BIO1228_L3: Cell Structures and Functions

Cell

The basic unit of life.

Organelles

“small organs”

Specialized structures within a cell that perform specific functions

Nucleus

• Contains genetic material.

• a large bubble with a double-walled membrane

Cytoplasm

• semi-liquid jelly-like material

• “cell stuff”

Plasma membrane or cell membrane

• Encloses the cytoplasm and nucleus

• Outer boundary of the cell Determines what enters and leaves the cell

CSCR:

1. Cell metabolism and energy use

2. Synthesis of molecules

3. Communication

4. Reproduction and inheritance

4 Functions of the cell

Extracellular

substances outside the cell

Intracellular

substances inside the cell

Fluid-Mosaic Model

Arrangement of molecules in the cell membrane.

Selectively permeable

allows some substances to pass into or out of the cells

Diffusion

Movement of a solute from an area of higher to a lower concentration gradient

Concentration gradient

difference in the concentration of a solute in a solvent minus the concentration of the solute at another point

Leak channels

Allow ions to pass through.

Gated channels

limit the movement of ions across the membrane

Osmosis

Diffusion of water across a selectively permeable membrane

Osmotic pressure

Force required to prevent movement of water across a selectively permeable membrane.

Hypotonic

lower concentration

Isotonic

same concentration

Hypertonic

higher concentration

Lysis

when cells swell, then ruptures

Crenation

Cell shrinking.

Carrier-mediated transport

movement of a substance across a membrane by means of a carrier molecule

Facilitated diffusion

moves substances from a higher to lower concentration; does not require ATP

Active transport

Moves substances from a lower to higher concentration; requires ATP.

Cystic fibrosis

genetic disorder that affects the active transport of Cl- into cells

Secondary active transport

moving concentration gradient to move another substance

Cotransport

Same direction (Secondary active transport)

Countertransport

opposite direction (Secondary active transport)

Endocytosis

movement of materials into cells by formation of vesicles

Phagocytosis

cell eating; solid particles are ingested

Pinocytosis

Cell drinking; smaller vesicles are formed and contain liquid.

Exocytosis

secretion of materials from cells

Nucleus

Contains genetic material of cell (DNA) and nucleoli site of RNA synthesis and ribosomal subunit assembly

Nuclear envelope

two-layered membrane that bounds the nucleus

Nuclear pores

where materials can can pass into or out the nucleus

Chromatin

loosely coiled chromosomes

Nucleoli

Consists of ribosomal RNA and proteins.

Ribosomes

• tiny bodies that serve as a site of protein synthesis

• some are found on the outer surface of the ER or scattered elsewhere w/in the cell

Endoplasmic Reticulum (ER)

• Forms tubules/sacs and canals throughout the cell

• transports proteins synthesized by ribosomes and other molecules synthesized w/in its membrane

• manufactures molecules that make up cellular membrane

Rough Endoplasmic Reticulum

protein synthesis and modification; contains ribosomes (tiny granules)

Smooth Endoplasmic Reticulum

Lipid synthesis, detoxification, and Ca storage.

Golgi Apparatus

flattened sacs; modifies protein structure; receives, processes, and packages materials from the ER in tiny vesicles (bubbles) for possible export from the cell; distributes lipids and proteins

Secretory vesicles

Transports and stores materials within cells Contains materials produced in the cell formed by the Golgi apparatus secreted by exocytosis

Lysosomes

Membrane-bound sacs containing hydrolytic enzymes; Contains enzymes that digest material taken into the cell; play a role in repairing plasma membrane

Peroxisomes

Enzymes that digest fatty acids and amino acids Enzymes that catalyze the breakdown of hydrogen peroxide

Mitochondria

Site of aerobic respiration and the major site of ATP synthesis

Cytoskeleton

Holds organelles in place; enables the cell to change shape

Microtubules

support the cytoplasm; assist in cell division; forms components of cilia and flagella

Microfilaments

involved in cell movement (cytoplasm)

Intermediate filaments

provide mechanical support (cytoplasm)

Centrosome

a.k.a. microtubule organizing center; a dense area of cell fluid near the nucleus; where microtubule formation occurs

Centrioles

specialized zone of the cytoplasm; Facilitate the movement of chromosomes during cell division; cylinders formed by parallel microtubules; the centrosome contains a pair of this

Spindle fibers

a network of microtubules involved in the separation of chromosomes during mitosis; distribute DNA equally to the resulting daughter cells

Cilia

moves substances over the surface

Flagella

propel sperm cells

Microvilli

increase the surface area of cells; aids in absorption

Gene

sequence of nucleotides

Transcription

making a copy of a gene

Messenger RNA (mRNA)

the copy itself of a gene

Codons

The information in mRNA is carried in groups of three nucleotides called __________. These specify a particular amino acid

Translation

converting that copied information into a protein

Anti-codon

a series of three nucleotides of tRNA, pairs with the codon of the mRNA.

Nucleotide Pairs

Cytosine - Guanine Thymine - Adenine Uracil - Adenine

adenine (A), cytosine (C), guanine (G), and thymine (T)

four bases in DNA

UAA

stop codon

Interphase & Cell Division

Two Phases of the Cell Life Cycle

Interphase

non-dividing phase

Cell Division

formation of daughter cells from a single parent cell

46 Chromosomes

diploid no. of chromosomes

Female

2 X Chromosome

Male

X + Y Chromosome

Autosomes

22 remaining pairs of chromosomes

Prophase, Metaphase, Anaphase, Telophase

Mitosis

Mitosis

The process by which most cells of the body divide

Prophase

chromatin condenses (in this stage of mitosis)

Metaphase

chromosomes align at the center (in this stage of mitosis)

Anaphase

chromatids separate at the centromere and migrate to opposite poles (in this stage of mitosis)

Telophase

chromosomes unravel to become chromatin (in this stage of mitosis)

Differentiation

Cells develop specialized structures and functions

Apoptosis

Programmed cell death

Cellular Aspects of Aging

Cellular clock. Death genes. DNA damage. Free radicals. Mitochondrial damage.

Membrane channels

involved with the movement of substances through the cell membrane

Receptor molecules

part of an intercellular communication system that enables cell recognition and coordination of the activities of cells.

hydrostatic pressure

The pressure produced by the weight of the water molecules moving by osmosis through the membrane into the tube, forcing the solution to move up the tube moves water out of the tube back into the distilled water surrounding the tube.

sodium-potassium pump

moves Na+ out of cells and K+ into cells

ribosomal ribonucleic acid (rRNA)

produced within the nucleolus and combines with proteins transported from the cytoplasm through nuclear pores to form large and small ribosomal subunits.

cristae

numerous folds of inner membranes that project like shelves into the interior of the mitochondria

gene expression

the process by which DNA directs the synthesis of proteins, influencing the organism's structural and functional characteristics.

gene

a sequence of nucleotides that provides a chemical set of instructions for making a specific protein. Each DNA molecule contains many different of these.

peptide bond

formed between amino acids bound to tRNAs by an enzyme associated with the ribosome, as it moves down the mRNA one codon at a time during protein synthesis.

polypeptide chain

formed as the ribosome catalyzes the formation of peptide bonds between amino acids bound to tRNAs, and this process continues until translation ends at the stop codon, resulting in the release of the ________ which then folds to form the three-dimensional structure of the protein molecule.

free radicals

atoms or molecules with an unpaired elec

phospolipid

The plasma membrane is composed of a double layer (or bilayer) of _________ molecules imbedded with other molecules.

Peripheral proteins

Imbedded in the membrane are integral proteins, which may have additional protein molecules called ____________________ attached to them on one side of the membrane or the other.

deoxyribonucleic acid (DNA)

The genetic code is in the form of _________________ strands called chromatin, which stain readily, giving the nucleus a dark appearance.

nucleolus

• “tiny nucleus”

• small area within the nucleus for the synthesis of a type of ribonucleic acid (RNA) called ribosomal ribonucleic acid (rRNA)

• can be multiple in one nucleus

cytosol

The material within the plasma membrane is the cytoplasm and includes both the organelles and the liquid, or _________, surrounding the organelles.

vesicles

membranous bubbles that may be formed by the Golgi body or by the pinching inward of the cell membrane to engulf external substances

electron microscope

instrument that uses a beam of electrons, rather than a beam of light, to form the image of a tiny specimen; greater magnification power and resolution

Transmission electron microscopes

send an electron beam through the specimen, similar to how a light microscope sends a light beam through a specimen.