31
Figure 2-1 Molecular Biology of the Cell (© Garland Science 2008) 教科書 2.1.1 陽子 中性子 電子 1
Figure 2-1 Molecular Biology of the Cell (© Garland Science 2008)
教科書 2.1.1
陽子
中性子 電子
1
Figure 2-5 Molecular Biology of the Cell (© Garland Science 2008)
教科書 2.1.2
共有
共有結合
移動
イオン結合
陽イオン 陰イオン
2
Figure 2-8 Molecular Biology of the Cell (© Garland Science 2008)
教科書 2.1.3
3
Figure 2-10 Molecular Biology of the Cell (© Garland Science 2008)
×
教科書 2.1.3
4
Figure 2-15 Molecular Biology of the Cell (© Garland Science 2008)
教科書 p.11
の解説
弱い水素結合（原子間距離が長い）
強い共有結合（原子間距離が短い）
水素原子供与体
水素原子受容体
5
Figure 2-16 Molecular Biology of the Cell (© Garland Science 2008)
教科書 p.11
の解説
6
Figure 2-3 Molecular Biology of the Cell (© Garland Science 2008)
→ 他の生物でもほとんど同じ
教科書 2.2.1
ヒトの体
地殻
7
Figure 2-6 Molecular Biology of the Cell (© Garland Science 2008)
教科書 2.2.1
8
Table 2-2 Molecular Biology of the Cell (© Garland Science 2008)
教科書 2.2.2
高分子（蛋白質、DNA、デンプン）
有機化合物
9
Figure 2-30 Molecular Biology of the Cell (© Garland Science 2008)
モノマー ポリマー 教科書 2.2.2b
糖 多糖
アミノ酸蛋白質
ヌクレオチド 核酸10
Figure 2-23 Molecular Biology of the Cell (© Garland Science 2008)
アミノ酸＝モノマー教科書 2.3.1b
pH7（生体内）ではイオン化している
↓
水に溶けやすい形
アミノ基 カルボキシル基
→20種類の多様性がある
11
Figure 2-24 Molecular Biology of the Cell (© Garland Science 2008)
蛋白質＝ポリマー
ペプチド結合
教科書 2.3.1
12
Myosin蛋白
Actin蛋白
四次構造を作る！
16.8 蛋白質（分子ナノマシーン）の例：筋肉蛋白質Myosinによる細胞運動
Muscle myosin is a dimer with two identical motor heads that act independently.
Each myosin head has a catalytic core and an attached lever arm. A
coiled-coil rod ties the two heads together, and tethers them to the thick filament
seen on top. The helical actin filament is shown at the bottom.
In the beginning of the movie, the myosin heads contain bound ADP and
phosphate, and have weak affinity for actin.
Once one of the heads docks properly onto an actin subunit, phosphate is
released. Phosphate release strengthens the binding of the myosin head to actin,
and also triggers the force-generating power stroke that moves the actin filament.
ADP then dissociates, and ATP binds to the empty nucleotide binding site,
causing the myosin head to detach from the actin filament.
On the detached head, ATP is hydrolyzed, which re-cocks the lever arm back
to its pre-stroke state. Thus, like a spring, the arm stores the energy released by
ATP hydrolysis, and the cycle can repeat.
The actin filament does not slide back after being released by the motor
head, because there are many other myosin molecules also attached to it, holding
it under tension.
The swing of the lever arm can be directly observed on single myosin
molecules, here visualized by high-speed atomic force microscopy.
教科書 2.3.1c
と表2.1
発展
13
Figure 2-18 Molecular Biology of the Cell (© Garland Science 2008)
糖質＝モノマー
ちなみに、このOHを放射性Fに変えるとPETイメージング（癌診断）ができる。
教科書 2.3.2
14
Figure 2-19 Molecular Biology of the Cell (© Garland Science 2008)
教科書 2.3.2単糖
二糖
縮合 加水分解
15
Figure 2-75a Molecular Biology of the Cell (© Garland Science 2008)
糖のポリマー
教科書 2.3.2
ブドウ糖の部分構造分岐点
16
Figure 2-21 Molecular Biology of the Cell (© Garland Science 2008)
脂質
石鹸みたいな分子
教科書 2.3.3親水性のカルボン酸（頭部）
疎水性の炭化水素（尾部）17
Figure 2-22 Molecular Biology of the Cell (© Garland Science 2008)
教科書 2.3.3
リン脂質の二重層（細胞膜）
親水性の頭部
２つの疎水性の脂肪酸（尾部） リン脂質分子
18
10.2 Lipids and Lipid Bilayer
Phospholipids contain a head group, choline in this case, that is attached via a
phosphate group to a 3-carbon glycerol backbone. Two fatty acid tails are
attached to the remaining two carbons of the glycerol.
The head groups and the phosphate are polar, that is, they prefer to be in an
aqueous environment.
In contrast the fatty acid tails are hydrophobic, that is, they are repelled from
water. The fatty acid tails on phospholipids can be saturated, with no double
bonds, or unsaturated, with one or more double bonds. The double bonds are
usually in the cis-configuration, which introduces sharp kinks. When forming a
bilayer, unsaturated fatty acid tails pack loosely, which allows the bilayer to
remain fluid. If there were no double bonds, bilayers would solidify to a consistency
resembling bacon grease.
Cholesterol is another lipid component of most cell membranes. It has a
hydroxyl group, a tiny polar head group so to speak, attached to a rigid
hydrophobic tail. Cholesterol can fill gaps between phospholipids and thus stabilizes
the bilayer.
In a lipid bilayer, lipids arrange themselves so that their polar heads are
exposed to water and their hydrophobic tails are sandwiched in the middle. In
this model, water molecules are shown in red.
教科書 2.3.3
19
Figure 2-26 Molecular Biology of the Cell (© Garland Science 2008)
ヌクレオチド＝モノマー
ATP（アデノシン三リン酸；上記）は特別な分子：DNA(核酸の一種)の原料でもあり、細胞内の通貨（ほとんどの反応のエネルギー源）でもある。
教科書 2.3.4
（三）リン酸
塩基
糖
20
Figure 2-28 Molecular Biology of the Cell (© Garland Science 2008)
DNA＝ポリマー
DNAやRNAは重要な分子なので、来週～再来週にて詳しく。
教科書 2.3.4
21
Figure 2-29 Molecular Biology of the Cell (© Garland Science 2008)
2.1-2.3章のまとめ：ポリマー
蛋白質
多糖
22
Figure 2-34 Molecular Biology of the Cell (© Garland Science 2008)
教科書 2.4.1
酵素反応１ 酵素反応２ 酵素反応３ 酵素反応４ 酵素反応５
23
Figure 2-35 Molecular Biology of the Cell (© Garland Science 2008)
複雑な電子回路図のよう
トランジスタやダイオードなどの１つ１つのパーツがバラバラではダメ。それらが協調して働いてはじめて、１つのシステム（ICラジオなど）を形成する。
教科書 2.4.1
24
Figure 2-44 Molecular Biology of the Cell (© Garland Science 2008)
教科書 図2.3
の補足
反応物
生成物
無触媒反応経路 酵素によって触媒される反応経路
25
Figure 2-46b Molecular Biology of the Cell (© Garland Science 2008)
教科書 図2.3
の補足
無触媒反応酵素によって
触媒される反応１26
エネルギー(ATP)を生む過程
（次ページの図に従って）エネルギー変換効率（ほぼ）100%の奇跡の分子タービン*を回転
エネルギー源（糖や脂質など）
（エネルギー源分子の結合を切断して）電子に変換
*：（ミトコンドリア内）ATP合成酵素という
エネルギーをATP分子内部に蓄積（様々なエネルギー源のエネルギーを唯一の分子内に集約）
教科書 2.4.2
-2.4.4と図2.4
発展
27
Figure 14-14 Molecular Biology of the Cell (© Garland Science 2008)
酸素のお蔭で、生命活動の源(ATP)がバンバンでき、エネルギーを大量消費する高性能の生物へと進化？（軽自動車(嫌気性細菌）→フェラーリ（陸上生物）？）
酸素！
酵素1 酵素3酵素2
教科書 2.4.2
-2.4.3と図2.4
ATP合成酵素
ミトコンドリア内でエネルギーがたくさん生まれる過程
電子伝達系
発展
28
14.4 ATP Synthase—A Molecular Turbine
ATP synthase is a molecular machine that works like a turbine to convert the
energy stored in a proton gradient into chemical energy stored in the bond
energy of ATP.
The flow of protons down their electrochemical gradient drives a rotor that
lies in the membrane. It is thought that protons flow through an entry open to
one side of the membrane and bind to rotor subunits. Only protonated subunits
can then rotate into the membrane, away from the static channel assembly.
Once the protonated subunits have completed an almost full circle, and have
returned to the static subunits, an exit channel allows them to leave to the other
side of the membrane. In this way, the energy stored in the proton gradient is
converted into mechanical, rotational energy.
The rotational energy is transmitted via a shaft attached to the rotor that
penetrates deep into the center of the characteristic lollipop head, the F1
ATPase, which catalyzes the formation of ATP.
The F1 ATPase portion of ATP synthase has been crystallized.
Its molecular structure shows that the position of the central shaft influences
the conformation and arrangement of the surrounding subunits. It is
these changes that drive the synthesis of ATP from ADP. In this animated model,
different conformational states are lined up as a temporal sequence as they
would occur during rotation of the central shaft.
Like any enzyme, ATP synthase can work in either direction. If the concentration
of ATP is high and the proton gradient low, ATP synthase will run in
reverse, hydrolyzing ATP as it pumps protons across the membrane.
To show the rotation of the central shaft, a short fluorescent actin filament
was experimentally attached to it. Single filaments attached to single F1 ATPases
can be visualized in the microscope.
When ATP is added, the filament starts spinning, directly demonstrating the
mechanical properties of this remarkable molecular machine.
教科書 2.4.3
発展
29
Figure 2-26 Molecular Biology of the Cell (© Garland Science 2008)
ＡＴＰ：ＤＮＡモノマーの一つでもある
高エネルギー結合（負電荷同士の反発に注目）
細胞内の「通貨」と例えられる。
くどいですが、大事なところなので・・ 教科書 2.4.4
30
本日のまとめ：
1. 生物は多くの分子によって構成されており、その殆どが水と有機化合物である。
2. 後者の代表例は、蛋白質、核酸、糖質、脂質である。
3. 蛋白質や核酸の殆どは高分子である。
4. 生体内で起こる化学反応は、酵素と呼ばれる蛋白質が触媒することが非常に多い。
5. 生物はエネルギーをATP分子内に蓄積して、様々な生命活動に利用する。ATP分子はDNAの合成原料(モノマー）の一つでもある。31
