30 Questions
What is the primary function of pumps in cells?
To force molecules from an area of low concentration to an area of high concentration
In primary active transport, what is the direct source of energy?
Breakdown of adenosine triphosphate (ATP)
What is the primary characteristic of voltage-gated channels?
Responds to electrical potential across the cell membrane
What type of transport is used for molecules that are too large to be moved by transport proteins?
Endocytosis
What is the name of the pump that moves sodium ions out of the cell and potassium ions into the cell?
Sodium-potassium pump
What is the main function of the glycocalyx in some cells?
To attach cells to one another
What is the term for the binding of a chemical substance to a channel protein, opening or closing the gate?
Chemical gating
Which of the following substances can penetrate the lipid layer of the membrane with ease?
Oxygen and carbon dioxide
What is the primary function of integral proteins?
To facilitate the transport of molecules across the membrane
What is the term for the loose carbohydrate coat on the outside surface of the cell?
Glycocalyx
Which of the following is NOT a function of membrane carbohydrates?
Regulating the activity of enzymes
What is the main function of cholesterol in the cell membrane?
To control the degree of permeability of the bilayer to water-soluble constituents
What type of proteins are involved in the regulation of metabolism and signal transfer?
Membrane enzymes
Which type of protein forms structural channels through which water-soluble substances can diffuse?
Integral Proteins
What is the primary role of structural proteins in the cell membrane?
To connect the membrane to the cytoskeleton and maintain the shape of the cell
What is the function of sphingolipids in the cell membrane?
To serve as adhesion sites for extracellular proteins
What is the primary function of carrier proteins in the cell membrane?
To transport substances in the direction opposite to their electrochemical gradients
What is the main function of peripheral proteins in the cell membrane?
To function as enzymes or controllers of transport of substances through pores
What is the result of the fusion of a vesicle with the plasma membrane during exocytosis?
The cellular product is now in the extracellular fluid
What type of endocytosis involves the engulfment of solid particles such as bacteria?
Phagocytosis
What is the role of clathrin in receptor-mediated endocytosis?
It helps in the formation of vesicles
What is the term for the process by which cells take in extracellular substances through the formation of vesicles?
Endocytosis
What type of endocytosis involves the uptake of liquid or very small particles?
Pinocytosis
What is the process by which cells release cellular products into the extracellular fluid?
Exocytosis
What is the purpose of actin and other contractile fibrils surrounding the phagocytic vesicle?
To facilitate the engulfing of foreign substances
What is the primary function of lysosomes in cells?
To digest and recycle cellular waste and foreign substances
What is the role of lysozyme in the phagocytic process?
To dissolve the bacterial cell membrane
What is the primary purpose of autophagy in cells?
To recycle cellular waste and damaged organelles
What happens to worn-out cell organelles inside the lysosome?
They are digested and their nutrients are reused by the cell
What is the role of autophagy in tissue development and cell survival?
It is a key mechanism for tissue development and cell survival
Study Notes
Cell Membrane Structure
- The cell membrane consists of a lipid layer with embedded proteins, as well as carbohydrates attached to the outer surface.
- The lipid layer is impermeable to water-soluble substances, such as ions, glucose, and urea, but allows fat-soluble substances, like oxygen, carbon dioxide, and alcohol, to pass through.
Membrane Carbohydrates
- Membrane carbohydrates, known as proteoglycans, are mainly carbohydrate substances bound to small protein cores.
- The glycocalyx, a loose carbohydrate coat on the cell surface, plays a crucial role in various functions, including:
- Repelling negatively charged substances
- Attaching cells to each other
- Acting as receptors for binding hormones
- Participating in immune reactions
Membrane Proteins
- Membrane proteins can be categorized into two main types:
- Integral proteins:Embedded in the lipid bilayer and span the entire membrane.
- Peripheral proteins:Attached to the outer or inner surface of the membrane.
Functions of Membrane Proteins
- Membrane proteins perform various functions, including:
- Structural roles: Connecting the membrane to the cytoskeleton and creating cell junctions.
- Enzymatic activities: Catalyzing chemical reactions.
- Transport: Facilitating the movement of substances across the membrane.
- Receptor functions: Binding to hormones and other signaling molecules.
Cell Transport Systems
- Cell membranes are selectively permeable, controlling the movement of substances into and out of the cell.
- There are three main types of cell transport systems:
- Passive transport: Substances move from an area of high concentration to an area of low concentration.
- Active transport: Substances move against their concentration gradient, requiring energy input.
- Bulk transport: Large molecules and particles are transported through endocytosis and exocytosis.
Passive Transport
- Passive transport mechanisms include:
- Diffusion: Substances move from an area of high concentration to an area of low concentration.
- Osmosis: Water molecules move from an area of high concentration to an area of low concentration.
- Facilitated diffusion: Substances move through specific channels or carriers.
Active Transport
- Active transport mechanisms include:
- Primary active transport: Energy is derived directly from ATP or other high-energy phosphate compounds.
- Secondary active transport: Energy is derived from ionic concentration differences created by primary active transport.
Bulk Transport
- Bulk transport mechanisms include:
- Endocytosis: Large molecules and particles are engulfed by the cell membrane, forming vesicles.
- Exocytosis: Vesicles fuse with the cell membrane, releasing their contents outside the cell.
Lysosomes
- Lysosomes are membrane-bound organelles that contain digestive enzymes and acids.
- Functions of lysosomes include:
- Digesting foreign substances, such as bacteria
- Removing damaged cellular components
- Recycling cellular materials
Autophagy
- Autophagy is a process in which cells recycle damaged or dysfunctional organelles and proteins.
- Autophagy involves the delivery of intracellular components to lysosomes for degradation and recycling.
- Autophagy plays a crucial role in maintaining cellular health and homeostasis.
Learn about the composition and properties of the cell membrane, including its lipid layer and associated carbohydrates. Understand how it regulates the passage of substances into and out of the cell.
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