What is the role of the cell-surface membrane at the boundary of a cell?
It forms a selectively permeable boundary that controls the movement of substances into and out of the cell.
AQA A-Level Biology - (7402) · 3.2.1.1
Revise AQA A-Level Biology - (7402) specification point 3.2.1.1, Structure of eukaryotic cells, with free active-recall flashcards. Flip through the set or review every question and answer below.
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What is the role of the cell-surface membrane at the boundary of a cell?
It forms a selectively permeable boundary that controls the movement of substances into and out of the cell.
What is the basic structure of the cell-surface membrane?
A phospholipid bilayer with proteins embedded in or associated with it.
How are phospholipids oriented in the cell-surface membrane?
Their hydrophilic phosphate heads face the watery environments on either side; their hydrophobic fatty acid tails face inwards.
What are two functions of membrane proteins?
Transport and cell signalling.
What are chloroplasts?
Organelles in plant and algal cells where photosynthesis occurs.
What is the structure of a chloroplast’s outer membrane?
It has a double membrane.
What are thylakoids?
Flattened membrane sacs inside chloroplasts.
What are grana in a chloroplast?
Stacks of thylakoids.
Where in a chloroplast is chlorophyll found?
In the thylakoids.
What does chlorophyll do in photosynthesis?
It absorbs light.
What three things are found in the stroma surrounding chloroplast thylakoids?
Enzymes involved in photosynthesis, chloroplast DNA and ribosomes.
What is the structure of the Golgi apparatus?
A stack of flattened, membrane-bound sacs.
How do substances such as proteins reach the Golgi apparatus?
They arrive in vesicles from the endoplasmic reticulum.
What does the Golgi apparatus do to the substances it receives?
It modifies and sorts them, then packages them into Golgi vesicles.
Where do Golgi vesicles transport their contents?
To other parts of the cell or to the cell-surface membrane for secretion.
What is a lysosome?
A membrane-bound organelle containing hydrolytic enzymes.
By what process do lysosomal enzymes break down material?
Hydrolysis.
What two types of material can lysosomal enzymes break down?
Material taken into the cell and worn-out cell components.
What is the role of the membrane surrounding a lysosome?
It separates the enzymes from the cytoplasm.
Where can lysosomes release their enzymes?
Into compartments containing material to be digested.
What are ribosomes made of?
Ribosomal RNA and proteins.
How are the subunits of a ribosome organised?
A ribosome has one large and one small subunit.
What membrane, if any, surrounds a ribosome?
None; ribosomes are not membrane-bound.
How do ribosomes synthesise proteins?
They use information carried by messenger RNA to join amino acids into a polypeptide.
Where can eukaryotic cytoplasmic ribosomes be found?
Free in the cytoplasm or attached to the rough endoplasmic reticulum.
What is the structure of rough endoplasmic reticulum?
A network of membrane-bound flattened sacs with ribosomes attached to their outer surface.
What do ribosomes attached to rough endoplasmic reticulum synthesise?
Proteins.
What happens to many proteins synthesised by ribosomes on rough endoplasmic reticulum?
They enter its interior for folding and initial processing.
Where do transport vesicles carry proteins from the rough endoplasmic reticulum, and for what purpose?
Towards the Golgi apparatus for further processing and sorting.
What is the structure of smooth endoplasmic reticulum?
A network of membrane-bound tubules and sacs without attached ribosomes.
What type of molecules does smooth endoplasmic reticulum synthesize?
Lipids.
Besides lipid synthesis, what process can smooth endoplasmic reticulum contribute to?
The processing of substances within cells.
What is a cell wall, and what structural role does it serve?
A layer outside the cell-surface membrane that provides mechanical strength and helps maintain cell shape.
How does a cell wall help prevent a cell from bursting when water enters?
It resists expansion of the cell.
Which materials are found in plant and fungal cell walls, respectively?
Plant walls contain cellulose; fungal walls contain chitin.
How does cell wall composition vary among algae?
It varies between algal groups.
What permeability property does the cell-surface membrane beneath a cell wall have?
It is selectively permeable.
What is a plant cell vacuole?
A membrane-bound compartment containing cell sap.
What is cell sap?
A solution of water and dissolved substances.
What is the membrane surrounding a plant cell vacuole called?
The tonoplast.
How does a large central vacuole contribute to turgor and support in a mature plant cell?
Water within the cell exerts pressure against the cell wall, helping support the cell and maintain its shape.
What makes a cell in a complex multicellular organism specialised?
Its features are suited to a particular function, for example its shape or the abundance or arrangement of its cell structures.
How should you explain a specialised cell’s adaptation?
Link a specific feature of the cell to how it helps the cell perform its function.
What is the order of biological organisation from specialised cells to organ systems?
Specialised cells → tissues → organs → organ systems.
What is a tissue?
A group of cells working together to carry out a function.
What is an organ?
A structure made of different tissues working together.
What is an organ system?
A group of organs that cooperate in a broader function.