(Brianna Murray) Chapter 3 Cells: The living units

All living organisms are composed of what

Cells

What are the three major regions of a generalized human cell?

• The nucleus

• Cytoplasm

• Plasma membrane

What are some extracellular materials found outside cells?

• Body fluids

• cellular secretions

• extracellular matrix

What is the plasma membrane

It is a fluid bilayer of lipids where proteins are inserted that regulates the movement of substances in and out of the cell and provides structural support.

• It also plays a role with cellular communication.

Lipids form what?

Lipids form the structural part of the plasma membrane.

What two regions do lipids have?

Hydrophilic

Hydrophobic

• that organize their aggregation and self repair

What are the two types of proteins?

Integral proteins: proteins that go all the way through the membrane

Peripheral proteins: proteins that sit on the surface of the membrane.

What are the specialized membrane functions?

• some are enzymes (speed up chemical reactions)

• some are receptors (receive signals)

• some mediate membrane transport functions. (move things in and out of the cell)

What do carbohydrates attach to and what do they form?

Carbohydrates attach to proteins (making glycoproteins) or to lipis(fats) making glycolipids

• forming glycocalyx helping cells recongize each other and communicate

What are cell junctions?

• hold cells together and can either help or block the movement of molecules between or through cells.

What are the different types of cell junctions?

• Tight junctions: sealed tightly together, nearly impermeable

• Desmosomes (mechanical junctions): hold cells together to help form a strong, functional tissue

• Gap junctions: connect cells and allow them to communicate by letting small molecules and ions to pass between.

What is diffusion?

Diffusion is the net movement of molecules from an area of high concentration to a lower concentration .

Lipid solutes can do what?

They can diffuse directly through the membrane by dissolving in the lipid

What is passive movement

Molecules move across the membrane without energy, from high to low concentration (diffusion)

What is active movement?

molecules move with energy (ATP) usually from low to high concentration

What is facilitated diffusion

• When molecules move across the cell membrane through a protein channel or carrier, high to low concentration without using energy

What is osmosis

It is the movement of water across a membrane from where theres more water to less water(high solute), without energy) stops when plasma membrane reaches equilibrium

what is a primary active transport?

it requires energy and it pushed substances from where they are less concentrated to where they are more concentrated ATP directly provides the energy

What is a secondary active transport?

Does not use ATP directly

• but relies on energy stored in the form of an ion gradient created by the primary active transport.

• this process allows the ion to move against its concentration

What is a cotransport?

• Uses the energy of one substance going down its concentration gradient to transport another substance against its concentration gradient.

• there are two main types of cotransport proteins

what are symport and antiport

• they are cotransport protiens

• symport: substances move in the same direction

• antiport: substances that move in opposite directions

What is vesicular transport?

A way cells move large molecules at once in little bubbles.

• molecules can either be brought into the cell though endocytosis or exocytosis

• Endocytosis: the cell engulfs the molecule by wrapping the membrane around it

• Exocytosis: the cell releases molecules by pushing the vesicle to the membrane and then it fuses which releases contents outside the cell

What is transcytosis?

• It is when a cell takes something on one side by endocytosis and then the vesicle moves across the cell to the other side where the vesicle releases the substance by exocytosis

What is resting membrane potential?

• All cells in the resting stage exhibit a voltage across their membrane

What is a negative membrane potential

The inside of the cells membrane is more negatively charged compared to the outside.

• example: inside the cell theres alot of potasium(K+) and outside theres more sodium (Na+)

• The cell membrane is selctively permeable allowing some ions especially (k+) to move more easily than others. As k+ leaks out of the cell they leave behind negatively charged proteins that cant cross the membrane. resulting in a charge difference across the the membrane

What are activated membrane receptors?

• they act as catalysts regulating channels by either directly opening or closing them in the membrane

• They act through secondary messengers: G-coupled receptors (GPCR) dont directly open channels. instead they activate inside messengers like cyclic AMP (cAMP)

• this triggers ligand binding which changes inside the cell like turning on enzymes or changing protein function

What is the cytoplasm

cellular region between the nuclear and plasma membrane that include cytosol (fuild), inclusions(nonliving nutrient stores) and cytoplasmic organelles. mediated by organelles

what is the mitochondria

organelles surrounded by a double membrane, are sites of ATP formation. internal enzymes carry out the oxidative reactions of cellular respiration.

• power house of the cell

• produce energy through cellular respiration

  • takes nutrients like glucose and convert it to ATP

Ribosomes

• make proteins by putting amino acids together

• -two subunits containing ribosomal RNA and proteins

rough endoplasmic reticulum

• network of membranes inside the cell that help make and transport proteins

• surface is covered with ribosomes making it look rough under a mircroscope

Smooth endoplasmic reticulum

• Works inside the cell but with out ribosomes and it makes lipids and steroids and breaks down drugs and alcohol

Golgi apparatus

• close to the nucleus

• made up of flatten stacked membrane bound sacs

• recieves the proteins and lipids from the rough and smooth er and then modifies them by adding sugar or phospahtes

• after it sorts the molecules and then puts them in vesicles and leave the golgi aparatus

lysosomes

• membraneous sacs packaged but golgi

• they contain digestive enzymes that breakdown worn out organelles and stresses or dead cells and release ionic clacium from bone

peroxisomes

• membraneous sacs

• contain oxidase and catalase enzymes

• break down fatty acids and nuetralize toxic molecules

endomembrane system

• incorporated the organelles that work together to produce, degrade, sotre, and export, biological molecules, and to degrade harmful molecules

cytoskeleton

• helps enable the cell to move

• includes microfilments, intermediate filaments, and microtubles.

• microfilmanets are important for cell motility adn chnages cell shape

centrosomes

• organize mircotubles in animals

• organizes the mitotic spindle and contains paired centrioles

• small structure found near the nucleus

• plays a critical role in cell division and the organization of the cytoskeleton

Cilia and flagella

hair like structures that are involved with cell movement.

• cilia propel other substances across the cell surface

• flagella propel the cell

microvilli

tiny finger like projections of the plasma membrane that increase the surface area for absorption

Nucleus

• control center of the cell

• most cells have a single nucleus

• without a nucleus a cell cant divide or synthesize more proteins so it will die

nucleoli

nuclear sites of ribosomal subunit synthesis

chromatin

complex of DNA and proteins found in the nucleus of eukaryotic cells

• it packages long DNA molecules into a more dense shape

Cell cycle

Series of changes that a cell goes through from the time it is formed until it divides

Interphase

the phase of the cell cycle where the cell grows, duplicates its DNA, and prepares to divide.

• three subunits G1 (cell grows and centriole replication begins), S (DNA replicates), G2 (Preparations for divisions are made)

DNA replication

• Happens before cell division

• The DNA double helix uncoils and each DNA nucleotide strand acts as a template for the formation of the complementary strand.

Semiconservative replication of DNA

• produces two identical copies of the original DNA molecule each formed of one old and one new strand.

Cell division

The process by which a parent cell divides into two or more daughter cells, consisting of two phases: Mitosis and cytokinesis.

Mitosis

Prophase

metaphase

anaphase

telophase

• replicate genetically identical two chomosomes to the parent nucleus. Cytokinesis divides the cytoplasmic into two parts

instructions for making a polypeptide chain

• intructions are carried from DNA to ribosomes via messenger RNA

• Ribosomal RNA forms part of the protein synthesis sites

• Transfer RNA ferries each amino acid to the ribosome and binds to a codon on the mRNA strand specifying its amino acid

protein synthesis steps

• transcription: synthesis of complementary mRNA

• translation: reading of the mRNA by tRNA

• peptide bonding of the amino acid into the polypeptide chain

MicroRNA

small interfering RNAs that are small noncoding RNA that can degrade or block translation of specific mRNA

• mRNA vaccines provide cells with genetic instructions for producing proteins that prepare the immune system to defend against a specific infectious disease

Autophagy

Organelles and large protein aggregates are picked up by autophagosomes and delivered to lysosomes for digestion

• this keeps the cytoplasm free of deteriorating organelles and other debris

Apoptosis

cell programmed death