Three main parts of the cell
- the plasma membrane
- the cytoplasm
- the nucleus
What is an organelle?
= any number or organised or specialised structures within the living cell
Structure of the cell (10)
- Nucleus - the control centre
- Nucleolus - site of RNA transcription
- cytoplasm - gel substance organelles it in giving the cell its structure
- Mitochondria - powerhouse
- Cytoskeleton - maintains cell like structure
- chloroplast - photosynthesis occurs
- rough ER - ribosomes and protein synthesis - transporting materials
- Smooth ER - lipid and steroid hormone
- Lysosomes - acidic organelles for waste breakdown and disposal
- golgibody - proteins from ER are processed and sorted ready for moving to correct destination.
What does the cell membrane do?
= controls what goes in and out of the cell
- Phospholipid biolayer
- surrounds the cell
- semi permeable membrane (selective) -> small non polar/ uncharged molecules
- Transmembrane proteins act as Chanel’s or transporters increase permeability
- channels –> facilitated diffusion
- Transport –> FD or active
Passive vs Active
Passive = Moving DOWN concentration gradient - simple diffusion - facilitated diffusion - osmosis
Active
- Moving AGAINST concentration gradient
= requires energy
What is Diffusion
= The movement of particles from a region of high concentration to a low region of concentration
Simple Diffusion VS Facilitated Diffusion
Simple diffusion = does not require assistance - passive process - molecules can only pass in direction of gradient - only small and non-polar molecule
Facilitated Diffusion
= transmembrane protein helps solute move through lipid layer
- passive/active
- can be inhibited
- solute specific to polar or high charged e.g. glucose
and aa
What is Osmosis?
= the net movement of a solvent through a selectively membrane of high and low
- Salt sucks - salt will suck the water
Endocytosis
- things going into the cells
Exocytosis
= things going out of the cell
ISOtonic
= A:B Same osmotic pressure
HYPERtonic
= C: A/B Water INTO
HYPOtonic
= A/B:C Water OUT
What are the major uses of energy?
= Glucose and fatty acids (when not starving)
- our body produces energy by burning glucose and fatty acids
Glucose - energy source for cells e.g. brain
Fatty acids - other key source e.g. heart muscles
When starving: ketone bodies
What is ATP
= Energy molecule
- energy source for 95% of cellular activity
How is ATP replenished?
= From high energy molecules - ADP = from metabolism of nutrients - glucose - fatty acids - ketone bodies - lactate
Negative feedback system?
= maintains homeostasis
- Stimulus
- Sensor/receptor = sends input to control centre through afferent pathway
- control centre = brain generates output needed through efferent
- effector = produces response
What does mitochondria do and what advantage would extra mitochondria give to a cell?
- Mitochondria produce ATP (adenosine tri-phosphate)
- ATP provides energy for the cell at the molecular level
e. g. sodium potassium pump needs ATP to function - Extra mitochondria = more ATP
What types of cells would have high number of mitochondria?
= Numerous mitochondria are found in liver cells, kidney cells, skeletal muscle etc. Increased ATP production to meet higher demand.
Which cells would have lower numbers of mitochondria and why?
= Cells that relatively inactive have very few mitochondria because they do not have a high energy demand.
Example:
bone cells:
unchallenged lymphocyte:
Are there any cells in the body that do not contain mitochondria?
- almost every cell in the body carries mitochondria
= Red blood cells do not contain mitochondria.
Their functions are limited and are only involved in passive transport.
They survive for 120 days.
Why is the production of energy in cells called “cellular respiration”
= because it requires oxygen
What do you think would happen at the cellular level in a patient with hypoxia? What cellular processes do you think may be compromised by a lack of oxygen?
Inadequate prefusion = cell hypoxia = energy defect of ATP = lactic acid accumulation and a fall in pH = metabolic acidosis and so on
