Cell Biology Exam 1

Cell Biology

• Cells are the fundamental units of life.

• Study of cells and their structure, function, and behavior.

Cell Theory

• All organisms consist of one or more cells.

• Cell is the basic unit of structure for all organisms.

• All cells come from pre-existing cells.

Is Viruses living and why?

• No, because it can’t perform the same functions as living things like metabolism or generating its own energy.

• Requires a host cell to live and reproduce.

Are all cells the same in appearance and function?

No, cells can vary in appearance and function.

Are all cells enclosed by a membrane, and if so, what is its function?

Yes, every cell is enclosed by a membrane that regulates passage of materials between the cell and the environment.

Do living cells have a similar basic chemistry?

Yes, all living cells have:

• Nucleotides, which are the building blocks for DNA and RNA

• Amino acids, which are used for building proteins

• DNA, which carries genetic information

• The same processes of replication, transcription, and translation

Does all present-day cells come from the same ancestral cell?

Yes, all present-day cells have apparently evolved from the same ancestral cell.

If all cells came from the same ancestral cell, how is there evolution?

Genetic changes and selection are the basis of evolution.

What does genes provide?

Provides instruction for cell form, function, and complex behavior.

In one organism, do all the cells have the same or different genomes?

Within the same organism, all the cells usually have the same genome.

• note: genome is the complete set of an organism’s DNA, including coded and non-coded areas.

Does differentiated cells express the same or different genes?

Differentiated cells does express different genes.

• note: genes is a specific set of DNA that codes for a trait.

What is magnification?

Enlargement of physical appearances of something

What is resolution?

The ability to distinguish two separate points

What length unit should be used to measure the size of a cell?

micrometers (μm)

Size of cells and their parts

Which one of the following statements about the cell is NOT true?

• A: The cell is the basic unit of structure for all organisms.

• B: The different tissues and organs in multicellular organisms arise from differences in their genomes.

• C: Every cell is enclosed by a cell membrane.

• D: Living cells all have a similar basic chemistry.

• E: All cells arise from pre-existing cells.

Answer: B

• It’s due to the differential expression of genes.

Light Microscope

Resolution: 0.2 μm

• Allow examination of cells and some of their content

What is the requirement of samples for light microscopes?

• Samples can be dead or alive

• Samples must be relatively transparent and thin (can be sectioned if too thick)

• Samples must contain contrast from either staining (dead) or use of different optics (alive)

What are the optics for Light Microscopy?

• (A) Bright-field optics: has low contrast and usually needs staining.

• (B) Phase-contrast optics: used for observing living cells and has halo effects.

• (C) Interference-contrast optics: has 3D-like image, no halo effects, and enhanced edge contrast. Also relatively expensive.

Fluorescence microscopy

• Resolution: 0.2 μm

• Cellular structures are labeled with fluorescent molecules (dyes, antibodies)

• The fluorescent molecules are excited, then emit light of a different wavelength

Confocal Microscopy

• Specialized type of fluorescence microscopy

• Resolution: 0.2 μm

• Clear optical section is created by focusing laser beam on individual points.

• Generates 3D image using a series of optical sections.

• Ideal for live and thicker samples.

Super-resolution microscopy

• Resolution: 10-20 nm (note: smaller than μm)

• Allows insights into intracellular processes at a molecular level

• Created by manipulating light in sophisticated ways or using computer methods to extract more information from the data

Electron Microscopy

• a beam of electrons is transmitted through the specimen

• was a major breakthrough for cell biology

• limit of resolution is around 100 times better than light microscopes

• magnification is much higher than light microscopes (up to 100,000 times)

Transmission Electron Microscopy (TEM)

• Resolution: 1 nm (smaller than μm)

• Electrons and magnets are used to create and focus the image

• Dead samples are sectioned and stained with electron dense materials to create contrast.

Scanning Electron Microscopy

• Resolution: 2-30 nm

• Uses dead samples that is heavy metal-coated

• Scans with an electron beam

• The pattern of electron scatter creates a 3D-like image

Which type of microscopy has the highest resolution?

Transmission electron microscopy

Which type of microscopy would you most likely chose if you want to analyze ultrastructural detail of chloroplasts?

A. Brightfield

B. Confocal fluorescence

C. Scanning EM

D. Transmission EM

D. Transmission EM

What is the family tree of life based on?

Based on genome sequence comparisons

What does the length of the branches represent on the family tree of life?

The lengths pf the branches are proportional to the differences among genomes.

Which of the following group is more recent and less diverse compared to the other two groups?

A. Eukaryotes

B. Bacteria

C. Archaea

A. Eukaryotes

Is Eukaryotes more closely related to Bacteria or Archaea?

Archaea

What are prokaryotes?

• Single-celled organisms

• Arose 3.5-3.8 billion years ago

• Lack nuclei and other membrane bound organelles

• Has 2 types: Bacteria and Archaea

• Prokaryotes: pro (before) karyon (kernel, or nucleus)

What are Eukaryotes?

• Contains nuclei and other membrane bound organelles

• Found in single or multicellular organisms

• Evolved 1.5 billion years ago

• Eukaryote: eu (true) karyon (kernel, or nucleus)

What are the differences between Animal and Plant cell?

Plant cells has:

• Cell wall

• Plastids

• Plasmodesmata

• Vacuoles (large)

Animal cells has:

• Centrioles

What are Organelles?

Specialized structures within a cell that performs specific functions

• True organelles are surrounded by at least one membrane.

What is a nucleus?

• Contains most of the cell’s genetic info (DNA)

• the site of replication and storage of chromosomes

• surrounded by two concentric membranes (nuclear envelope)

How can molecules pass in and out of the nucleus?

Nuclear pores within the nucleus envelope allow molecules to pass in and out of the