Podcast
Questions and Answers
What is required for primary active transport mechanisms to move solutes against their concentration gradient?
What is required for primary active transport mechanisms to move solutes against their concentration gradient?
What type of endocytosis involves engulfing large particles such as viruses or dead cells?
What type of endocytosis involves engulfing large particles such as viruses or dead cells?
Which statement is true about bulk-phase endocytosis?
Which statement is true about bulk-phase endocytosis?
Which process moves materials out of a cell by vesicle fusion with the plasma membrane?
Which process moves materials out of a cell by vesicle fusion with the plasma membrane?
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What do secondary active transport mechanisms use to drive the transport of solutes against their concentration gradient?
What do secondary active transport mechanisms use to drive the transport of solutes against their concentration gradient?
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In receptor-mediated endocytosis, what forms a basketlike structure on the cytosolic side of the membrane?
In receptor-mediated endocytosis, what forms a basketlike structure on the cytosolic side of the membrane?
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What are the two main phagocytes involved in phagocytosis?
What are the two main phagocytes involved in phagocytosis?
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Which of the following is essential for maintaining cell volume and ionic gradients in primary active transport?
Which of the following is essential for maintaining cell volume and ionic gradients in primary active transport?
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Which part of the phospholipid bilayer is hydrophobic?
Which part of the phospholipid bilayer is hydrophobic?
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Which type of membrane transport requires energy?
Which type of membrane transport requires energy?
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What drives the process of diffusion?
What drives the process of diffusion?
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Which molecules assist in facilitated diffusion?
Which molecules assist in facilitated diffusion?
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What is a characteristic of isotonic solutions?
What is a characteristic of isotonic solutions?
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Which factor slows down diffusion?
Which factor slows down diffusion?
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What role do ion channels play in membrane transport?
What role do ion channels play in membrane transport?
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What is the primary function of cilia on the cell surface?
What is the primary function of cilia on the cell surface?
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What is the movement of water across a semi-permeable membrane called?
What is the movement of water across a semi-permeable membrane called?
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Which type of endoplasmic reticulum is involved in synthesizing fatty acids and steroids?
Which type of endoplasmic reticulum is involved in synthesizing fatty acids and steroids?
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What is the function of the Golgi complex?
What is the function of the Golgi complex?
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Which of the following is true about hypertonic solutions?
Which of the following is true about hypertonic solutions?
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Which of the following is NOT a type of passive transport?
Which of the following is NOT a type of passive transport?
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What is the role of lysosomes within a cell?
What is the role of lysosomes within a cell?
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Which organelle is known as the 'powerhouse' of the cell?
Which organelle is known as the 'powerhouse' of the cell?
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Flagella are primarily involved in:
Flagella are primarily involved in:
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Which structure contains a double membrane that separates the nucleus from the cytoplasm?
Which structure contains a double membrane that separates the nucleus from the cytoplasm?
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What is a primary characteristic of rough ER?
What is a primary characteristic of rough ER?
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Study Notes
Cell Membrane Structure
- Phospholipid bilayer with hydrophilic heads and hydrophobic tails
- Embedded proteins: integral (crossing the entire membrane) and peripheral (attached to the membrane surface)
- Selectively permeable, allowing some substances to pass through more easily than others
Mechanisms of Membrane Transport
- Passive transport: diffusion (down concentration gradient) and facilitated diffusion (using channel or carrier proteins)
- Active transport: moving molecules against their concentration gradient, requiring energy (ATP)
Types of Membrane Transport
- Diffusion: movement from high to low concentration
- Facilitated diffusion: passive transport using protein channels or carrier proteins
- Active transport: movement against concentration gradient, requiring energy input
- Osmosis: movement of water across a semi-permeable membrane from high to low concentration
- Ion channels: selective transport of ions down their electrochemical gradient
- Transporters (carriers): binding to specific molecules, transporting them across the membrane
Factors Affecting Diffusion
- Amount of substance: more substance, faster diffusion
- Concentration gradient: steeper gradient, faster diffusion
- Temperature: higher temperature, faster diffusion
- Surface area: larger surface area, faster diffusion
- Diffusion distance: shorter distance, faster diffusion
Tonicity
- Isotonic solution: same solute concentration as the cell, no change in size
- Hypotonic solution: lower solute concentration, water flows into the cell, causing it to swell
- Hypertonic solution: higher solute concentration, water flows out of the cell, causing it to shrink
Primary Active Transport Mechanisms (Pumps)
- E.g. Sodium-Potassium pump (Na-K-ATPase)
- Requires energy for solutes moving against their concentration gradient
- Requires energy through ATP hydrolysis
- Exhibits saturation kinetics
- Crucial for maintaining cell volume and ionic gradients
Vesicular Transport
- Vesicle: a small spherical sac formed by budding off from a membrane
- Endocytosis: materials move into a cell in a vesicle
- Exocytosis: vesicles fuse with the plasma membrane, releasing their contents into the extracellular fluid
- Transcytosis: a combination of endocytosis and exocytosis
Phagocytosis
- Form of endocytosis where a cell engulfs large particles
- Two main phagocytes: macrophages and neutrophils
Bulk-phase Endocytosis (Pinocytosis)
- No receptor proteins involved
- Transport of extracellular fluid
- Plasma membrane folds inward
Receptor-mediated Endocytosis
- Receptor protein recognizes and binds a specific particle
- Clathrin molecules form a basket-like structure on the cytosolic side of the membrane
- Fuses with endosome, receptors recycled, and vesicles bud off endosome
Exocytosis
- Releases materials from cells
- Important for neurotransmitter signaling
Secondary Active Transport Mechanisms
- Use energy stored in Na+ or H+ concentration gradients to drive transport of other solutes against their concentration gradients
Cilia and Flagella
- Cilia: short, hair-like projections from the cell surface, moving fluids along a cell surface
- Flagella: longer than cilia, moving an entire cell (e.g. sperm cell's tail)
Endoplasmic Reticulum
- Network of membranes in the shape of flattened sacs or tubules
- Rough ER: connected to the nuclear envelope, produces secretory, membrane, and organellar proteins
- Smooth ER: synthesizes fatty acids and steroids, detoxifies certain drugs
Ribosomes
- Sites of protein synthesis
- Contain large amounts of ribosomal RNA (rRNA)
- Attached to the outer surface of the nuclear membrane and Endoplasmic Reticulum
Golgi Complex
- Consists of 3-20 flattened, membranous sacs called cisternae
- Modifies, sorts, and packages proteins for transport to different destinations
Lysosomes, Peroxisomes, and Proteasomes
- Lysosomes: vesicles that form from the Golgi complex, containing powerful digestive enzymes
- Peroxisomes: smaller than lysosomes, detoxify toxic substances using oxidase enzymes
- Proteasomes: continuously destroy unneeded, damaged, or faulty proteins
Mitochondria
- Generate ATP by aerobic respiration
- Prevalent in active cells: muscles, liver, and kidneys
- Self-replicate during times of increased cellular demand or before cell division
- Contain own DNA, inherited only from the mother
- Plays an important role in apoptosis
Nucleus
- Spherical or oval shaped
- Nuclear envelope: a double membrane separating the nucleus from the cytoplasm
- Nuclear pores: numerous openings in the nuclear envelope, controlling movement of substances
- Nucleolus: spherical body producing ribosomes
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Description
Learn about the composition of the cell membrane, including the phospholipid bilayer and embedded proteins, as well as the mechanisms of membrane transport, such as passive and active transport.
