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Cells and Molecules

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Introduction

Cells are fundamental units of the body. They are arranged into tissues. Cells are made up of molecules. The cell surface membranes and nucleus membranes are made up of fats, with chunks of protein studding them.

Carbohydrate chains and trees are attached all over the place, playing an absolutely critical role in the highly specialized signals required for life as a cell and a person.

Proteins make up the receptors on the cell surface, enabling them to respond to signals from themselves, other cells, pathogens, environmental conditions, or damage. Proteins also make up the machines that make a cell work (so called kinases), the structural framework of the body (like collagen), and many of the body's signaling mechanisms (like insulin).

Watch Harvard University's Inner life of a cell, first without narration and then with narration

Cell Structure

nucleus

cytoskeleton
plasma membrane
cytoplasm
mitochondria
Golgi apparatus
endoplasmic reticulum
lysosomes

Cytoskeleton

Microtubules

Microtubules are important.

Plasma Membrane

Content 2

Mitochondria

Mitochondria are the cell's energy source.

Sync with glycolysis.

Mitochondria in Various Cell Types

cardiomyocytes are about 35% mitochondria.

Golgi apparatus

Endoplasmic Reticulum

Lysosomes

Cell Molecules

"People are walking collections of molecules". In this section, various molecules are discussed.

proteins are responsible for essentially everything that happens in the body. They are composed of amino acids.
carbohydrates provide energy and perform important sigaling and recognition functions.
lipids form cell membranes, provide energy, and are used to synthesize various other molecules.
nucelic acids represent the storage and manifestation of information responsible for cell, tiusse, and organism behaviour.
ions produce osmotic gradients and signals.
Water is by far the most prevalent and important molecule of the body.
gases... are hard to explain in one line.

receptors
ion channels
second messengers
signaling pathways

Receptors

Structural Classification

Functional Classification

Ion Receptors

Endocrine Receptors

Ion Channels

Ion channels are key proteins. Most have contain multiple domains with 6 transmembrane segments.

Many ion channels are gated, only allowing ions through at certain times.

Voltage sensitive ion channels open given the voltage within the cell. During depolarization or repolarization of cells, specific channels open or close.

Fast sodium channels

Fast sodium channels open during depolarization, but remain this way for a few thousandths of a second. They then spontaneously close to an inactive state, remaining this way until the cell has repolarized to almost its resting state.

Furthermore, maintenance of less negative transmembrane voltage results in inactivation of sodium channels without initial opening. This is the case in cardiac pacemaker cells, which thereby have persistently inactivated fast sodium channels.

Local anesthetics such as lidocaine, as well as TTX, inhibit sodium channels.

L-Type Calcium Channels

inhibited by nifedipine, verapamil

An ugly table

Current	Channel	Ions	Reversal Potential of Current	Inhibitors
I Na	Voltage-gated Na+ channel	Na+	+60
I Ca	L-type Ca2+ channel	Ca2+	+120
I KR	HERG + minK	K+	-100	Ba2+, Cs+, TEA
I Ks	KvLQT1 + minK	K+	-100	Ba2+, Cs+, TEA
I Kf (pacemaker)	HCN	Na+, K+	-35	Cs+

Second Messengers

SMs are important components of cellular signaling pathways.

These include cAMP, used in the PKA, etc pathways.

Signaling Pathways

Signaling pathways confer information outside cells, on their surface, and inside them, using proteins, ions (ie calcium, sodium, etc), fats, carbohydrates, and other molecules and atoms.

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Cell Types

epithelial
cells
endothelial
cells
connective tissue
cells
muscle
cells
nervous tissue
cells
stem
cells

Epithelial cells

Endothelial Cells

Connective Tissue Cells

fibroblasts
adipocyte

Muscle Cells

skeletal muscle

Smooth muscle cells are involuntary cells found primarily around stuctures under autonomic control, including the vasculature, airways, gut, and glands.