitated diffusion?
A: Transport proteins, known as carriers, bind to solutes and change shape to move them across the membrane.
133
Q: How do ion channels function in channel-mediated diffusion?
A: They form pores in the membrane, allowing ions to pass through based on concentration gradients.
134
Q: What is the role of carriers in carrier-mediated facilitated diffusion?
A: Carriers bind to specific molecules and undergo conformational changes to transport them across the membrane.
135
Q: What is channel-mediated facilitated diffusion?
A: It involves specific transmembrane channel proteins that allow ions or molecules to move across the cell membrane.
136
Q: What types of ions typically use channel-mediated diffusion?
A: Potassium (K+), chloride (Cl−), sodium (Na+), and calcium (Ca2+).
137
Q: How do ion channels work? (facilitated diffusion)
A: Ions move down their concentration gradient through selective channels without needing extra energy, like rolling a ball down a hill.
138
Q: What are gated channels? (facilitated diffusion)
A: Channels that can open or close, controlled by voltage changes or chemical signals.
139
How fast is ion transport through channels in facilitated diffusion?
A: Very fast, with large numbers of ions moving through the channels in seconds.
140
Q: What is carrier-mediated facilitated diffusion?
A: Specific proteins in the cell membrane assist in transporting molecules like glucose across the membrane, down their concentration gradient.
141
Q: How do carrier proteins function in facilitated diffusion?
A: A molecule binds to the carrier protein, causing it to change shape and transport the molecule across the membrane.
142
Q: How do glucose transporters (GluT) work in facilitated diffusion?
A: They facilitate glucose entry into cells, a process enhanced by insulin.
142
Q: What is the transport maximum in facilitated diffusion?
A: It's the maximum rate of diffusion, limited by the number of available carriers. Once saturated, the rate cannot increase further.
143
Q: What role does insulin play in glucose transport via facilitated diffusion?
A: It increases the number of glucose transporters in the cell membrane, crucial for regulating blood sugar levels.
144
Q: What happens in facilitated diffusion when insulin function is impaired?
A: In conditions like diabetes mellitus, reduced glucose transport leads to elevated blood sugar levels.
145
Q: Why is having more glucose transporter proteins beneficial for cells?
A: More transporters allow cells to take up glucose faster and more efficiently, helping lower blood sugar levels and providing more energy, especially during exercise.
146
Q: How does insulin affect glucose transport in facilitated diffusion?
A: Insulin increases the number of glucose transporters on the cell surface, enhancing glucose uptake.
147
Q: Why is increased glucose uptake important?
A: It aids in lowering blood sugar levels and provides more energy for cellular activities.
148
Q: How can increasing glucose transporters be therapeutically beneficial?
A: It improves blood sugar control and has potential for managing diabetes effectively.
149
What is an optimal way to increase these transport proteins?
exercise, healthy eating, medications, insulin management, lifestyle
150
Q: What is osmosis?
A: Osmosis is the passive movement of water across a cell membrane from areas of high water concentration (low solute concentration) to low water concentration (high solute concentration) until equilibrium is reached.
151
Q: Does osmosis require energy?
A: No, osmosis is a passive process and does not require energy.
152
In what direction does water move during osmosis?
Water moves from an area of high concentration to an area of low concentration.
153
What role do aquaporins play in osmosis?
Aquaporins are proteins in the cell membrane that act as channels specifically for water, facilitating its movement across the membrane.
154
Why is selective permeability important for osmosis?
A: Selective permeability is crucial because the membrane must allow water to pass through while preventing solutes from moving through the membrane.
155
Q: Can osmosis occur if the membrane is permeable to solutes?
A: No, osmosis can only occur if the membrane is permeable to water, not solutes.
156
Q: How do water molecules pass through the cell membrane during osmosis?
A: Water molecules can pass directly through gaps between lipids in the membrane or through aquaporins.
157
Q: What are some health issues caused by defects in aquaporins?
A: Defects in aquaporins can lead to cataracts, certain types of diabetes, and issues with saliva production and brain function.
158
Q: What is tonicity?
A: Tonicity is the ability of a surrounding solution to cause a cell to gain or lose water, affecting the cell's shape.
159
Q: How does tonicity influence the shape of a cell?
A: By causing the cell to either gain or lose water, which leads to the cell swelling or shrinking.
160
Q: On what does tonicity depend?
A: Tonicity depends on the solute concentration outside the cell relative to inside the cell.
161
Q: How does tonicity affect water movement in cells?
A: Tonicity influences water movement via osmosis, based on the solute concentration gradient.
162
Q: What happens to a cell in a hypotonic solution?
A: In a hypotonic solution, the cell gains water and may swell or even burst.
note: A hypotonic solution is one that has a lower concentration of solutes compared to another solution across a semipermeable membrane. When a cell is placed in a hypotonic solution, water will enter the cell due to osmosis, as the water moves from an area of lower solute concentration (the hypotonic solution) to an area of higher solute concentration (inside the cell).
163
Q: What happens to a cell in a hypertonic solution?
A: In a hypertonic solution, the cell loses water and may shrink.
164
Q: What happens to a cell in an isotonic solution?
A: In an isotonic solution, there is no net water movement, so the cell's shape remains constant.
165
Q: What is a hypotonic solution?
A: A hypotonic solution has a lower solute concentration outside the cell than inside.
166
Q: What is active transport?
A: Active transport is the process of moving substances across cell membranes against their concentration gradient, from an area of low concentration to an area of high concentration.
167
Q: Why does active transport require energy?
A: Because it moves substances against their natural flow, which requires energy, usually in the form of ATP.
168
Q: What role do carrier proteins play in active transport?
A: Carrier proteins act as pumps in the cell membrane, helping to move substances against their concentration gradient.
169
Q: Can you name examples of substances that use active transport?
A: Glucose, amino acids, and ions like Na+ and K+ are transported via active transport.
170
Q: What is the difference between primary and secondary active transport?
A: Primary active transport uses direct energy from ATP, while secondary active transport uses energy from ionic gradients.
171
Q: Why can't some solutes passively cross the plasma membrane?
A: Some solutes can't passively cross because they need to move against their concentration gradient, which requires active transport.
172
Q: What is transport maximum in active transport?
A: It is the limit to how fast substances can be transported, based on the availability of carrier proteins.
173
Q: How does active transport help in maintaining cell metabolism?
A: By actively transporting nutrients like glucose and amino acids into cells, even when their concentrations are higher inside.
174
Q: What energy source is used in primary active transport?
A: Energy from ATP is used to change the shape of a carrier protein to pump substances across the membrane against their concentration gradient.
175
Q: How much of a cell's ATP is used for active transport?
A: Active transport uses about 40% of a cell's ATP.
176
Q: What happens to active transport if ATP production stops?
A: Active transport ceases, which can be deadly; for example, cyanide poisoning can stop ATP production.
177
Q: What is the most common example of primary active transport?
A: The sodium-potassium pump (Na+-K+ ATPase), which moves sodium ions out of and potassium ions into the cell.
178
Q: How does the sodium-potassium pump function?
A: It uses ATP to expel Na+ from the cell and bring K+ in, maintaining necessary ion concentrations.
179
Q: Why does the sodium-potassium pump need to operate continuously?
A: Because Na+ and K+ ions can leak back through the membrane, the pump works continuously to maintain the ion balance.
180
Q: What role does the sodium-potassium pump play in cell function?
A: It maintains low Na+ and high K+ concentrations inside cells, which is crucial for cell function.
181
Q: How is energy from ATP used in primary active transport?
A: Energy is released through the hydrolysis of ATP into ADP and an inorganic phosphate, which is used to change the shape of transporter proteins.
note: Hydrolysis is a chemical reaction in which a water molecule is used to break down a compound.
182
Q: What happens to transporter proteins during active transport?
A: They change shape to bind to a specific substance on one side of the membrane and then release it on the opposite side.
183
Q: Why is the sodium-potassium pump important for cell functions?
A: It maintains concentration gradients essential for processes like nerve impulse transmission and muscle contraction.
