weak Flashcards
roles of cholesterol
- Membrane Fluidity Regulation
Cholesterol inserts itself between the phospholipid molecules in the bilayer.
In Cold Temperatures:
Prevents the fatty acid tails of phospholipids from packing too closely together.
This prevents the membrane from becoming too rigid or solid, maintaining flexibility.
In High Temperatures:
Restricts excessive movement of phospholipid molecules.
This prevents the membrane from becoming too fluid and losing its structural integrity. - Membrane Stability
Cholesterol adds mechanical stability to the membrane by interacting with both hydrophilic (polar head) and hydrophobic (fatty acid tails) regions of phospholipids.
This stabilizing effect ensures the cell membrane can withstand various mechanical stresses.
roles of glycolipids
Cell Recognition:
Glycolipids serve as markers that help cells identify one another.
For example, they play a role in the immune system by helping the body recognize its own cells versus foreign invaders.
Cell Adhesion:
Glycolipids participate in cell-cell adhesion by helping cells stick together to form tissues.
Their carbohydrate chains can interact with similar molecules on neighboring cells.
Stability of the Cell Membrane:
The carbohydrate chains of glycolipids contribute to the overall stability of the membrane by forming hydrogen bonds with water molecules in the surrounding environment.
roles of glycoproteins
Cell Communication and Signaling:
Glycoproteins act as receptors for signaling molecules (e.g., hormones, neurotransmitters).
They transmit signals from outside the cell to the inside, triggering cellular responses.
Immune System Functions
Transport:
Some glycoproteins function as transport proteins (e.g., in facilitated diffusion or active transport) to move substances across the cell membrane.
Cell-Cell Recognition:
Glycoproteins help cells recognize each other, which is essential for tissue formation and immune responses.
For instance, glycoproteins on red blood cells determine blood type (e.g., ABO system).
Adhesion:
Glycoproteins mediate adhesion to other cells or the extracellular matrix, facilitating the formation and maintenance of tissues.
what are the significance of cristae in mitochondria
they increase surface area for the enzymes during ATP production
describe the role of stroma in chloroplasts
fluid in chloroplasts, contains ions and pH to regulate rate of enzyme activity during photosynthesis
what are the sizes of ribosomes in eukaryotes and prokaryotes
eukaryotes - 80S
prokaryotes - 70S
what are the roles of the smooth endoplasmic reticulum
- synthesizes lipids
- detoxifies chemicals
what is the middle lamella
pectin layer between plant cells, provides adhesion between cell and strength and flexibility to the plant tissue
what are the roles of the permanent vacuole and tonoplast
vacuole:
- maintains turgor pressure
- stores nutrients
tonoplast;
- regulates passage of nutrients
roles of microfilaments, microtubules and intermediate filaments
microfilaments:
- made of actin
- support cell shape
- used for motility
microtubules:
- made of tubulin
- 9+2 arrangement - form core structure of cilia and flagella
- used for intracellular transport
- form mitotic spindle fibres
intermediate filaments:
- made of various proteins (keratin, lamin, etc.)
- mechanical strength and structural support
what is 9+2 arrangement
- Nine pairs of microtubule doublets (outer microtubules) are arranged in a circle.
- Two central microtubules are single and run longitudinally in the middle.
differences between cilia and flagella
cilia:
- short
- numerous
- moves subtances
flagella:
- cell motility
- long
- few
role of centrioles
organize spindle fibres for cell division
what are peroxisomes
break down fatty acids
what is the extracellular matrix
- network of molecules located outside the cell membrane within the tissue
- it is used for structural support and signaling in animal cells
what are plasmodesmata
- pores/channels in the cell wall
- enable exchange of materials between adjacent plant cells
what are the cis and trans faces of the golgi apparatus
cis face - the side that faces the endoplasmic reticulum, receives vesicles that contain proteins/lipids
trans face - other side, faces cell membrane or lysosomes, ships out processed lipids/proteins
describe how the cytoskeleton contributes to cell motility
it facilitates movement through motor proteins
what is autophagy
the process by which lysosomes degrade damaged organelles
what does the basal body do in cilia/flagella
it anchors the cilia/flagella and organises microtubules
Explain why the addition of ascorbic acid prevents potato slices from browning.
- (ascorbic acid) lowers the pH, which denatures the enzyme (tyrosinase)
- tyrosine can no longer fit into the active site of tyrosinase
Explain how a protease enzyme can have the same effect as ascorbic acid
- (the protease enzyme) digests/hydrolyses the tyrosinase enzyme
- because tyrosinase is a protein AND protease digests proteins
When does independent assortment occur?
metaphase I and II
What do chloride ions and zinc ions do in relation to enzymes?
- zinc ions (Zn2+) that serve as a prosthetic group on the enzyme carbonic anhydrase in red blood cells
- chloride ions act as a cofactor for amylase
What is end product inhibition?
one of the products of a reaction acts as a reversible inhibitor for an enzyme involved in the pathway, temporarily preventing further formation of products
What are cofactors?
- coenzymes
- inorganic cofactors
- prosthetic groups
What is a transcription factor?
a protein that controls the transcription of genes so only certain parts of DNA are expressed (to allow the cell to differentiate)
Do enzymes affect structure or function?
both.
How do enzymes work?
the formation of enzyme-substrate complexes lower activation energy by putting a strain on substrate bonds, facilitating bond-breaking
What does catalase catalyse?
hydrogen peroxide into water and oxygen (intercellular)
What are the uses of stem cells?
- repairing damaged tissue (e.g. burns, retina tissue)
- researching developmental biology (e.g. growing organs, embryos)
- treating neurological conditions
Why is the induced fit model more widely accepted than the lock and key model?
- more evidence supporting it
Marking points for enzyme-related practicals
- take samples at regular time intervals
- same volumes of samples used each time
- heat with Benedict’s
- obtain filtrate use calorimeter
- calibrate calorimeter using water sample
- use red/yellow filter
- use known concentrations of substrate (credit serial dilutions)
- plot UV absorbance against conc.
Describe how the cells in a multicellular organism are organised.
- cells differentiate
- groups of similar cells form tissues
- groups of tissues form organs
- groups of organs form organ systems
- interact together
- credit named examples
Explain what homologous chromosomes are.
- one maternal one paternal
- genes are in the same loci
- centromere in the same position
- usually similar length/size
What is the function and location of squamous epithelial cells?
function:
- acts as a surface OR short diffusion pathway
location:
- alveoli
- cheek lining
- blood vessels
What is the consequence of the G1 checkpoint not working properly?
- errors in genetic info
- wrong proteins are made
- cells carry out wrong function
What does lignin do?
- impregnates cell wall and make it impermeable to water
- provides structure and support
What are the adaptations of neutrophils?
- lobed to be able to squeeze through narrow capillaries
- lysosomes to digest pathogens
- mitochondria for movement
- flexible cytoskeleton
What do erythrocytes lack?
- nucleus and all organelles involved with protein synthesis (because without nucleus how are you gonna synthesize proteins)
- no mitochondria as no need to move (carried by blood)
- lacks long lifespan because cannot undergo cell division
How does cell division in plants differ to animals?
in plants:
- cell wall plate forms
- cytokinesis starts in the middle of the cell (as opposed to animal cells where it starts from the edge)
- no centrioles
- only occurs in meristems
