S2 - BIOS251 - Weeks 3 and 4

The cell’s three subsections are:

The cell is split into the following three subsections for ease of study:

the plasma membrane/cell membrane

the cytoplasm (and its organelles)

the nucleus (and its division)

What are the 2 parts to a cell’s cytoplasm?

The cytoplasm consists of the cytosol and organelles.

3 divisions of the nucleus of a cell

Chromosomes (46; 23 from each parent)
Genes (inside the DNA)

Nucleolus (core of the nucleus)

Houses the genetic material (DNA) which direct all of the cells activities

Cell Nucleus

Is enclosed in a nuclear envelope with nuclear pores (tiny holes)

Cell Nucleus

Site of ribosome synthesis, new ribosomes exit through pores of…

Cell Nucleus

What are the Organelles of the cytoplasm?

• Nucleus

• Mitochondria

• Endoplasmic Reticulum (ER)

• Golgi Apparatus/Complex

• Lysosomes

• Peroxisomes

• Ribosomes

• Vacuoles

• Vesicles

• Chloroplasts

• Centrosomes

• Centrioles

• Basal bodies

What are the 2 types of Endoplasmic Reticulum?

• Rough

  • Makes proteins

    • has ribosomes

• Smooth

  • Makes lipids

    • no ribosomes

Mitochondria

Powerhouse of the cell, they produce energy in the form of ATP through cellular respiration

Endoplasmic Reticulum (ER)

A network of membranes involved in producing, processing, and transporting proteins (rough ER) and lipids (smooth ER).

Golgi Apparatus

Processes, sorts, and packages proteins and lipids from the ER for secretion or delivery to other organelles.

A system of cisterns that synthesizes carbohydrates and puts finishing touches on protein synthesis

Lysosomes

Contain digestive enzymes that break down waste materials, foreign invaders, and old cell parts.

“Garbage disposals” of cells contain digestive enzymes that dispose of cellular debris & worn cellular parts

• Autophagy—digestion of the cell’s surplus organelles

• Autolysis—“cell suicide”: digestion of a surplus cell by itself

• Abundant in the cells of the liver and kidneys

Peroxisomes

• Break down fatty acids and detoxify harmful substances, such as alcohol.

• similar to lysosomes, made by ER

• Neutralize free radicals, detoxify alcohol, other drugs, and a variety of blood-borne toxins

• Abundant in the cells of the liver and kidneys

Ribosomes

The site of protein synthesis; they can be free in the cytosol or attached to the rough ER.

They “read” coded genetic messages (messenger RNA) and assemble amino acids into proteins specified by the code

Vacuoles

Membrane-bound sacs used for storage of water, nutrients, or waste, particularly large in plant cells.

Chloroplasts

Found in plant cells, these are the sites of photosynthesis, converting light energy into chemical energy.

Which organelles of the cell cytoplasm are membranous?

• Nucleus

• mitochondria

• lysosomes

• peroxisomes

• endoplasmic reticulum

• Golgi complex

Which organelles of the cell cytoplasm are non-membranous?

• Ribosomes

• centrosomes

• centrioles

• basal bodies

What are the building blocks of proteins?

Amino Acids

Golgi Apparatus

• 4 functions

  • Refines (QC) (sorts, splices, adds to)

  • Packages (in the form of vesicles)

  • Delivers via vesicles to cell membrane to be secreted, or stores protein in vesicle to be used later in the cell

  • Carb/sugar production

Vesicles

Membranous sacs pinched from Golgi which surrounds the protein product to the cell membrane for secretion or to another organelle within the cell for use.

Centrioles

A short cylindrical assembly of microtubules arranged in nine groups of three microtubules each

Two lie perpendicular to each other within the centrosome

Play important role in cell division

Cytoskeleton

Protein structures that help maintain cell shape, anchors organelles, or assist in movement

What are the 3 Types of Filaments involved with Cytoskeleton

1. Microfilaments

   1. 6nm thick, made of actin protein, form terminal web

2. Intermediate filaments

   1. 8-10 nm thick, within skin cells, made of keratin protein, give cells shape, reduce stress

3. Microtubules

   1. 25 nm thick, protein tubulin, radiate from centrosome (can come or go), Maintain cell shape, hold organelles, act as railroad tracks for walking motor proteins

Cell Membrane composition

Composed of phospholipid bilayer

Lipid soluble(nonpolar) items pass through (examples) = Thyroid hormone

Water soluble(charged, polar) items can’t pass through (ex..) = Glucose, NA+

Small molecules = 02+CO2

Cell Membrane (Structure)

98% of molecules are lipids

Hydrophilic phosphate heads face water on each side

Hydrophobic tails are directed toward the center, avoiding water

Cell Membrane Structure

The bilayer consists of phospholipids, cholesterol, and glycolipids

Membrane lipids and proteins are mobile in their own half of the bilayer

Cholesterol serves to stabilize the membrane and reduce membrane fluidity

Two main types of membrane proteins are

1. Transmembrane proteins (integral) go through the membrane, creating a “tunnel”. Ex = Channel proteins

2. Peripheral proteins - surface proteins Ex = G proteins

Cell Membrane Functions

1. Barrier and protection

It acts as a selectively permeable barrier, controlling what enters and exits the cell.

2. Selectively Permeable Transport

The membrane regulates the passage of molecules, allowing necessary substances in while keeping harmful ones out.

3. Cell signaling

It contains receptors that respond to external stimuli, enabling the cell to communicate with its environment.

4. Cell recognition

The membrane carries specific markers that allow cells to identify each other, crucial for immune responses and cell-cell interactions.

5. Compartmentalization

It defines the cell's boundaries and helps create specialized internal environments.

6. Structural support

The membrane provides a framework for organizing cellular components and supporting biochemical activities.

Functions of Membrane Proteins

The different proteins help determine many of the functions of  the cell ____________ including membrane transport

Interstitial fluid

The fluid cells are bathed in, derived from blood

Contains salts, sugars, amino acids, vitamins, fats, hormones, neurotransmitters

Passive = NO energy (ATP) required from cell for membrane transport

Simple Diffusion

Facilitated diffusion

Osmosis

Types of Active Transport = energy(ATP) required for cell to move substances across membrane.

Exocytosis

Endocytosis (Phagocytosis, Pinocytosis)

The Sodium-Potassium Pump (Na+-K+ ATPase)

Simple Diffusion

Movement of molecules from an area of higher concentration to an area of lower concentration..

Move “down” the concentration gradient

Simple Diffusion: Factors affecting diffusion rate through a membrane

Temperature: ↑ temp., ↑ motion of particles

Molecular weight: larger molecules move slower

Steepness of concentrated gradient: ↑ difference, ↑ rate

Membrane surface area: ↑ area, ↑ rate

Membrane permeability: ↑ permeability, ↑ rate

Facilitated Diffusion

The molecules are ferried across the membrane by a carrier allowed entrance by a channel

Osmosis

Water only

water moves toward a higher concentration of solutes (WHERE IS THE PARTY?)

The movement of water from an area of low solute concentration inside the cell to an area of high solute concentration outside the cell.

Tonicity (3 options)

Hypertonic

Isotonic

Hypotonic

Hypertonic

More solutes outside than inside

Cell shrinks

Isotonic

Equal solute outside and inside the cell; cell remains the same

Hypotonic

More solute inside than outside the cell; cell swells and may burst

Active Transport (ATP)

Substance moving from an area of lower concentration to an area of higher concentration

Moving “against” the concentration gradient

Requires ATP energy

Solute pumps – Na+, K+, Ca2+

DNA

• made of

  • hereditary units called genes

  • Nucleotides

    • Base

    • Sugar

    • Phosphate Group

Genes

arranged along chromosomes

4 Bases of DNA

Adenine (A) – Thymine (T)

Guanine(G) – Cytosine (C)

4 Bases of RNA

Thymine does not exist – changes for Uracil

Adenine (A) – Uracil (U)

Guanine(G) – Cytosine (C)

DNA Sugar

deoxyribose

RNA Sugar

ribose

Chromosomes are made of ___________________, which when unraveled are called _____________, which is composed of the ___________

2 Sister Chromatids, Chromatin, DNA helix

Gene

Segment of DNA coding for the synthesis of a specific protein

Genome

All the genes of one person

Humans have about 20,000 genes

Base Triplet

A sequence of three nucleotide bases in DNA or RNA that provides genetic information; eventually will represent an amino acid.

Codon

A three-base sequence in messenger RNA (mRNA) that codes for a specific amino acid or signals protein synthesis termination. Each codon represents a specific instruction in protein production.

Anticodon

A complementary three-base sequence found in transfer RNA (tRNA) that matches and binds to a specific codon in mRNA during protein synthesis.

Protein Synthesis: Special Codons - Start Codon AUG

Signals the beginning of protein synthesis and codes for the amino acid methionine.

Protein Synthesis: Stop Codons

Three specific codons (UAA, UAG, UGA) that signal the end of protein translation, indicating where the protein synthesis should terminate.

During protein Synthesis

The genetic code uses 64 possible triplet combinations to specify 20 amino acids, with some codons representing the same amino acid (redundant code) and others serving as start or stop signals.

Transcription

occurs in the nucleus and is the process by which genetic information encoded in DNA is copied onto a strand of RNA to direct protein synthesis

Translation

occurs in the cytoplasm (at the ribosome) and is the process of reading the mRNA nucleotide sequence to determine the amino acid sequence of the newly formed protein

DNA Central Dogma

is self-replicating and is transcribed into RNA

RNA Central Dogma

is translated into a protein

The cell cycle includes

interphase and the mitotic phase

Interphase

includes three subphases:

First gap phase (G1)

Synthesis phase (S)

Second gap phase (G2)

Mitotic phase

includes multiple subphases:

Prophase

Metaphase

Anaphase

Telophase

Cytokinesis

Interphase

period from cell formation to division

3 “subphases” during interphase

G₁ (Gap 1 ) – metabolically active, making proteins

S (Synthesis) – DNA replicating or copying

G₂ (Gap 2) – active, growing

When cell is no longer growing and permanently cease to divide, they are said to be in G₀ phase

A somatic cell

Is a typical body cell

Has 46 chromosomes in a human

23 pairs of homologous chromosomes

Autosomes

Humans have two different sex chromosomes, X and Y, & 22 other pairs of matching chromosomes, called

XX

Female

XY

Male

Diploid (2n)

2 copies of each chromosome

Haploid (n)

1 copy of each chromosome

Mitosis

1. Somatic cells

2. Start 1 diploid cell and end with 2 diploid daughter cells

3. One division

Phases of Mitosis

Prophase – Spindle fibers forms, centrioles moving to opposite ends of the cell. Nuclear membrane begins to disappear

Metaphase – chromosomes align midway along the spindle fibers

Anaphase – the chromosomes begin to separate from their daughters and appear “v-shaped”. Cytokinesis begins.

Telophase – identical sets of chromosomes at opposite ends of the cell. Spindle fibers disappear, nucelar membranes reappear, cytokinesis completes.

Cytokinesis – division of cytoplasm

Process of Meiosis

1. Sex cells (gametes)

2. Start 1 diploid cell and end 4 haploid daughter cells.

3. Two divisions

diploid organisms, haploid

Humans are _________________

Their somatic (body) cells contain pairs of chromosomes, Their gametes (sex cells: sperm, egg) are ____________, having only one set of chromosomes

meiosis Crossing over

Exchange of genetic material between non sister chromatids.

Metabolism

All of the chemical reactions in the body needed to maintain homeostasis

Can be divided into:

Anabolism

Catabolism

Anabolism

requires the input of energy to synthesize large molecules

Catabolism

releases energy by breaking down large molecules into small molecules

prokaryotic cells are _________

Prokaryotic cells are exclusively unicellular, consisting of a single cell, whereas eukaryotic cells can exist as unicellular or multicellular, contingent upon the specific organism in question.

A Cell - Our bodies are made of approximately three trillion cells!

an organized unit that can live and reproduce on its own by utilizing energy, raw materials, and DNA instructions.​

Cell

Every organism is made up of one or more, and can only form from pre-existing ___________

Prokaryotic Cells. Example of prokaryotic organisms: bacteria.

• "Pro" means before.​

• "Karyon" means nucleus.​

are more primitive.

are always unicellular.​

The internal environment is not divided into membrane-bound compartments.​

Eukaryotic Cells - Example of a eukaryotic organism: the human cell.

• "Eu" means normal.

• "Karyon" means nucleus.

can exist as unicellular or multicellular, contingent upon the specific organism in question. ​

The internal environment is divided into membrane-bound compartments called organelles.​

Four Structures Common to Most Cells

​Most cells, whether prokaryotic or eukaryotic, share four structures in common:

• The plasma membrane (cell membrane) surrounds all living cells, separating internal and external aspects. ​

• DNA is the genetic material that controls an organism's composition and can replicate with the cell, resulting in new cells that contain the same genetic material as the parent cell. ​In eukaryotic cells, DNA is found in the nucleus.

• Cytoplasm is a rich, semi-fluid material found in cells. The cytoplasm is found between the nucleus and the cell membrane.​

  • Cytosol is the liquid part of the cytoplasm.​

• Ribosomes are the site of protein synthesis.

Is bacteria unicellular or multicellular?

Bacteria are prokaryotic organisms. Prokaryotes are always unicellular.

Nucleoid

the irregularly shaped area in the prokaryotic cell that contains genetic information. Remember that the nucleoid is a region housing DNA found only in prokaryotic cells.

nucleolus

spherical body in eukaryotic cell that allows for the synthesis of Ribosomal RNA

What does “Eu” mean? (as in eukaryotic)

= normal

What does "pro" mean? As in Prophase

= before, As in Prophase, the first step of mitosis.

What does “Inter” mean?

= between

What does "circum" mean?

= around

What does "post" mean?

= after

Mitochondria

convert nutrients into usable energy through a process called cellular respiration

Peroxisome

contains enzymes that are responsible for cell detoxification and the breakdown of fatty acids and hydrogen peroxide

lysosomes

contains hydrolytic enzymes that are responsible for the break down of waste materials and damaged organelles

Microfilaments

Dynamic, double helix strands of actin proteins that contribute to cell structure, movement, and division.

• Composition: made of the protein actin; are also called actin filaments ​

• Function/Location: forms the membrane skeleton to support the plasma membrane

(part of cytoskeleton)