Bio - Unit 8 - Cells and Cellular Transport

  1. What are 3 parts of the cell theory

All living things are made up of one or more cells. The cell is the basic unit of structure and function in living things. All cells come from pre-existing cells.

  1. What is the definition of Prokaryote; Give an example

A single-celled organism whose cells lack a nucleus and other membrane-bound organelles. Their genetic material is typically found in a nucleoid region. Examples include bacteria and archaea.

  1. What is the definition of Eukaryote; Give an example

A complex organism whose cells contain a nucleus and other membrane-bound organelles. Examples include plants, animals, fungi, and protists.

  1. What are the 2 categories of Eukaryotes

Plant and animal

  1. What is the structure and function of the nucleus

A large, membrane-bound organelle containing the cell's genetic material (DNA) organized into chromosomes; it regulates cell growth, metabolism, and reproduction by controlling gene expression.

  1. What is the structure and function of the DNA

Deoxyribonucleic acid (DNA) is a double helix polymer made of two strands of nucleotides twisted around each other; it is the primary carrier of genetic information in living organisms, providing the blueprint for cellular structure and function.

  1. What is the structure and function of the rough ER

A network of folded membranes covered with ribosomes; involved in the synthesis, folding, modification, and transport of proteins destined for secretion or insertion into membranes.

  1. What is the structure and function of the smooth ER

A network of folded membranes without ribosomes; synthesizes lipids (like steroids), metabolizes carbohydrates, detoxifies drugs and poisons, and stores calcium ions.

  1. What is the structure and function of ribosomes

Small, round particles made of RNA and proteins; they are the site of protein synthesis, reading mRNA to assemble amino acids into proteins.

  1. What is the structure and function of golgi body/ golgi apparatus

Made up of stacked, flattened membrane-bound sacs (cisternae); it modifies, sorts, and packages proteins and lipids for secretion or delivery to other organelles.

  1. What is the structure and function of the vesicle

Small, round, membrane-bound sacs; involved in transporting substances within the cell, to the cell surface for secretion, or for taking in external materials.

  1. What is the structure and function of the mitochondria

Bean-shaped organelles with two membranes; they are the powerhouses of the cell and the site of cellular respiration, converting glucose and oxygen into ATP to power cell activities.

  1. What is the structure and function of lysosomes

Membrane-bound organelles containing digestive enzymes; they break down waste materials, cellular debris, and foreign invaders, essentially cleaning up junk in cells.

  1. What is the structure and function of the cell membrane

Also called the plasma membrane; made of a phospholipid bilayer with embedded proteins and cholesterol; it protects the cell, provides support, and selectively controls what enters and leaves the cell, playing a crucial role in maintaining cellular homeostasis.

  1. What is the structure and function of the cell wall

A rigid outer layer found in plant, fungal, algal, and bacterial cells; it provides structural support, protection, and prevents excessive water uptake.

  1. What is the structure and function of the cytoplasm

The jelly-like substance filling the cell, composed of cytosol (the fluid portion) and organelles; it is the site of many metabolic reactions and provides structural support, holding organelles in place.

  1. What is the structure and function of the chloroplasts

Oval-shaped organelles containing chlorophyll; they are the site of photosynthesis, converting light energy into chemical energy (sugars).

  1. What are the 3 functions of the cell membrane

Defines the boundaries, regulates what enters and leaves the cell, intercellular communication.

  1. What things make up the cell membrane

Primarily a phospholipid bilayer, along with various proteins and cholesterol.

  1. What does semi-permeable mean

Also known as selectively permeable, it means that some substances can pass through the membrane while others cannot, based on their size, charge, and lipid solubility.

  1. Structure of a phospholipid

Composed of a hydrophilic head (containing a phosphate group) and two hydrophobic tails (fatty acid chains).

  1. What does bilayer mean

Two layers.

  1. Why is the cell membrane made of two layers

Due to the amphipathic nature of phospholipids, the hydrophilic heads face the aqueous environment inside and outside the cell, while their hydrophobic tails cluster together to avoid water, naturally forming a stable and flexible phospholipid bilayer that controls what goes in and out.

  1. What is a solution

A homogeneous mixture of two or more substances, typically a solute dissolved uniformly in a solvent.

  1. What is a solute

The substance that is dissolved in a solvent to form a solution.

  1. What is a solvent

The substance that dissolves a solute to form a solution.

  1. What is the most common solvent

Water.

  1. What is passive transport

The movement of substances across a cell membrane without the expenditure of cellular energy (ATP), occurring along their concentration gradient.

  1. What is active transport

The movement of substances across a cell membrane against their concentration gradient, requiring the expenditure of cellular energy (ATP).

  1. Def of diffusion

The net movement of particles from an area of higher concentration to an area of lower concentration, occurring passively without energy along their concentration gradient.

  1. What are two types of diffusion

Simple diffusion and facilitated diffusion.

  1. Def of facilitated diffusion

Molecules move across a cell membrane from high to low concentration with the help of specific transport proteins (like channel or carrier proteins), without the direct expenditure of energy.

  1. What is osmosis

The net movement of water molecules across a semipermeable membrane from an area of higher water potential (low solute concentration) to an area of lower water potential (high solute concentration). It is a special type of passive transport.

  1. How long does diffusion/osmosis occur

It is an ongoing process that continues until equilibrium is reached. Once at equilibrium, the net movement stops, but individual molecules continue to move randomly across the membrane.

  1. What are three types of solutions

Isotonic, hypertonic, hypotonic.

  1. Isotonic

A solution that has the same solute concentration as the cell's cytoplasm; water moves in and out of the cell equally, resulting in no net water movement and the cell maintaining its normal shape.

  1. Hypertonic

A solution that has a higher solute concentration than the cell's cytoplasm; water moves out of the cell by osmosis, causing the cell to shrink (crenation in animal cells, plasmolysis in plant cells).

  1. Hypotonic

A solution that has a lower solute concentration than the cell's cytoplasm; water moves into the cell by osmosis, causing the cell to swell (potentially leading to lysis in animal cells, or becoming turgid in plant cells).

  1. Def of plasmolysis

The process where a plant cell's cytoplasm shrinks and the plasma membrane pulls away from the cell wall because water moves out of the cell into a hypertonic solution; this is specific to plant cells due to their rigid cell wall.

  1. Explain example we talked about in class

In the context of the sodium-potassium pump, potassium (K^1) is actively moved into the cell, and sodium (Na^1) is actively moved out of the cell, maintaining specific concentration gradients crucial for nerve impulses and other cellular functions.

  1. Exocytosis and Endocytosis

Exocytosis: A process where a cell releases materials to the outside by fusing a vesicle containing the substances with the plasma membrane. This is an active transport process.
Endocytosis: A process where a cell takes in substances from the outside by engulfing them with its membrane, creating a vesicle inside the cell. This is also an active transport process.

  1. Endocytosis def + examples

The process where a cell takes in substances from the outside by engulfing them with its cell membrane, forming a vesicle inside the cell. It is an active transport mechanism. Examples include:

  • Phagocytosis: "Cell eating," involves the engulfment of large solid particles, such as bacteria or cellular debris.

  • Pinocytosis: "Cell drinking," involves the uptake of extracellular fluids and dissolved solutes.

  1. How is the bilayer formed

The lipid bilayer structure forms spontaneously in an aqueous environment because phospholipids are amphipathic molecules. Their hydrophilic (water-loving) phosphate heads face the water on both the exterior and interior surfaces of the cell, while their hydrophobic (water-fearing) fatty acid tails spontaneously orient towards each other, away from the water, forming the core of the membrane.

  1. What would happen to a human cell if it was placed in a 1.5% NaCI solution? Assume that salt cannot pass through the cell membrane

The human cell would shrink (crenate) because the 1.5% NaCl solution is hypertonic relative to the cell's cytoplasm. Water would move out of the cell by osmosis in an attempt to reach equilibrium, causing the cell to lose volume.

  1. Explain sodium-potassium pump

A vital active transport protein that pumps 3 sodium ions (Na^1) out of the cell for every 2 potassium ions (K^1) pumped into the cell. This process uses ATP and moves ions against their concentration gradients, which is crucial for maintaining electrochemical gradients necessary for nerve impulse transmission and regulating cell volume.

  1. Explain the fluid mosaic model

This model describes the cell membrane as a fluid structure—meaning its components, such as phospholipids and proteins, can move laterally within the membrane. It is also a mosaic because it is made of various components including phospholipids, proteins (integral and peripheral), and cholesterol, embedded within the lipid bilayer, creating a dynamic and heterogeneous structure.

  1. Function of cholesterol in a cell membrane

Cholesterol molecules are embedded within the lipid bilayer. They act as a fluidity buffer: at warm temperatures, they restrain the movement of phospholipids, decreasing fluidity; at cold temperatures, they prevent phospholipids from packing too closely, thereby increasing fluidity. This ensures the membrane maintains optimal fluidity over a wider range of temperatures and prevents the tails from sticking together too much or becoming too rigid.

  1. Function of carbohydrates in a cell membrane

Carbohydrates (glycolipids and glycoproteins) are typically found on the outer surface of the cell membrane, forming the glycocalyx. They function as cell-to-cell recognition markers, allowing cells to identify each other, which is crucial for cell communication, adhesion (forming tissues), and immune responses (distinguishing 'self' from 'non-self').