CH. 3: CELLS

What are cells?

the simplest structural and functional living units of an organism

Approximately, how many cells are in the human body?

75 trillion

What are the 3 common parts in each cell?

* Plasma membrane
* Cytoplasm
* Nucleus

Plasma membrane definition

Outer boundary of a cell

Cytoplasm definition

The semifluid material located between the nucleus and plasma membrane of a cell

Nucleus Definition

The spherical cellular organelle containing the chromosomes; the core of an atom; or a mass of nerve cell bodies in the central nervous system.

Know the cell structure

picture in head

What are the plasma membrane functions?

* Maintains cell integrity
* Separates intercellular fluid and extracellular fluid

What is the composition of a plasma membrane?

* Two layers of phospholipids
* Cholesterol

Know the structure of the plasma membrane

picture in head

What are the proteins embedded in the plasma membrane that perform specific functions?

* channel proteins
* carrier proteins
* receptor protein
* cell identify markers

What are channel proteins?

A tunnel-shaped membrane protein that creates a pore or opening, which allows for a specific substance to pass across a plasma membrane.

What are carrier proteins?

A membrane protein that physically binds to and transports a specific type of substance across a plasma membrane.

What are receptor proteins?

they bind substances, such as hormones, that influence the function of the cell

What are cell identity markers?

proteins in combination with carbohydrate molecules, serving as identification markers that allow cells to recognize each other

What is a plasma membrane?

selectively permeable membrane

What does it mean that the plasma membrane is selectively permeable membrane?

selectively permeable membrane

What are factors that help determine if a molecule can pass across the selectively permeable membrane?

* Substance’s size
* Lipid solubility (electrical charge)
* Attachment to carrier proteins

Organelles definition

A complex of macromolecules acting like a “mini-organ” within a cell that performs specific functions.

What is cytosol?

A gellike fluid of the cytoplasm.

Organelles can be distinguished by:

size, shape, structure, and specific function

The nucleus is the ________ organelle

largest

Nuclear Envelope definition

The double membrane surrounding the nucleus of a cell.

What is the function of a nuclear envelope?

separates it from the cytoplasm

What do nuclear pores do?

allow movement of materials between the nucleus and cytoplasm

What are chromosomes composed of?

DNA and protein

What is a chromosome?

A threadlike or rodlike structure in the nucleus that is composed of DNA and protein

DNA contains what that determines cell functions?

genes

What are chromatin?

when a cell is not dividing, chromosomes are extended to form thin threads

A nucleolus contains that?

RNA and protein

What is a nucleolus?

A dark-staining spherical structure within a cell nucleus that is composed of protein and rRNA.

What is going on inside the nucleus?

it is a site for ribosome production

What are ribosomes?

A tiny cellular organelle composed of protein and rRNA and serving as the site of protein synthesis.

How do ribosomes occur when made?

singly or in clusters on either endoplasmic reticulum or free in cytoplasm

What is the endoplasmic reticulum?

A network of membranous channels used to transport substances within a cell

What are the endoplasmic reticulum’s functions?

* Support the cytoplasm
* Form channels to facilitate movement of materials within the cell

What are two types of endoplasmic reticulum?

rough ER and smooth ER

What characteristics do rough ER have?

* has numerous attached ribosomes
* is a site of protein synthesis

What characteristics do smooth ER have?

* lacks ribosomes
* is a site of lipid synthesis

What is the golgi apparatus/complex?

A cellular organelle that packages substances for secretion from the cell.

Where is the golgi apparatus?

near the nucleus and ER

What does the golgi apparatus do?

Processes and sorts synthesized substances into **vesicles**

What are vesicles?

A fluid-filled, membranous sac in the cytoplasm of a cell.

What are secretory vesicles?

vesicles that transport substances to the plasma membrane and release them outside of the cell

What is the mitochondria?

A cellular organelle that is the site of aerobic respiration.

What is the mitochondria composed of?

outer and inner membranes

Mitochondrias are the what of the cell?

powerhouse

What are mitochondrial cristae?

folds of the inner membrane of the mitochondria

What is aerobic respiration?

the use of oxygen to release energy from nutrients and form ATP

Mitochondria possesses DNA called

mitochondrial DNA

What are lysosomes?

A cellular organelle consisting of a sac of digestive enzymes

Lysosomes function to digest what?

* Bacteria entering cell
* Cell parts needing replacement
* Worn out or damaged cells

What is the cytoskeleton composed of?

microtubules and microfilaments

Microtubules definition

A microscopic tubule of protein within cells that is part of the cytoskeleton.

What are microtubules?

* Long, thin protein tubules
* Support for the cell

What is the role of the microtubules?

movement of organelles

What are microtubules composed of?

spindle fibers and found within cilia and flagella

microfilaments definition

A microscopic protein strand within cells that is part of the cytoskeleton.

What make up microfilaments?

Tiny rods of contractile protein

What is the function of microfilaments?

* Support cell
* Role cell movement and cell division

Centrioles definition

Paired cylindrical organelles that form the mitotic spindle during cell division.

What does the centrioles look like and where are they in the cell?

Two short cylindrical organelles near nucleus and oriented at right angles

What is the function of centrioles?

Form the mitotic spindle during cell division

Centrioles are involved in what?

Involved in forming the microtubules within cilia and flagella

Cilia and flagella definition

projections from cells are capable of wavelike movement

What is cilia?

* Numerous, short hairlike projections containing microtubules


* Move substances along free cell surfaces

Examples of cilia

 respiratory and reproductive tracts

What are flagella?

* Long, whiplike projections containing microtubules
* Enables movement of cells

Example of flagella

sperm

Microvilli definition

Microscopic projections of the plasma membrane on the free surfaces of certain epithelial cells.

What is the function of microvilli?

Increase cell surface area and aid in substance absorption

Where are the microvilli?

Abundant on free surface of cells lining the intestines

What is passive transport?

requires no expenditure of cell ATP

What is active transport?

requires expenditure of cell ATP

Passive transport definition

Movement of substances across plasma membranes without the expenditure of energy.

Active transport definition

Movement of substances across a plasma membrane, requiring the expenditure of energy by the cell.

What are three types of passive transport?

* diffusion
* osmosis
* filtration

Diffusion definition

The passive movement of substances from an area of higher concentration to an area of lower concentration.

What is a concentration gradient?

The difference in the concentration of a substance at two different locations.

Osmosis definition

The passive movement of water across a selectively permeable membrane.

Filtration definition

the passing of a liquid through a filter

What is diffusion?

Net movement of a substance from an area of higher concentration to an area of lower concentration.

Where does diffusion occur?

in gases and liquids due to constant, random motion of substances.

What are the 3 types of diffusion?

Diffusion model

picture in head

Simple diffusion definition

Movement of small, lipid-soluble molecules across a plasma membrane down their concentration gradient, without the use of energy and membrane proteins.

Channel-mediated diffusion definition

water-soluble substances like ions pass through pores in channel proteins to cross the plasma membrane

Carrier-mediated diffusion definition

Carrier proteins bind and move water-soluble substances across the plasma membrane along their concentration gradients

What is happening in osmosis?

Moves from an area of higher water concentration (lower solute concentration) to an area of lower water concentration (higher solute concentration)

How does concentration move in osmosis?

By crossing plasma membrane directly or moving through channel proteins

What does osmosis have the ability to do?

alter a cell’s volume and chemical concentrations

Tonicity definition

the ability of a solution to affect a cell’s tone or shape by altering its water content.

Hypotonic solution definition

Has a lower concentration of solutes and higher concentration of water

Hypertonic solution definition

Has a higher concentration of solutes and lower concentration of water

Isotonic solution

Solutions have the same concentration of solutes and water.

Know them all

picture in head

carrier-mediated active transport definition

Carrier proteins use ATP to move substances across the plasma membrane against (opposite to) their concentration gradient.

Endocytosis definition

The process by which the plasma membrane engulfs, or internalizes, solid particles and droplets of liquid.

Exocytosis

The process by which a cell releases substances by fusion of a secretory vesicle with the plasma membrane.

What does the Carrier-Mediated Active Transport do?

Carrier protein binds to and moves substance across the plasma membrane.