A2.2 cell structure

What is the first tenet of Cell Theory?

All living organisms are made of one or more cells.

What is the second tenet of Cell Theory?

The cell is the basic unit of structure and function.

What is the third tenet of Cell Theory?

Cells arise only from pre-existing cells.

Which functions of life are present in all cells?

Metabolism, growth, response, homeostasis, nutrition, excretion, reproduction

Why is water essential to life?

It acts as a solvent and a medium for chemical reactions.

What are the steps for a temporary mount?

Specimen then drop of water/stain then cover slip at an angle to avoid bubbles.

What stain is used for animal cells?

Methylene blue. (negatively charged DNA & RNA in animal cells are attracted to the positively charged methylene blue)

What stain is used for plant cells?

Iodine.

What is the correct sequence for focusing a microscope?

Always start on low power then use coarse focus then use fine focus.

How is cell size measured?

Using an eyepiece graticule calibrated with a stage micrometer.

What is the formula for Magnification?

Image divided by Actual size.

What is the formula for Actual size?

Image divided by Magnification.

What is a common mistake in microscopy?

Forgetting to recalibrate the graticule at each magnification.

What characterizes light microscopy?

Uses light and has lower resolution.

What is the purpose of fluorescent stains and immunofluorescence?

To highlight proteins or organelle locations.

What does a Transmission Electron Microscope (TEM) show?

Internal ultrastructure (like an X-ray scan inside the cell).

What does a Scanning Electron Microscope (SEM) show?

3D surfaces (like a 3D photo of the surface).

What is Cryo-EM used for?

Imaging proteins at atomic detail.

What three structures are common to cells in all living organisms?

Plasma membrane, cytoplasm, DNA

What is the function of the plasma membrane?

Selective barrier and communication.

What is the function of the cytoplasm?

Site of metabolism.

What is the function of DNA?

Hereditary material for proteins and RNAs.

What is the cell wall of prokaryotic cells made of?

Peptidoglycan.

What are the features of prokaryotic DNA?

Found in a nucleoid and it is naked.

What type of ribosomes are found in prokaryotes?

70S ribosomes.

What extra structures might prokaryotes have?

Pili, flagella, plasmids

What is the unicellular organism Paramecium?

A heterotroph that uses cilia for movement and contractile vacuoles for osmoregulation.

What is the unicellular organism Chlamydomonas?

An autotroph that uses photosynthesis

What mnemonic is used for the processes of life?

MR H GREN (Metabolism, Reproduction, Homeostasis, Growth, Response, Excretion, Nutrition.

What are the characteristics of a Eukaryotic nucleus?

Contains linear DNA and has pores.

What type of ribosomes are in Eukaryotes?

80S ribosomes (free or on rER).

What is the function of the rough Endoplasmic Reticulum (rER)?

Protein synthesis.

What is the function of the smooth Endoplasmic Reticulum (sER)?

Lipid synthesis and detoxification.

What is the function of the Golgi Body?

Modifies and packages proteins into vesicles.

What is the function of Mitochondria?

ATP production, contain their own DNA and 70S ribosomes.

What are unique features of plant/algal cells?

Chloroplasts, cellulose walls and large vacuoles

How should membrane-bound organelles always be stated?

As a eukaryotic feature.

Contrast cell walls in Animal, plant and fungal cell

Animal: absent, plant: cellulose, fungal: chitin

Contrast vacuoles in animal cell vs plant cell vs fungal cell

Animal cell: small, temporary. Plant cell: large central (turgor pressure). Fungal cell: small, variable

Contrast plastids in Animal vs plant vs fungal cell

A: none, P: chloroplast + other plastids, F: none

Contrast centrioles in Anima, plant and fungi cell

A: present. P: absent, except some gametes. F:

Plant: Large central (turgor pressure)

Fungal: Small and variable.

Which eukaryotic cells have centrioles?

Animal cells (present)

What are Aseptate hyphae?

Atypical fungal cells that are multinucleated with no cross walls.

What are Skeletal muscle fibers?

Atypical cells that form a syncytium with many nuclei.

Why are Red Blood Cells (RBCs) atypical?

They are enucleated to maximize oxygen carrying capacity.

Why are Phloem sieve tube elements atypical?

They have no nucleus and rely on companion cells.

Which atypical cells are used as exceptions to cell theory?

RBCs and sieve tube elements.

How do you identify Prokaryotes in micrographs?

Small

How do you identify Plant cells in micrographs?

Cell wall

How do you identify Animal cells in micrographs?

No wall

What are the rules for drawing and annotation (EM)?

Clean lines