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Praxis (5236) - Biology > 2B3 Maintaining Balance: Cells > Flashcards

2B3 Maintaining Balance: Cells Flashcards

Describe how the cell membrane controls homeostasis. Differentiate between active and passive transport, including diffusion, osmosis, endocytosis, and exocytosis.

1
Q

What is the function of the cell membrane?

A

To separate the cell from its environment and control the movement of substances in and out of the cell.

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2
Q

What is the cell membrane composed of?

A

Two layers of phospholipids, forming a phospholipid bilayer.

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3
Q

What does the term ‘selectively permeable’ mean in relation to the cell membrane?

A

It means that the cell membrane only allows certain substances to pass through while restricting others.

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4
Q

Why is the cell membrane selectively permeable?

A

To control the specific substances that are allowed in and out of the cell, thereby maintaining homeostasis.

Example: The cell is selectively permeable to glucose, which requires glucose transporter proteins to allow diffusion into the cell.

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5
Q

What type of molecules can diffuse directly through the cell membrane?

A

Small, hydrophobic molecules.

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6
Q

What are the two main parts of phospholipids?

A
  • Tails - Hydrophobic, fatty acid chains
  • Heads - Hydrophilic phosphate groups
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7
Q

How do phospholipids contribute to the selective permeability of the cell membrane?

A

They have hydrophilic heads facing the aqueous environment and hydrophobic tails sandwiched in between, preventing large or hydrophilic molecules from diffusing through.

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8
Q

What does hydrophilic mean in relation to phospholipids?

A

It means it can dissolve in water.

Hydrophilic refers to the phosphate head of a phospholipid, which can dissolve in water.

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9
Q

What does hydrophobic mean in relation to phospholipids?

A

It means it cannot dissolve in water.

Hydrophobic refers to the lipid tail of a phospholipid, which cannot dissolve in water.

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10
Q

What is a phosphate group of a phospholipid composed of?

A

A phosphorous atom covalently bonded to four oxygen atoms.

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11
Q

What are the hydrophobic tails of phospholipids made of?

A

Two chains of non-polar fatty acids.

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12
Q

What role do proteins play in the cell membrane?

A

They act as channels or doors that allow larger and charged molecules to pass through.

Example: Glucose passes through transport proteins.

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13
Q

What is the function of carbohydrates in the phospholipid bilayer?

A

They are used for cell signaling and attaching to other cells.

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14
Q

What is the function of cholesterol in the phospholipid bilayer?

A

It helps regulate membrane fluidity.

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15
Q

What is the main source of energy for active transport?

A

ATP

(Adenosine Tri-Phosphate)

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16
Q

What are the main types of active transport?

A
  • Primary Active Transport
  • Secondary Active Transport
  • Endocytosis and Exocytosis
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17
Q

What is primary active transport?

A

Active transport of small molecules that directly use ATP as an energy source.

Example: The sodium-potassium (Na/K) pump.

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18
Q

What is secondary active transport?

A

Transport where the energy required comes from moving a second molecule down its electrochemical gradient, involving either symport or antiport proteins.

Example: Movement of sodium ions to power the transport of amino acids out of the cell.

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19
Q

What is the difference between symport and antiport proteins in secondary active transport?

A
  • Symport involves molecules moving in the same direction.
  • Antiport involves molecules moving in opposite directions.
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20
Q

What is the purpose of endocytosis and exocytosis in the cell?

A

To transport large macromolecules across the plasma membrane.

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21
Q

What is the primary function of proton pumps?

A

Transporting protons (H+ ions) against their concentration gradient.

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22
Q

What is the role of the CFTR protein in primary active transport?

A

Transporting chlorine ions out of the cell, triggering water movement.

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23
Q

What is the function of the GABA transporter (GAT) protein in the brain?

A

Regulating the removal of GABA from the synapse.

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24
Q

What is the role of the Na+/Ca2+ exchanger in muscle cells?

A

Regulating the concentration of calcium ions to trigger muscle contractions.

Very prevalent in cardiac (heart) muscle cells.

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25
What is the primary function of **exocytosis**?
**Export of proteins** made by ribosomes to the extracellular space. ## Footnote Insulin is an example of a protein hormone secreted via exocytosis.
26
How is **phagocytosis** utilized in cellular processes?
* Obtaining food for microorganisms like bacteria and amoebas. * Destroying invasive organisms in animals' immune responses. ## Footnote White blood cells engulf foreign particles through phagocytosis.
27
What is the main purpose of **pinocytosis**?
**To take in liquids** and nutrients dissolved in liquids. ## Footnote Example: Cells lining the intestines use pinocytosis for nutrient absorption.
28
What are the **two main types** of cellular transport?
* Passive Transport * Active Transport ## Footnote These processes are complete opposites in terms of energy requirements and direction of transport.
29
What are the characteristics of **active transport?**
* Requires energy. * Moves molecules against the concentration gradient. ## Footnote ATP is a common energy source for active transport.
30
What is **active transport** essential for in cells?
Enabling cells to transport a range of essential substances across membranes.
31
What is the **concentration gradient**?
The difference in a substance's concentration between two regions.
32
What is the **sodium-potassium pump** responsible for?
Maintaining a specific concentration gradient of sodium and potassium in nerve cells.
33
What is **passive transport**?
The movement of ions or particles from an area of **high concentration to an area of low concentration**. ## Footnote Does not require energy.
34
What is **diffusion**?
The overall passive movement of particles or ions from high-concentration regions to low-concentration regions.
35
What is **facilitated diffusion**?
The **movement of solutes through a membrane** from higher to lower concentrations with the help of transmembrane proteins. ## Footnote Example: The movement of glucose and amino acids from the circulation into the cell.
36
What is **osmosis**?
The movement of solvent molecules from **high water potential to low water potential** through a semipermeable membrane. ## Footnote Example: Plants absorb water through their roots.
37
What is the function of **channel proteins** in the cell membrane?
They **generate holes that span the membrane**, allowing target molecules or ions to move across them without contact. ## Footnote Examples: Ion channels, aquaporins
38
How do **carrier proteins** function in the cell membrane?
They attach to molecules or ions on one side of the membrane and then release them on the opposite side. ## Footnote Examples: Glucose-sodium cotransport, sodium-potassium pump
39
What is the main **difference** between channel proteins and carrier proteins?
* **Channel proteins** use no energy to transfer molecules and ions along concentration gradients. * **Carrier proteins** require energy to carry chemicals across a concentration gradient.
40
Explain the concept of **hypotonic solutions.**
These solutions have the least amount of solute, with a high solvent concentration. ## Footnote There is a lower concentration of solute outside the cell than there is inside the cell.
41
Describe **hypertonic solutions**.
These solutions have the greatest solute concentration, with a low solvent concentration. ## Footnote There is a higher concentration of solute outside the cell than there is inside the cell.
42
What are **isotonic solutions?**
These are solutions with an equal amount of solutes.
43
What happens to red blood cells in a **hypotonic solution**?
They receive water by osmosis, **expand**, and burst.
44
How do red blood cells respond in a **hypertonic solution**?
They **lose water** by osmosis and shrivel.
45
What occurs when red blood cells are in an **isotonic solution**?
There is no movement of water, leading to **no change in the cells**.
46
Define **active transport**.
The movement of ions and particles from a low concentration location to a high concentration area, requiring the use of energy.
47
What are the two types of **integral membrane proteins** that help transport molecules through the cell membrane?
* Carrier proteins * Channel proteins
48
What is the primary factor that drives **passive transport**?
Concentration gradient.
49
What is the main purpose of **osmoregulation**?
To **prevent** cells from either taking in or losing too much **water**.
50
What are the **two main types of proteins** found in the cell membrane?
* Peripheral proteins * Integral proteins
51
What are the **roles of proteins** in the cell membrane?
* Transport * Signaling * Structural support
52
What is the **difference** between passive and active transport?
* **Passive** transport *does not* use energy. * **Active** transport *requires* energy.
53
What are **aquaporins** and what is their function in cells?
They are small, integral membrane transport proteins that serve as channels **enabling water to cross the plasma membrane**.
54
What are **ligands** and what is their role in cell signaling?
They are signaling molecules that bind to receptors on the plasma membrane to **initiate cell signaling pathways**.
55
What is the function of **cell adhesion molecules** (CAMs) in cell adhesion?
They are used by cells to **adhere to each other** and to the extracellular matrix.
56
What is the **fluid mosaic model** of the plasma membrane?
The plasma membrane is a mosaic composed of phospholipids, proteins, and carbohydrates, separating the intracellular space from the extracellular space.
57
What is **cell communication**?
A process where a cell influences the behavior of other cells through signaling mechanisms.
58
**How** do cells communicate?
Along a **signal transduction pathway**, starting with a signaling cell releasing a signaling molecule that binds to a receptor protein on the target cell. ## Footnote Can be found in both eukaryotic and prokaryotic cells. Example: Nerve cells involved in long-distance signaling through neurotransmitters.
59
What are the **three main steps** involved in signal transduction response?
1. Reception 2. Transduction 3. Response
60
What is the process of **reception** in signal transduction?
The process by which a cell **detects** a signal in the environment.
61
What is **transduction** in cell signaling?
The process of *converting the external signal to action* within the cell.
62
What is **response** in cell communication?
The final stage of cell signaling triggered by the **activation of a protein** that has received the signaling message.
63
What are the four main types of **signaling molecules**?
* Hormones * Neurotransmitters * Local transmitters * Pheromones
64
Give examples of **hormones**.
* Insulin * Estrogen * Human growth hormone * Antidiuretic hormone * Testosterone * Aldosterone * Oxytocin
65
How does **insulin** function as a hormone?
It is produced by the pancreas as part of a negative feedback loop, in response to high blood glucose levels. Insulin then travels through the blood to bind to receptors on the surface of cells.
66
What are **neurotransmitters**?
*Chemical messengers that send signals between neurons* or between neurons and their effector tissues.
67
Explain the function of **local transmitters** as signaling molecules.
* **Work over short distances** by diffusion * Play a role in **bodily processes** like blood pressure regulation, nervous system functions, reproduction, immune responses, cell differentiation.
68
What are **pheromones** as signaling molecules used for?
**Act outside the body**, used by many species to communicate by marking territories, warning predators, attracting potential mates.
69
What is the *function* of **receptor proteins** in signal transduction?
**Receive signals** from the external environment.
70
What are **second messengers** in cell signaling?
Small, water-soluble molecules that relay signals.
71
What is the *function* of **second messengers** in signal transduction?
Transmit signals from receptors to the internal compartments of the cell.
72
What is the *function* of **transcription factors** in signal transduction?
Proteins that **turn on** gene expression.
73
What is the process where protein kinases **trigger the phosphorylation** of other protein kinases?
Phosphorylation cascade.
74
What is the *purpose* of **amplification** in signal transduction?
Allows the cell to quickly activate many molecules using fewer steps. ## Footnote Protein kinases are activated to trigger signaling cascade.
75
What are **protein kinases**?
Enzymes that **transfer** phosphate groups to a protein. ## Footnote Once the phosphate has been attached, it activates the protein for the purposes of signal transduction.
76
What are **protein phosphatases**?
Enzymes that quickly **remove** phosphate groups from proteins. ## Footnote Removal of phosphates is known as dephosphorylation. Dephosphorylation signals to the proteins that they no longer are needed for signal transduction.
77
What does **phagocytosis** involve?
The process where large molecules or other cells are eaten by **engulfing them**. ## Footnote A form of endocytosis.
78
What is **receptor-mediated endocytosis**?
A process that recognizes and targets a specific substrate through the help of integral membrane proteins on the cell membrane surface.
79
What is **caveolae**?
**Pockets in the plasma membrane** that do not have a clathrin-based protein lining them, instead having caveolins as membrane proteins.
80
What are the **three types of caveolins** found in mammals?
* Caveolin-1 * Caveolin-2 * Caveolin-3
81
Which type of caveolin protein is employed by **cardiac and skeletal muscle cells**?
Caveolin-3
82
What is the function of **lysosomes**?
They are structures within the cell that contain digestive enzymes and are responsible for **breaking down various substances**. ## Footnote Lysosomes utilize endocytosis to engulf substances and break them down.
83
Describe the process of **exocytosis**.
It is the **export of substances** from the cell through a vesicle that fuses with the cell membrane, releasing the contents outside of the cell.
84
What is the function of **endocytosis**?
It is the **import of molecules** and particles into the cell by folding the cell membrane inward to form vesicles.
85
List the four kinds of endocytosis.
* Phagocytosis * Pinocytosis * Receptor-mediated endocytosis * Caveolae-based endocytosis
86
Why is **exocytosis** important?
It secretes material outside the cell.
87
What are the **two mechanisms** to create a steady internal environment in the human body?
* Negative feedback * Positive feedback
88
What **components** are involved in all feedback loops?
* Signal * Set point * Receptor * Control center * Effector
89
What is **negative feedback**?
A process where the initial increase in the signal is reduced by the end-product of the same process.
90
How is the relationship between the change in the signal in **negative feedback** described?
As the signal goes up, then the **feedback is decreased**. ## Footnote Example: Signals travel to the hypothalamus signaling your body is getting to warm. The response targets blood vessels and sweat glands in the skin for cooling. Once the body has reached a normal temperature again signals travel to the hypothalamus signaling for sweating to stop.
91
What is **positive feedback**?
A type of feedback control where the signal **continues to be amplified**.
92
What is the relationship between the signal and the response in **positive feedback**?
As the signals increase, the **response from the brain increases**. ## Footnote Example: Oxytocin is released to start contractions in labor. As the fetuses head moves down towards the birth canal, the cervix is stimulated leading to the release of more oxytocin. This will continue until the baby is born.
93
How does **positive feedback** control blood clotting?
Chemical signals released by damaged tissue attract platelets to form a clot that can stop the flow of blood.
94
How do negative and positive feedback loops **differ** in their relationship between the signal molecule and response?
In the relationship between the signal molecule and response, the mechanism of action, and the stability of each loop. ## Footnote In negative feedback, the signal for a response is increased and then decreased, creating an inversely proportional relationship. In positive feedback, the signal for a response is increased and continues to increase, forming a directly proportional relationship.
95
What is the role of feedback loops in **maintaining homeostasis**?
These loops, including positive and negative feedback, help maintain homeostasis by **regulating the levels of regulatory molecules** like hormones and controlling physiological processes like body temperature and blood clotting.

Praxis (5236) - Biology (39 decks)

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