BIOL 130

Cell

Basic unit of life

Robert Hooke

First described chambers in cork as “cells”

Anton van Leeuwanhoek

Pioneer of microscopy, first to observe single-celled organisms.

1st Tenant of Cell Theory

All living organisms are composed of one or more cells (proposed by Schleiden and Schwann).

2nd Tenant of Cell Theory

Each cell is the structural and functional unit of life (proposed by Schleiden and Schwann).

3rd Tenant of Cell Theory

Cells can arise only from pre-existing cells (proposed by Virchow).

3 exceptions to Cell theory

1. Viruses

• Inert outside a living cell

• Host needed for reproduction

2. Viroids

• Need host machinery to replicate

3. Prions

• Infectious particles, no nucleic acids

Cytoplasm

All contents within the cell membrane

Cytosol

Internal fluid environment of a cell, contains water, ions, and molecules

8 Basic Properties of Cells

1. Highly complex but all enclosed by physical barrier (cell membrane)

2. Genetic program (DNA & Central Dogma)

3. Capable of reproduction

4. Acquire & utilize energy

5. Carry out chemical reactions (cellular motabolism, eg. glycolysis & citric acid cycle)

6. Engage in mechanical activities

7. Respond to stimuli

8. Self-regulate

Prokaryote

Single-celled organism that does not have a nucleus or membrane-bound organelles

Bacteria

Prokaryotic domain, have plasmids (single circular chromosome) and a cell wall,

Archaea

Prokaryotic domain, have isoprenoid cell membranes, often inhabit extreme environments, single circular chromosome

Binary fission

Reproduction method of prokaryotes

Protists

Eukaryotic domain, includes algae, slime molds, protozoa, etc.

Eukaryotic Domains

1. Protists

2. Fungi

3. Plants

4. Animals

Fungi

Domain of eukaryots, chitin cell walls, heterotrophs

Plants

Domain of eukaryotes, cell walls, vacuoles, autotrophs

Plasmodesmata

Plant intercellular connections

Animals

Domain of eukaryotes, multicellular, no cell walls, heterotrophs

Eukaryotes

• Membrane bound nucleus

• EMS

• other organelles

Model organism

non-human species used in research to understand biology

Oligosaccharides

A few monosaccharides joined together

Triacyglycerol

Lipid made of 3 fatty acids attached to a carboxyl, used for energy storage

Steroids

4 fused carbon rings, found in animal cell mebranes

Phospholipid

Glycerol backbone attached to phosphate, 2 fatty acid tails

Amphipathic

Molecule with both hydrophilic and hydrophobic regions

Membrane functions

1. Compartmentalization

2. Selectively permiable barrier

3. Transporting solutes

4. Scaffold for biochemical activities

5. Responding to external signals

6. Intercellular interaction

7. Energy transduction

Micelles

Spontaneous arrangement of phospholipids with large heads and 1 tail

Liposome

Spontaneous arrangement of phospholipids when added to water

Cholesterol

Steroid that changes fluidity of animal membranes in response to temperature

Lipid Rafts

Specialized microdomains that serve as platforms for cell processes

4 Membrane protein Functions

1. Transporters

2. Receptors

3. Enzymes

4. Anchors

Membrane Carbohydrates

Face outward toward extracellular space, glycoproteins or glycolipids

Endomembrane System (EMS)

Plasma membrane & nuclear envelope, ER & Golgi apparatus, lysosomes, vesicles that move between

Nuclear Envelope

Double membrane that surrounds the nucleus, perforated by nuclear pores

Endoplasmic Reticulum

Network of interconnected tubes and flattened sacs, produces many lipids and proteins used inside and outside the cell, continuous with nuclear envelope

RER

Ribosomes associated with membrane which are exposed to the cytosol, sites of protein synthesis

SER

No ribosomes, parts bud off to form vesicles, site of fatty acid and phospholipid synthesis

Golgi Apparatus

Next stop for ER vesicles contains enzymes to modify, sort, and add carbohydrates to proteins and lipids produced in the ER, each step performed in a different region

Cisternae

Flattened sacs of the Golgi apparatus, surrounded by small vesicles which transport proteins to and from the Golgi

Lysosomes

Specialized vesicles derived from Golgi, degrade unneeded macromolecules, contain protein pump to keep internal pH around 5

Mitochondria

Harness energy from chemical compounds such as sugars and convert it into ATP

Mitochondrion regions

Outer membrane: Integral proteins (porins)

Intermembrane space: aqueous compartment

Inner membrane: highly convoluted, site of ETC and ATP synthase

Matrix: site of citric acid cylce

Chloroplasts

Site of photosynthesis, surrounded by double membrane

Thylakoids

Internal membrane-bound component of chloroplasts, flattened membrane sacs (membrane contains chlorophyll)

Lumen

Space inside a thylakoid

Grana

Stacks of thylakoids

Stroma

Space surrounding thylakoids

Diffusion

Spontaneous process, net movement of molecules from an area of high [molecules] to an area of low [molecules] until no concentration gradient

Simple diffusion

Diffusion of small or hydrophobic molecules through the cell membrane, driven by concentration gradient

Facilitated Diffusion

Diffusion of molecules through a protein transporter, driven by concentration gradient

Channel Protein

Integral membrane protein permeable to specific molecules (facilitated diffusion)

Carrier protein

Integral membrane protein that binds to specific molecules and triggers a conformational change (protein changes shape) which exposes molecule to other side of membrane

Osmosis

Diffusion of water across a semi-permiable membrane from high [H₂O] to lower [H₂O]

Isotonic

Equal osmotic pressure on both sides of a membrane

Hypertonic Solution

Higher [solute] than cell, shrinks cell causing crenation in animal cells and plasmolysis in plant cells

Hypotonic Solution

Lower [solute] than cell, swells cell causing lysis and making plant cells more turgid

Primary Active Transport

Molecules are pumped against their concentration gradient by use of chemical energy of ATP

Sodium-Potassium Pump (Na⁺/K⁺-ATPase)

Only present in animal cells, moves 3 Na⁺ ions out of the cell and 2 K⁺ ions into the cell by hydrolyzing ATP. (Primary active transport)

Secondary Active Transport/Co-transport

Molecules are pumped against their concentration gradient by use of the electrochemical gradient

Protein Pump

The electrochemical gradient formed by primary active transport allows protons to move with their [gradient] while simultaneously moving other molecules against their [gradient] (secondary active transport)

Antiport

Type of co-transport, 2 solutes move in opposite directions

Symport

Type of co-transport, 2 solutes move in the same direction

Exocytosis

Process where vesicle fuses with the cell membrane

Endocytosis

Process where material form outside the cell is brought into a vesicle

Invagination

Cell membrane forming a pocket around the target material (endocytosis)

Phagocytosis

Type of endocytosis, uptake of particulate matter, delivered to lysosomes, provides nutrition and defence

Pinocytosis

Type of endocytosis, uptake of extracellular fluids taken up without recognition

Receptor-mediated Endocytosis

Invagination only occurs when molecules bind to receptors on extracellular site attached to Clathrins on the cytoplasmic side, material delivered to endosomes.

F. Griffith

Demonstrated DNA is genetic material by infecting live cells with virulent dead ones

Avery, MacLeod, & McCarty

Proved DNA is genetic material by dissolving a virulent solution with DNase

Watson & Crick

Built 3D model of DNA

Genome

Genetic material of an organism

Gene

Unit of heredity affecting traits of an organism; the DNA sequence that corresponds to a specific protein

The Central Dogma

DNA transcribed into RNA translated into protein

3 Stages of Transcription

1. Initiation

2. Elongation

3. Termination

Sigma Factor

Protein that mediates promoter recognition in bacteria

General Transcription Factors

Proteins in eukaryotes that work together to initiate transcritption

Primary Transcript

RNA sequence that comes off the template DNA strand. The same as mRNA in prokaryotes

Polycistronic RNA

Primary transcripts in prokaryotes that contain information for more than one gene

7-methylguanosine

5’ cap attached to primary transcript in eukaryotes