Chapter 3: Cells Flashcards
What is a cell?
This is a living structural and functional unit enclosed by a membrane
What are the three main parts of a cell?
Plasma membrane
Cytoplasm
Nucleus
Describe the structure of the plasma membrane
This makes the cell’s flexible outer surface, which separates the internal and external environment
It is made up of a lipid bilayer which itself is made up of (2x) phospholipids, cholesterol, and glycolipids
What are the two types of proteins in the plasma membrane?
Integral and peripheral
What are the roles of the plasma membrane?
Regulates flow of materials in and out of the cell
Key role in communication among cells and between cells in external environment
What are integral proteins?
These are proteins that extend through the lipid bilayer. These proteins allow small and medium-sized water-soluble materials to cross through the membrane
What are peripheral proteins
These are proteins that loosely attach to the exterior or interior surface of the membrane
How is the plasma membrane selectively permeable?
The lipid bilayer is permeable to water and non-polar molecules like fatty acids, O2, CO2, etc. but is impermeable to ions and large, uncharged polar molecules like glucose and amino acids.
Large molecules like proteins usually require transport via vesicles to travel through the plasma membrane
What are the proteins in the plasma membrane that determine the membrane’s function?
Receptors
Ion channels
Carrier proteins/transporters
Enzymes
Cell identity markers
What is cholesterol used for in the plasma membrane?
This binds with adjacent phospholipids to help make the phospholipid bilayer stronger
It also maintains fluidity in cell membranes at normal body temperatures
What is extracellular fluid? Give some examples
This is the fluid outside of cells. This includes interstitial fluid, blood plasma, and lymph
What is interstitial fluid?
This is a type of extracellular fluid found between cells in tissues
What is blood plasma?
This is a type of extracellular fluid found in blood vessels
What is lymph?
This is a type of extracellular fluid found in lymphatic vessels
What are the methods for which substances move across the plasma membrane?
Passive transport and active transport
What is passive transport?
This is when a substance moves down its concentration gradient through the membrane, only using its own kinetic energy.
Simple diffusion and osmosis
What is active transport?
This is when a substance is pushed through the membrane against its concentration gradient. This requires cellular energy, usually from ATP
Define diffusion
This is a passive process in which a substance will move due to its kinetic energy, travelling from high concentration to low concentration
What is simple diffusion?
This is when substances diffuse across a membrane through the lipid bilayer.
What is facilitated diffusion
This is when a substance can’t move through the membrane via simple diffusion or a passive process.
An integral membrane protein helps the substance move across the membrane. The protein will be either a membrane channel or carrier
Describe the facilitated diffusion of potassium ions
Gated ion channels are present in the plasma membrane that allows intracellular K+ ions to move out into the cell (following concentration gradient) when the gate is open.
Describe the facilitated diffusion of a glucose molecule
The glucose transporter, the carrier protein, is an integral protein which teeters back and forth. In one position, the carrier protein is open to the extracellular fluid, where glucose can onto slots of the carrier protein. The protein will undergo a change in shape, causing it to open to the intracellular fluid, allowing glucose to enter the cell, following its concentration gradient
Describe how water moves in osmosis
Water will move from an area of higher water concentration to an area of lower concentration. Or it will move from an area of lower solute concentration to higher solute concentration.
Describe what will happen next in this experiment:
A selectively permeable membrane that permits water but not sucrose molecules to pass is filled with a 20% sucrose 80% water solution. The upper part of the cellophane sac is wrapped tightly about a stopper through which a glass tube is fitted.
The sac is placed into a beaker containing 100% water
Because the cellophane is selectively permeable to water only, the amount of sucrose inside the sac will not change, but water from the beaker will move into the cellophane because of the higher solute concentration in the sac. Volume in the sac will increase, while the volume of water in the beaker itself will drop