Cells Flashcards
Content • Plant and Animal Cells • Specialised Cells, Tissues and Organs + few qns from papers (sch, tys)
What does a nucleus contain?
- nuclear envelope
- nucleoplasm: small round mass of denser protoplasm
- nucleolus: play a part in making of protein in cell
- chromatin: long thread-like structures made up of deoxyribonucleic acid (DNA) & condenses into highly coiled structures- chromosomes
Characteristics of rough endoplasmic reticulum (RER)
- surface appear rough due to ribosomes attached to its surface
- outer surface of RER is continuous w/ nuclear envelope
Function of RER
It transports proteins made by ribosomes to the Golgi apparatus for secretion out of cell
Function of ribosomes
attached to ER & lying freely in cytoplasm
- (attached to ER) make proteins that are usually transported out of the cell
- (lying freely in cytoplasm) make proteins that are used within cytoplasm of that cell
Functions of smooth endoplasmic reticulum (SER)
- synthesises substances such as fats and steroids (sex hormones in mammals - steroids)
- converts harmful substances into harmless materials - detoxification
Functions of golgi apparatus
- chemically modifies substances made by ER
- stores & packages these substances in vesicle for secretion out of the cell
How are substances synthesised secreted out of the cell?
- Vesicles containing substances made by the ER are pinched off the ER
- Vesicles then fuse with Golgi apparatus & release contents into Golgi apparatus. These subs may be modified inside
- Secretory vesicles containing these modified subs are pinched off Ga
- Then move to cell surface membrane
- Secretory vesicles fuse with CSM and their contents are released outside the cell
Vacuoles in animals & plants
Animal cells:
- numerous small vacuoles, contain water & food substances
- exist temporarily
Plant cells
- large central vacuole, stores cell sap which contains dissolved subs like sugars, mineral salts & AA
- enclosed by a partially permeable membrane - tonoplast
Adaptations of red blood cells
- contains haemoglobin that binds reversibly with oxygen & transports it around the body
- has circular, biconcave shape - increases SA:V ratio, faster rate of diffusion of oxygen in & out
- lacks nucleus - enables cell to store more haemoglobin, transport more oxygen around the body
- flexible - able to squeeze through narrow blood capillaries
Adaptations of xylem vessels
- presence of lignin deposits - prevent collapse of plant
- continuous hollow lumen, no cross-walls - prevent obstruction of water flow through lumen
Adaptation of root hair cells
- have long, narrow protrusion - increases SA:V ratio, water & mineral salts - absorbed at a faster rate
- numerous mitochondria - release of energy for active transport
1 similarity & 2 differences between RER & ribosome
Similarity: Both involved in protein synthesis
Differences:
- Ribosome: not membrane bound while RER: membrane bound organelle
- Ribosome syntheise polypeptides from AA while RER modifies polypeptides after they are syntesised by ribosomes
Relationship between cells, tissues & organs
use a named part of the human body
- stomach
- organ is different tissues that structurally form a functional unit specialised to perform a particular function
- tissue is a group of cells that have a similar structure and act together to perform a specific function
Explain how a large number of miochondria in root hair cells allows the plant to survive in soils that contain a short supply of mineral ions.
3m
- When mineral ions are in short supply, there will be a lower conc of mineral ions in soil than in root hair cells
- The large no. of mitochondria ensures that the root hair cell can carry out aerobic respiration to release sufficient energy.
- Energy is used by the cell to absorb mineral ions against its conc gradient via active transport.
Explain why liver cells have a large number of mitochondria
- Liver carries out many metabolic reactions like detoxification & deamination
- A large no. of mitochodria: required to release energy needed to carry out these reactions effectively
