Biochemistry L03 - Cell Structure and Function Flashcards Preview

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Flashcards in Biochemistry L03 - Cell Structure and Function Deck (16):

How vital is the actual amino acid sequence in proteins?

It varies. The primary structure (sequence of AA’s) is vital in determining the shape and therefore function of the protein. But it can have no effect (genetic variation within species), little effect (interspecies variation), or enormous effect (i.e. disease causing mutation).


What is a simple protein?

A protein containing only AA’s and no other chemical groups


What is a conjugated protein?

A protein containing AA’s AND other chemical components. The non-AA part is called a prosthetic group.

Examples of prosthetic groups:
- Lipoproteins (contain lipids)
- Metalloproteins (contain a specific metal, such as myoglobin which contains iron).
- Glycoproteins (contain sugar groups)


What is a denatured protein?

“Native” proteins are stabilized in 3D by secondary, tertiary and quaternary structures. If it’s conformation is altered/destroyed, the protein is denatured and won’t function normally. Denaturing does not alter the primary structure, and can sometimes be reversible.


What are some of the main functional types of proteins?

- Transport protein
- Nutrient and Storage Proteins
- Movement (motile) proteins
- Defense proteins
- Regulatory Proteins
- Structural Proteins – support cell and organ shape
- Enzymes
- Others – i.e. anti freeze proteins.


What are the main components/features of a cell membrane?

- Phospholipid bilayer with peripheral proteins (attached loosely) and integral proteins (tansmembrane proteins).
- ‘Fluid mosaic’ – lipid (and some protein) molecules can move laterally.
- Selectively Permeable. H20, O2 and CO2 cross freely, while ions and other polar molecules must move through selective pores.


What effects do saturated or unsaturated fatty acids have on the cell membrane?

Unsaturated fats kink at the double bond, and have greater fluidity. Whereas Saturated fatty acids give close packing.

Cholesterol enhances order and rigidity, and stabilizes the straight chain arrangement of saturated fatty acids.


What is the nucleus?

- Location of main genome, site of most DNA/RNA synthesis.
- It is surrounded by a double membrane – the nuclear envelope, which is continuous with the ER and is perforated by nuclear pores.
- It is selectively permeable
- Usually contains nucleoli – which is the site of rRNA synthesis and assembly of ribosomal subunits.


What is the cytoskeleton?

- It’s comprised of microtubules and microfilaments.
- It gives and maintains structure and shape of the cell, and governs its internal organisation.
- It is essential in cell division.


What are ribosomes?

- Ribosomes are the site of protein synthesis.
- They may be free in the cytosol of attach to ER
- They are NOT organelles


What is mitochondria?

- Site of energy-yielding oxidation reactions – cellular respiration.
- It has its own DNA
- Inner membrane is folded into cristae


What is the endoplasmic reticulum?

- Continuous membrane throughout cell
- Network of sacs (cisternae)
- Rough ER is where polypeptides are synthesized
- Smooth ER lacks ribosomes, and is where lipids are synthesized
- materials are shuffled from one part of cell to another
- It involves biosynthesis, packaging and secretion.


What is the golgi apparatus?

Series of flattened membranes (stacks of cisternae) involved in protein secretion & sugar linkage.


What are Lysosomes ?

- Membrane bound organelles containing hydrolytic enzymes
- They digest unwanted materials in the cytoplasm


What are peroxisomes

They are involved in the catabolism of some fatty acids, amino acids, and polyamines, reduction of reactive oxygen species - specifically hydrogen peroxide - and biosynthesis of plasmalogens


What are endosomes?

Vesicles contain endocytosed substances