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Cells, tissue types

and organs

MFEL3010 Ingunn Bakke (MD, PhD) Dept of Cancer research and Molecular Medicine Faculty of Medicine

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I: •Structural and functional organization •Cell structure and functions

•Plasma membrane •Movement through the Plasma membrane

•Cytoplasm containing organelles II:

•Relationship between cell structure and function •How do cells make proteins? •Cell cycle •Why do cells differ? •How do cells communicate?

Outline

3 Structural & functional organizations

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Organ system of the body

•Lymphatic •Respiratory •Digestive •Intergumentary •Skeletal •Muscular •Nervous •Endocrine •Cardiovascular •Urinary •Female reproductive •Male reproductive

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Organs of the body

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Four basic tissue types: 1 2 3

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You are made up of millions of cells

However, you started your life as a single fertilized egg……

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Day 6: Blastocyst

Four-cell stage of a human embryo

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ectoderm gives rise to skin and nervous system mesoderm give rise to muscle, skeleton, and organs of circulation reproduction, and excretion endoderm gives rise to lining of gut and associated organs

Tissues General: embryo becomes arranged into three different tissues

Nature Biotechnology 23, 699 - 708 (2005)

Differentiation

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Cell structure and function

11 • Basic structure of the cell – Plasma membrane – Cytoplasm containing organelles – Nucleus

• Functions of the cell

– Basic unit of life – Protection and support through production and secretion

of various kinds of molecules – Movement. Various kinds occur because of specialized

proteins produced in the cell – Communication. Cells produce and receive electrical and

chemical signals – Cell metabolism and energy release – Inheritance. Each cell contains DNA. Some cells are

specialized to gametes for exchange during sexual intercourse

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Plasma membrane

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Plasma membrane

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Membrane lipids

Cholesterol

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• Functioning depends on 3-D shape and chemical characteristics • markers • attachment sites • channels • receptors • enzymes • or carriers

Membrane proteins

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Glycoprotein(cell surface marker)

Membrane proteins

receptor enzymes carrier channel

marker

attachment sites

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Movement through the Plasma Membrane • Diffusion • Osmosis • Filtration

• Mediated transport mechanisms

– Facilitated diffusion – Active transport – Secondary active transport

• Endocytosis and exocytosis

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Diffusion • Movement of solutes from an area of higher

concentration to lower concentration in solution – Concentration or density gradient: difference

between two points – Viscosity: how easily a liquid flows

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Osmosis

• Diffusion of water (solvent) across a selectively permeable membrane. Water moves from an area of low concentration of solute to an area of high concentration of solute

• Osmotic pressure: force required to prevent water from moving across a membrane by osmosis

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Osmosis and cells • Important because large volume changes caused by water

movement disrupt normal cell function • Cell shrinkage or swelling

Isotonic: cell neither shrinks nor swells Hypertonic: cell shrinks (crenation) Hypotonic: cell swells (lysis)

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Filtration • Works like a sieve

• Depends on pressure

difference on either side of a partition

• Moves from side of greater pressure to lower

• Example: urine formation in the kidneys. Water and small molecules move through the membrane while large molecules remain in the blood

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Mediated transport mechanisms • Involve carrier proteins or

channels in the cell membrane

• Characteristics – Specificity for a single type

of molecule – Competition among molecules

of similar shape – Saturation: rate of transport

limited to number of available carrier proteins

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Mediated transport mechanisms • Move large, water soluble

molecules or electrically charged molecules across the plasma membrane.

• Amino acids and glucose in, manufactured proteins out. – Facilitated diffusion:

carrier- or channel-mediated. Passive.

– Active transport – Secondary active transport

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Active transport • Requires ATP. The use of energy

allows the cell to accumulate substances

• Rate of transport depends on concentration of substrate and on concentration of ATP

• Example: Na/K exchange pump that creates electrical potentials across membranes

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Secondary active transport

• Ions or molecules move in same (symport) or different (antiport) direction

Na+

27 Endocytosis

• Internalization of substances by formation of a vesicle

• Types Phagocytosis Pinocytosis Receptor-mediated

endocytosis

Particle

Cellprocesses

Phagocyticvesicle

Exocytosis

Accumulated vesicle secretions expelled from cell

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Cytoplasm containing organelles

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Cytoplasm • Cellular material outside

nucleus but inside plasma membrane

• Composed of Cytosol, Cytoskeleton, Cytoplasmic Inclusions, Organelles

• Cytosol: fluid portion. Dissolved molecules (ions in water) and colloid (proteins in water)

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Cytoskeleton • Supports the cell but has to allow

for movements like changes in cell shape and movements of cilia – Microtubules: hollow, made of

tubulin. • Internal scaffold, transport,

cell division – Microfilaments: actin.

• Structure, support for microvilli, contractility, movement

– Intermediate filaments: mechanical strength

• Cytoplasmic inclusions: aggregates of chemicals such as lipid droplets, melanin

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Organelles

• Small specialized structures with particular functions

• Most have membranes that separate interior of organelles from cytoplasm

• Related to specific structure and function of the cell

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Nucleus

• Membrane-bound • Nucleoplasm, nucleolus and nuclear envelope • Much of the DNA in a cell located here

TEM 20,000x SEM 50,000x

Nuclearenvelope

Interior ofnucleus

Nucleolus

Chromatin

Outer membraneof nuclear envelope

Inner membraneof nuclear envelopeNuclear pores

Nuclearenvelope

Chromatin

Nuclear poresRibosomes

NucleoplasmOuter membraneSpaceInner membrane

Nucleolus

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Cells: 10-50 µm Chromosomes: 2n =46 (diploid) DNA: 2m Organic base pairs: 3000mill

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How your DNA is packaged into your cells

DNA

ChromatinChromosome

Kinetochore

Centromere

ChromatidProteins

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Ribosomes

• Sites of protein synthesis

• Composed of a large and a small subunit

• Types – free – attached

(to endoplasmic reticulum)

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Endoplasmic Reticulum (ER)

• Types – Rough

• Has attached ribosomes

• Proteins produced and modified here

– Smooth • No attached

ribosomes • Manufactures lipids

• Cisternae: Interior spaces

isolated from rest of cytoplasm

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Golgi apparatus

• Modification, packaging, distribution of proteins and lipids for secretion or internal use

• Flattened membrane sacs stacked on each other

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Action of Lysosomes Peroxisomes

Smaller than lysosomes Contain enzymes to break down fatty acids and amino acids Hydrogen peroxide is a by-product of breakdown

Proteasomes Consist of large protein complexes Include several enzymes that break down and recycle proteins in cell

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Mitochondria • Major site of ATP synthesis • Mitochondria increase in number when cell energy requirements increase.

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Overview of Cell metabolism

• Production of ATP necessary for life

• ATP production takes place in the cytosol (anaerobic) and mitochondria (aerobic) – Anaerobic does not

require oxygen. Results in very little ATP production

– Aerobic requires oxygen. Results in large amount of ATP

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I: •Structural and functional organization •Cell structure and functions

•Plasma membrane •Movement through the Plasma membrane

•Cytoplasm containing organelles II:

•Relationship between cell structure and function •How do cells make proteins? •Cell cycle •Why do cells differ? •How do cells communicate?

Outline

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Relationship between cell structure and cell function

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Eukaryotic cell

Form and function!

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cultured hippocampal neurons

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Human Cervical Adenocarcinoma Cells (HeLa Line)

The HeLa line is one of the best-known cell lines in the world. Derived in 1951 from an adenocarcinoma of the cervix found in a 31-year-old woman (Henrietta Lacks),

•peroxisomes and intracellular microtubular network,

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Human Cervical Adenocarcinoma Cells (HeLa Line)

Nuclear DNA Filamentous actin Golgi apperatures

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Human Bone Osteosarcoma Cells (U-2 OS)

endoplasmic reticulum filamentous actin nuclear DNA

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How do cells make proteins?

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Overview of protein synthesis

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Overview of protein synthesis

Transcription: DNA used to form RNA Translation: synthesis of protein at the ribosomes

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Transcription

Deoxyribonucleic acid (DNA) Ribonucleic acid (RNA)

53 Post-transcriptional modification of mRNA

The genes of most living things are divided up into exons (coding) and introns (non-coding).

Splice

Pre-mRNA formedTranscription

Specific RNA regions

Pre-mRNA

DNA

Pre-mRNA Exon 1 Exon 2Intron

Intron

Cut Cut

Exon 1 Exon 2

Exon 1 Exon 2mRNA

Processing

54 Translation

http://www.stolaf.edu/people/giannini/flashanimat/molgenetics/translation.swf

Animation:

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Protein structure

• Primary, secondary, tertiary, quaternary

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Cell cycle

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DNA-replication CytosineThymine Adenine

Guanine

3′

5′

5′ 3′

OriginalDNA molecule

DNA strandsseperate

Nucleotide

Old strand(template)

Old strand(template)

Newstrands

5′

5′

3′

New DNA moleculeNew DNA molecule

3′

The protein BRCA1 helps repair DNA. Suhail Islam, Imperial Cancer Research Fund, London

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Steps of Mitosis

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Steps of Mitosis

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Steps of Mitosis

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Steps of Mitosis

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Steps of Mitosis

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Steps of Mitosis

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Steps of Mitosis

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Steps of Mitosis

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Steps of Mitosis

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Meiosis

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Why do cells differ?

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Regulation of protein synthesis

• All nucleated cells except germ cells have the full complement of DNA.

• During development, differentiation occurs and some segments of DNA are turned off in some cells while those segments remain “on” in other cells (gene expression).

• During the lifetime of a cell, the rate of protein synthesis varies depending upon chemical signals that reach the cell.

70 Transcription factors

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Structural & functional organizations

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Four basic tissue types: 1 2 3

4

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Sebaceousgland Skin

Epidermis

Dermis

Hypodermis(subcutaneoustissue)

Hairs

Fat

Arrector pili(smooth muscle)

Sweat glandArtery

VeinNerve

Hair follicle

Skin and hypodermis

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How do cells communicate?

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Homeostasis Stimuli ex. cold exposure

Hypothalamus

Pituitary

Thyroid gland

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Cell connection Found on lateral and basal surfaces of cells Functions •Form •permeability layer •Bind cells together •Provide mechanism for intercellular communication

Types

Desmosomes Tight junctions Gap junctions

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Signaling can be LOCAL or DISTANT

Neuroendocrine ECL cell in a gastric gland

Gustafsson et al 2011; 46: 531-7.

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Intracellular signal transduction

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http://www.stolaf.edu/people/giannini/flashanimat/celldivision/crome3.swf http://www.johnkyrk.com/meiosis.html

http://www.cellsalive.com/howbig.htm

Selected websites CellsAlive.com: Animations and images of human cells.