基础生物实验 7 - 实验三理论简介：Cell Types and Structure

本期内容是 细胞种类与结构 的基础理论部分，实验手册与实验模拟请看后两期。本部分内容来自 University of California, Berkeley - UC Berkeley Extension, 虚拟实验的内容来自 Labster. 本部分内容均不会标记为为原创，但由于是UP主购买的课程，因此不接受非授权的转载，谢谢您的理解。

每一个生物基础实验均会分为三部分：第一部分为实验的生物理论；第二部分为实验的指导手册；第三部分为 Labster 的虚拟实验模拟。第一部分的基本信息由 Ying Liu, Ph.D. 提供，第二部分的实验手册来自 Labster, 第三部分的实验模拟过程由UP主操作。

Lab 3 - Cell Structure: Basic Information

将进化的时间按比例化为一年：

Phylogenetic Tree

    Unity: all life on Earth came from one universal ancestor (bacteria, fungi, plants and animals all use DNA as genetic code).

    Diversity: organiSms adapted to local environment, leading to ‘adaptive radiation.’

Prokaryotes and Eukaryotes

    Prokaryotes: -kary = nucleus; pro- = before

    Domains Bacteria and Archaea (0.1 - 5 μm)

    Eukaryotes: -kary = nucleus; eu- = true

    Domain Eukarya (10 - 100 μm)

Prokaryotes vs. Eukaryotes

    Despite structural differences, common metabolic activities

    Eukaryotic cells: more compartmentalization

Microscopes

    Antonie van Leeuwenhoek: manufactured simple microscopes

        - First to observe and describe bacteria, yeast, protists in rain water, etc. (~1674)

    Robert Hooke: English father of microscopy

        - Observed ‘cells’ found in a cork (1665)

        - Reaffirmed Leeuwenhoek’s findings later upon improvement of the microscope design

Cell Theory

    Matthias Schleiden: Plants were made of cells

    Theodor Schwann: Animals were made of cells

    Rudolf Virchow: Cells were derived from other cells

    Robert Remak: First to describe cells came from other cells

Life in the world - made of two types of cells: eukaryotic and prokaryotic cells.

Prokaryotic Cell

    DNA in the nucleoid region

    Have 70S ribosomes

    Bacterial cell wall contains peptidoglycan

Cyanobacteria

    Photosynthetic prokaryotes

    Also called ‘blue green algae’

    Gave rise to chloroplasts

Eukaryotic Cell Evolution 1:

    - Infolding of plaSma membrane forms the nucleus and the endomembrane system;

    - Nuclear membrane (envelope), ER membrane, Golgi apparatus and plaSma membrane make up a continuous membrane system, with vesicles travel in between.

Endomembrane System

    - EndoplaSmic reticulum (ER) makes lipids and proteins;

    - Golgi apparatus is involved in protein trafficking;

    - Lysosomes are where intracellular digestion occurs.

Lysosome

    - Lysosome contains digestive enzymes that can break down large molecules;

    - Phagocytosis: engulfment (food, bacteria, etc.).

Eukaryotic Cell Evolution 2: 

    - Endosymbiosis explains the development of mitochondrion (proteobacterium) and chloroplast (cyanobacterium);

    - Primitive eukaryotic cell engulfed a proteobacterium capable of aerobic respiration, which became a mitochondrion;

    - Later, eukaryotic cell engulfed a cyanobacterium, which became a chloroplast.

    - Mitochondria and chloroplasts both contain their own DNA and ribosomes;

    - Their DNAs are circular (prokaryote) not linear (eukaryote);

    - Their ribosomes are more similar to bacterial ribosomes (70S) not to eukaryotic ribosomes (80S);

    - Both reproduce by binary fission;

    - Mitochondria can be affected by antibiotics.

DNA

    - Prokaryotic DNA: 1 circular DNA;

    - Eukaryotic DNA: multiple linear DNA wrapped around histones to form chromosomes.

Ribosome - in both eukaryotic and prokaryotic cells

    - Composed of rRNA (60%) and proteins (40%)

    - Prokaryotic ribosomes: 70S (30S + 50S)

    - Eukaryotic ribosomes: 80S (40S + 60S)

Key Cellular Structures

- Smooth ER: synthesis of lipids;

- Rough ER: synthesis of proteins;

- Golgi: sort & deliver secreted & membrane proteins;

- Lysosome: digest food, worn out organelles, etc.

Animal Cell:

Plant Cell:

Cytoskeleton

- Three types of cytoskeleton:

    Actin filaments: long protein strands (thin, 7 nm)

    Intermediate filaments: ropelike strands (10 nm)

    Microtubules: long hollow tubes (thick, 25 nm)

Extracellular Matrix (ECM)

    ECM contains protein fibers (collagen), proteoglycans, (polysaccharides), etc. 

    Contributes to adherence (bind adjacent cells to form tissue) and signal reception (communication).

Cell Junctions

    - Tight junctions: watertight seal between adjacent cells (skin);

    - DeSmosomes link adjacent cells, provide mechanical strength;

    - Gap junctions: channels between adjacent cells, allowing transport and communication.

Tissue:

    Tissue: a collection of cells of the same type that perform a common function

    There are 4 major tissue types in the body:

        - Epithelial: covers body surfaces and lines body cavities

        - Connective: binds and supports body parts

        - Muscular: moves the body and its parts

        - Nervous: receives sensory information and conducts nerve impulses

Epithelial Cells

    - Polarity: apical side facing the Small intestine lumen; basal side;

    - Tight junctions around the apical region maintain the polarity.

Bone Cells (Osteocytes)

    - Cells (osteocytes) are connective tissues in chambers called lacunae;

    - Solid and rigid matrix is made of collagen and calcium salts.

    - Osteon: functional unit of compact bone;

    - Canaliculi: canals between the lacunae.

Muscle Cells (Myocytes)

    - Skeletal muscle: long striated fibers, attached to bone, voluntary movement;

    - Sarcomere: contractile unit of muscle.

    - Sarcomere is a structure only present in muscles.

Nerve Cells (Neurons)

- Neuron: 1 axon (long projection) and multiple dendrites (short projections).

感谢阅读！下一期为实验手册 & 下下期将进行 Labster 实验！