Ch. 3: Cells - The Living Units Flashcards
What are the 3 parts of a cell?
- Plasma (cell) membrane
- Cytoplasm
- Nucleus
Describe the Plasma (Cell) Membrane
Flexible, yet sturdy barrier that surrounds & contains the cytoplasm of the cell
- 2 layers of phospholipids (hydrophilic head, hydrophobic tail)
- Selectively permeable
What are the 2 types of membrane proteins?
- Integral (transmembrane) proteins
- Peripheral proteins
What are the functions of an ion channel membrane protein?
Ion Channel (integral): forms a pore that a specific ion can flow to get across membrane
What are the functions of a carrier membrane protein?
Carrier (integral): transports substance across membrane by changing shape
What are the functions of a receptor membrane protein?
Receptor (integral): recognizes ligand & alters cell’s function in some way
What are the functions of an enzyme membrane protein?
Enzyme (integral & peripheral): catalyzes reaction inside or outside cell
What are the functions of a linker membrane protein?
Linker (integral & peripheral): anchors filaments inside & outside plasma membrane, providing structural stability & shape
What are the functions of a cell identity marker membrane protein?
Cell Identity Marker (glycoprotein): distinguishes your cells from anyone else’s
Why are membranes fluid structures?
Most of the membrane lipids & many of the membrane proteins move easily in the bilayer
- Membrane lipids & proteins are mobile in their own half of the bilayer
What does cholesterol do in the membrane?
Cholesterol serves to stabilize the membrane & reduce membrane fluidity
What is the lipid bilayer always permeable to?
Small, nonpolar, uncharged molecules
What increases the permeability of the membrane?
Transmembrane (integral) proteins that act as channels/transporters
How can Macromolecules pass through the plasma membrane
Only able to pass by vesicular transport
Define Concentration Gradient
Difference in concentration of a chemical between 1 side of the plasma membrane & the other
- Unequal distribution of chemicals inside & outside the cell
Define Electrical Gradient
Difference in concentration of ions between 1 side of the plasma membrane & the other
Together, what do the concentration gradient & electrical gradient make up?
Electrochemical gradient
What are the transport processes that move substances across the cell membrane?
- Passive: does NOT require energy, follows concentration gradient
- Active: requires energy (ATP), moves against gradient
Describe the passive process: Simple Diffusion
Passive movement of molecules (solute) from high to love concentration
- Influenced by: steepness of concentration gradient, temperature, mass of diffusion substance, surface area, diffusion distance
Describe the passive process: Facilitated Diffusion
Transmembrane proteins help solutes that are too polar or too highly charged move through the lipid bilayer
- Channel mediated: transport ions or water through aqueous channels from 1 side to another
- Carrier mediated: transport certain polar molecules (i.e. sugars & amino acids); changes shape to move molecules from different sides of membrane
Describe the passive process: Osmosis
The net movement of a solvent (water) through a selectively permeable membrane from an area of high concentration to an area of low concentration
Describe Tonicity
How a surrounding solution affects cell volume
Describe Isotonic
Solutions have same solute concentration as that of the cell; produces no net movement of water
Ex. normal RBC shape
Describe Hypertonic
Solutions have greater solute concentration that of the cell; water must move out of the cell
Ex. RBC undergoes crenation (shrinks)
Describe Hypotonic
Solutions have lesser solute concentration that that of the cell; water must move into the cell
Ex. RBC undergoes hemolysis
Describe the active process: Primary Transport
Energy derived from ATP changes the shape of a transporter protein; pumps substance across membrane against its concentration gradient
Describe the active process: Secondary Transport
Energy stored particle (in a hydrogen or sodium concentration gradient) is used to drive other substances against their own concentration gradients; 2 particles move at the same time
- Antiporters: 2 ions move in opposite directions at the same time
- 2 ions move in same direction at 1 time
- Glucose uses this
Describe the active process: Vesicular Transport
Transport of large particles & macromolecules into or out of a cell or between its compartments in membrane-bound sacs (transported in vesicles)
Describe Endocytosis (vesicular transport)
Move substance (bulk solids, macromolecules) into cells by forming a vesicle (sac)
- Phagocytosis: cell eating (takes in large material)
- Pinocytosis: cell drinking (takes in liquid particles)
Describe Exocytosis (vesicular transport)
Membrane-enclosed secretory vesicles fuse with the plasma membrane and release their contents into the extracellular fluid (moves stuff out)
Describe Transcytosis (vesicular transport)
Combination of endocytosis and exocytosis used to move substances from one side of a cell, across it, and out the other side
Define Cytoplasm
Cellular material surrounding the nucleus & enclosed by the plasma membrane
Describe the 2 components of the Cytoplasm
- Cytosol - intracellular fluid portion of the cytoplasm
- Organelles - specialized structures that have specific shapes & perform specific function
Describe the Cytoskeleton
Gives shape to the cell, forms some organelles
Describe Centrosome/Centrioles
- Centrosome: region near the nucleus, contains centrioles
- Centrioles: participate in cell division
Describe Cilia
Moves substances across the cell surface
Describe Flagella
Propels the cell itself (tail of sperm)
Describe Ribosomes
Found mostly in Rough ER; conduct protein synthesis
Describe Rough Endoplasmic Reticulum (Rough ER)
Contains ribosomes — assists in protein synthesis
Describe Smooth Endoplasmic Reticulum (Smooth ER)
Participates in lipid production, calcium storage, & detoxification
Describe the Golgi Complex/Apparatus
Packages proteins & lipids for export
Describe Lysosomes
Contains digestive enzymes
Describe Peroxisomes
Similar in shape to lysosomes, small. Contains enzymes that use oxygen to oxidize (break down) organic substances
- Contains hydrogen peroxide
Describe Proteasomes
Barrel-shaped strictures that destroy unneeded, damaged, or faulty proteins by cutting long proteins into smaller peptides (contain proteolytic enzymes)
Describe Mitochondria
Major site of ATP synthesis
Describe Nucleus
“Control center”; contains the hereditary units of the cell (genes)
Describe Cell Division
Process by which cells reproduce themselves
Describe Interphase of Cell Division
Period from cell formation to cell division (resting phase)
Describe the G1 (Gap 1) phase of Interphase
Cell metabolically active, synthesizing proteins & growing; virtually no activities directly related to cell division; centrioles start replicating
Describe the S (synthetic) phase of Interphase
DNA is replicated; new histones are made and assembled into chromatin
Describe the G2 (Gap 2) phase of Interphase
Enzymes & other proteins needed for division are synthesized and moved to the proper sites; centriole replication complete; cell ensures that all DNA is replicated & damage is repaired; cell is ready to divide
Describe the G0 phase of interphase
Stage that cells permanently stop dividing
Define Somatic Cells
All body cells (except reproductive cells/gametes); go through mitosis
Describe Mitosis
Division of Somatic Cells
- Occurs when the nucleus of a cell divides
- Results in the distribution of 2 sets of chromosomes into 2 separate nuclei
- Divided into 4 steps: Prophase, Metaphase, Anaphase, Telophase
Describe Prophase (Mitosis Step 1)
Chromatin condenses into chromosomes, the nuclear membrane disappears, centrosomes move to opposite poles
Describe Metaphase (Mitosis Step 2)
Centromeres of chromosomes line up at the metaphase plate
Describe Anaphase (Mitosis Step 3)
Centromeres of chromosomes split and sister chromatids move toward opposite poles of the cell
Describe Telophase (Mitosis Step 4)
Mitosis spindle dissolves, chromosomes regain their chromatin appearance, and a new nuclear membrane forms
Describe Cytokinesis
Cleavage furrow forms during anaphase & telophase and eventually the cytoplasm of the parent cell fully splits (when complete, interphase begins)
What are the 3 possible cell destinies?
- Remain alive & functioning without dividing
- Grow and divide
- Die
Define Meiosis
Reproductive Cell (Gamete) Division
Describe Prophase 1 (Meiosis)
Nuclear envelope disappears, crossing over occurs
Describe Metaphase 1 (Meiosis)
Tetrads line up along the metaphase plate
Describe Anaphase 1 (Meiosis)
Homologous chromosomes separate (sister chromatids stay together)
Describe Telophase 1 (Meiosis)
Each cell has one of the replicated chromosomes from each homologous pair of chromosomes
Describe Prophase 2 (Meiosis 2)
Nuclear envelope disappears
Describe Metaphase 2 (Meiosis 2)
Chromosomes line up along the metaphase plate
Describe Anaphase 2 (Meiosis 2)
Sister chromatids separate
Describe Telophase 2 (Meiosis 2)
Cytokinesis occurs (cytoplasm of parent cell splits)
Describe what happens to cells as we age
- Cells gradually deteriorate in their ability to function normally & in their ability to respond to environmental stresses
- The numbers of our body cells decreases
- We lose the integrity of the extracellular components of our tissues
