Pack 1 – Organelles, magnification and cell membranes Flashcards
(57 cards)
1
Q
Nucleus structure:
A
Largest cell organelle, enclosed by a double membrane which is perforated by pores
2
Q
Nucleus functions:
A
- Controls all cell activities
- Contains chromosomes (genetic information
3
Q
Nucleolus structure:
A
A dense body within the nucleus
4
Q
Nucleolus function:
A
Makes RNA and assembles ribosomes
5
Q
Mitochondria structure:
A
- Double membrane structure, with folded inner membrane (folds are called cristae)
- Fluid inside is called matrix, and contains DNA, proteins, lipids and respiratory enzymes
6
Q
A
7
Q
Mitochondria function:
A
Carries out aerobic respiration to make ATP (energy)
8
Q
rER structure:
A
- A system of interconnected membrane-bound, flattened sacs called cisternae
- Ribosomes are attached to the outer surface
9
Q
rER functions:
A
- Ribosomes make proteins (protein synthesis)
- Proteins fold into their 3D shape as they are transported through this organelle
- Proteins are packaged into vesicles for transport
10
Q
sER structure:
A
- A system of interconnected membrane-bound, flattened sacs called cisternae
- No ribosomes are attached
11
Q
sER function:
A
Makes lipids and steroids
12
Q
Golgi apparatus function:
A
Modifies proteins and lipids, and packages them into vesicles for transport
13
Q
Golgi apparatus structure:
A
Stacks of flattened, curved, membrane-bound sacs called cisternae
14
Q
Vesicles structure:
A
Simple round sacs surrounded by a single membrane, formed from the Golgi apparatus
15
Q
Lysosomes structure:
A
- A type of vesicle that contains digestive enzymes
- A spherical sac bound by a single membrane.
16
Q
Vesicles function:
A
They may hold particular chemicals or may carry proteins to the plasma membrane to be released outside the cell
17
Q
Lysosomes functions:
A
- Digest worn out cell structures using digestive enzymes
- Can destroy and break down cells (apoptosis).
18
Q
Ribosomes structure:
A
- Formed of two subunits
- Made of protein and rRNA
- May be free in cytoplasm or attached to the rER.
19
Q
Ribosomes function:
A
Protein synthesis
20
Q
Centrosome structure:
A
- An area of the cytoplasm that contains centrioles
- Centrioles are hollow cylinders made up of a ring of nine microtubules
- Animal cells have one pair
21
Q
1 mm = ?µm
A
1000µm
22
Q
1µm = ?nm
A
1000nm
23
Q
Magnification formula:
A
Magnification = Size of image/Actual size of object
24
Q
Basic structure of a cell surface membrane:
A
Two layers of phospholipids
25
Phospholipid structure:
Two fatty acids bonded to glycerol with ester bonds, and a phosphate group. The phosphate head of the molecule is polar or hydrophilic (water-attracting). The fatty acid tails are non-polar or hydrophobic (water-repelling)
26
How do fatty acid tails of phospholipids arrange themselves when added to water?
So that there is no contact between the hydrophobic tails and the water
27
How do phosphate heads of phospholipids arrange themselves when added to water?
So that there is contact between the hydrophilic tails and the water
28
How does bilayer arrangement occur?
Due to the aqueous (watery) environment on both sides of the membrane (cytoplasm inside, tissue fluid outside)
29
What does a lipid bilayer tend to do?
It will tend to close on itself so that there are no ends with exposed fatty acid chains, thus forming compartments as happens around and within cells
30
What else is within a cell surface membrane as well as a phospholipid bilayer?
- Proteins
- Cholesterol
- Glycoproteins
- Glycolipids
31
Fluid mosaic model of mebrane structure:
It is thought that some of the proteins are fixed within the membrane, but others are not and can move around in the fluid phospholipid bilayer
32
Why is it called fluid in the fluid mosaic model?
The phospholipids move slightly from side to side (in the plane of the membrane). Many proteins move through the ‘sea’ of phospholipids (note: some proteins are fixed in place)
33
Why is it mosaic in the fluid mosaic model?
A random arrangement of proteins, phospholipids, cholesterol (different sizes and shapes) within membrane
34
Cholesterol
- Disturbs the close packing of the phospholipids
- Regulates membrane fluidity
- Important for membrane stability
35
Glycolipids
Act as surface receptors and stabilise the membrane structure
36
Glycoproteins
- Cellular recognition, to identify cells as “self”
- Role in signalling - act as receptors for hormones & neurotransmitters - Stabilise membrane structure by forming hydrogen bonds with water
37
Protein channels
- Completely span the bilayer
- They control the entry & removal of specific molecules from the cell
38
Proteins
- Sit on top, within or below the bilayer
- They have a role in cell signalling pathways and help to stabilise the membrane structure
39
Passive membrane transport processes:
- Simple diffusion
- Facilitated diffusion
- Osmosis
40
What is a passive process
Doesn't require energy (ATP)
41
What is an active process
Does require energy (ATP)
42
Active membrane transport processes:
- Active transport
- Endocytosis
- Exocytosis
43
Simple diffusion
- Small uncharged molecules, or hydrophobic molecules (lipid soluble / non-polar) can cross the lipid bilayer by simple diffusion
- They can diffuse between the phospholipids
44
Facilitated diffusion
- Channel proteins span the membrane
- There is a specific protein for each molecule or ion that needs to be transported
- Gated channel proteins can be opened or closed depending on the presence or absence of a signal
- Carrier proteins – the molecule or ion binds to onto a specific site on the protein
- The carrier protein changes shape and the molecule crosses the membrane
45
Osmosis
The net movement of water molecules from a solution with a higher concentration of free water molecules to a solution with a lower concentration of free water molecules through a partially permeable membrane.
46
Active transport
The movement of molecules or ions across a membrane against a concentration gradient, using energy (ATP) to drive protein pumps in the membrane
47
Exocytosis
The movement of substances out of the cell
48
Exocytosis process:
The molecules to be transported out of the cell is first enclosed in a vesicle, then the vesicle fuses with the membrane and releases the contents outside the cell
48
Endocytosis
The movement of substances into a cell
49
Endocytosis process:
The membrane bulges inwards, wraps around the particle and pinches off to form a vesicle inside the cell
50
Example of signalling molecules:
- Hormones (such as insulin and ADH), neurotransmitters (such as dopamine) and cytokines (involved in immune response)
- These interact with cell membranes in various ways, such as binding to a receptor on the cell membrane or crossing the cell membrane
51
Steroid hormones
- Are made from lipids
- They can pass through the cell membrane and bind directly to a receptor molecule in the cytoplasm
52
Peptide hormones
- Are polar molecules so they cannot pass through the cell membrane
- They bind to a cell surface receptor
53
What allows cells to recognise each other?
Glycoproteins and glycolipids
54
Why is it important cells recognise each other?
For cellular signalling processes that influence tissue and organ formation during early development
55
Why is it important cells recognise each other in relation to immune response
“Self”-versus-“non-self” distinction of the immune response
56
Example of "Self”-versus-“non-self” distinction of the immune response:
- Marker proteins on human red blood cells allow the body to recognise those cells as its own and to reject cells that have different marker proteins
- This is what determines your blood type
