BBS1001 Case 5 The cells inside

Case 5: The cells inside

Learning goals:

 How do prokaryotic cells look like?

Prokaryotic: Bacteria and archaea, one cell, lack nucleus and membrane bound –
organelles. Circular DNA. Divide by …….

Archea different built cell wall

 Structure

Prokaryotic cells are made out of peptidoglycan, a polymer composed of linked
carbohydrates and small proteins.

- Flagella: Whip-like structures that act as rotary motors to help bacteria
move.
- Fimbriae: Hair-like structures that are used for attachment to host cells
and other surfaces
- Pili: allow to transfer DNA text molecules to other bacteria, while others
are involved in bacterial locomotion, helping the bacterium move

Two membrane bacteria, more difficult to kill

 Different organelles and their functions

- Cytoplasm: Cytoplasm is a gel-like substance composed mainly of water
that also contains enzymes, salts, cell components, and various organic
molecules.
- Cell membrane: The cell membrane surrounds the cell's cytoplasm and
regulates the flow of substances in and out of the cell.
- Mesosome
- Plasmids: gene-carrying, circular DNA structures that are not involved in
reproduction.
- Cell wall: Provides protection, maintains shape and prevents dehydration
- Capsule: Sticky outer layer helps the cell attach to the outer environment
- Nucleoid (not membrane bound): Contain circular DNA
- Ribosomes:
 Translation: Prokaryotes lack a nucleus, so their mRNAs are
transcribed in the cytoplasm and can be translated by ribosomes
immediately.
 Lack of inner membranes, more disorganisation, takes longer, they can’t form
together.

 How do eukaryotic cells look like?

Eukaryotic: Animals, plants, fungi, and protists, they have multiple cells

 Structure

- Plasma membrane: Two-layered structure of phospholipids and proteins,
and it controls what can enter and exit the cell.

,  Phospholipid bi-layer: hydrophobic tails pointing inward and
their hydrophilic heads facing outward, they are amphipathic
Microvilli: Finger like folds in the membrane to increase the
exchange area.
 Cellular transport: Selectively permeable: maintain homeostasis
 Passive transport: Does not require energy
 Diffusion: A substance tends to move from an
area of high concentration to an area of low
concentration until its concentration becomes
equal throughout a space.
 Concentration gradient: A region of space over
which the concentration of a substance changes,
and substances will naturally move down their
gradients, from an area of higher to an area of
lower concentration
 Facilitated diffusion:
 Channels: Allow polar and charged compounds
to avoid the hydrophobic core
 Aquaporins: channel proteins that allow water
to cross
 Barriers: Shape changing, provide hydrophilic
molecules with a way to move down an existing
concentration gradient.
 Active transport: Needs energy
 Membrane potential: An electrical potential
difference across the cell membrane. Inside is
more negative than outside the cell.
 Electrochemical gradient: The combination of
concentration gradient and voltage that affects
an ion’s movement.
 Primary active transport: Uses ATP.
 Sodium-potassium pump: Moves Na+
out and K+ into cells.
1. The pump binds with 3 sodium ions in
the cell.
2. ATP gets hydrolysed and one
phosphate group from ATP is attached to
the pump, which is then said to be
phosphorylated. ADP is released as a by-
product.
3. Phosphorylation makes the pump
change shape, it opens towards the
extracellular space and releases the
three sodium ions.
4. The pump now binds with two
potassium ions. This triggers removal of
the phosphate group attached to the
pump in step 2.