bio exam Flashcards
Mitochondria
produces energy, is the site of aerobic, cellular respiration. (the process of organisms breaking down sugar into energy
Golgi apparatus
stacked flattened sacs that are the site of protein sorting and modification for use in cell or export.
Nucleus
surrounded by a double membrane, protects the genetic materials. Contains chromosomes and DNA. Nucleolus inside nucleus.
Rough Endoplasmic reticulum
a membranous chain of connected and flattened sacs which are coated in ribosomes. Modify proteins, typically located close to nucleus
Smooth Endoplasmic reticulum
a membranous chain of connected flattened sacs which are not coated with ribosomes. Responsible for production of lipids in a cell
Chloroplast
Contains chlorophyll, is where photosynthesis takes place. Contain their own DNA and ribosomes
Cell wall
A sturdy boarder outside the plasma membrane that provides strength and structure to plant, bacterial and fungal cells.
Vacuole
A membrane-bound sac that is used for water and solute storage. Small in animal, large in plants
Phospholipids
They are arranged in a phospholipid bilayer that consists of two layers of phospholipids. Phospholipids have a hydrophilic phosphate head and two hydrophobic fatty acid tails.
Channel proteins
Water filled proteins (hydrophilic) that are in the plasma membrane allowing organic ions to pass through, requires no energy.
Carrier Proteins
allow large molecules to move across the plasma membrane via simple diffusion into the cel
What happens to cholesterol at high and low temperatures
At high temps, cholesterol keeps phospholipids together. At low temps, cholesterol disrupts the fatty acid tails, stopping phospholipids from becoming a solid boundary
Cholesterol
A lipid steroid that is located between the fatty acid tails, regulates the fluidity of the membrane.
Simple diffusion
Molecules move across the plasma membrane, that doesn’t require energy so no assistance is needed
Facilitated diffusion
a type of passive transport where molecules move through a phospholipid bilayer with the aid of a protein channel or a carrier protein.
Osmosis
The passive transport of solvents through a semi-permeable membrane from a region of high solute to low. (high solute = low solvent, high solvent = low solute)
Active transport
Requires energy, uses protein pumps to move ions against the concentration gradient - high to low concentration.
exocytosis
Contents of a vesicle are released from a cell. 3 steps:
1) Vesicular transport – a vesicle containing secretory products is transported to the plasma membrane
2) Fusion – the membranes of the vesicle and cell fuse
3) Release – the secretory products are released from the vesicle and out of the cell.
endocytosis
Transports molecules into the cell. There are 3 steps:
1) Fold – the plasma membrane folds inwards to form a cavity that fills with extracellular fluid and the target molecules.
2) Trap – the plasma membrane continues folding back on itself until the two ends of the membrane meet and fuse. This traps the target molecules inside the vesicle.
3) Bud – the vesicle pinches off from the membrane. It can then be transported to the appropriate cellular location or fused with a lysosome for digestion.
Bulk transport
the movement of groups of molecules across the plasma membrane using vesicles, comes in two forms: exocytosis and endocytosis.
Surface Area to Volume ratio
Higher SA:V = more effective transport of substances in and out of cells. Higher V:SA = less effect transport
Surface Area formula
Face A = l x w
Face B = l x h
Face C = h x w
Multiply each face area by 2 and add all together to get surface area
Binary Fission
During binary fission the cell duplicates its genetic material (DNA) and divides into two parts, with each new organism receiving one copy of DNA.
G1
The cell grows and increases the volume of both protein and organelles
S
The cell copies its chromosome (DNA) into two sister chromatids (DNA replication)
G2
Further cell growth and organisation of cellular content in preparation of Mitosis
M
separation of sister chromatids and the formation of two new nuclei
G0
Cells that are not required to replicate rest in the G0 phase
Prophase
Chromosomes (DNA) replicate into centromeres. The nucleus almost fully dissolves. The centriole migrates to the end of the cell and spindle fibres form.
Metaphase
The nucleus fully dissolves, spindle fibres attach to centrosomes, aligning them at the centre of the cell
Anaphase
Mitotic spindle fibres pull the centrosomes to opposite poles, The cell membrane begins to pinch at the centre
Telophase
Mitotic spindle fibres disappear, nuclear membranes form around the separated chromosomes
DNA replication in S phase
the cell replicates its DNA turning one chromosome into two
genetically identical sister chromatids
Helix
adenine - thymine, cytosine - guanine (A-T, C-G)
Chromatin
chromosomes (DNA and proteins) that have been unwound and loosely packed during interphase
Condensed chromosomes
G2 checkpoint
The G2 checkpoint ensures that DNA has replicated properly in the S phase, and that the cell has enough resources for mitosis.
G1 checkpoint
Ensures cell has grown to correct size and has synthesised enough protein for DNA replication. Checks if DNA has been damaged and if there is enough nutrients and oxygen (inspects for DNA damage)
Metaphase chechpoint
confirms that spindle fibres have correctly attached to the centromeres of chromosomes.
Apoptosis: Intrinsic (internal)
Cell stress identified by mitochondria. When internal components of the cell (such as DNA) are damaged mitochondria detect this damage and release cytochrome c into the cytosol, which activates caspases, initiating apoptosis.
Apoptosis: Extrinsic (external)
death receptors on the outside of the cell recognise death signalling molecules. When these molecules bind to a death receptor , caspases are activated, initiating apoptosis
Apoptosis: Consequence of too much
If the rate of apoptosis is too high, killing healthy cells, neurological disorders may develop.
Apoptosis: Consequence of too little
If the rate of apoptosis is too low, allowing cells to replicate to quickly, tumours will develop.
Totipotent
can become any type of cell, including placenta or umbilical
Pluripotent
can become any type of embryonic cell (cannot become umbilical or placenta)
Multipotent
Can become certain cell types:
Ectoderm - skin cell, nerve cell
Mesoderm - skeletal cell, muscle cell, blood cell
Endoderm - stomach cell, liver
Ogliopotent
Can create closely related cells
Unipotent
Can only produce one type of cell
Stem Cells: Embryonic
a pluripotent stem cell present during the early stages of human development
Stem Cells: Adult
stem cells that can differentiate into a limited number of specialised cell types belonging to a specific tissue or organ
Structure and function of: Xylem
Tubular with hard-walled cells. Transport water and dissolved minerals from roots to the stem and leaves. Unidirectional (up the stem)
Structure and function of: Phloem
Tubular with soft-walled cells. Transports food and nutrients from leaves to storage organs and growing parts of the plant. Bidirectional (up and down)
Structure and function of: Stomata (guard cells)
Tiny pores that let gasses and water in and out of the leaf. The pore is called and stoma, and has guard cells on either side. (too much water = stomata expands) (not enough water = stomata contracts)
Structure and function of: Process of transpiration
The continuous flow of water through a plant is known as the transpiration stream. It is driven by the evaporation of water from leaves. The underside of a leaf is covered in thousands of tiny pores, called stomata. As water evaporates out, the liquid inside becomes more concentrated. This draws water in by osmosis.
Structure and function of: Process of translocation
Transport of organic solutes (phloem sap) around the plant from
the leaves. Actively pumped into companion cells. Flow involves a pressure gradient and involves energy. Increased sugar brings in water
Purpose of homeostasis
Homeostatic mechanisms produce a relatively stable internal environment by maintaining key variables (temp, blood glucose, water, ions, blood pressure, ions, pH of blood etc)within narrow limits
Role of hormones in homeostasis
essentially tell cells what to do, hormones travel through the blood and can change the behaviour of target cells
Negative feedback model: Stimulus
An event or molecule that can initiate a response
Negative feedback model: Receptor
A structure that detects a signal or external change, usually a protein
Negative feedback model: Control centre
an organ that processes and controls the response to the stimulus (aka central nervous system)
Negative feedback model: Effector
What the control centre does to correct the stimulus issue and return body to original condition (homeostasis)
Negative feedback model: Response
the effector initiates the response to the stimulus. The response is any change in the function of a target cell, organ, or organism after stimulation from an initial signal.
Homeostatic regulation: Blood glucose increase
1) Blood glucose levels increase
2) Receptors on the pancreas detect this change and it releases insulin
3) Liver cells convert glucose into glycogen
4) Blood glucose levels reduce. Insulin secretion stops
Homeostatic regulation: Blood glucose decrease
1) Blood glucose levels decrease
2) Receptors on the pancreas detect this change and it releases glucogen
3) Liver cells convert glycogen into glucose
4) Blood glucose levels increase. Glucogen secretion stops
Homeostatic regulation: Water balance
If the extracellular fluid around a cell has a high solute concentration then water will rush out of the cell via osmosis – when this happens a cell is said to be crenate, and can’t function normally. Conversely, if the extracellular fluid has a low solute concentration, then water will rush into the cell, causing it to swell and potentially even burst
Osmoregulation
More water to extracellular fluid = osmolality will decrease as the concentration of solutes will be lower. (The extracellular fluid is essentially being diluted)
Water removed from extracellular fluid = osmolality will increase as concentration of solutes will be higher
