Unit 1 Aos 1 Flashcards

Question

SA:V ratio formula steps

Answer 1

1 Calculate surface area (face A – length × width, face B – length × height, face C – width × height) 2 Calculate volume (lxwxh) 3 Calculate (surface area)/(volume) to work out every unit of surface area per unit of volume 4 Convert into a ratio.

Answer 2

The plasma membrane is primarily composed of phospholipids, which form a phospholipid bilayer consisting of two layers. Phospholipids have a phosphate head and two fatty acid tails, which are chemically distinct. The phosphate head is made of glycerol and a phosphate group. It is negatively charged, making it hydrophilic (water-loving) and polar. The fatty acid tails are long chains of carbon and hydrogen, uncharged, hydrophobic (water-fearing), and nonpolar. Because the phosphate heads are hydrophilic, they are attracted to water and are oriented towards the aqueous environments inside and outside the cell. The hydrophobic fatty acid tails face away from the water, forming the middle layer of the bilayer. Phospholipids are amphipathic, meaning they have both hydrophilic (water-loving) heads and hydrophobic (water-fearing) tails. This property helps the plasma membrane stay stable. The hydrophobic tails avoid water, while the hydrophilic heads face it, forming a stable bilayer. Around oil, which is nonpolar, phospholipids form a monolayer instead.

Answer 3

PROTEINS: Integral protein: Permanently embedded in the membrane. Transmembrane protein: A type of integral protein that spans the entire bilayer. Peripheral protein: Temporarily attached to the plasma membrane. FUNCTIONS: Transport: Channels or pumps that control the movement of substances in and out of the cell. Catalysis: Proteins (enzymes) that speed up chemical reactions. Communication: Receive signals and recognize cells or molecules, often linked to the cytoskeleton to transmit signals. Adhesion: Help cells stick to each other, the extracellular matrix, or the cytoskeleton. CARBOHYDRATES Usually in chains that extend outside the cell, rooted in the membrane to lipids (glycolipids) or proteins (glycoproteins) FUNCTION Aid with cell-cell communication, signalling, recognition of self or non-self (foreign) molecules, and adhesion CHOLESTEROL A lipid steroid that embeds itself between the fatty acid tails of the phospholipid bilayer in animal cells. Cholesterol is replaced with similar molecules in other kingdoms, but all are functionally similar. FUNCTION Cholesterol regulates membrane fluidity. At higher temperatures, it keeps phospholipids together, while at lower temperatures, it disrupts the fatty acid tails, preventing the phospholipids from forming a solid boundary.

Answer 4

The "fluid mosaic model" describes the plasma membrane's structure. It's called fluid because phospholipids move side to side and occasionally "flip-flop" between layers. The "mosaic" part comes from the proteins and carbohydrates embedded in the membrane, which also move freely. Like mosaic art made of different tiles, the plasma membrane is made up of various molecules of different shapes and sizes.

Answer 5

Diffusion is the movement of molecules from an area of high concentration to an area of low concentration (down their concentration gradient). This happens because the kinetic energy in each molecule causes them to move randomly and bounce off each other, eventually leading to an even distribution of particles. Molecules that can freely diffuse: Small, nonpolar, or hydrophobic molecules (e.g., O₂, CO₂, lipids). Small uncharged molecules like water. Molecules that cannot freely diffuse: Charged molecules (e.g., ions like H⁺, K⁺, Cl⁻). Larger or hydrophilic molecules (e.g., amino acids, proteins, glucose). Diffusion Process: Molecules move from areas of high to low concentration (down their concentration gradient). Factors Affecting Diffusion Speed: Concentration Gradient: Diffusion is faster when there is a steeper concentration gradient (greater difference in concentration between the inside and outside of the cell). Temperature: Diffusion speeds up at higher temperatures.

Answer 6

Definition: Passive movement of molecules down their concentration gradient through a membrane-bound protein. Transported Molecules: Large and/or polar molecules like glucose and ions. Types of Proteins: Protein Channels: Pores in the membrane that allow specific substances to pass through. Carrier Proteins: Bind to the substance, change shape, and move the molecule across the membrane before returning to their original shape. Specificity: Both channels and carrier proteins are specific to the molecules they transport, contributing to the selective permeability of the plasma membrane. Speed: Facilitated diffusion can be faster than simple diffusion, and even small/nonpolar molecules (like water) may have dedicated protein channels.

Answer 7

Definition: Osmosis is the diffusion of water across a selectively permeable membrane from areas of low solute concentration to areas of high solute concentration. Water Movement: Despite being hydrophilic, water can move through the phospholipid bilayer due to its small size. Movement is faster with the help of protein channels called aquaporins. Tonicity: Tonicity describes the relative solute concentration between two compartments: Hypertonic: Higher solute concentration. Water moves into the hypertonic solution. Isotonic: Equal solute concentrations. Water moves in and out at the same rate, so there is no net movement. Hypotonic: Lower solute concentration. Water moves into the adjacent area with higher solute concentration. Impact on Cells: Plant Cells: Hypertonic: Water moves into the cell, causing it to swell and become turgid (firm) due to the cell wall. Hypotonic: Water moves out, causing the cell to shrink and become plasmolysed. Animal Cells: Hypertonic: Water moves out, causing the cell to shrink. Hypotonic: Water moves into the cell, causing it to swell and potentially lyse (burst) since there’s no cell wall. Biological Importance: Turgor Pressure: In plants, high turgor pressure prevents wilting and helps maintain cell rigidity. Saline Solutions: In hospitals, isotonic saline solutions are used to avoid cell shrinkage or bursting by matching the tonicity of our blood cells.

Answer 8

movement of substances across cell membranes without the cell expending energy - simple diffusion - facilitate diffusion - osmosis

Answer 9

Active transport of substances across membranes involves using protein pumps to move molecules against their concentration gradient

Answer 10

Protein-Mediated Active Transport: When Needed: Cells use active transport when molecules need to be moved against their concentration gradient. For example, if there is a higher concentration of potassium ions (K⁺) inside the cell, but more K⁺ is still needed, the cell must move K⁺ into the cytoplasm, despite the concentration difference. Why Diffusion Won’t Work: K⁺ ions are charged, so they can't diffuse across the plasma membrane, and they also can't use facilitated diffusion because they need to move against their concentration gradient. Energy Requirement: Active transport requires energy, usually in the form of ATP, and involves protein pumps and carrier proteins. Steps of Active Transport: Binding: The molecule to be transported binds to a specific protein pump. Conformational Change: ATP breaks down into ADP + Pi, releasing energy. This causes the protein pump to change shape. Release: The target molecule is pushed through the protein and released to the other side of the membrane. Active transport is essential for moving molecules against their concentration gradient using energy from ATP. Active Transport and Water Movement: Control of Water Movement: Active transport helps regulate water movement in and out of the cell. Since water moves from areas of low solute concentration to high solute concentration (osmosis), the active transport of solutes can influence water flow. Water Influx: By pumping solutes into the cell, the solute concentration inside the cell increases, causing water to follow via osmosis into the cell. Water Removal: To remove excess water, the cell can pump solutes out into the extracellular space, creating a hypertonic region that causes water to diffuse out of the cell. Thus, active transport is crucial not only for maintaining proper concentrations of molecules but also for controlling water balance in the cell.

Answer 11

Overview: Bulk transport is an active transport process that moves large molecules or groups of molecules (e.g., proteins, amino acids, hormones) into or out of the cell via vesicles. It occurs in two main forms: exocytosis (molecules exiting the cell) and endocytosis (molecules entering the cell). Exocytosis (Out of the Cell): Definition: The process by which vesicles release their contents outside the cell. Steps: Vesicular Transport: A vesicle containing secretory products moves to the plasma membrane. Fusion: The vesicle membrane fuses with the plasma membrane. Release: The contents of the vesicle are released outside the cell. Function: Commonly used to release large molecules like hormones, neurotransmitters, and antibodies. Large molecules too big for channels are expelled via exocytosis. Adds phospholipids to the plasma membrane, increasing surface area. Endocytosis (Into the Cell): Definition: The process of transporting large molecules or groups of molecules into the cell. Steps: Fold: The plasma membrane folds inward, forming a cavity that fills with extracellular fluid and target molecules. Trap: The membrane folds back, enclosing the molecules in a vesicle. Bud: The vesicle (endosome) pinches off from the membrane and is transported inside the cell. Function: Cells use endocytosis to bring in large molecules that can't enter through protein channels. Can be used for defense, as cells can engulf pathogens or toxins, and then digest them with lysosomes. Types of Endocytosis: Phagocytosis: "Cell eating" – engulfing solid materials or food particles (e.g., immune cells like macrophages engulfing pathogens). Pinocytosis: "Cell drinking" – engulfing dissolved molecules in extracellular fluid Note on Tonicity: Endocytosis can remove phospholipids from the plasma membrane, potentially causing the cell to shrink if excessive endocytosis occurs.

Answer 12

Overview: Cell replication is a crucial process for both eukaryotes and prokaryotes, enabling growth, maintenance, repair, and reproduction. 1. Growth and Development: All humans start as a single cell and replicate to form an embryo, fetus, and eventually a baby. As organisms grow, their cells replicate, increasing the number of cells, not their size. Cell replication is essential for growth and development in multicellular organisms. 2. Maintenance and Repair: Cells die due to aging or damage. Cell replication replaces these cells to maintain proper functioning and tissue health. 3. Reproduction: Both prokaryotic (e.g., bacteria) and eukaryotic cells replicate for reproduction. This process ensures population growth and the continuation of species. Exponential Growth in Cell Replication: Cells replicate exponentially, meaning the number of cells doubles after each round of replication.

Answer 13

Binary Fission in Prokaryotes: Asexual Reproduction: Binary fission is a type of asexual reproduction used by prokaryotes like bacteria. Process Stages: Before Replication: The prokaryotic cell has a single, circular chromosome, which uncoils and replicates. Plasmids, small independent DNA molecules, also replicate. Cell Elongation: The cell elongates in preparation for splitting, and the duplicated chromosomes move to opposite ends of the cell. Cytokinesis: The cell begins pinching inwards to form a septum (a dividing wall). Plasmids may not be evenly distributed between the two new cells. Formation of New Cells: A new cell wall and membrane form down the center, resulting in two genetically identical daughter cells. Binary fission allows for rapid reproduction in prokaryotes, doubling their population in a short time.

Answer 14

Stages of the Eukaryotic Cell Cycle: Interphase: The longest stage where the cell grows and duplicates its chromosomes. It's made up of three phases: G1, S, and G2. Mitosis: The stage where sister chromatids are separated and two new nuclei are formed. Cytokinesis: The division of the cytoplasm, leading to the formation of two daughter cells.

Answer 15

Interphase is the longest stage of the cell cycle and is crucial for preparing the cell for division. During this phase, DNA exists as chromatin (long threads, not discrete chromosomes), and the cell synthesizes necessary components for growth and replication. Sub-stages of Interphase: Gap 1 (G1) Phase: The cell grows by increasing its cytosol and synthesizing proteins needed for DNA replication. Organelles replicate. At the end of G1, the cell either progresses to the S phase or enters the G0 phase (resting phase), where it remains until required to replicate. Gap 0 (G0) Phase: Cells in the G0 phase are in a resting state, either quiescent (can re-enter the cell cycle) or terminally differentiated (cannot re-enter the cycle). Synthesis (S) Phase: DNA replication occurs, where each chromosome becomes two identical sister chromatids. These chromatids are held together by a centromere and are considered a single chromosome until they separate during mitosis. Gap 2 (G2) Phase: The cell continues to grow and synthesizes proteins needed for mitosis. It's similar to G1 but focuses more on preparing for cell division.

Answer 16

Types of cell division that results in two identical daughter cells Mitosis is divided into four sub-stages: Prophase Metaphase Anaphase Telophase Sub-stages of Mitosis: Prophase: Chromatin condenses into distinct chromosomes, making them visible under a microscope. Centrioles move toward opposite poles of the cell. Spindle fibers start forming. The nuclear membrane begins to break down, and the nucleolus disappears. Metaphase: Spindle fibers attach to the centromere of each chromosome. Chromosomes align at the cell's equator, guided by the spindle fibers. Anaphase: Spindle fibers contract, splitting the centromere and pulling sister chromatids to opposite poles of the cell. Telophase: Chromosomes de-condense at both poles. New nuclear membranes form around each set of chromosomes, creating two genetically identical nuclei. Spindle fibers disintegrate.

Answer 17

Cytokinesis After Mitosis After mitosis, the cell undergoes cytokinesis, the final stage of cell division where the cytoplasm divides and organelles are evenly distributed into two daughter cells. In animals: Cytokinesis occurs when a cleavage furrow forms, pinching the plasma membrane and separating the cell into two. In plants: Because of the rigid cell wall, a cell plate forms at the equator, eventually dividing the cell into two daughter cells. Regulation of the Cell Cycle The cell cycle has three checkpoints where the cell checks itself for errors before proceeding to the next phase. If any issues are detected, the cell can pause for repairs or, if the damage is too severe, undergo programmed cell death. G1 Checkpoint: Ensures the cell has grown to the correct size. Verifies that sufficient protein has been synthesized for DNA replication. Checks for DNA damage during mitosis and cell growth. Confirms favorable conditions (adequate nutrients, oxygen). G2 Checkpoint: Verifies proper DNA replication in the S phase. Ensures the cell has enough resources for mitosis. Metaphase Checkpoint: Checks that the chromosomes are properly aligned on the spindle fibers. If everything is correct, the cell proceeds to anaphase. These checkpoints help maintain the integrity of the cell cycle and prevent the division of cells with errors.

Answer 18

The liquid component of the cytoplasm. Composed of water, ions, proteins, and small molecules. Surrounds organelles and supports cellular processes. Involved in protein synthesis, cell signaling, and metabolism. Helps maintain cell shape and facilitates movement of materials.

Unit 1 Aos 1 Flashcards

(42 cards)