Teas 7 Biology Study Guide

Membrane

- All cells have this.
- Composed of phospholipids, transport holes, and cytoplasm.

Transport holes

Proteins that help certain molecules and ions move in and out of the cell.

Cytoplasm (cytosol)

Jelly like substance that contains the cell’s organelles, helps support and suspend the structures inside the cell membrane, transfers material required for cellular processes

Organelles

Group of complex molecules that help a cell survive. The larger the cell, the more organelles it will need to live.

Cell structural organization

- All cells contain DNA and RNA and can synthesize proteins.
- Each cell consists of nucleic acids, cytoplasm, and a cell membrane.
- Mitochondria and chloroplasts have specific functions within the cell.

Single-celled vs multicellular organisms

Single cell
- Contains all components needed to live.

Multicellular
- Become specialized.

How does life begin as a single cell?

Through asexual or sexual reproduction.

How are cell, tissues, and organs grouped together?

Cells are grouped together in tissues.
Tissues are grouped together in organs.
Organs are grouped together in systems.
An organism is a complete individual.

Nucleus

- A membrane-bound structure that encloses nearly all genetic material of a eukaryotic cell.
- Storage of DNA, site of DNA replication and transcription (RNA).
- Coordinates the activities of the cell.

Eukaryotic cell

- Has a nucleus.
- Has mitochondria, endoplasmic reticulum, Golgi bodies, peroxisomes, and (in animal cells) lysosomes.
- Undergo mitosis.

Mitosis

- Duplicated chromosomes that form two identical daughter nuclei.
- Stage of cell cycle where the nucleus divides.

Prokaryotes

- Does NOT have a nucleus.
- Also has ribosomes and cytoskeleton like eukaryotic cells, but they are not enclosed by membranes.
- Reproduce by binary fission.

Binary fission

Asexual reproduction that splits into two new bodies.

Ribosomes

- Synthesizes proteins from amino acids.
- Numerous and a quarter size of the cell.
- Embedded in the rough endoplasmic reticulum or can be floating around in the cytoplasm.

Golgi complex (Golgi apparatus)

- Synthesizes proteins that are transported out of the cell.
- Located near nucleus and consists of layers of membranes.

Vacuoles

- Sacs used for storage, digestion, and waste removal.
- One large one in plant cells.
- Animal cells have small, numerous vacuoles.

- Helps maintain cell shape

Vesicle

- Small organelle within a cell.
- Has a membrane and performs varying functions, including moving materials within a cell.

Cytoskeleton

Consists of microtubules that help shape and support the cell.

Microtubules

- Part of the cytoskeleton and help supports the cell.
- Made of protein.

Cytosol

- Liquid material in the cell.
- Mostly water, but contains floating molecules.

Cytoplasm

- A fluid within the plasma membrane of the cell, but not within the nucleus.

Cell membrane (plasma membrane)

- Acts as a barrier for the cell.
- Keeps cytoplasm in and substances located outside the cell out.
- Determines what can enter and exit the cell.

Endoplasmic reticulum (ER or RER)

Two types:
- Rough
- Smooth

Rough
- Ribosomes on the surface, helps package and transport molecules within the cell, synthesis of proteins

Smooth
- No ribosomes on the surface, helps package and transport LIPIDS.

- A tubular network that comprises the transport system of a cell.
- Fused to the nuclear membrane and extends through the cytoplasm to the cell membrane.

Mitochondrion (mitochondria)

- Cell structures that vary in size and quantity.
- One cell may have one mitochondrion or thousands.
- Generates ATP and helps in cell growth and cell death.
- Contain their own DNA that is separate from the nucleus.

Golgi apparatus: structure and function

- Has a series of curved, flattened sacs called cisternae.
- The cis face receives vesicles sent by the ER that contain immature proteins.
- Vesicles fuse with the membrane and release the proteins into the Golgi.
- Proteins move stack to stack, budding off a new vesicle that fuses to the next cisterna layer each time.
- Modified "tags" help influence the structure and function of the protein which helps aid in the sorting and delivery of the protein destinations.
- Proteins are packaged in vesicles that bud from trans face of the Golgi.
- Secreted from the cell through exocytosis while other become part of the membrane.

Lysosomes

- Organelles that function in the breakdown of various substances. (aid in digestion)
- Bud from Golgi apparatus and enclose hydrolytic enzymes that would damage the cell if not separated from cytosol.
- H+ ion are pumped into the lysosome to maintain acidic environment.
- Function in cell homeostasis by dismantling various substrates and nonfunctioning intracellular components and recycling them in a process called autophagy.
- Destroy any invading bacteria and viruses

If lysosomes are damaged?

Cell undergoes apoptosis, but if it is severe damage, then necrosis.

Cytoskeleton function

- In eukaryotes, there are microfilaments, intermediate fibers, and microtubules.
- Cell shape and structure, movement of materials within the cell and movement of the cell itself.
- Can extend and retract, allowing cells to maintain their shape or change shape as needed.
- Network of protein fibers stabilizes most of the organelles and provides a way for motor proteins to use to direct vesicles to their destinations.
- Help anchor the cell to the neighboring cells and form extensions with cilia and flagella for cell movement.
- Cell division would be impossible without cytoskeleton as it pinches the cell into daughter cells during cytokinesis.

Microfilaments

- Thinnest components of cytoskeleton.
- Composed of protein molecules called actin that join together to form a twisting, flexible filaments.
- Organized into bundles and are involved in maintaining cell shape and events like cytokinesis, muscle contraction, and movement of the cell itself.
- Cytokinesis cause microfilaments to organize in a ring shape that decreases in size during contraction.

Microfilaments during contraction

- Cytoplasm is constricted until the original cell goes through mitosis.
- Protein myosin binds to actin filaments forming myofibrils.
- The two components slide past each other as the cell contracts and the muscle shortens.

Actin polymerization

Elongating the plus end for microfilaments.

Actin depolymerization

Shortening the minus end for microfilaments.

Microtubules function

- Thickest part of the cytoskeleton.
- Made of globular protein; tubulin.
- Stacked dimers to form linear rows called protofilaments of 13 that create a ring.
- Can lengthen and shorten by polymerization and depolymerization.
- Resists compressional forces while giving framework for motor proteins.
- Segregates sister chromatids during mitosis.

Intermediate fibers

- Thinner than microtubules, but thicker than microfilaments.
- 50 types of proteins.
- Lamins line the inside portion of the nuclear envelope that ONLY help in support and adhere cells to desmosomes.
- Can withstand tensile forces and prevent cell distortion under mechanical stress.
- Do not polymerize and depolymerize the way that microtubules and and microfilaments do.

Cilia and flagella

- Part of microtubules that extend from some types of cells.
- Flagella is longer than cilia.
- Cilia is high in quantity than flagella.
- Cilia for locomotion or sweeping materials along surface.
- Cilia moves mucous out of lungs and female RT use cilia to mobilize the egg.
- Cilia can detect signals and transmit information to the inside of the cell.
- Cilia move back and forth.
- Flagella move whip-like with a beating pattern. Only used for locomotion.

Centrioles

- Cylindrical structures that are formed from 9 triplets of microtubules arranged in a circle around a hollow center.
- Animal cells ONLY use this.
- Microtubules extend from centrioles as plus end grow toward metaphase plate to form spindle fibers of the mitotic spindle.

Centrosome

- Two perpendicular centrioles in animal cells form this organelle.
- Found near nucleus, but migrate to opposite poles of the cell division.
- Polar fibers extend from one centrosome to the other while kinetochore fibers attach to the chromosomes, pulling the sister chromatids apart during anaphase.

Plasma membrane

- Regulation and transportation of materials, cell to cell recognition, and cell signaling.
- Most basic function is cell containment.
- Fluid-like barrier that is reinforced by cholesterol and protein molecules.
- The barrier helps contain the structures and molecules within the cell's interior, and maintain desired concentrations of substances on either side of the membrane.
- Interior of membrane is hydrophobic which causes it to remain intact and in its aqueous environment while being impermeable to substances that are soluble to water.

Phospholipids

- Amphipathic both hydrophilic (polar hear) and hydrophobic (nonpolar tails)
- Arranged in micelles or bilayers.

Micelles

- A small spherical structure made of a single layer of phospholipids with the tails pointed inward to from a hydrophobic core.
- Used to transport lipid soluble materials.

Bilayer

- Formed when the phospholipids assemble into parallel layers with the tails pointed in toward each other and the head pointed out.
- Surround liposomes and other vesicles, and they enclose the organelles in a eukaryotic cell.
- Form cell membranes, which regulate the passage of materials into and out of all types of cells.

Protein functions in the membrane

- Shuttling of various ions and molecules through the membrane.
- Catalyzing reactions.
- Joining adjacent cells.
- Cell signaling.
- Cellular support and stability.
- Cell recognition.

Integral proteins

Proteins that penetrate the hydrophobic interior of the membrane.

Glycoproteins

Integral proteins with an attached sugar chain that aid in cell recognition.

Transmembrane

- When integral proteins extend completely through the membrane.
- Used as receptors for cell signaling.
- Required for transport across the membrane.

Cell signaling

A signal molecule (like a hormone) will bind to the receptor from the extracellular side, and relay a message to the cytoplasmic side.

Channel proteins

Transport proteins that have a tunnel-like conformation that allows materials to move passively.

Carrier proteins

Change conformation to move materials either by active or passive transport.

Peripheral proteins

Loosely bound to either side of the membrane and often act as enzymes or receptors proteins.

Osmosis

- Diffusion of water across a semipermeable membrane.
- Net movement of water is down its concentration gradient where it will move from an area of higher water concentration to lower or lower solutes concentration to higher.
- Restore balance when the solute cannot cross the membrane or if not cross fast enough.
- Passive transport of water across the membrane.

Hypertonic (out of cell)

Extracellular fluid that has a higher solute concentration as compared to the cytoplasm (interior).

Hypotonic (into cell)

Extracellular fluid has a lower solute concentration as compared to the cytoplasm.

Isotonic (in and out of cell)

Extracellular fluid has the SAME solute concentration as the cytoplasm.

Colligative property

Property of a solution that depends only on the AMOUNT of solute.

Osmotic pressure

Minimum amount of pressure required to stop the diffusion of pure water across the membrane.
- A colligative property because it is determined by concentration of solute.

𝜋 = 𝑖𝑀𝑅𝑇

𝜋 = osmotic pressure (in atmospheres)
𝑖 = Van't Hoff factor (# of particles formed from one unit of solute)
𝑀 = molar concentration
𝑅 = ideal gas constant
𝑇 = temperature (in Kelvin)

Semipermeable membrane

One chamber is filled with water while the next chamber is filled with a greater solution concentration. Water will rise on the side of the solution until osmotic pressure becomes too great.

Passive transport

Movement of substances across a cell membrane without the input of energy.
- Simple diffusion, osmosis, and facilitated diffusion are forms of passive transport.

Simple diffusion

Substances cross the membrane directly without the aid of a transport protein.
- Small molecules like oxygen, carbon dioxide, and uncharged lipids are not affected by hydrophobic interior of the membrane.

Polar molecules

- Can't use simple diffusion, but water molecules are small enough to slowly squeeze between the phospholipids.

Aquaporins

- Water channel proteins to increase the rate of osmosis.
- Without them, osmosis would occur slowly.

Facilitated diffusion

When proteins are used to transport substances down their concentration gradients.

Large, polar, and/or charged substances

- Require shielding from the interior of the membrane and may use channel or carrier proteins to assist in transport.
- Don't need ATP, but are driven by difference in solute concentration.

Active transport

- Energy is used to move solutes into or out of the cell.
- Substances are pumped against their concentration gradients from areas of low to high concentration.
- Required for maintenance of a membrane potential and uptake of glucose by intestinal cells.

Primary active transport

- Pumping of solutes by a carrier protein is directly coupled to the hydrolysis of ATP.
- Binding of a phosphate group causes a conformational change in the protein, allowing it to transport solutes across the membrane.

Secondary active transport

- Relies on ATP to generate an electrochemical gradient.
- When one solute moves down its gradient, another is pumped up its gradient.

Electrochemical gradient

Directly drives the active transport of a different solute.

Symport

When both solutes move in the same direction.

Antiport

When solutes move in opposite directions.

Endocytosis and exocytosis

- Types of active/vesicular transport that employ vesicles to import or export substances.
- Requires ATP and do not move solutes up their concentration gradients.
- For large particles or quantities of small particles.

Membrane channels

- Belong to a class of transport proteins that form pores to allow the passage of small, charged particles.
- Specific to solutes they transport and act as a sort of tunnel for particles of a certain size and charge.
- Move substances down their concentration gradient by facilitated diffusion, no energy needed.
- Interact weakly, letting solutes move fast across the membrane.

Ion channels

Usually gated; open and close in response to various stimuli.

Voltage-gated channels

Respond to changes in membrane potential by generating electrical impulses in nerve and cardiac cells.

Ligand-gated ion channels

Open in response to the binding of ligand like a hormone or neurotransmitter.

Mechanically-gated ion channels

Respond to a physical stimulus like stretching of the membrane and are useful in sensory tissues.

Exocytosis

- Cellular products and wastes are transported via vesicle to the cell membrane where the vesicle fuses, releasing its contents into the extracellular environment.
- Certain membrane components (glycoproteins and glycolipids) become incorporated into the cell membrane.

Endocytosis

- Ingestion of fluid, large particles, or target molecules.
- Cell membrane folds inward, engulfing the material and pinching off into a vesicle.

Pinocytosis

Ingestion of fluids and it is non-specific, meaning it takes in any enzymes and nutrients that happen to be available.

Phagocytosis

Engulfing of particles, sometimes even entire cells.

Receptor-mediated endocytosis

- Form of endocytosis that targets certain molecules (low-density lipoproteins) that are in low concentration outside the cell.
- Bind to receptors on the cell membrane, which then invaginates to form a vesicle.

Rough ER

- Continuous with the nuclear envelope with ribosomes.
- Ribosomes synthesize polypeptides which are then guided into the lumen of the rough ER before being modified, packaged in a vesicle and sent to different regions within the cell, often the Golgi apparatus.
- The Golgi will modify the proteins and sort them based on their destinations.
- Shipped out of the cell through exocytosis.

Smooth ER

- The cisternae are more tubular in shape than the rough ER and lack ribosomes.
- Synthesis of lipids such as phospholipids and cholesterol.
- In liver cells, detoxifies drugs.
- Muscles regulates and stores calcium ions.

Glycoprotein

Enzymes in the lumen may modify proteins by covalently bonding a carbohydrate for this protein from the rough ER to Golgi as the Golgi finishes the modification.

Shipped proteins

First packaged into transport vesicles and the vesicle fuse with its target.

Endoplasmic reticulum

- Takes up almost half of all the plasma membrane in a cell.
- Outer membrane of this structure is connected to the outer nuclear membrane, forming flattened sacs (cisternae).

Terasaki ramps

Helicoidal sheets

Purpose of mitochondria

- "Powerhouse"
- Produces most of cell's ATP.
- Outer membrane: selective barrier
- Inner membrane: where most of the ATP is made.
- Apoptosis.
- Proteins with the inner mitochondrial membrane move into the cytoplasm in response to oxidative stress and activate other proteins that begin the degradation of the cell.
- Semi-autonomous

Inner membrane of mitochondria

Folded into structures called cristae and this is where electron transport chain of aerobic respiration is located.

Chemiosmosis

- Synthesis of ATP
- Intermembrane space where a proton motive force is. The protons that are pumped across the intermembrane space during oxidative phosphorylation re-enter the mitochondrial matrix through the protein ATP synthase.

Mitochondria self-replication

- Has its own genome and ribosomes and produces many of its own proteins.
- Copy their own circular DNA molecules before undergoing fission.
- Relies on nuclear genes to produce many of the proteins required for DNA replication.
- Proteins from cytosol.

Endosymbiont theory

Mitochondria is likely evolved from an autonomous heterotrophic prokaryote in a symbiotic relationship with an ancestral host cell. Engulfed by the host cell that provides that cell with ATP.
- Once free-living prokaryotes.

Inside a nucleus

- Chromosomes and regulates DNA of a cell.
- Eukaryotic cells.
- Responsible for passing on genetic traits between generations.
- Has a nuclear envelope, nucleoplasm, a nucleolus, nuclear pores, chromatin, and ribosomes.

Chromosomes

Highly condensed, threadlike rods of DNA.

DNA

Deoxyribonucleic acid of genetic material that stores information about the plant or animal.

Base pairs

A - T

C - G

(atv and cgi)

Codon

sequence of three nucleotides that code for specific amino acids

(64 possible codons, and 3 are “stop signal” codons)

Chromatin

Consists of DNA and protein that make up chromosomes.

Nucleolus

- Contained within the nucleus of protein.
- Small, round, and does not have a membrane.
- Protein synthesis.
- Synthesizes and stores RNA.

Nuclear envelope

- Double membrane that encloses the structures of the nucleus while it consists of inner and outer membranes of lipids.
- Continuous with the ER and lumen of the ER open to the perinuclear space which allows for easy exchange of materials between the two organelles.

Nuclear pores

- Exchange of material between the nucleus and the cytoplasm.
- Aqueous channels made of nucleoporins.
- Interact with transporter proteins called karyopherins that shuttle large molecules like RNA and certain proteins back and forth.