Cells: The Living Units Ch. 3

What is Cell Theory?

A cell is the structural and functional unit of life.
Cells can arise only from other preexisting cells.
How well the entire organism functions depends on individual and combined activities of all of its cells.
Structure and function are complementary (Biochemical functions of cells are dictated by shape of cell and specific subcellular structures)

what are the thre basic parts of a human cell

Plasma membrane, Cytoplasm, and Nucleus

What is the function of plasma membrane?

Acts as an active barrier separating intracellular fluid (ICF) from extracellular fluid (ECF).

Plays dynamic role in cellular activity by controlling what enters and what leaves cell

What is the structure of a plasma membrane?

Consists of membrane lipids that form a flexible lipid bilayer.

Specialized membrane proteins float through this fluid membrane, resulting in constantly changing patterns (fluid mosaic)

Surface sugars form glycocalyx.

What is the a membrane lipids made up of?

75% phospholipids, (phosphate head - polar, charged, hydrophilic) (fatty acid tails - nonpolar, no charge, hydrophobic)

5% glycolipids (lipids with sugar group on outer membrane surface

20% cholesterol (increases membrane stability)

What are the two types of membrane proteins?

Integral proteins & peripheral proteins

What is an integral protein and what is its function?

Firmly inserted into membrane.

Function as transport proteins (channels and carriers), enzymes, or receptors

What is a peripheral proteins and what is its function?

Loosely attached to integral proteins.

Function as enzymes, motor proteins for shape change during cell division and muscle contraction, cell-to-cell connections

What is Glycocalyx and what is it function?

Consists of sugar (carbohydrates) sticking out of cell surface.

Function as specific biological markers for cell-to-cell recognition. Allows immune system to recognize “self” vs “nonself”

What is a glycolipid?

Sugar that is attached to lipids

What is glycoproteins?

sugar attached to proteins

What cells are “free” not bound to another cell

Blood cells and sperm cells

What are the three ways cell can be bound to each other?

Tight junctions, Desmosomes, and Gap Junction

What is a tight junction? What is it function?

Integral proteins on adjacent cells fuse to form an impermeable junction that encircles whole cell.

Prevents fluids and most molecules from moving in between cells

What is a desmosomes?

Rivet-like cell junction formed when linker proteins (cadherins) of neighboring cells interlock like the teeth of a zipper.

Desmosomes allow “give” between cells, reducing the possibility of tearing under tension

What is gap junction? What is its function?

Transmembrane proteins (connexons) form tunnels that allow small molecules to pass from cell to cell.

used to spread ions, simple sugar, or other small molecules between cells.

Allows electrical signals to be passed quickly from one cell to next cell; Used in cardiac and smooth muscle cells

What is cytoplasm? What is it made up of?

All cellular material that is located between the plasma membrane and the nucleus.

Composed of: cytosol, inclusions, and organelles

cytosol: gel-like solution made up of water and soluble molecules such as proteins, salts, sugars, etc.

inclusions: insoluble molecules (ex. glycogen granules, pigments, lipid droplets, vacuoles, crystals)

organelles: metabolic machinery structures of cell

What cytoplasmic organelles have membranous and what have nonmembranous

Membranous: Mitochondria, Endoplasmic reticulum, Golgi apparatus, Peroxisomes, Lysosomes

Nonmembranous: Ribosomes, Cytoskeleton, Centrioles

What is Mitochondrion?

The “power plant” of cells because they produce most of the cell’s energy molecules (ATP) via aerobic (oxygen-requiring) cellular respiration

What is cristae?

Inner membrane that has many folds

How many membranes does mitochondrion have?

Double membrane: outer membrane and inner membrane

What is a ribosomes? What is it function?

Nonmembranous organelles that are site of protein synthesis.

Made up of protein and ribosomal RNA (rRNA).

What are the two forms of ribosomes?

Free ribosomes: free floating

Membrane-bound ribosomes: attached to membrane of endoplasmic reticulum (ER)

What is endoplasmic reticulum (ER)?

continuous membrane system that forms a network of flattened sacs and tubes used for making, folding, and transporting proteins and lipids

What are the two varieties of Endoplasmic Reticulum (ER)?

Rough ER & Smooth ER

What is Rough ER? What is it function?

External surface appears rough because it is studded with attached ribosomes.

Site of synthesis of proteins that will be secreted from cell.

Site of synthesis of many plasma membrane proteins

What is Smooth ER? what is it function?

Network of looped tubules continuous with rough ER.

Function in:

lipid metabolism; lipids, cholesterol, and steroid-based hormone synthesis

synthesis of glycogen

Absorption, synthesis, and transport of fats

Detoxification of certain chemicals (drugs, pesticides, etc.)

Storage and release of calcium

What is golgi apparatus? what is it function?

Stacked and flattened membranous cistern sacs

Modifies, concentrates, and packages proteins and lipids received from rough ER

What is peroxisomes? what is the function?

Membranous sacs containing powerful detoxifying substances that neutralize toxins.

Oxidase: uses oxygen to convert toxins to hydrogen peroxide (H2O2), which is itself toxic

Catalase: which converts H2O2 to harmless water

What is Lysosomes? What is its function?

Spherical membranous bags containing digestive enzymes (acid hydrolases).

Digest ingested bacteria, viruses, and toxins

Degrade nonfunctional organelles

Remove cellular debris

Intracellular release in injured causes cells to digest themselves (autolysis)

What is autolysis?

The destruction of a cell or tissue by its own internal enzymes; intracellular release in injured causes cells to digest themselves

What is cytoskeleton? what is it function?

Elaborate network of rods that run throughout the cytosol

Act as cell’s “bones, ligaments, and muscle” by playing a role in movement of cell components

What are the three types of cytoskeleton?

Microfilaments, Intermediate filaments, Microtubules

What are the 3 cellular extension? what are their function?

Cilia & Flagella: aid in the movement of the cell or of materials across the surface of the cell

Microvilli: fingerlike projections that extend from the surface of the cell to increase surface area

What is a nucleus? what is it function?

Largest organelle; contains the genetic library of blueprints for synthesis of nearly all cellular proteins.

Responds to signals that dictate the kind and amount of proteins that need to be synthesized

What is uninucleate, multinucleeate and anucleate?

uninucleate: one nucleus (most cells)

multinucleate: many nuclei (skeletal muscles, certain bone cells, and some liver cells)

anucleate: no nucleus (RBC)

What are the three main structure of a nucleus?

Nuclear envelope, Nucleoli, and Chromatin

What is a nucleoli?

Dark-staining spherical bodies within nucleus that are involved in ribosomal RNA (rRNA) synthesis and ribosome subunit assembly

Usually one or two per cell

What is Chromatin?

Consists of 30% threadlike strands of DNA, 60% histone proteins, and 10% RNA

What is nucelosomes?

consists of DNA wrapped around histones

What is Chromosomes?

Condensed chromatin; condensed state help protect fragile chromatin threads during cell division

What is autophagy?

cells that have become obsolete or damage need to be taken out of system

Autophagy (self-eating) is the process of disposing of nonfunctional organelles and cytoplasmic bits by forming autophagosomes, which can then be degraded by lysosomes.

What is apoptosis?

Programmed cell death; causes certain cells (cancer cells, infected cells, old cells) to neatly self-destruct

What is the steps for Apoptosis?

Process begins with mitochondrial membranes leaking chemicals that activate enzymes called caspases.

Caspases causes degradation of DNa dn cytoskeleton, which leads to cell death

Dead cell shrinks and is phagocytized by macrophages