IB Biology Study Guide

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The following is (or will hopefully eventually be) an explanation of the entire IB Biology Syllabus: For first examinations in 2003.

The Syllabus provided by the International Baccalaureate Organization (IBO) consists of the titles displayed in bold. The explanations written in plain text below these titles have been added as supplementation and/or when further clarification is required. Basically, it takes away the need to research the "answers" to the syllabus and gives everyone a study-guide which can be accessed from anywhere, whenever needed.

Contents 1 Topic 1: Cells 1.1 Cell Theory 1.1.1 Outline the cell theory. 1.1.2 Discuss the evidence for the cell theory. 1.1.3 State that a virus is a non-cellular structure consisting of DNA or RNA surrounded by a protein coat. 1.1.4 Explain three advantages of using light microscopes. 1.1.5 Outline the advantages of using electron microscopes. 1.1.6 Define organelle. 1.1.7 Compare the relative sizes of molecules, cell membrane thickness, viruses, bacteria, organelles and cells, using appropriate SI units. 1.1.8 Calculate linear magnification of drawings. 1.1.9 Explain the importance of the surface area to volume ratio as a factor limiting cell size. 1.1.10 State that unicellular organisms carry out all the functions of life. 1.1.11 State that all cells are formed from other cells. 1.1.12 Explain that cells in multicellular organisms differentiate to carry out specialized functions by expressing some of their genes but not others. 1.1.13 Define tissue, organ and organ system. 1.2 Prokaryotic Cells 1.2.1 Draw a generalized prokaryotic cell as seen in electron micrographs. 1.2.2 State one function for each of the following: cell wall, plasma membrane, cytoplasm, ribosomes and naked DNA. 1.2.3 State that prokaryotes show a wide range of metabolic activity including fermentation, photosynthesis and nitrogen fixation. 1.3 Eukaryotic Cells 1.3.1 Draw a diagram to show the ultrastructure of a generalized animal cell as seen in electron micrographs. 1.3.2 State one function of each of these organelles: ribosomes, rough endoplasmic reticulum, lysosomes, Golgi apparatus, mitochondrion and nucleus. 1.3.3 Compare prokaryotic and eukaryotic cells. 1.3.4 Describe three differences between plant and animal cells. 1.3.5 State the composition and function of the plant cell wall.

[edit] Topic 1: Cells

[edit] Cell Theory

[edit] Outline the cell theory.

Cells are the structural and functional units of all living organisms ("the building blocks of life"). The Cell Theory states:

1. All organisms are composed of one or more cells.
2. All cells come from pre-existing cells.
3. All vital functions of an organism occur within cells.
4. Cells contain the hereditary information necessary for regulating cell functions and for transmitting information to the next generation of cells.
5. The cell is the smallest unit that retains the characteristics of life

[edit] Discuss the evidence for the cell theory.

Exceptions: Skeletal muscle and some fungal hyphae are not divided into cells but have a multinucleate cytoplasm. Some biologists consider unicellular organisms to be acellular.

Matthias Schleiden (1838)

1. Concludes that all plants are made of cells or their derivatives, a theory he called Phytogenesis.

Robert Hooke (1665)

1. Was the first person to describe cells, coin the term while he was looking at the compartments in cork

von Leeuwenhoek

1. was the first person to look at living cells

Theodore Schwann (1839)

1. Working with Schleiden, proposed the Cell Theory, which suggested that all animals and plants were made of cells, and that within an organism these cells are identical.

Rudolph Virchow (1855)

1. Studied pathogenic organisms and showed that "omnis cellula e cellula", All cells arise from pre-existing cells, by means of cell division.

Advances in technology and manipulative techniques had to be developed before any theory could be developed. Historical timelone on the invention of the microscope:

1590 - Janssen Brothers construct first compound microscope.

1660's - Antoni von Leeuwenhoek (Dutch) credited with inventing the microscope; observed tiny living organisms.

1665 - Robert Hooke (English) views non-living samples, coins the term "cells" from looking at cork specimens.

The Hierarchal Biology Relationship:

Molecule, Organells, Cell, Tissues, Organ, Organ Systems, Multi-cellular organism.

In multi-cellular organisms, cells are usually divided into tissues, groups of similar cells forming a functional unit.

[edit] State that a virus is a non-cellular structure consisting of DNA or RNA surrounded by a protein coat.

They are not cells, but are very small simple particles consisting of some DNA or RNA wrapped up in a protein coat. They use the same genetic material as living organisms and can evolve through natural selection. However, they require a host cell in order to survive. Therefore, they are not considered to be living organisms and are not named or classified in the same way.

[edit] Explain three advantages of using light microscopes.

Light microscopes:

1. Display colour instead of monochrome (black and white) images.
2. Provide a large field of view.
3. Facilitate preparation of sample material.
4. Allow for the examination of living material and the observation of movement.
5. Cheaper.
6. Easier to use.

[edit] Outline the advantages of using electron microscopes.

Electron microscropes:

• Provide images of higher resolution and magnification than light microscopes.

• Resolution refers to the ability to distinguish two objects as seperate entities.
• Magnification refers to the ability to increase the size of a viewed objects.

Scanning Electron Microscopes (SEM) provide images of the specimen's surface while Transmission Electron Microscopes (TEM) provide images of a sample's interior. The resolution of an SEM is approximately half that of a TEM.

[edit] Define organelle.

An organelle is one of several formed bodies with a specialized function, suspended in the cytoplasm and found in eukaryotic cells.

[edit] Compare the relative sizes of molecules, cell membrane thickness, viruses, bacteria, organelles and cells, using appropriate SI units.

1. Molecules (1 nm)
2. Cell membrane thickness (10 nm)
3. Viruses (100 nm)
4. Bacteria (1 µm)
5. Organelles (<10 µm)
6. Most cells (<100 µm)

Note: All objects are three-dimensional. These dimensions are a result of cross-section analysis.

[edit] Calculate linear magnification of drawings.

Drawings should show cells and cell ultrastructure.

Include:

A scale bar: |------| = 1 µm

Magnification: ×250

To calculate magnification:

Magnification = Measured Size of Diagram ÷ Actual Size of Object

[edit] Explain the importance of the surface area to volume ratio as a factor limiting cell size.

The rate of metabolism of a cell is a function of its mass:volume ratio.

The rate of exchange of materials (nutrients/waste) and energy (heat) is a function of its surface area.

Thus: As a cell grows in size (volume), the distance increases between the cytoplasm at the center of the cell and the cell membrane. The rate of chemical exchange with the surrounding environment may hence become too low to maintain the cell.

[edit] State that unicellular organisms carry out all the functions of life.

Unicellular organisms carry out all the functions of life. (Metabolism, response, homeostatis, growth, reproduction, nutrition.)

[edit] State that all cells are formed from other cells.

All cells only arise from pre-existing cells, cells are formed by division.

[edit] Explain that cells in multicellular organisms differentiate to carry out specialized functions by expressing some of their genes but not others.

- Cellular Differentiation: is the development of cells in specific ways.

- Hormones, cell to cell signals, and chemicals determine how a cell develops.

- Cells in multicellular organisms differentiate to become specialized.

- Each cell is specialized for one particular function.

Ex. nerve cells transmit messages

- Group of differentiated cells form a tissue

- Cells contain nucleus, chromosomes, DNA, divide into genes

- All cells have all genes and could develop in any way but not all are turned on – some are switched on.

Ex. cells in your toes have information on how to make pigment for your eye color but this gene is turned off.

[edit] Define tissue, organ and organ system.

• Tissue: An integrated group of cells that share stucture and function.
• Organ: A combination of two or more tissues which function as an integrated unit, performing one or more specific functions in an organism.
• Organ system: A group of organs that specialize in a certain function together.

[edit] Prokaryotic Cells

[edit] Draw a generalized prokaryotic cell as seen in electron micrographs.

[edit] State one function for each of the following: cell wall, plasma membrane, cytoplasm, ribosomes and naked DNA.

Cell Wall - Maintains cell shape, provides physical protection, and prevents cell from bursting in a hypotonic environment. In contrast from Eukaryotic cell walls, usually made of cellulose or chitin, cell walls in prokaryotes [bacterial cells] contain peptidoglycan; a network of modified-sugar polymers cross-linked by short polypeptides.

Plasma Membrane – separates the content of the cell from its surroundings, regulates the passage of material

Cytoplasm – supports the organelles, and also contains important chemicals for the cell

Ribosomes – contributes to the manufacture of substances important to the cell function e. Protein Synthesis

Naked DNA – DNA (deoxyribonucleic acid) that is not in a nucleus

[edit] State that prokaryotes show a wide range of metabolic activity including fermentation, photosynthesis and nitrogen fixation.

• Photosynthesis: blue-green bacteria make their own food by photosynthesis.

• Nitrogen fixation: nitrogen-fixing bacteria convert nitrogen from the air into nitrogen compounds.

• Fermentation: many bacteria absorb organic substances, convert them into other organic substances and release them.

[edit] Eukaryotic Cells

[edit] Draw a diagram to show the ultrastructure of a generalized animal cell as seen in electron micrographs.

[1]

[edit] State one function of each of these organelles: ribosomes, rough endoplasmic reticulum, lysosomes, Golgi apparatus, mitochondrion and nucleus.

Ribosomes – create proteins

Rough Endoplasmic Reticulum - has ribosomes attached; material are transported through these canals to different parts of the cell

Lysosomes – breaks down food and digest waste and worn out cell parts

Golgi Apparatus – packages useful material and secrete them to the outside of the cell for use else where in the organism

Mitochondrion – transform energy for the cell

Nucleus – brain of the cell; contains DNA and is the control center of the cell

[edit] Compare prokaryotic and eukaryotic cells.

Prokaryotic cells

-Genetic material is a naked loop of DNA located in the cytoplasm, in a region called the nucleoid.

-Mitochondria is not present: the mesosome is used instead.

-Ribosomes are small, about 70 Svedburg units.

-Few or no membrane-bound organelles are present.

Most importantly, Prokaryotes have no nucleus present whereas Eukaryotic cells have a nucleus present.

Eukaryotic cells

-Genetic material takes the form of chromosomes (usually 4 or more) within the nucleus.

-Mitochondria is always present.

-Ribosomes are larger than in Prokaryotic cells, about 80 Svedburg units.

-Most organelles are membrane-bound.

[edit] Describe three differences between plant and animal cells.

Animal cell

-Glycogen is used for carbohydrate storage.

-Shape is flexible, but is usually rounded.

- chloroplasts and cell wall not present.

- Vacuole usually NOT present.

Plant cell

-Chloroplasts, and cell wall present.

-Vacuole usually present.

-Starch is used for carbohydrate storage.

-Fixed(rectangular)shape.

[edit] State the composition and function of the plant cell wall.

Made mainly of cellulose. Supports cell and limits its volume

Draw a diagram to show the fluid mosaic model of a biological membrane.