Cell structure Flashcards
Nuclear envelope structure and function
Double membrane that surrounds nucleus.
Outer membrane continuous with EM and has ribosomes on surface. Controls entry and exit of materials in nucleus.
Nuclear pores structure and function
Allow passage of large molecules such as mRNA.
Nucleolus structure and function
Spherical region within nucleoplasm, manufactures rRNA and assembles ribosomes (can be more than 1).
Function of nucleus
Control centre of the cell through production of mRNA and tRNA and protein synthesis.
Retain genetic material of cell in DNA within chromosomes.
Manufacture rRNA and ribsomes.
Mitochondria structure and function
Double membrane around organelle.
Inner membrane folded to form cristae - provide large surface are for attachment of enzymes and proteins used in respiration.
Matrix of protein, lipids, ribosomes and DNA allow production of own proteins in mitochondria along with enzymes.
Site of aerobic respiration and responsible for production of ATP.
Present in cells where active transport happens and muscle.
Chloroplast structure and function
Chloroplast envelope - highly selective double plasma membrane.
Grana, made up of thylakoids, contains chlorophyll and is where light absorption happens. Grana have high surface area for attachment of chlorophyll.
Stroma is matrix that contains enzymes to make sugars in light independent phase.
Contain DNA and ribosomes.
Present in leaf cells.
Rough ER structure and function
Ribosomes present.
Provides large SA for synthesis of proteins and glycoproteins.
Provides pathway for transport of materials such as proteins throughout cell.
Secretory cells have lots of ER.
Smooth ER structure and function
Synthesises, stores and transports lipids and carbohydrates.
Secretory cells have lots of ER.
Cells that store carbo and lipids also have lots of ER (liver).
Golgi apparatus structure and function
Releases substances out of cell through golgi vesicles after passed through ER.
Adds carbohydrates to proteins to form glycoproteins.
Produces secretory enzymes.
Secretes carbohydrates (for cell walls in plants).
Transport, modify and form lipids.
Form lysosomes.
Apparent in secretory cells.
Lysosome structure and function
Contain lysozymes, enzymes that hydrolyse cell walls.
Hydrolyses material ingested in phagocytosis.
Releases enzymes out of cell (exocytosis) to destroy material outside cell.
Digests worn out organelles to recycle chemicals.
Apoptosis and autolysis.
Ribosomes structure and function
80S in eukaryotes, 70S in prokaryotes.
One large and one small subunit.
Site of protein synthesis.
Cell wall structure and function
Made of cellulose embedded in matrix in plants (glycoproteins and cellulose in algae and chitin in fungi.
Thin layer that cements adjacent cells together.
Provide mechanical strength to prevent cell bursting.
Mechanical strength to plant.
Allow water to pass along to contribute to movement of water.
Vacuole structure and function
Tonoplast membrane.
Contains solution of mineral salts, sugars, amino acids, pigments and wastes.
Make cells turgid to support plants.
Sugars and amino acids act as food store.
Pigments colour petals to attract insects.
Cell specialisation advantage
Cells of multicellular organisms have cells adapted to their own function and perform more effectively in order for the whole organisms to function more effectively.
Tissue definition
Similar cells that perform a specific function.
Organ definition
Combination of tissues that are coordinated to perform a variety of functions with one collective major function.
Organ system definition
Organs work together as a single unit to perform a particular function more efficiently (e.g. digestive system).
Eukaryotic cell
Larger with nucleus bounded by nuclear envelope.
Prokaryotic cell
Smaller with no nucleus or nuclear envelope (single DNA molecule), smaller ribosomes, no membrane-bound organelles, cell wall with murein.
Organelles that prokaryotes have that eukaryotes do not
One or more plasmids.
A capsule.
One or more flagella.
Structure of a virus
Genetic material, capsid, attachment protein
What is mitosis
Part of cell cycle where a eukaryotic cell divides to produce two daughter cells with identical copies of DNA.
In which phase does DNA replication occur
Interphase
Prophase
The chromosomes condense into 2 chromatids each and the nuclear membrane breaks down. Nucleolus disappears.
Centrioles divide and go to poles.
Centrioles at poles produce spindle fibres. (plant cells lack centrioles)
Metaphase
Chromosomes seen to made of two chromatids. Each chromatid = identical copy of DNA from parent cell joined to one other by centromere.
Chromosomes line up along centre of cell and attach to spindle via centromere.
Anaphase
Centromeres divide into two and spindle fibres pull chromatids apart to opposite poles (now called chromosomes).
Telophase and cytokinesis
Chromosomes reach poles and become longer and thinner, leaving only thin threads of chromatin.
Spindle fibres disintegrate and nuclear envelope and nucleolus reform.
Cytoplasm divides in cytokinesis.
Binary fission in prokaryotes
Circular DNA molecule replicates and both copies attach to cell membrane.
Plasmids replicate.
Cell membrane grows inwards between two DNA molecules and pinches inwards to divide cytoplasm.
New cell wall forms between molecules of DNA, creating two daughter cells with one copy of DNA and number of plasmids originally.
Replication in viruses
Attach to host cell with attachment proteins and inject nucleic acid to host cell that provide instructions on how to produce viral components and assemble virus.
Importance of mitosis
Growth
Repair
Reproduction
Three stages of cell cycle
Interphase - resting phase
Nuclear division - when nucleus divides into two (mitosis) or four (meiosis).
Cytokinesis - cytoplasm divides to produce 2 or 4 new cells.
How is a cancer formed
Growth disorder of cells. Damage to DNA that regulates mitosis and cell cycle. Leads to uncontrolled division of cells.
Treatments of cancer
Preventing DNA from replicating.
Inhibiting metaphase by interfering with spindle formation.
Role of phospholipids in plasma membrane
Hydrophilic heads point outside as they are attracted by water.
Hydrophobic tails point inwards as they are repelled by water on both sides.
They allow lipid soluble substances to enter and leave.
Prevent water soluble substances entering and leaving.
Make membrane self-sealing and flexible
Role of proteins in plasma membrane
Embedded in phospholipid bilayer.
Provide structural support.
Act as channels to transport water soluble substances.
Carrier proteins allow active transport.
Form cell surface receptors for identification
Help cells adhere to each other.
Receptors for hormones
Role of cholesterol in plasma membrane
Cholesterol is hydrophobic and add strength.
Restricts movement of other molecules making up membrane at higher temperatures.
Glycolipids in plasma membrane
Carbohydrate covalently bonded with lipid.
Acts as cell surface receptor for recognition.
Maintain stability of membrane.
Help cells attach to one another (forms tissues).
Glycoproteins in plasma membrane
Recognition sites.
Help cells attach to form tissues.
Allows cells to recognise self/non-self.
Why might molecules not pass through plasma membrane
Not soluble in lipids.
Too large to pass through channels.
Same charge as protein channel - repelled.
Electrically charged, cannot pass through non-polar layer.
Fluid in fluid-mosaic model
The phospholipid molecules can move relative to one another so the membrane is flexible.
Mosaic in fluid-mosaic model
Embedded proteins vary in shape and size.
Diffusion def
Net movement of molecules or ions from an area of high concentration to an area of low concentration until the concentration is evenly distributed.
Facilitated diffusion
Channels and carriers in membrane facilitate the movement of charged ions and polar molecules across the membrane. Passive process.
How does protein channel work
Hydrophilic channels allow water soluble ions to pass through.
Channels open when presence of specific ion, otherwise remain closed (ions bind with protein so it changes shape to close off one side of membrane and open to inside of cell). Passive
How does carrier protein work
When molecule specific to protein is present, it binds with protein and protein changes shape to release molecule to inside membrane. Passive
Osmosis def
Passage of water from region of high water potential to a region of low water potential through selectively permeable membrane.
How to lower water potential
Add solute
What happens if animal cell is in solution that has a higher water potential
Net movement of water into cell and swelling and bursting of cell.
What happens if animal cell is in solution that has an equal water potential
No change
What happens if animal cell is in solution that has a lower water potential
Net movement of water out of cell and cell shrinks.
What happens if plant cell is in solution that has a higher water potential
Net movement of water into cell and cell swells and becomes turgid (protoplast pushes against cell wall).
What happens if plant cell is in solution that has an equal water potential
No change, cell in incipient plasmolysis
What happens if plant cell is in solution that has a lower water potential
Net movement of water out of cell and cell shrinks and becomes plasmolysed (protoplast pulls away from cell wall.
Active transport def
Movement of molecules or ions into or out of cell from region of higher concentration to a region of lower concentration using ATP and carrier proteins.
How is ATP used in active transport
Directly move molecules.
Move molecules using a concentration made by active transport (co-transport).
Difference between active transport and passive transport
Metabolic energy from ATP needed.
Substances moved against conc. gradient.
Carrier protein molecules used.
Selective substances only transported.
Active transport of a molecule
Carrier protein binds to molecule.
Molecule binds to receptor site on carrier protein.
ATP binds to protein and splits into ADP and phosphate.
Protein molecule changes shape and opens to opposite side of membrane as a result.
Phosphate released from protein and protein reverts to original shape. ATP formed again for repeat.
Role of diffusion in absorption
Greater concentration of glucose and amino acids in ileum than in blood, therefore they move from ileum to bloodstream via facilitated diffusion. Blood being circulated maintains concentration gradient.
Co-transport of glucose
Sodium ions actively transported out of epithelial cells into blood by sodium-potassium pump in protein carrier molecule to maintain high conc of Na+ in lumen of intestine relative to epithelial cells.
Sodium ions diffuse into epithelial cells from lumen through different protein-carrier into epithelial cells while carrying glucose or amino acids.
Glucose/amino acids pass into blood plasma by facilitated diffusion.
