Micro: Cell

What is a cell?

the smallest unit of life

What are some structures common to all cells?

cell membrane, cytoplasm, ribosome, DNA, RNA, proteins

Do all cells have membranes? Why or why not? Do viruses have membranes?

• Yes, all cells have a cell membrane because the membrane separates the inside of the cell from the outside environment and controls what enters and leaves.

• Viruses are not cells, so they do not have a cell membrane like cells do. Some viruses have a lipid envelope surrounding their capsid, but not all viruses have one.

What is diffusion? Can all molecules diffuse across a membrane? Why or why not?

• Diffusion is the movement of molecules from an area of high concentration to low concentration.

• All molecules cannot diffuse across a membrane as it is selectively permeable

What is equilibrium?

is a state where the concentrations are equal so that there is no net change of solute concentration from diffusion

How does a cell membrane affect the equilibrium of a cell? (Why do some things move across but not others?)

Cell membranes are selectively permeable, allowing certain things to diffuse. This keeps certain solutes in the cell higher than others

Describe two different ways equilibrium across a membrane can occur.

• Diffusion – solute molecules move from high → low concentration.

• Osmosis – water moves across a membrane from high → low water concentration.

Understand what happens to cells under isotonic, hypertonic and hypotonic conditions.

• Isotonic: no net movement

• Hypertonic: water moves out of the cell because it has a higher solute outside—> cell shrinks

  • Crenation: animal cells shrink

  • Plasmolysis: plant cells shrink

• Hypotonic: Water moves into the cell because it has lower solute outside —> cells can burst, swell

  • Osmotic lysis:

    • without a cell wall—> will burst

    • with cell wall—> can prevent cells from growing to the point of bursting

How do bacterial cells avoid bursting in hypotonic conditions? How do protozoan cells avoid bursting in hypotonic conditions?

• Bacterial cells have cell wall which stops the cell from growing to the point that they burst

• Protozoa have contractile vacuoles to avoid bursting by removing excess water

Why do cells have cell walls? Do all cells have them?

• Cells wall prevent osmoticlysis and provide structural support

• Not all the cells have cell walls.

• Cell that have cell wall: plants, fungi, bacteria, algae,..

How do cells without cell walls survive without them?

They can use the contractile vacuoles mechanism to remove excess water

What is the difference between a Gram-positive bacterial cell wall and a Gram-negative bacterial cell wall? Know the difference!!

• Gram(+): have thick peptidoglycan cell wall, have 1 outer membrane

• Gram (-): have thinner peptidoglycan cell wall and have 2 outermembrane

How does penicillin affect bacteria? Why does it kill cells? Which kind of bacterial cell does it affect more? Why?

Penicilin is an antibiotic that kills bacteria by inhibiting peptidoglycan formation, weakening the cell wall. This causes the cell to die by osmoticlysis.

It affects gram (+) bacteria more becasue gram (-) bacteria has an outer membrane blocking peiniclin

How do cells get nutrients inside?

through cell membrane by using simple diffusion, active transport,

Describe how transport proteins work.

they are speciific to certain compounds. Moves those compounds across the cell membrane

Understand the following terms, their similarities and differences: active transport, passive transport, diffusion, facilitated diffusion.

• Active transport: use ATP, can go against concentration gradients

• Passive transport: movement of molecules across membrane without needing energy

• Diffusion: move through phospholipid bilayer

• Facilitated diffusion: move by using transport protein

Understand exocytosis, endocytosis and phagocytosis.

• Endocytosis: cell membrane surrounds material and brings it into the cell using a vesicle.

• Exocytosis: vesicle fuses with the cell membrane and releases material out of the cell.

• Phagocytosis: a type of endocytosis where the cell takes in large particles/cells. → “cell eating”

  
  

What are the major differences between eukaryotic and prokaryotic cells?

• Eukaryote: have nucleus, mitochondrion

• Prokaryote: doesnt

What is a nucleus? What is a nucleoid? Know where these structures are found.

• Nucleus: is membrane-bound structure that contains the cell's DNA.

• Nucleoid: region where DNA is concentrated near the center of a prokaryotic cell. Not surrounded by a membrane

What is a circular chromosome? How is this different from a linear chromosome? Which kinds of organisms have each kind of chromosome?

• Circular chromosome: DNA forms a closed loop found in bacteria and archaea

• Linear chromosome: DNA has 2 ends found in eukaryote

 What is a plasmid?

is a small pieces of DNA, and are extrachromosomal DNA . Plasmids can be copied and transferred to adjacent bacterial cells through conjugation

What are ribosomes? Where are they found in eukaryotes? In prokaryotes?

Ribosomes are structures that make proteins.

• Eukaryotes: free in the cytoplasm or attached to the rough ER.

• Prokaryotes: free in the cytoplasm.

What are mitochondria? What takes place there? What kinds of cells have them?

Mitochondria are organelles involved in cellular respiration and ATP production.

Found in eukaryote

What are chloroplasts? What kinds of cells have them?

Chloroplasts are organelles where photosynthesis take place

They are found in plants and algae, and some protozoa.

What is the different morphologies and arrangements of bacterial cells. Why do bacilli never form clusters? (Remember, there are no Staphylobacillus)

• Morphology is the shape of an individual bacterial cells while the arrangement is how they organized

• Bacillus only can divide in 1 plane which make it can nto form a cluster as a result while the coccus can divide in many planes

What are flagella? What is their function?

is a lon structure that provide motility for bacteria

What are fimbriae? What is their function?

is a short, hair-like structures that help the bacterial cells attach to the surface of the other cells

What are capsules? What is the glycocalyx? What are they made of? What is their function?

• Glycocalyx: are carbohydrates surrounding cells and it can be made of polysaccharide. If it organized, it can called a capsule

• Capsule: a well-organized, firmly attached type of glycocalyx.

• Functions:

  • Evade immune system (slippery)

  • Camouflage

  • Attachment to surfaces:

What are endospores? What is their function? Be able to name at least one kind of bacterium that can make endospores, and one that cannot.

• Endospores are highly resistant structures formed by some bacteria to survive harsh/unfavorable conditions.

• Found in Bacillus and Clostridium

• Cant found in E.coli