Unit 1 Biology

Gated Channels

• Are able to switch states between open, closed and intermediate to allow ion movement

• channel proteins found in all eukaryotic cells

• critical to the movement of most ions and opened/ closed by voltage channels

Nucleoid

the region in prokaryotic cells where DNA replication and RNA transcription occur, lacks a membrane

Pinocytosis

a form of endocytosis where extracellular water is taken in along with dissolved molecules

Features of Prokaryotic Cells

1. lack a true nucleus

2. DNA is in the nucleoid and circular, floating around the cytoplasm

3. Contains no membrane bound organelles

4. Smaller and simple cell

5. unicellular

6. have a cell wall

7. smaller ribosomes

Carrier Proteins

during facilitated diffusion they form passageways through the lipid bilayer and bind specific solutes

Ribosomes

small, roughly spherical particles in the cytoplasm that are responsible for protein synthesis by translating mRNA into amino acid chains

Sterols

act as membrane buffers, restraining lipid movement at high temperatures and disrupting fatty acids at low temperatures

Capsule

gelatinous glycocalyx firmly attached to cells, sticky and slimy external layer of polysaccharides

Bacterial Flagellum

helically shaped and rotating in a socket to push the cell through a liquid medium

Lysosomes

small membrane-bound vesicles filled with hydrolytic enzymes that digest damaged organelles or the contents of endocytic vesicles

What are the three steps of a signal transduction pathway?

1. reception

2. transduction

3. response

Simple Diffusion

lacks a transporter

Facilitated diffusion

• uses specific transporters such as channel proteins and carrier protons

• faster and can be saturated by substrates like enzymes

Symport Mechanisms

the cotransported solute moves in the same direction of the driving ion

Antiport Mechanisms

molecules move in opposite directions

Passive Membrane Transport

• substances moving across a membrane without using ATP or chemical energy

• includes simple diffusion and facilitated diffusion

What are the main functions of active membrane transport?

1. nutrient uptake

2. waste removal

3. maintenance of intracellular ion concentrations

Primary Active Transport

• the same protein that transports the molecules also hydrolyzes ATP to power transport directly

Cell Theory

1. All organisms consist of cells

2. Cells are the basic unit of life

3. Cells only come from pre-existing cells

Cell Membrane

outer boundary of the cytoplasm that controls the passage of substances in and out of the cell

Hypothesis

possible explanation

Theory

explanation based on observations

Calcium Pumps

Push calcium ions from the cytoplasm to the cell exterior and into vesicles of the ER

Mitochondria

membrane bound organelle enclosed by two membranes and the site of cellular respiration producing ATP

Exocytosis

when secretory vesicles fuse with the plasma membrane, releasing contents to the cell exterior

Aquaporins

specific transport proteins facilitating the diffusion of water

Protein Kinases

relay a signal in a cell by transfering a phosphate group from ATP to specific proteins, catalyzing phosphorylation reactions to pass on the signal during the signalling pathway

What is the structure of integral membrane proteins?

non polar inner region and polar outer region

Protein Phosphatases

balance or reverse the effects of protein kinases by removing phosphate groups from target proteins during signal transduction pathways

How do receptors bind signal molecules?

the receptor signal binding site extends from the outer membrane surface

How does the sodium potassium pump function?

Pushes 3 Na ions out of the cell and 2 K ions into the cell in the same cycle

Plasmodesmata

allows ions and small molecules to move directly between plant cells

Chloroplasts

lens or disk-shaped organelles and the site of photosynthesis

Thylakoid

flattened closed sacs that make up the third membrane of the stroma and the structure in the chloroplast that absorbs light energy during photosynthesis

Nucleoli

irregular masses that copy rRNA genes into rRNA molecules within the nucleus

Vacuole

large vesicles that perform specialized functions unique to plants

What are membrane surface receptors?

• integral proteins extending through the membrane involved in signal transduction

• the receptor binding signal site extends from the outer membrane surface and folds to closely fit the particular signal for the specific receptor and changes the structure of the receptor to transmit the signal through the plasma membrane activating the cytoplasmic end of the receptor protein and initiating the signalling cascade

Membrane Proteins Functions

1. transport

2. enzymatic activity

3. signal transduction

4. attachement /recognition

What are the types of Prokaryotes?

bacteria and archaea

What are the types of Eukaryotes?

fungi, animals, plants and protists

Peripheral Membrane Proteins

• proteins positioned on the plasma membrane’s surface by non covalent bonds

• interact with the exposed part of integral proteins and directly with lipid molecules

• found on the cytoplasmic side of the plasma membrane and form part of the cytoskeleton

• key enzymes in respiratory and photosynthetic electron transport

• mix of polar and nonpolar amino acids

Integral Membrane Proteins

proteins embedded in the phospholipid bilayer, the inner region is nonpolar and the outer regions are polar

Proton Pumps in the plasma membrane

move hydrogen ions from the cytoplasm to the cell exterior

Rough Endoplasmic Reticulum

produces, sorts and transports proteins

What is the purpose of the cell wall?

it provides rigidity

Pili

hairlike shafts of proteins that attaches cells to surfaces or other cells

Flagella in Prokaryotes

a long and threadlike structure that allows bacteria and archaea to move through liquids and across wet surfaces

What is the type of sterol found in membranes?

Cholesterol

Fluid Mosaic Model

• describes the membrane as a fluid with proteins with moving around within lipid molecules

• membrane proteins anchor cytoskeleton filaments to the membrane

Chromatin

the combination of DNA and proteins within the nucleus

Nucleoplasm

liquid or semi liquid substance within the nucleus

Nuclear Pore Complex

the structure formed by nucleoporins that controls material exchange between the nucleus and cytoplasm

Nuclear Envelope

separates the nucleus from the cytoplasm with two layered membranes

Gap Junctions

open channels allowing ions and small molecules to pass between animal cells

Tight Junctions

junctions with small regions that some ions cannot pass between layers

Anchoring Junctions

form button-like spots that connect adjacent animal cells together

Extracellular Matrix

provides support, protection and linkages in animal cells

Cell Junctions

seals the spaces between animal cells to provide direct communication

Grana

thylakoids stacked on top of each other

Stroma

the inner compartment of a chloroplast enclosed by two boundary membranes

Chromoplasts

red and yellow pigmented organelle that is responsible for the colour of ripening fruits and fall leaves

Amyloplast

colourless plastid that stores starch in plants

Centrosome

main microtubule organizing centre of a cell which organizes the microtubule cytoskeleton during interphase and positions many of the cytoplasmic organelles

Crista

fold that expands the surface area of the inner mitochondrial membrane

Cytoskeleton

interconnected system of protein fibers and tubes that extends throughout the cytoplasm of a eukaryotic cell consisting of microtubules, intermediate filaments and microfilaments

Endocytosis

molecules are brought into the cell from the exterior by a bulging of the plasma membrane that pinches off to form vesicles

Endoplasmic Reticulum

an extensive interconnected network of cisternae that is responsible for the synthesis, transport and initial modification of proteins and lipids, can have ribosomes or no ribosomes

Exocytosis

when a secretory vesicle fuses with the plasma membrane and releases the vesicle contents outside of the cell

Golgi Complex

stack of flattened membranous sacks called cisternae, responsible for the final modification, sorting and distribution of proteins and lipids

Intermediate Filament

a cytoskeletal filament that provides strength to cells in tissues

Matrix

material between cells

Microfilament

protein filaments in the cytoplasm of eukaryotic cells that for part of the cytoskeleton

Microtubule

a cytoskeletal component formed by the polymerization of tubulin into rigid hollow rods

Plastid

a family of plant organelles

Slime Wall

loosely and diffuse glycocalyx

Flagella in Eurkaryotes

elongated slender and motile structures that extend from the cell surface that create whiplike movements to propel cells

Eukaryotic Chromosome

each individual DNA molecule with its associated proteins

Membrane Assymetry

how proteins or components of one half of the bilayer are different than the other half

Phospholipids

water soluble molecules with half hydrophobic and half hydrophilic

Channel Proteins

• form hydrophillic pathways in the membrane for molecules to pass through by providing an area shielded from the hydrophobic core

Active Membrane Transport

• the transport of molecules across a membrane against a concentration gradient requiring energy usually in the form of ATP

• includes primary, secondary, endocytosis and exocytosis

Secondary Active Transport

• transport is indirectly driven by ATP and transport proteins use a favourable concentration gradient of ions built up by primary active transport as the energy source to drive the transport of a different molecule using symport and antiport mechanisms

Receptor Mediated Endocytosis

• molecules are bound to the outer cell surface by proteins that only bind recognized molecules collecting into a depression in the plasma membrane with proteins called clathrin that coat and reinforce the cytoplasmic side

• the vesicle will pinch free from the plasmamembrane and rapidly lose its clathrin coat in the cytoplasm and may fuse with a lysosome to breakdown the vesicle into smaller useful molecules

Cell Signalling

membranes play a crucial roles in the perception of signals and the transduction of the signal to alter cell function from physical or chemical signals and is critical for the maintenance of homeostasis

Reception

binding of a signal molecule with a specific receptor of the target cell found on the plasma membrane, internal membrane and soluble proteins in the cytoplasm

Transduction

process of signal reception triggering other changes within the cell necessary to cause cellular respiration and typically involves a cascade of reactions that include several different molecules called the signalling cascade

Response

the transduced signal causes a specific cellular response which leads to different downstream responses such as activation of a specific enzyme or change in gene expressions

Amplification

an increase in the magnitude of each step in the signal pathway as enzyme activity can activate more proteins