Biology: Chapter 3

List all tenets of Cell Theory

1. All organisms are made of one or more cells

2. The cell is the fundamental unit of life

3. All cells come from preexisting cells/every cell came from a preexisting cell

4. All cells have the same basic chemical composition

5. All Cells use energy

Cell Theory

the ideas that all living matter consists of cells, cells are the structural and functional units of life, and all cells come from preexisting cells.

Why are cells so small?

Smaller cells have more surface area relative to their volume. High surface area allows the cell to quickly exchange materials with its surroundings.

List the features common to all cells

DNA, RNA, Ribosomes, Cytoplasm, Cytosol, Cell Membrane, and High surface area relative to volume

DNA

Nucleic Acid that stores cell’s genetic information.

RNA

Nucleic acid that participates in the production of proteins.

Cytoplasm

the watery mixture that occupies much of a cell’s volume; in eukaryotic cells, it consists of all materials, including organelles, between the nuclear envelope and the cell membrane. (All contents except the nucleus (if the cell has one))

Cytosol

the fluid portion of the cytoplasm 

Cell Membrane

the boundary of a cell, consisting of proteins embedded in a phospholipid bilayer; also called the plasma membrane. Separates the cytoplasm from the surrounding environment.

List the Major Functions of the Plasma Membrane

1. Separates the cytoplasm from the cell’s surroundings

2. Transports Substances into and out of the cell through selective permeability/Regulates passage of substances in and out of the cell

3. Receives and responds to external stimuli

4. Helps maintain homeostasis

Selectively Permeable (Plasma Membrane)

In the phospholipid bilayer, the tails are hydrophobic, so they allow lipids and nonpolar molecules to move freely in and out, but they do not allow ions or large polar molecules to move freely in and out.

How Ions and Polar molecules Move Through the Cell Membrane

they do so through the help of transport proteins, as proteins are embedded in the membrane along with the phospholipids.

Difference Between the Nucleus and a Nucleoid

The difference is that the nucleoid is the part of a prokaryotic cell where the DNA is located and is not bounded by a membrane, while a nucleus is found in eukaryotic cells and is membrane-bounded.

Cell Wall

often made up of peptidoglycan or proteins. Helps with protection and gives it a rigid shape to the bacteria cell. Prevents it from bursting if it absorbs too much water. (a rigid boundary surrounding cells of many prokaryotes, protists, plants, and fungi)

Nucleoid Region

part of a prokaryotic cell where DNA is present.

Capsule

Sticky polysaccharide surrounding cell wall. Helps it attach to surfaces and gives some protection. (Found in some bacteria)

Plasmids

some bacteria have this. It is additional DNA molecules that carry certain genes which helps them digest/adapt to unusual circumstances (Ex. being antibiotic resistant).

Flagellum

a long whiplike appendage made up of long proteins which helps it propel. Helps in the movement of the bacterial cell as many bacteria can swim in fluids.

Pili

finger-like projections. Rigid fibers made up of proteins. Helps them attach to surfaces.

List all the organelles of Eukaryotic Cells

Nucleus, Endoplasmic Reticulum, Golgi Apparatus, Cell Membrane, Lysosomes, Vacuoles, Peroxisomes, Mitochondria, Chloroplasts, Centrosomes, Ribosomes, and Vesicles

Nucleus

1. Structure: surrounded by double membrane (nuclear envelope). Has nuclear pores on outside (help move things in and out). Contains DNA, RNA, and protein. Space within nucleus is the nucleoplasm. Nucleolus at center.

2. Function: Separates DNA from rest of cell; site of first step in protein synthesis; nucleolus produces ribosomal subunits.

Endoplasmic Reticulum

an extension of the nuclear envelope that forms a continuous, folded compartment. A network of membranous sacs and tubules. Has rough and smooth ER.

Rough Endoplasmic Reticulum

1. Structure: Membrane network studded with ribosomes.

2. Function: Produces proteins (polypeptides) destined for secretion from the cell. Polypeptides enter the inner compartment of this, where they fold into their tertiary form. Proteins exit organelle in vesicles (then fuse to golgi apparatus).

Smooth Endoplasmic Reticulum

1. Structure: Membrane network without ribosomes.

2. Function: synthesizes lipids, breaks down carbohydrates, and detoxifies drugs and poisons.

Golgi Apparatus

1. Structure: Stacks of flat, membranous sacs. Folded membrane.

2. Function: Packages materials to be secreted; produces lysosomes. Processes polypeptides and lipids delivered by ER and makes them functional. Its enzymes add carbohydrates to proteins and lipids, making them glycoproteins and glycolipids. Packages finished products in vesicles (to plasma membrane/lysosomes/other organelles).

Lysosomes

1. Structure: Vesicles containing digestive enzymes manufactured in RER and processed and shipped from the Golgi apparatus; surrounded by single membrane. Enzymes contain hydrolases.

2. Function: Enzymatically dismantles molecules, bacteria, pathogens, and worn-out cell parts. Helps with digestion and waste processing. The enzymes inside break down the large organic molecules into smaller subunits by hydrolysis, releasing them into the cytoplasm for the cell to use.

3. Malfunctioning: Tay-Sachs disease

Vacuoles

Structure: Present in plant cells. Sac containing a watery solution of enzymes that degrade and recycle molecules and organelles (cellular digestion). Occupies 90% of the cell’s volume. Surrounded by a single membrane.

Function: serves similar function to lysosomes. Degrades wastes, exerts turgor pressure (keeps plant upright and rigid), and stores acids, pigments, water, etc., and helps regulate size/water balance of plant cells.

Peroxisomes

1. Structure: Sac containing enzymes, forming visible protein crystals; surrounded by single membrane. Originate at ER.

2. Function: disposes of toxins; breaks down fatty acids; eliminates hydrogen peroxide. Where oxidation occurs. Breaks down substances into cholesterol and other lipids.

3. Malfunction: Adrenoleukodystrophy (brain damage and death).

Mitochondria

1. Structure: Two membranes; inner membrane is folded into enzyme-studded cristae; contains DNA and ribosomes. The outer membrane is smooth. Has its own DNA. Inside fluid is matrix.

2. Function: Releases energy from food by cellular respiration to supply the cell with energy. (Energy is ATP).

Chloroplasts

1. Structure: present only in plant cells and some protists. Two outer membrane layers enclose an enzyme-rich fluid sac called the Stroma. Within the Stroma is a third membrane system folded into flattened sacs called thylakoids, which are stacked and interconnected into a structure called Grana. Photosynthetic pigments are embedded in thylakoids. Contains DNA and ribosomes.

2. Function: Produces food (sugars) by photosynthesis for the cell.

Centrosomes

1. Structure/Function: present only in animal cells. They are the part of the cell that organizes microtubules. Contains two centrioles, which form the basis of basal bodies that give rise to cilia and flagella (extensions that enable some cells to move)

Ribosomes

1. Structure: Two globular subunits composed of RNA and protein, which are synthesized in the nucleolus of eukaryotic cells.

2. Function: Location of protein synthesis.

2 Important Functions of the Nucleus in A Eukaryotic Cell

1. Is where the genetic information is stored (DNA)

2. Where mRNA is sent from so that other parts of the cell can receive the “recipes” that DNA has encoded in it.

Endomembrane System and Its Major Organelles

Organelles inside the cell, which work together as a unit. Major organelles: Nucleus/Nuclear Envelope, Endoplasmic Reticulum, Golgi Apparatus, Lysosomes, Vacuoles, Cell membrane, and Vesicles. 

Vesicle

a sac made of membrane which helps in transport of macro molecules from one organelle to another. Formed by enoplasmic reticulum when a piece of membrane bulges outward and disconnects, forming into a tiny sphere that holds whatever molecules it is transporting. Pinches off from one organelle, travels within the cell, and fuses with another.

Endosymbiotic Theory

the theory that mitochondria and chloroplasts were once free living bacteria but were engulfed by certain ancestors and developed a mutually beneficial relationship.

Evidence Supporting the Endosymbiotic Theory

both mitochondria and chloroplasts have their own DNA, ribosomes, can divide independently, and are surrounded by double membranes. These characteristics point towards the theory that they used to be their own bacterial cells. Also, the structures and genetic sequences of today’s bacteria, mitochondria, and chloroplasts supply powerful evidence for this theory.

Tight Junctions

Found in animals. Fuses the membranes of adjacent animal cells together, preventing substances from flowing between the cells. Found in cells in inner lining of the stomach and small intestine.

Anchoring (adhering) Junctions

Found in animals. use intermediate filaments to hold cells together so there is a gap and so things can move. Connect adjacent animal cell membranes in one spot; connect cells to the extracellular matrix. Found in cells in outer skin layer.

Gap Junctions

Found in animals. connecting animal cells are analogous to plasmodesmata. Is a protein channel that links the cytoplasm of neighboring cells. Protein channel helps with the movement of a substance from one cell to another. Form channels between animal cells, allowing exchange of substances. Found in muscle cells in heart and digestive tract.

Plasmodesmata

Found in plants. the cytoplasmic connections in plant cells. Plant cells communicate through plasmodesmata. Nutrients and biochemicals travel through these channels to adjacent cells. Allow substances to move between plant cells. Found in plant cell walls.

Where are Cell Junctions Found?

Between cells, where they connect.

Cytoskeleton

a network of protein tracks and tubules in a cell (made from these protein filaments: microfilaments, intermediate filaments, and microtubules). Functions: structural support, aids in cell division, organelle transport, and cell movement.

Microfilaments

Long rod made of protein actin which helps with muscle contraction and provides strength for cells to survive stretching and compression, and they help to anchor one cell to another.

Intermediate Filaments

component of the cytoskeleton; intermediate in size between microtubule and a microfilament. Proteins that form these vary by cell type. Their function is to maintain a cell’s shape by forming an internal scaffold in the cytosol and existing mechanical stress. Also help bind some cells together.

Microtubules

component of the cytoskeleton; made of subunits of the protein tubulin. Have many functions including: can form a “trackway” along which substances move within a cell and they split a cell’s duplicated chromosomes apart during cell division. Form the internal framework of cilia and flagella. Help is movement of sperm.  Helps in movement of cells and to propel food.

3 major Difference Between a Plant Cell and an Animal Cell

1. Outermost layer of animal cell is cell membrane. Outermost layer of plant cell is cell wall. (Plants have both a cell membrane and cell wall).

2. Plants have a large central vacuole. Animal cells do not.

3. Plants have chloroplast. Animal cells do not.

Difference Between Domain Bacteria and Archaea

1. Chemical composition of flagella

2. The molecules that compose cell membranes

3. Evolutionary relationship to eukaryotes. Archaea are more closely related to eukaryotes than bacteria. Bacteria are not as closely related to eukaryotes.

Eukaryotic Cell

Cell interior is divided into functional compartments, (organelles), including a nucleus. Includes: animals, plants, fungi, and protists.

Prokaryotic Cell

Small, simple cells without a nucleus. Includes Bacteria and Archaea. Smaller in size as compared to eukaryotic.

Animal Cells

eukaryotic. Have membrane bounded organelles.

Plant Cells

eukaryotic, but have cell walls and chloroplasts as compared to animal cells.

Fluid Mosaic Model

 the model that explains the structure of the plasma membrane. Called mosaic because the membrane has a pattern of proteins embedded in it. 

Chromatin

All DNA and its associated proteins in the nucleus

Chromosome

A single DNA molecule with its attached proteins. During cell division, chromosomes condense and become visible in micrographs. Human body cells have 46 chromosomes.

Cell Wall (plants)

rigid. Gives plants protection and shape. Interact with other molecules to help determine how a cell in a complex organism specializes. Made of polymers like cellulose pectin.

Membrane Proteins

some of the proteins extend through the phospholipid bilayer, whereas others face only the inside or outside of the cell. 

Transport Proteins

proteins embedded in the phospholipid bilayer create passageways through which ions, glucose, and other polar substances pass into or out of the cell.

Enzymes

These proteins facilitate chemical reactions that otherwise would proceed too slowly to sustain life. (Not all of them, however, are associated with membranes).

Recognition proteins

Carbohydrates attached to cell surface proteins serve as “name tags” that help the body’s immune system recognize its own cells. The immune system attacks cells with unfamiliar surface molecules, which is why transplant recipients often reject donated organs. Surface proteins also distinctively mark specialized cells within an individual, so a bone cell’s surface is different from that of a nerve cell or a muscle cell.

Adhesion Proteins

These membrane proteins enable cells to stick to one another.

Receptor Proteins

Receptor proteins bind to molecules outside the cell and trigger an internal response, a process called signal transduction. (Ex. when a hormone binds to a receptor, the resulting chain reaction produces the hormone’s effects on the cell).

Nuclear Pores

a hole in the nuclear envelope. They are specialized channels composed of proteins through which regulatory proteins enter and mRNA molecules leave to send copies of directions to proteins cells can make.

Cilia

short, numerous extensions; movable protein extensions from a cell. Enables some cells to “swim” like in some protists. Present in the human respiratory tract; coordinate cilia movement allows particles to be propelled up and out. Cilia moves egg cell through female reproductive tract.

Flagella

occur singly or in pairs. Much longer than a cilium. Whiplike movement propels cells. Present in sperm cells in many species.

Eukaryote

organism composed of one or more cells containing a nucleus and other membrane-bounded organelles

Organelle

 compartment of a eukaryotic cell that performs a specialized function

Prokaryote

a cell that lacks a nucleus and other membrane-bounded organelles; bacteria and archaea 

Phospholipid Bilayer

double layer of phospholipids that forms in water; forms the majority of a cell’s membranes 

Nuclear Envelope

 the two membranes bounding a cell’s nucleus

Fluid Mosaic

two-dimensional structure of movable phospholipids and proteins that form biological membranes

Nucleolus

a structure within the nucleus where components of ribosomes are assembled 

Cristae

fold of the inner mitochondrial membrane along which many of the reactions of cellular respiration occur