Exam 2 Flashcards
Which statement is true?
A cell placed in a hypotonic solution will swell
A concentration gradient ceases to exist when
there is no net movement
The method of movement that requires the expenditure of ATP molecules is
active transport
Cell membranes show selective permeability, which means that
some substances can cross freely; others cannot
A red blood cell will lyse (burst) when placed in which of the following kinds of solution?
Hypotonic
A red blood cell will crenate (shrink) when placed in which of the following kinds of solution?
hypertonic
What type of membrane proteins bind extracellular substances (example: hormones) that can trigger changes in cell activities?
receptor proteins
What type of membrane proteins acts as channels for direct signaling between two adjacent cells?
communication proteins
What type of membrane proteins keep cells together (i.e., form spot welds between cells)?
adhesion proteins
Cell membranes are primarily composed of phospholipids.
True
Lipid Bilayer
- main compontent of cell membranes
- gives membranes its fluid properties
Lipid Bilayer
fatty acid tails (hydrophobic) sandwhiched between hydrophilic heads
Hydrophilic parts
dissolves in water
Hydrophobic parts
repels water
Membrane is a mosaic (mixture) of:
- Phospholipids
- Glycolipids (lipids w/ sugar mono attrached
Membrane is a mosaic (mixture) of:
- Sterols (cholesterol; phytosterols
- Proteins
What can drift through membrane?
most phospholipids and some proteins
Nature of phospholipids (spinning an presence of unsaturated fats in tail)
contribute to membrane’s fluid nature
Postions of proteins in the membrane
- Integral membrane proteins
- Peripheral membrane proteins
Integral membrane proteins
span the lipid bilayer, with their hydrophilic regions extending past the surface of the membrane.
Peripheral membrane proteins
positioned at the surface of the membrane (do not span the bilayer)
Functions of Membrane proteins
-Adhesion protein, Communication protein, Receptor proteins, Recognition proteins, Transport proteins
Adhesion proteins
glycoproteins that helps cells stay connected to one another in a tissue
Communication proteins
form channels that match up across the plasma membranes of two cells (signals flow between their cytoplasms).
Receptor proteins
presence of binding sites for hormones (other signals) that can trigger changes in cell action
Recognition proteins
identify the cell as a certain type (tissue or individual). Identified as self or nonself (foreign).
Transport proteins
allow water-soluble substances to move through the membrane. open to both sides of the bilayer (passive and active)
WHat must rely on passage through transport proteins?
glucose and other large, polar molecules
Membrane crossinf mechanisms
Diffusion across lipid bilayer, passive transoport, active transport, endocytosis, exocytosis
Diffusion
the net movement of “like” molecules or ions down a concentration gradient
Factors affecting diffusion rate
-steepness of concentration gradient(steeper gradient, faster diffusion)
Factors affecting diffusion rate
-molecular size smaller=faster (smaller molecules, faster diffusion
Factors affecting diffusion rate
-Temperaturehigher=faster (higher tem, faster diffusion
Factors affecting diffusion rate
-Electrical difference in charge or pressure gradients
Exocytosis
A cytoplasmic vesicle fuses with the plasma membrane and contents are released outside the cell
Endocytosis
A small patch of plasma membrane sinks inward and seals back on itself, forming a vesicle inside the cytoplasm–membrane receptors often mediate this process
Hydrostatic pressure (fluid pressure)
pressure exerted by fluid on the walls that contain it (in plants, turgor pressure)
Osmotic pressure (fluid pressure)
amount of pressure necessary to prevent further increase of a solution’s volume
Tonicity
refers to relative solute concentrations of two fluids (hypotonic- fewer solutes, hypertonic- more solutes, isotonic- same amount)
Passive Transport
-doesn’t require energy inputs, solutes diffuse through channel inside the protein’s interior, net movement is down concentration gradient
Active Transport
requires ATP, protein is an ATPase pump, pumps solute against its concentration gradient
In _______ pathways, small molecules are assembled into large molecules.
biosynthetic
In _______ pathways, large molecules are broken down into smaller molecules.
catabolic
Essentially, the first law of thermodynamics says that:
energy can be neither created nor destroyed
ATP contains:
adenine
The addition of electrons is known as:
reduction
The removal of electrons is known as:
oxidation
The concept that concentration differences in H+ and electric gradients across a membrane are responsible for ATP formation is known as:
the chemiosmotic model
No energy conversion is ever 100% efficient. Further, each conversion produces energy (heat) that is unavailable for cellular work.
True
Cells spend ATP in exergonic reactions
False
Enzymes are catalytic molecules (alter rates) for biological reactions.
True
What is energy?
capacity to do work (forms: potential-capacity to make things happen, kinetic-motion(includes heat), and chemical energy-potential energy of molecules)
What do cells use energy for?
chemical work-build, stockpile, and break apart substances; mechanical work-movement (flagella); electrochemical work-movement charged molecules across membranes
First Law of Thermodynamics
the total amount of energy in the universe is constant; energy can undergo conversions from one form to another, but it cannot be created or destroyed.