Cells & OrganellesRecommended reading: Mader Chapter 4, pages 60-84

Ebook chapter link:

Fig. 4.1

Connect website

• Differences between eukaryotic and prokaryotic cells

• Key differences between bacteria and archaea• Differences between animal cells and plant cells• Structure and function of key organelles• Understand the different levels of biological

organisation

Cells and organelles – what you need to know

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1. What 4 chemical elements make up over 96% of living organisms?

2. What are all living organisms made up of?

3. Name 4 characteristics shared by all living things:(i)(ii)(iii)(iv)

4. Are these living organisms?(a) bacteria Yes/No(b) virus Yes/No(c) tree Yes/No(d) rabbit Yes/No(e) chloroplast Yes/No(f) car Yes/No(g) nucleus Yes/No

Quiz on Living Things

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• Biology is the study of living organisms

• Living things:1) are made from C, H, O and N2) are made from cells 3) are organised4) need energy/nutrients (respire/metabolise)5) produce waste products/excrete6) respond to stimuli (move)7) reproduce, develop and grow8) contain DNA9) are homeostatic (remain constant)10) adapt / evolve11) die

Living Things Summary

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• Viruses cause diseases in plants and animals(e.g. HIV, polio, rabies, ebola, avian influenza, colds)

• Viruses have DNA or RNA genomes.• BUT they CANNOT reproduce on their own.• Viruses need to use the machinery of the host cell to

reproduce.• Therefore they are not true cells.

What is a NOT a ‘living thing’?

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• 2 main types of cell: Prokaryotes & Eukaryotes

• All cells have 3 major features:1) A plasma membrane2) contain DNA3) Cytoplasm

Cells• Cells are the smallest unit of living matter • The internal structure of cells can be seen using a microscope - Light microscope or electron microscope

Cell membrane – Separates cell from the environment. It controls what enters & leaves cell.

Cytoplasm – Semi-fluid. Contains all the chemicals the cell needs to do its daily activities (eg sugars, amino acids etc)

DNA – Genetic information. ‘Blueprints’ for the cell. 6

Viewing Cells - microscopesLight microscope•See structures as small as 0.5 μm – limited by wavelength of light•Staining•Live specimens inc. video

Electron microscope•Invented 1930s•See structures as small as 2nm •Includes large macromolecules•Dead, thin sections only

See page 63 & 64 of textbook for more details7

Cells

1) All living things are made up of cells2) Cells are the basic unit of structure and function3) Cells come only from pre-existing cells because cells

are self-reproducing

Cell Theory:

Cells are small because:•They need a large surface-area-to-volume ratio so that they can rapidly exchange substances with the environment. This is important to

- get enough nutrients/energy into the cell- get waste products out of the cell

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• One cell on its own (eg bacteria/protozoa) = single celled or unicellular organism

Reproduces/divides:1 cell/organism 2 cells/organisms

• Many cells working together (eg human)= multicellular organism

Many cells divide = growthSpecialised cell division for reproduction (meiosis)

Cells

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Differences between the 2 basic types of cell

Prokaryotes Eukaryotes

• Small (e.g. ~1μm)

• No nucleus (but do have DNA)

• No membrane bound organelles

• Small ribosomes

Animal Plant

• Larger (40 - 100 μm)

• Nucleus with chromosomes

• Membrane bound organelles

• Large ribosomes

Bacteria and Archaea All other cells

(Pro = before, karyon=nucleus)

Archaea

Bacteria

(Eu = true, karyon=nucleus)

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Fig. 4.4, page 66

Inside a prokaryotic cell

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• Prokaryotes (no proper nucleus)• Diverse in shape and size• Cell wall is made of different sugars and proteins to bacteria

(NOT peptidoglycan)• Live in extreme environments all over Earth

(eg very salty, very hot environments)

Archaea

Deep sea vent12

Cell wall

Glycocalyx(capsule)

Nucleoid (DNA)

Ribosomes

Cell membrane

Flagellum

Fimbriae

Cytoplasm

Sex pili

Bacterial Cell – Cell Envelope• Cell envelope:

-Glycocalyx-Cell wall-Cell membrane

• Capsule (glycocalyx): - capsule or slime layer (sugars) - protects against drying out - helps bacteria to attach

• Cell walls: -are strong -are made of peptidoglycan (sugar) -protect the cell (shape & water) • Cell (plasma) membrane:- barrier between cell & environment- controls what can enter & leave cell (eg O2, H2O, nutrients, waste)- made of 2 sheets of lipid molecules with proteins in/through it. 13

Cell wall

Glycocalyx(capsule)

Nucleoid region (DNA)

Ribosomes

Cell membrane

Flagellum

Fimbriae

Cytoplasm

Sex pili

• Cytoplasm:- semifluid substance- contains molecules needed by cell eg H2O, sugars, enzymes, amino acids etc

Cytoplasm also contains:

- DNA (single coiled up chromosome = nucleoid region)

- Ribosomes: make proteins

- Plasmids: extra circles of DNAextra genesonly sometimes present

Bacterial Cell - Inside

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Cell wall

Glycocalyx(capsule)

Nucleoid (DNA)

Ribosomes

Cell membrane

Flagellum

Fimbriae

Cytoplasm

Sex pili

Bacterial Cell - Appendages• Sometimes bacteria have flagella:

- rotate to help bacteria move - sometimes used in feeding

• Fimbriae: - small fibres on surface - help bacteria stick to surfaces

• Pili: - small tubes - allow DNA to pass between bacterial cells or from environment

Bacteria moving

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Please note that due to differing operating systems, some animations will not appear until the presentation is viewed in Presentation Mode (Slide Show view). You may see blank slides in the “Normal” or “Slide Sorter” views. All animations will appear after viewing in Presentation Mode and playing each animation. Most animations will require the latest version of the Flash Player, which is available at http://get.adobe.com/flashplayer.

B__________

C___________

E_______

F___________

H________

A________

D________

G_________

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Prokaryotic cells - Summary• Capsule

• Cell wall

• Fimbriae

• Sex pili

• Plasma membrane

• Ribosomes

• Nucleoid region

• Plasmid

Jelly-like layer outside of the cell wall. Helps bacteria stick to surfaces

Rigid structure – made of peptidoglycan (sugar), surrounds, supports and protects cell

Surface appendages that allow bacterium to stick to a surface.

Small tubes that allow DNA to pass between bacterial cells

Selective barrier – allows certain molecules, nutrients and wastes to pass between cell and the environment

Make proteins

This is where the cells DNA is found – the DNA contains genes that control the cell.

Additional circular DNA molecule in cytoplasm 18

Eukaryotic cells• All other cells are eukaryotic

e.g. protozoa, fungi, plants, animals…

EUKARYOTIC CELLS HAVE A NUCLEUS

• A nucleus contains a cells DNA.It is a compartment in the cytoplasm that is surrounded by a double membrane.

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Nucleus• The nucleus contains:Chromatin is semifluid with strands.- mainly DNA and protein.- coils up tightly to form chromosomes.Nucleolus is a dark region of chromatin where rRNA (ribosomal RNA) is made and combines with protein to make ribosomal subunits.

• The nuclear envelope separates the nucleus from the cytoplasm.

• Nuclear pores are holes in the envelope. These allow ribosomal subunits to leave the nucleus and communicate with the rest of the cell using mRNA (messenger RNA)

Plant cells – you can clearly see the nucleus ineach cell (the small black dots!)

The cell nucleus is made of several parts

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• The "factories" of the cell - involved in making proteins

• Are free in cytoplasm or attached to ER (ribosomes+ER = RER)

• Made up of two subunits, the large and the small subunit

• Both subunits are made of protein and ribosomal RNA (rRNA)

• Ribosomes in prokaryotes are smaller than in eukaryotes.

Ribosomes

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Mitochondria = plural, mitochondrion = singular

Mitochondria

Mitochondria make ATP. They convert energy from sugars (eg glucose) into ATP. ATP is the kind of chemical energy that the cell can use to carry out all of its functions.

[We will study this in more detail in Week 7]

Fig. 4.1722

Endoplasmic Reticulum (ER): is a network of many membranes. Substances are transported around in the spaces between them.

The smooth ER (SER) helps make and transport lipids.

The rough ER (RER) is dotted with ribosomes. - Makes & modifies proteins.

Endomembrane System

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Fig. 4.10

Endomembrane systemGolgi apparatus - flattened stack of sacs

(each surrounded by membrane).

- modifies, stores and repackages important substances from the ER, mostly for secretion (delivering outside of the cell).

Vesicles - small sacs (surrounded by a membrane) containing substances eg enzymes, proteins, lipids etc.

- store or transport substances around cell or to outside of cell.

http://www.biologymad.com/resources/golgi.swf

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Please note that due to differing operating systems, some animations will not appear until the presentation is viewed in Presentation Mode (Slide Show view). You may see blank slides in the “Normal” or “Slide Sorter” views. All animations will appear after viewing in Presentation Mode and playing each animation. Most animations will require the latest version of the Flash Player, which is available at http://get.adobe.com/flashplayer.

Eukaryotic cellsAnimal cell

Rough endoplasmic reticulum (RER)with ribosomes

Cell membrane

Centrioles

Lysosomes

Mitochondrion

Cytoplasm

Golgi apparatus

Nucleus

Smooth endoplasmic reticulum (SER)

Plant cellChloroplast

Mitochondrion

Vacuole

Cell wall

Cell membrane

Rough endoplasmic reticulum (RER)with ribosomes

SER

Nucleolus

Nuclear envelopeNuclear pore

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Animal cells also have:• Lysosomes: special vesicles that contain digestive enzymes.

The enzymes help to break down & recycle nutrients & cell parts and destroy bacteria.

• Centrioles: where microtubules are initiated for cell division (mitosis).• Flagella: organelle to help cells move. Is present in some animal cells –

made of microtubules.• Cytoskeleton: (microtubules,

centrioles, fibres) protein fibres that support the cell. Provide network for organelles to move around on.

• Cilia: hair like projections often used in moving or moving liquids/particles over a cell surface.

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Plant cells also have:• Chloroplasts: organelles involved in photosynthesis. Convert

energy from sunlight into chemical energy which is then stored as sugar molecules.

• Large vacuole: storage, structural support, breakdown of waste products

• Cell wall: made from cellulose. Maintains cells shape and protects cell from mechanical damage.

• Plasmodesmata: thin tubes of cytoplasm through the cell wall. Connects the cytoplasm of neighbouring plant cells.

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Cell Quiz1. All eukaryotic cells have:

a) chloroplasts True/Falseb) mitochondria True/Falsec) a nucleus True/False

2. Prokaryotic cells have:a) nuclei True/Falseb) mitochondria True/Falsec) chloroplasts True/False

3. Prokaryotic cells are larger than eukaryotic cells.True/False

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4. What are the 3 features that ALL cells have in common?(i)(ii)(iii)

5. List 3 of the features that plant cells have but animal cells do not:(i)(ii)(iii)

6. What type of cell are Bacteria and Archaea?

7. What do animal and plant cells have in common?

Cell Quiz

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• What defines a living thing (what makes it ‘alive’)• Why cells are the basic unit of life• The differences between eukaryotic and prokaryotic cells• The differences between bacteria and Archaea• The features shared by animal and plant cells and the

unique features of each• The function of key membrane-bound organelles and

how their structure facilitates these functions• Why cells are small!

After studying this topic, you should know…

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Remember to check Blackboard for help and worksheets

Extra help and support…

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Connect website

Cells Alive!

Thuyết nội cộng sinh liên quan đến nguồn gốc của ty thể và thể hạt (thể hạt có chứa diệp lục a và b gọi là lục lạp, một số thể hạt khác được gọi là cyanelle và rhodoplast), hai trong số những bào quan của tế bào sinh vật nhân chuẩn. Theo thuyết này, những bào quan đó có nguồn gốc từ những sinh vật nhân sơ Prokaryotic sống bên trong các tế bào nhân chuẩn Eukaryotic như một sinh vật cộng sinh ở bên trong (nội cộng sinh). Nói cách khác, thuyết nội cộng sinh đưa ra giả thuyết là những tế bào nhân chuẩn xuất hiện lần đầu tiên khi một tế bào nhân sơ bị hấp thụ vào trong một tế bào khác mà không bị tiêu hoá. Giả thuyết này cũng mặc nhận rằng ty thể tiến hoá từ một nhóm vi khuẩn hiếu khí (có lẽ là Proteobacteria, có liên quan đến trùng rận rickettsias), và cho rằng lục lạp tiến hoá từ một loài vi khuẩn lam nội cộng sinh (sinh vật nhân nguyên thuỷ quang tự dưỡng). Bằng chứng của thuyết này đã thuyết phục được hầu hết các nhà khoa học và ngày nay đang được chấp nhận một cách rộng rãi.

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