Biology Exam 2- Chapter 4

One or more cells comprise all living things, cells are the basic unit of life, and all cells arise from pre-existing cells.

What does cell theory state?

A plasma membrane, cytoplasm, ribosomes, and genetic material (DNA or RNA).

What are the four components that all cells share?

A prokaryotic cell is a __________ celled organism that _______ a nucleus and membrane-bound organelles.

single; lacks

A prokaryotic cells ______ floats freely in the cell’s cytoplasm in an area called the _______.

DNA; nucleoid region (nucleoid contains genomic DNA and the genomic DNA is one circular DNA)

Bacteria and Archaea

Prokaryotes

Animal cells, plants, fungi, and protists

Eukaryotes

What are the four main shapes used to describe prokaryotic cells?

Coccus, Bacillus, Spirillum, Spirochete

Coccus

round like a circle

Bacillus

straight like a bar (rod shape)

Spirillum

spiral, but stiff with corkscrew form

Spirochete

spiral, but flexible and moves like a snake or twisting motion

Why are most cells small (less than 1mm in diameter)?

Metabolically active cells need a large surface area to volume ratio to efficiently absorb nutrients and eliminate waste.

What do smaller cells have?

a larger ratio or surface area : volume

What structure in a prokaryotic cell is a phospholipid bilayer with embedded proteins, analogous to the eukaryotic plasma membrane?

Plasma membrane

What is the plasma membrane of a prokaryotic made up of?

Phospholipid bilayer with embedded proteins

What structure does the plasma membrane of a prokaryotic cell form to increase surface area for metabolic activities like respiration?

Mesosomes (modern biology considers mesosomes artifacts of chemical fixation not actual structures) ☆The plasma membrane folds inward to form mesosomes (or membrane infoldings) which increase surface area for metabolic processes.

What does the cell wall of a prokaryotic cell contain?

Peptidoglycan

What is the sticky sugar rich outer layer outside of the prokaryotic cell wall?

Glycocalyx

What is glycocalyx made of and what are its functions?

• Glycocalyx is made of a layer of polysaccharides (sometimes proteins too)

• Resists dehydration ⇨ keeps the cell from drying out

• Resists host immune system ⇨ protects against immune attacks

• Helps attach to surfaces ⇨ lets the bacteria stick to things, form colonies or biofilms

What is the gel-like substance inside a prokaryotic cell where plasmids, ribosomes and other structures are found?

Cytoplasm

What are small, circular DNA molecules in prokaryotic cells that are separate from the main chromosome?

Plasmids

What structures in prokaryotic cells synthesize proteins and are made of 30S and 50S subunits?

Ribosomes

Prokaryotic ribosomes are made up of which two subunits, forming a 70S ribosome?

30S (small) and 50S (large) subunits.

What are thylakoids and where are they located?

Flattened, disc shaped membrane structures inside chloroplasts that carry out light dependent reactions of photosynthesis

What term measures how fast a particle sediments in a centrifuge, reflecting size, shape, and density, used for Svedberg units?

Sedimentation coefficient

Prokaryotic Cells have no:

Membrane bound organelles

What are the external structures and functions of a prokaryotic cell?

• Flagellum ⇨ Long tail for locomotion, can rotate 360 degrees and cells may have 1 or many flagella

• Fimbriae ⇨ Short thin fibers that allow the cell to attach to surfaces or other cells

• Pilus ⇨ Hair like structures used to transfer DNA to other bacteria (conjugation)

According to the Endosymbiotic Theory, what engulfed organism led to the evolution of mitochondria?

Aerobic bacteria

According to the Endosymbiotic Theory, what evolved from inward folding of the plasma membrane of prokaryotes?

Endomembrane system:

What feature of mitochondria and chloroplasts supports the Endosymbiotic Theory regarding their origin?

They divide by binary fission, similar to bacteria.

What defines a eukaryotic cell?

A cell that has a true nucleus and membrane-bound organelles

What are the five parts of the nucleus in a eukaryotic cell

Nuclear Envelope, Nuclear Pores, Chromatin, Nucleolus, Nucleoplasm

What is the function of the Nuclear Envelope?

It is a double membrane that protects DNA and separates nuclear contents from the cytoplasm.

Function of Nuclear Pores

• Structure: protein lines openings in the nuclear envelope

• Function: Allow selective transport of molecules in and out of the nucleus Ex. transporting proteins, RNA, ribosomes (simple: lets molecules in and out)

What structures in the nuclear envelope allow selective transport of molecules like RNA and proteins in and out of the nucleus?

Nuclear Pores

What is Chromatin composed of, and what is its primary function?

DNA + proteins (histones); it stores genetic information.

What is the function of the Nucleolus?

It synthesizes ribosomal RNA (rRNA) and assembles ribosome subunits.

Nucleoplasm

• Structure: gel like substance inside the nucleus

• Function: supports the chromatin and nucleolus. Site of nuclear reactions (simple: supports nucleus, site of reactions)

What is the 'jelly-like' material filling a eukaryotic cell (excluding the nucleus) where organelles are suspended?

Cytoplasm

What is cytoplasm made up of?

Cytosol and organelles

Where is the cytoplasm located in the eukaryotic cell?

Between the plasma membrane and the nuclear envelope

What is the fluid “soup like” portion of the cytoplasm where organelles are suspended and many cellular reactions occur?

Cytosol

. What are the “little organs” inside a cell that each have unique jobs to keep the cell alive?

Organelles

What is the Endomembrane System?

An interactive system of organelles connected physically or functionally through vesicle transfer, working to synthesize, modify, package, and transport lipids and proteins.

What are the major organelles of the eukaryotic cell?

Nucleus, Mitochondria, Endoplasmic reticulum, Golgi apparatus, Ribosomes, Lysosomes, and vacuoles

What are the major components of prokaryotic cells?

Cell wall, Cell membrane, Cytoplasm, and Ribosomes

Nucleus

•  Stores DNA and controls cell activities

• Nuclear envelope: double membrane

• Nuclear pores: for transportation of substances like proteins, RNA, and ribosomes

Nucleous

• makes ribosomal RNA (rRNA) and assembles ribosome subunits

• No membrane

• A condensed region containing: rDNA, rRNAs, Proteins (imported from cytosol), and Ribosomal subunit

Chromatin

•  the complex of DNA and proteins (primarily histones) that forms chromosomes within the nucleus of eukaryotic cells

• Nucleosome

• DNA winding on histone proteins

• Linker DNA

Mitochondria

• produces ATP (energy) through cellular respiration

• Powerhouse of the cell: produces ATP

• Exists in nearly all eukaryotes

• Number per cell varies: very few in fat cells, many (~1,000) in liver cells

• Two layers of membrane: - Outer membrane: leaky - Inner membrane: folds to form cristae - Matrix: enzymes, ribosomes, RNA, and DNA

Which organelle is considered the 'powerhouse of the cell' and produces ATP through cellular respiration?

Mitochondria

Endoplasmic reticulum (ER)

Has smooth ER and rough ER

Smooth ER

• no ribosomes attached. 

• Synthesizes lipids (in oil glands, testes, ovaries) 

• Detoxifies drugs and breaks down glycogen (in liver)

• Stores calcium (in muscle)

Rough ER

• has ribosomes on external surface

• synthesizes proteins and deposits proteins into lumen for folding and modification

What is the primary function of the Rough Endoplasmic Reticulum (RER)?

To synthesize proteins and deposit them into the lumen for folding and modification (due to attached ribosomes).

What are three main functions of the Smooth Endoplasmic Reticulum (SER)?

Synthesizes lipids, detoxifies drugs/breaks down glycogen (in liver), and stores calcium (in muscle).

What organelle modifies, sorts, and packages proteins and lipids received from the ER?

Golgi Apparatus

Lysosomes

• digests and recycles cellular waste/foreign particles/unneeded structures

• Membranous vesicle containing hydrolases

• Acidic: pH 4.5

• Usually not in plant cells

In the Golgi Apparatus, which face receives vesicles from the ER?

Cis face

Golgi Apparatus 

• modifies, sorts, and packages proteins and lipids

• Membranous sacs: Cis face receives vesicles from ER / Trans face sends out

• packs proteins in vesicles and delivers contents outside of the cell (also called secretion) to cell membranes and organelles like lysosomes

What organelle contains hydrolases and functions to digest and recycle cellular waste?

Lysosomes

What is the acidic pH typically maintained inside a lysosome?

pH 4.5

Peroxisomes

• breaks down fatty acids and detoxifies harmful substances

• Membranous vesicles

• Contains oxidase and catalase made by free ribosomes Oxidase: RH2 + O2 → R + H2O2 Catalase: H2O2 +RH2 → R + 2H2O 2H2O2 → 2H2O + O2

• Break down of long chained fatty acids 

• Detoxifies (alcohol) and neutralizes free radicals

What substance do peroxisomes produce during the breakdown of fatty acids, which is then broken down by catalase?

Hydrogen peroxide

Ribosomes

• synthesizes proteins

• Free in the cytosol or attached to rough ER

• Assembled in the nucleolus

• Consists of proteins and rRNAs

• 2 subunits: 40S and 60S

Eukaryotic ribosomes (80S) are assembled where?

in the nucleolus

What are the three main types of protein filaments that compose the cytoskeleton?

Microfilaments (Actin filaments), Intermediate filaments, and Microtubules.

What is the diameter of a microfilament (actin filament)?

~7nm

Which cytoskeleton component is a hollow tube made of tubulin and acts as a track for motor molecules like kinesin and dynein?

Microtubules (25nm diameter)

Intermediate filament

• several strands of fibrous proteins that are wound together

• Diameter of 8-11nm

• Maintains cell shape

• Participates in cell to cell junctions (keratin)

In plant cells only, what organelle stores pigments in fruits, flowers, and aging leaves?

Chromoplasts

Leucoplast

synthesizes and stores starch, oil, and protein in roots, bulbs, and seeds

Chloroplasts

• (plant/algae cells only) ⇨ carries out photosynthesis

• double membrane

• granum: a stack of thylakoids

• stroma: semifluid containing enzymes

What is the function of a central vacuole in a plant cell regarding structure?

It stores water, nutrients, etc., and provides turgor pressure.

What is turgor pressure?

The pressure of water inside a plant cell pushing the cell membrane against the cell wall, keeping the plant firm and upright.

Contractile vacuole in protists:

• Eliminates excess water

• Food vacuole in protists

• Breaks down food

Plasma membrane

• controls entry and exit of substances

• Protects the cell

Tell me the four building blocks of life

• Carbohydrates

• Lipids

• Proteins

• Nucleic Acids

What is an Amino Acid?

Building block of life

Nucleus: Prokaryote (bacteria, archaea)

No true nucleus; DNA is free in the cytoplasm (nucleoid).

Nucleus: Eukaryote (eukarya)

Has a true, membrane-bound nucleus.

Membrane-bound organelles not present in:

Prokaryote

Membrane-bound organelles present in:

Eukaryote, has mitochondria, endoplasmic reticulum, and Golgi apparatus

Cell size (Prokaryote)

Smaller (usually 0.1–5 µm).

Cell size (Eukaryote)

Larger (usually 10–100 µm)

Cell type (Prokaryote)

Only Unicellular

Cell type ( Eukaryote)

Unicellular or multicellular.

DNA structure (Prokaryote)

Circular DNA

DNA structure ( Eukaryote)

Linear DNA (what we have)

Ribosomes (Prokaryote)

Smaller (70S).

Ribosomes (Eukaryote)

Larger (80S).

Cell division (Prokaryote)

Binary fission

Cell division (Eukaryote)

meiosis or mitosis

Cell Wall (Prokaryote)

Usually present; made of peptidoglycan (in bacteria).

Cell Wall ( Eukaryote)

Present in plants (cellulose) and fungi (chitin); absent in animal cells.

Complexity (Prokaryote)

Simple

Complexity (Eukaryote)

Complex

What are the main components of the extracellular matrix (ECM) in animal cells?

Collagen fibers interwoven with proteoglycans (which contain carbohydrates).

What animal intercellular junction forms a watertight seal to prevent leaking (e.g., in the intestine)?

Tight Junctions

What animal intercellular junction acts like anchors to hold cells together and provide tissue strength?

Desmosomes