Questions and Answers
What is the major type of lipid found in the cell membrane?
What structure do phospholipids form when they have bulky heads and one hydrophobic tail?
Micelles
What are the two types of fatty acids based on double bond presence?
Saturated and Unsaturated
Cholesterol decreases membrane fluidity at normal cell temperatures.
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What is the primary function of transporters in membranes?
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Membrane proteins are classified into ______ types based on their relationship with the membrane.
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What is homeostasis?
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What is osmosis?
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Which structure maintains cell shape in plant cells?
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Eukaryotic cells contain membrane-bound organelles.
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What is the role of the Golgi apparatus?
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What do lysosomes do?
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Mitochondria are involved in energy conversion. What do they convert into ATP?
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What process do chloroplasts perform using sunlight?
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Study Notes
Phospholipids
- Major lipid type in cell membranes, characterized as amphipathic with hydrophobic fatty acid tails and hydrophilic head groups (glycerol, phosphate, polar group).
Lipid Structures
- Phospholipids spontaneously arrange into structures based on head group size: large heads form micelles, while smaller heads with two tails create bilayers or liposomes.
- Membranes are self-healing due to the ability of phospholipids to rearrange spontaneously.
Saturated vs Unsaturated Fatty Acids
- Lipids associate via weak van der Waals forces, allowing for membrane fluidity and flexibility.
- Saturated fatty acids (e.g., stearic acid) have no double bonds; unsaturated fatty acids (e.g., oleic acid) contain double bonds, affecting tail interactions and fluidity.
Cholesterol
- An amphipathic component of animal cell membranes that influences fluidity based on temperature.
- At normal temperatures, cholesterol restricts phospholipid mobility; at lower temperatures, it prevents tight packing, increasing fluidity.
Membrane Proteins
- Proteins serve various functions: transporters, anchors, receptors, and enzymes.
- Transporters facilitate ion or molecule movement, receptors receive environmental signals, and enzymes catalyze reactions.
Integral vs Peripheral Proteins
- Integral proteins are permanently embedded in the membrane; peripheral proteins associate temporarily via noncovalent interactions.
- Integral proteins may span the entire bilayer, while peripheral proteins can reside on either side.
Diffusion and Homeostasis
- Plasma membranes separate cells from their environment and maintain homeostasis by serving as selective barriers.
- Passive transport occurs via diffusion, moving molecules from high to low concentration.
Simple and Facilitated Diffusion
- Some molecules cannot cross the lipid bilayer directly and must use facilitated diffusion through membrane protein channels or carriers.
Active Transport
- Primary active transport moves substances against concentration gradients and requires energy.
- Secondary active transport utilizes electrochemical gradients for molecule transport.
Osmosis
- Water movement in and out of cells occurs passively but is facilitated by aquaporin channels.
- Osmosis is critical for maintaining cell volume and function.
Effects of Osmosis
- Cells in hypertonic solutions shrink due to water loss; in hypotonic solutions, cells swell and may burst.
- Active transport helps maintain isotonic conditions within cells.
Plant Cell Wall and Vacuoles
- Plant cells have rigid cell walls that resist expansion and maintain shape through turgor pressure from water in vacuoles.
- Loss of water leads to wilting due to decreased turgor pressure.
Prokaryotic and Eukaryotic Cells
- Prokaryotic cells lack membrane-bound organelles; eukaryotic cells contain them, facilitating specialized functions.
Features of Animal Cells
- Animal cells possess organelles such as the endoplasmic reticulum (ER), Golgi apparatus, lysosomes, and mitochondria for various cellular processes.
Features of Plant Cells
- In addition to organelles found in animal cells, plant cells have a cell wall, large vacuoles, and chloroplasts that conduct photosynthesis.
The Endomembrane System
- Comprises nuclear envelope, ER, Golgi apparatus, lysosomes, plasma membrane, and vesicles, allowing compartmentalization for specific cellular functions.
The Nuclear Envelope
- Consists of inner and outer membranes with nuclear pores facilitating communication and transport between the nucleus and cytoplasm.
The Endoplasmic Reticulum
- Continuous with the nuclear envelope, producing lipids and proteins; consists of a network of tubules and sacs with a large surface area.
Rough and Smooth ER
- Rough ER contains ribosomes for protein synthesis; smooth ER is involved in lipid synthesis and not associated with ribosomes.
The Golgi Apparatus
- Modifies, sorts, and synthesizes carbohydrates; receives vesicles from the ER for processing and delivery.
Protein Sorting
- Proteins are targeted to their functional locations within the cell based on amino-acid signal sequences.
Protein Transport Pathways
- Proteins synthesized on RER ribosomes end up in the endomembrane system, either secreted or embedded in membranes.
Lysosomes
- Derived from the Golgi apparatus and contain enzymes for degrading macromolecules; important for cellular waste management.
Mitochondria
- Harness energy from nutrients to produce ATP, possess their own genomes, and are believed to have evolved from engulfed bacteria.
Chloroplasts
- Capture solar energy for photosynthesis, containing pigments like chlorophyll in thylakoid membranes, and surrounded by a double membrane.
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Description
Explore key concepts of lipids, membranes, and cell compartments in Biology Chapter 5 through interactive flashcards. Test your understanding of phospholipids and lipid structures, and grasp the fundamental principles organizing cellular components.
