2.5 Biological Membranes Flashcards
Role of the phospholipid.
Form a partially permeable barrier to substances that separate organelle interiors from cytoplasm or cytoplasm from extra cellular environments.
Role of proteins in fluid mosaic model?
Channel and carrier proteins
Role of glycoproteins and glycolipids
Form the glycocalx which acts as a material that binds together.
Role of cholesterol in fluid mosaic model
Decrease the fluidity of membrane and increase mechanical stability.
Is a phosphate head hydrophilic or hydrophobic?
Hydrophilic
Is a fatty acid tail hydrophobic or hydrophilic?
Hydrophobic
What’s the difference between simple and facilitated diffusion?
Simple diffusion is along the direction of the conc gradient whereas facilitated is both.
In what solutions can facilitated diffusion occur?
Water or charged ions
In what solution can simple diffusion occur?
Lipids (oestrogen) Non polar (gas)
What is osmosis?
Movement of water molecules from a high to low water potential across a partially permeable membrane
What is water potential?
The tendency of water molecules to diffuse to another region
What is water potential measured in?
kPa water=0kPa
What does having a low water potential mean?
There is a low tendency of water to diffuse elsewhere.
What does hypertonic mean?
environment outside of cell has a higher conc than in the cell itself.
What does isotonic mean?
Concentration is equal inside and outside the cell.
What does hypotonic mean?
Conc outside of cell is lower than inside the cell.
What are the hypertonic affects?
Cremated or plasmolysed cells lack water which means that soluble substances can’t take part in chemical reactions.
WhT are the hypotonic effects?
Animal cells will undergo lysis and die. Plant cells will become turgid as their vacuoles fill with water
Explain the steps of co transport.
- Na+ actively transported from intestinal epithelial cells to the blood.
- This decreases the Na+ conc at the cytoplasm.
- Na+ move by facilitated diffusion from intestinal lumen into cells.
- Glucose is co transported with Na+ into intestinal epithelial cells.
- This increases glucose conc in cell. It will go out of the cell to the blood by facilitated diffusion
Name the factors affecting membranes?
Temp: phospholipid bilayer melts
Solvents: dissolve phospholipid bilayer
Temp: proteins will denature which decreases strength of membrane.
What is the interphase in the cell cycle?
Preparation
What is mitosis in the cell cycle?
Actual division
What is cytokinesis in the cell cycle?
End of division
What is G1 in the interphase?
Protein synthesis
What is S in the interphase?
DNA replication
What is G2 in the interphase?
New organelles produced
Name the order of the interphase
G1
S
G2
What are the checkpoints in the interphase?
They prevent uncontrolled division and repair damaged DNA aswell as maintain undirectionalitity.
Stages of mitosis?
Chromosome condensing
Chromosome separation
Nuclear division
Role of mitosis?
Growth
Tissue repair
Asexual reproduction
What is it called when a chromosome is attached to a copy of itself.
Sister chromatids
What are chromatically joined together by?
Centomere
Name the 5 stages of the cell cycle?
Interphase Prophase Metaphase Anaphase Telophase
What happens in the prophase?
Nuclear envelope breaks down
Chromosomes condense
Centrioles replicate and form spindle fibres
What happens in the metaphase?
Spindle fibres attach to centromere of chromosome
What happens in the anaphase?
Spindle fibres contract
Centromere splits
Sister chromatids are pulled apart
What happens in the telophase?
2nuclear envelopes from around the set of chromosomes
Why happens to the cytoplasm during cytokinesis?
It splits forming 2 identical daughter cells
