Chapter 6/7: Cell and Cell Membranes Flashcards
Cell Fractionation
- Useful technique for studying cell structure and function
- Takes cells apart and separates major organelles
- Centrifuge: instrument used which spins test tubes holding mixtures of disrupter cells at increasing speeds
- Each speed causes a fraction of the cells components to settle to the bottom of the tube
- Lower speeds: pellet consists of larger components
- Higher speeds: pellet consists of smaller components
- Enables researchers to prepare specific cell components in bulk and identify their functions
Both Prokaryotic and Eukaryotic
- All bounded by a selective barrier= plasma membrane
- Inside all cells is a semifluid, jelly like substance =cytosol
- All cells contain chromosomes which carry genes in the form of DNA
- All cells have ribosomes which are tiny complexes that make proteins according to instructions from the genes
Eukaryotic Cell
- Most of the DNA is in an organelle called the nucleus, which is bounded by a double membrane
- Much larger than prokaryotic cells
- The cells compartments provide diff local environments that facilitate specific metabolic functions
- Eukaryotes are able to be bigger because of compartmentalization, they ave parts inside them that are small, allows them specialization and increase in SA.
Prokaryotic Cell
- DNA is concentrated in a region that is not membrane enclosed, called the nucleoid region
- Lack membrane-bound organelles
- Prokaryotic Cells evolved before Eukaryotic Cells
Cytoplasm
- interior of either type of cell
- within the cytosol are a variety of organelles of specialize form and function
- In eukaryotic cells: the term refers only to the region between the nucleus and the plasma membrane
Plasma Membrane
- Functions as a selective barrier that allows passage of enough oxygen, nutrients, and wastes to service the entire cell
- Only a limited amount of substance can cross per second
Volume to SA Ratio
- As a cell increases in size, its volume grows proportionally more that its surface area
- a smaller object has a great ratio of surface area to volume
- Larger organisms have more cells
- A high ratio of SA to volume is especially important in cells that exchange a lot of material with their surroundings
- Microvilli: increase SA without an increase in volume
Cell
Simplest collection of matter that can be alive
Biological Membranes
- basic fabric feature is a double layer of phospholipids and other lipids, embedded in this lipid bilayer or attached to its surfaces are diverse proteins
- lipids and proteins
Nucleus
- Contains most of the genes in the eukaryotic cell
- Contains DNA
- directs protein synthesis by synthesizing messenger RNA according to instructions provided by the DNA
- The mRNA is then transported to the auto plasm via the nuclear pores.
- Once an mRNA molecule reaches the cytoplasm, the ribosomes translate the mRNA’s genetic message into the primary structure of a specific polypeptide
Nuclear Envelope
Encloses the nucleus, separating its contents from the cytoplasm
-A double membrane-each a lipid bilayer with associated proteins
Pore Complex
- Intricate protein structure
- Lines each pore and plays an important role in the cell by regulating the entry and exit of proteins and RNA’s
Nuclear Lamina
-The nuclear side of the envelope is lined by the nuclear lamina, a netlike array of protein filaments that maintains the shape of the nucleus by mechanically supporting the nuclear envelope
Nuclear Matrix
- A framework of protein fibers extending throughout the nuclear interior
- May help organize the genetic material so it functions efficiently
Chromosomes
- Within the nucleus, DNA is organized into discrete units called chromosomes
- Structures that carry the genetic information, each chromosome contains one long DNA molecule associated with many proteins
Chromatin
- The complex of DNA and proteins making up chromosomes
- As a cell prepares to divide, the chromosomes coil further, becoming thick enough to be distinguished as separate structures.
Nucleolus
- Prominent structure within the non dividing nucleus, which appears through the electron microscope as a mass of densely stained granules and fibers adjoining part of the chromatin
- proteins imported from the cytoplasm are assembled with rRNA into large and small subunits of ribosomes
- subunits then exit the nucleus through the nuclear pores to the cytoplasm, where a large and small subunit can assemble into a ribosome
Ribosomal RNA
-rRNA is synthesized from instructions in the DNA
Ribosomes
- Complexes made of ribosomal RNA and protein, are the cellular components that carry out protein synthesis
- Cells that have high rates of protein synthesis, have particularly large numbers of ribosomes
- Free Ribosomes: suspended in cytosol
- Bound Ribosomes: attached to the outside of the endoplasmic reticulum or nuclear envelope (EX: lysosomes or cells that specialize in protein secretion frequently have a high proportion of bound ribosomes
Endomembrane System
- Regulates protein traffic and performs metabolic functions in the cell
- INCLUDES: the nuclear envelope, endoplasmic reticulum, the Golgi apparatus, lysosomes, vesicles and vacuoles, and the plasma membrane
- Carries out a variety, like synthesis of proteins, transport proteins into membranes and organelles or out of the cell, metabolism and movement of lipids and detoxification of poisons.
Vesicles
- Sacs made of membrane
- related either through direct physical continuity or by the transfer of membrane segments as tiny vessels
- may be modified
Endoplasmic Reticulum
- An extensive network of membranes that it accounts for more than half the total membrane in many eukaryotic cells
- cisternae: consists of a network of membranous tubules and sacs
- Separates the internal compartment of the ER called the ER lumen cavity or cisternal space from the cytosol
- Rough ER and Smooth ER
- Rough ER: ribosomes (mRNA and make proteins)
- Smooth ER: Make lipids, make steroids, detoxifies, responsible for metabolism of carbs, regulates calcium ion concentration
Passive Transport
-Requires no cell energy
Diffusion
-The movement of molecules from an area of high concentration of those molecules to an area of lower concentration
Concentration Gradient
-A metaphorical “downhill” from high concentration to low concentration
Dynamic Equilibrium
-A balance
Active Transport
- Uses energy to move molecules either into or out of the cell
- Uses energy in the form of ATP
Hypertonic
- Experiences a net loss of water
- contains high concentration of solutes than the cell and therefore a lower concentration of water
- Water will flow out of the cell from the region of higher water concentration to the region of lower concentration
Hypotonic
- Experiences a net gain of water
- Contains lower concentration of solutes than the cell and therefore a higher concentration of water
- Water will flow into the cell from the region of higher water concentration to the region of lower concentration
Isotonic
- It will experience neither a net gain or loss of water
- Contains equal concentration of solutes as the cell and therefor an equal concentration of water
- Water will flow equally into and out of the cell
Plasmolysis
- The shrinking of the cytoplasm of a plant cell in response to diffusion of water out of the cell and into a hypertonic solution surrounding the cell
- During plasmolysis, the cell membrane pulls away from the cell wall.
Cell Membrane
- Regulates what comes into and out of the cell
- Has a hydrophilic( -) and hydrophobic head (+)
- Heads face the water, tails face away from the water
- All cells that we have, have a cell membrane
- All the membrane inside of a cell is moving around, if it ever stops moving, then it doesn’t function as the membrane
- A membrane is made up of phospholipids and proteins
Amphipathic Cell
-A molecule that is both hydrophilic and hydrophobic
Phospholipid
- Keeps water on either side
- Inside a cell membrane
Proteins
- Give proteins their specific characteristics
- Allows material in and connects to the out
- Within the membrane, regulate transport, allow things that are large and uncharged
- Allows big things and things that have a charge to cross
Cytoplasm
Inside the membrane
Extracellular Fluid
Outside the membrane
Glycoprotein
- has protein on inside
- Sugar attached to it
- Antibodies
Cell Membrane Fluidity
- float back and forth
- unsaturated lipid tail
- cholesterol
Materials That Can Enter/Leave Cell
- Oxygen (diffusion)
- CO2
- Things that are uncharged can go through the cell
Water
- Water enters and leaves the cell by proteins
- Allows material into and out of the cell
- Water can’t go through the membrane because it is non polar through the inside
Aquaporins
-protein will allow water to move through
Selective Permeability
- Cells only allow certain things in and certain things out
- Can regulate this and does this by using the cell membrane
Cell Walls
- Only plant cells have cell walls
- provide structure
- aid in plant cells= more structure
- Cell walls are made of cellulose, additional selection and rigidity
- Plants-cellulose/membrane
- Bacteria-cell wall/capsule/cellmembrane/peptidoglycin
- Fungi-cell wall-chitin
Fluid Cell Membrane
- Made up of a number of things
- Fluid because everything is moving
- Phospholipids float
- In flux
- If not flowing then material won’t go through
Cholesterol In Membrane
- Connects phospholipids together
- Keeps phospholipids from drifting off
- It keeps together and at the same time keeps apart
Glycolipids
- Made up of fats and sugars
- Important for signaling
Fat
- Phospholipids are fat
- Mostly made up of carbon and hydrogen
- Has head with charge
Substances That Move Through The Membrane
- Small and not charged molecules
- Examples: O2 and CO2
Cell Size
- Cells are small because the material moves in through a cell through diffusion. The distance between material has to move is small
- Cells aren’t infinitely small because the DNA has to be able to fit, everything has to be able to fit
Cytoskeleton
-It is a lattice made up of a number of difference macromolecules, organelles fit inside the lattice, motor proteins walk
Central
- Cytoskeleton
- Only in animal cells, 9+2, replicate, makes spindle fibers, chromosomes-separating, sets up formation
Lysosomes
-The suicide sac, digestive enzymes, contained within membrane and breakdown
Cytosol
-fluid, dissolved material with solutes
Compartmentalization
- Parts within parts, specialization, and surface area
- Example: Endoplasmic Reticulum which allows multiple jobs and increase in surface area
Mitochondria
- Make ATP
- Used to be bacteria cells on own, use them now for compartmentalization
Organelle
- Tiny organ, and part of the cell
- Allows for specialization
Microtubules
-Compressional support in the cytoplasm
Microfilaments
-Tensional support in the cytoplasm
Osmoregulation
- The general term for the processes by which animals control solute concentrations and balance water gain and loss
- Balances the uptake and loss of water and solutes
Excretion
-The process that rids the body of nitrogenous metabolites and other metabolic waste products
Osmolarity
–Whenever two solutions separated by the membrane differ in osmotic pressure
-(total solute concentration expressed as molarity, that is, moles of solute per liter of solution)
-milliOsmoles per liter (mOsm/L)
-
Isoosmotic
-Two solutions separated by a selectively permeable membrane have the same osmolarity
Hyperosmotic
-Two solutions differ in osmolarity, the one with greater concentration of solutes
Hypoosmotic
-Less concentration of solutes