Chapter 3 Cells Flashcards
Prepare for first test
What are the three regions of a cell?
- Plasma Membrane
- Cytoplasm
- Nucleus
What is a cell? And what does cell theory say?
Defining cells is to define life.
Cells are the smallest unit of life.
All life forms contain one or more cells.
Cells only arise from other cells.
What are the functions of the plasma membrane?
Physical barrier - separates cytoplasm from extracellular fluid.
Selectively permeable - determines which substances enter and exit.
Communication - plasma membrane proteins interact with chemical messengers and relay messages to cell interior.
Cell recognition - cell surface carbohydrates (glycocalyx) allow cells to recognize each other.
What is the cytoplasm?
It’s the intracellular fluid packed with organelles.
What is the nucleus?
It’s an organelle that controls cell activities.
What is extracellular fluid?
It is like a nutritious soup which contains amino acids, sugars, fatty acids, regulatory substances and wastes.
Cells extract what they need from our ECF.
What are cellular secretions?
These include: digestive fluids and lubricants (saliva, mucus, and serous fluids).
What is the extracellular matrix?
Cells exist in a composite of polysaccharides and proteins. These molecules self assemble into an organized space where they serve as a “cell glue” that help bind body cells. These are particularly abundant in connective tissues.
What two body components does the plasma membrane separate?
It separates intra- and extracellular fluid.
What is the fluid mosaic model?
It refers to the floating proteins that reside in the lipid bi-layer of the plasma membrane. The are continually moving in the membrane and create a fluid mosaic pattern.
What are the features of phospholipids?
They have hydrophilic heads and hydrophobic tails.
How much of the phospholipid bilayer is comprised of cholesterol, and what is it’s function?
About 20% and it stiffens the bilayer.
What are the roles of cell proteins?
Transport - they may provide a channel across the bilayer for a solute or work as a pump.
Receptors for a signal - they may receive hormones, or be altered by there presence in order to elicit a chemical change.
Enzymatic activity - may catalyze metabolic pathways.
Cell-cell recognition - glycoprotiens serve as identification tags.
Attachment to cytoskeleton and ECM.
Cell to cell joining.
Key features of Tight Cell Junctions…
Interlocking junction proteins.
Impermeable junctions
Form continuous seals around the cell
Prevent molecules from passing between cells.
Key features of Desmosomes…
Formed with linked proteins - cadherins.
Anchoring junctions.
Bind adjacent cells together like molecular velcro.
Help keep cells from tearing apart.
Key features of Cell Gap Junctions…
Formed by connexons.
Communicating junctions.
Allow ions and small molecules to pass from cell to cell.
Particularly important in heart cells and embryonic cells.
What is Diffusion?
The movement of molecules, or ions, from an area of higher concentration to a lower concentration. This is the concentration gradient.
What are three factors that affect diffusion?
Concentration - more collisions occur when the concentration difference is high.
Molecule size - smaller molecules are faster at diffusing
Temperature - more kinetic energy increases speed
What are two types of diffusion?
Simple - substances diffuse directly through lipid bilayer they tend to be small or gaseous, steroids or fatty acids.
Facilitated - substances either bind to proteins and are ferried or they pass through water filled channel proteins. These are selective in relation to pore size or charge of amino acids lining the channel.
What binds cells?
The glycocalyx.
Their contours fit together.
Special cell junctions.
What are microvilli?
Fingerlike projections that increase surface area for absorption.
Common in epithileal cells lining hollow body organs.
