Cell Structure and Function Flashcards

Flashcards about Cell Structure and Function.

Characteristics of ALL Cells

Bounded by a plasma membrane, contain cytosol, contain chromosomes, contain ribosomes, cytoskeleton.

Eukaryotes

DNA is Linear Chromosomes within a membrane-bound nucleus, Size is 5-100 µm ,Organization is often multicellular (some are single celled), some have cell walls, Organelles are membrane bound organelles like mitochondria, ER, Golgi, etc., Examples are plants, animals, protists, fungi

Prokaryotes

DNA is Circular Chromosome found in the cytosol, Size is 0.2-10 µm , Organization is single-celled, have cell walls, Organelles are no membrane bound organelles, different size ribosomes than eukaryotes, Examples bacteria, archaea.

All Eukaryotes have…

Nucleus, Membrane-bound organelles, Endomembrane systems, Linear chromosomes

Mitochondria Origin

early eukaryotic heterotroph engulfed an aerobic bacteria, but did not digest them, mutually beneficial relationship, Resources for mitochondria, Extra ATP for host cell

Chloroplasts Origin

eukaryote engulfed a photosynthetic bacterium (cyanobacteria), but did not digest it, mutually beneficial relationship, Resources for the chloroplast, Sugars for the host cells

Cell Structures unique to Plant Cells

Chloroplasts, Cell Wall, Central Vacuole, Plasmodesmata

Cell Structures unique to Animal Cells

Gap Junctions

Why are Cells Small?

As a cell increases in size, the volume grows at a faster rate than the surface area, Cells require a high surface area to volume ratio

Plasma Membrane

Semi-permeable Lipid Bilayer, phospholipids are the major constituent of the membrane, Separates the internal from the external environment, Involved in cell adhesion, cell signaling, & transport of materials in and out of the cell

Cytoplasm

The entire contents of the cell, exclusive of the nucleus, and bounded by the plasma membrane, Includes the cytosol and the organelles within the cytosol, In prokaryotes it includes the entire contents of the cell, Many cell reactions take place here, Cytosol is a semifluid substance in the cytoplasm

Organelle

is a specialized subunit within a cell that has a specific function

Nucleus

Contains the genetic material (DNA) of a eukaryotic cell

Ribosome

Site of protein synthesis, the translation of the genetic instructions yields specific polypeptides, Composed of ribosomal RNA (rRNA) and protein

Free-Ribosomes

Most of these proteins function within the cytosol

Rough ER Membrane Bound Ribosomes

Proteins destined for secretion, Proteins destined for insertion into the cell membrane, Proteins for organelles such as lysosomes, Golgi, Endoplasmic Reticula

Endoplasmic Reticulum

Interconnected system of tubules, Is continuous with the nuclear envelope

Smooth ER

Lacks Ribosomes, Site of lipid synthesis, Drugs & Poison Detoxification

Rough ER

compartmentalizes the cell, contains ribosomes, ribosomes here produce proteins for: secretion out of the cell, insertion into the cell membrane, for organelles

Golgi Apparatus

Consists of flat membranous sacs, receives proteins via vesicles from the rough ER, modifies those proteins, places them within another vesicle and routes them to their final destination secretion of the cell, insertion into the membrane, for organelles such as the lysosome

Vesicles

small membrane-bound sacs they are often used to move chemicals to other locations in or outside the cell

Lysosome

Contains hydrolytic enzymes

Lysosome Functions

certain cells breaks down bacteria, intracellular digestion, autophagy – breaks down unnecessary or dysfunctional cell parts and organelles, apoptosis – programmed cell death

Tay-Sachs

a genetic disorder caused by an insufficient activity of an lysosomal enzyme called beta-hexosaminidase A

Vacuole

a membrane - bound sac that plays roles in intracellular digestion and the release of cellular waste products

Food Vacuole

stores food taken into the cell

Central Vacuole

stores water to maintain turgor pressure in plant cells, can also store nutrients

Contractile Vacuole

found in only freshwater protists, maintains water balance by pumping out excess water

Endomembrane System Components

Nuclear Envelope, Rough ER, Smooth ER, Golgi Apparatus, Lysosomes, Vacuoles, Vesicles, Cell Membrane

Endomembrane System Functions

Synthesis of proteins and their transport into membranes and organelles or out of the cell, Metabolism and movement of lipids, Detoxification of poisons

Chloroplast

performs photosynthesis converts light energy to chemical energy in the form of carbohydrates, found within algae and plants

Mitochondria

site of cell respiration, uses oxygen to breakdown organic compounds and produce ATP, found in eukaryotic cells

Cytoskeleton

a network of fibers that organizes structures and activities in the cell, Maintains cell shape (morphological integrity), Anchorage for organelles, Allows for the movement of organelles and vesicles within the cell, Help separate the chromosome copies in dividing cells

Types of Cytoskeleton Fibers

microtubules, microfilaments , intermediate filaments

Centrosomes

the microtubule organizing centers that forms the mitotic spindle in dividing cells

Cell Wall

Maintenance of cell shape and skeletal support, Provides protection for plant cells

Flagella

Tail-like projection powered by motor proteins, Involved in cell movement

Cilia

Short finger-like projections powered by motor proteins, Cell Movement

Pseudopod

temporary arm-like cellular extension, Used for cell movement and Ingestion

Plasmodesmata

channel in the cell wall connecting two plant cells allowing water and solutes to pass between cells

Gap Junction

intercellular connection between animal cells that allows water and solutes to pass between cells

Phospholipids

Phosphate head is hydrophilic, Fatty acid tails are hydrophobic, Arranged as a bilayer

Cell Membrane

Serves as a cellular barrier / border, Controls traffic in & out of the cell, Semipermeable

Cell Membrane IS permeable to…

small nonpolar molecules (e.g. lipids, CO2, O2)

Cell Membrane is Impermeable to…

polar and charged molecules (e.g. sugar, water, ions)

Cholesterol

Stabilizes the fluidity of the cellular membrane

How do Polar and Charged Molecules Get Across the Membrane?

Specific protein channels and pumps enable polar and charged molecules to cross the membrane

Glycoproteins & Glycolipids

Play a key role in cell-cell recognition ability of a cell to distinguish one cell from another, important in tissue & organ development, basis for rejection of foreign cells by immune system

Mosaic

The cell membrane is made of many components: i.e. phospholipids, cholesterol, proteins, glycoproteins, glycolipids

Fluid

all the components flow past each other

Transport

High to Low concentration – molecules move down the gradient, Gradient – progressive difference in concentration from one area to another, High energy gradient to low energy equilibrium states

Passive Transport

No energy is required from the cell, Molecules move from areas of higher concentration to areas of lower concentration

Simple Diffusion

Molecules that can naturally cross the cell membrane without help, Molecules move from areas of higher concentration to areas of lower concentration, Does not require energy from the cell

Facilitated Diffusion

Diffusion of polar and charged molecules through transport proteins, Molecules move from areas of higher concentration to areas of lower concentration

Channel protein

A channel protein has a channel through which water molecules or a specific solute can pass.

Carrier Protein

A carrier protein alternates between two conformations, moving a solute across the membrane as the shape of the protein changes.

Gated Channel

A stimulus causes the gate to open or close, Stimulus can be a chemical or an electrical signal

Active Transport

Requires the cell to input energy into the system, Moves molecules against the concentration gradient - from Low to High, Energy from ATP causes a conformational shape change in the pump transporting solute from one side the of membrane to the other

Sodium-potassium pump

Moves sodium and potassium against their concentration gradient (requires energy – breakdown of ATP), Each cycle moves 3 Na+ out and 2 K+ in, Makes the interior of the cell relatively negative compared to the extracellular fluid

Electrochemical gradient

Ions move down the concentration gradient based upon the interaction between two forces

Chemical force (diffusional)

molecules move high to low concentrations

Electric force

• ions attracted to negative membrane potential and vice versa

Membrane potential

The difference in charge across the membrane (voltage)

Cotransport

Coupling the movement of a substance down its gradient (releases energy) to drive a different substance against its gradient (requires energy)

Bulk Transport

movement of large molecules or large quantities of smaller molecules across the membrane

Exocytosis

the cellular secretion of macromolecules through the fusion of vesicles with the plasma membrane

Endocytosis

The cellular uptake of molecules by a region of the plasma membrane surrounding the substance and pinching off to form an intracellular vesicle

Phagocytosis

cellular intake of a large substance or a small organism such as a bacterium via a vesicle

Pinocytosis

cellular intake of extracellular fluids and its dissolved solutes

Receptor-mediated endocytosis

The movement of specific molecules into a cell by the inward budding of membranous vesicles containing proteins with receptor sites specific to the molecules being taking in

Ligand

A molecule that binds specifically to a receptor site of another molecule

Osmosis

Diffusion (passive transport) of water across a selectively permeable membrane

Hypertonic

Higher solute, Lower water

Hypotonic

Lower solute, Higher water

Isotonic

Equal solute & water

Water Potential

The physical property predicting the direction water will flow (osmosis), governed by solute concentration and applied pressure

ΨP

pressure potential, called turgor pressure in plants

ΨS

solute potential, also called osmotic potential

Turgor Pressure

The force directed against a cell wall after the influx of water and the swelling of a walled cell due to osmosis

Turgid

A walled cell that has a greater solute concentration than its surrounding hypotonic environment, resulting in an entry of water

Flaccid

Limp. A walled cell is flaccid in surrounding isotonic environments where there is no net movement of water into the cell

Plasmolysis

The plasma membrane pulls away from the cell wall when the cell loses water to a hypertonic environment

i

ionization constant

C

molar concentration

R

pressure constant

T

temperature in Kelvin

Regulators

Maintain relatively constant internal conditions no matter the outside environment

Conformers

Allow internal conditions to match the external environment

Homeostasis

steady state, maintain internal body conditions despite fluctuating external conditions

Negative Feedback

The primary mechanism of homeostasis, whereby a change in a physiological set point that is being monitored triggers a response that counteracts the initial fluctuation

Receptor

monitors the environment, sends signals to the control center

Control Center

responds to changes in the environment

Effector

a muscle or gland receives signals from the control center and corrects the deviation

Osmolarity

A measure of the concentration of solute particles in a solution that contribute to osmotic pressure

Osmoregulation

The process of monitoring and maintaining a certain osmolarity in a solution such as blood through negative feedback mechanisms

Contractile Vacuole

Maintains water balance (homeostasis) by pumping excess water out of a cell

Excretion

The disposal of nitrogen- containing metabolites and other waste compounds