A LEVEL BIOLOGY OCR EXAM QUESTIONS
AND ANSWERS.
What is the structure and function of the nucleus? - CorreCt Answers -
Surrounded by a double membrane (the nuclear envelope). Contains
chromatin (DNA wound around histones). Stores the human genome,
controls the cell by providing instructions for protein synthesis.
What is the structure and function of the nucleolus? - CorreCt Answers -
Made of RNA, produces ribosomes.
What is the structure and function of the nuclear envelope? - CorreCt
Answers -A double membrane embeded with channel proteins forming
pores. Separates the nucleus from the rest of the cell. Pores allow ribosomes
and mRNA to leave the nucleus.
What is the structure and function of the rough endoplasmic reticulum
(RER)? - CorreCt Answers -A system of fluid filled membranes studded
with ribosomes. Continuous with the nuclear membrane. Large surface area
formed by folding, enables lots of protein synthesis. Proteins pinched off in
vesicles transported to the Golgi apparatus.
What is the structure and function of the smooth endoplasmic reticulum
(SER)? - CorreCt Answers -A system of fluid filled membranes. No
ribosomes. Contain enzymes for cholesterol, lipid and phospholipid
synthesis.
What is the structure and function of the Golgi apparatus? - CorreCt
Answers -A stack of flattened membrane bound sacs. Vesicles from the RER
,join at the cis face. Here they are modified, by adding sugar to make
glycoproteins, adding lipids to form glycolipids. Folding proteins into their
3D shape. Modified proteins are pinched off from the trans face into
transport vesicles.
What is the structure and function of the ribosomes? - CorreCt Answers -2
subunits, large and small. Made of rRNA . Proteins synthesised here.
What is the structure and function of the mitochondria? - CorreCt Answers
-Double membrane bound. Inner membrane folded into cristae within a
fluid filled matrix. Contain own DNA and 70s ribosomes. Site of aerobic
respiration.
What is the structure and function of the lysosomes? - CorreCt Answers -
Membrane bound sacs containing hydrolytic (digestive) enzymes. break
down old organelles and foreign matter for reuse.
What is the structure and function of the chloroplasts? - CorreCt Answers -
Double membrane bound. Inner membrane forms flat discs filled with
chlorophyll called thylakoids, in stacks called granum. These are
surrounded by a fluid matrix called the stroma. Contain own DNA and 70s
ribosomes. Site of photosynthesis.
What is the structure and function of the plasma membrane? - CorreCt
Answers -Phospholipid bilayer, cholesterol, proteins, glycoproteins,
glycolipids. Separates cell contents from external environment. Controls
what enters and leaves the cell. Identifies cell as self. Acts as a receptor for
various chemicals. site of chemical reactions.
,What is the structure and function of the centrioles? - CorreCt Answers -
Present in animals only. Two bundles of microtubules at right angles. Used
as an anchor point to separate chromosomes during cell division. Form the
basis of cilia.
What is the structure and function of the cell wall? - CorreCt Answers -
Present in plants and fungi only. Bundles of cellulose fibres in plants. Chitin
in fungi. Provides support and strength, maintaining the cell's shape.
prevents the cell from bursting when turgid. Permeable to allow solutions
through.
What is the structure and function of the flagella? - CorreCt Answers -9
pairs of microtubules surround 2 lone microtubules. A membrane covers
the whole thing. Used for moving unicellular organisms around.
What is the structure and function of the cillia? - CorreCt Answers -9 pairs
of microtubules surround 2 lone microtubules. A membrane covers the
whole thing. Present in great numbers. Move together in a wafting pattern
to move single celled organisms. When present on tissues waft to move
fluids such as mucus.
Which structures are involved in the production of proteins? - CorreCt
Answers -Nucleus; RER; transport vesicle; Golgi apparatus
What is the structure and function of the cytoskeleton? - CorreCt Answers -
Microfilaments made of actin - allow cell movement and cytokinesis.
Microtubules made of tubulinsscaffold like structures to give cell shape.
Intermediate fibres give mechanical strength, maintaining integrity.
, What do prokaryotic and eukaryotic cells have in common? - CorreCt
Answers -Plasma membrane; cytoplasm; ribosomes; DNa and RNA
What is different between prokaryotic and eukaryotic cells? - CorreCt
Answers -Prokaryotes have no: Nucleus; centrioles; membrane bound
organelles (mitochondria, chloroplast, RER, SER, Golgi apparatus).
Prokaryotes also have: peptidoglycan cell wall; smaller ribosomes; naked
loop of DNA; plasmids.
How do prokaryotes divide? - CorreCt Answers -Binary fission
State the three main factors that affect the need for an exchange system -
CorreCt Answers -Size, SA:Vol ratio and level of activity
Explain why smaller organisms have a lower demand for oxygen than larger
organisms - CorreCt Answers -Smaller organisms have a larger SA:V ratio
than larger organisms; simple diffusion can be sufficient for unicellular
organisms but due to many-layered multicellular organisms, it would be too
slow. Multicellular organisms therefore need transport systems
Describe and explain three features of a good exchange surface - CorreCt
Answers -Large SA (folded walls; provides more space for relevant
molecules to pass through); thin, permeable barriers (reduces diffusion
distance); good blood supply (keeps high concentration gradients for rapid
diffusion)
Describe how human alveoli are adapted to reduce diffusion distances -
CorreCt Answers -Alveolus wall one cell thick; capillary wall one cell thick;
walls of alveoli/capillaries contain squamous (flattened) cells; caoillaries
AND ANSWERS.
What is the structure and function of the nucleus? - CorreCt Answers -
Surrounded by a double membrane (the nuclear envelope). Contains
chromatin (DNA wound around histones). Stores the human genome,
controls the cell by providing instructions for protein synthesis.
What is the structure and function of the nucleolus? - CorreCt Answers -
Made of RNA, produces ribosomes.
What is the structure and function of the nuclear envelope? - CorreCt
Answers -A double membrane embeded with channel proteins forming
pores. Separates the nucleus from the rest of the cell. Pores allow ribosomes
and mRNA to leave the nucleus.
What is the structure and function of the rough endoplasmic reticulum
(RER)? - CorreCt Answers -A system of fluid filled membranes studded
with ribosomes. Continuous with the nuclear membrane. Large surface area
formed by folding, enables lots of protein synthesis. Proteins pinched off in
vesicles transported to the Golgi apparatus.
What is the structure and function of the smooth endoplasmic reticulum
(SER)? - CorreCt Answers -A system of fluid filled membranes. No
ribosomes. Contain enzymes for cholesterol, lipid and phospholipid
synthesis.
What is the structure and function of the Golgi apparatus? - CorreCt
Answers -A stack of flattened membrane bound sacs. Vesicles from the RER
,join at the cis face. Here they are modified, by adding sugar to make
glycoproteins, adding lipids to form glycolipids. Folding proteins into their
3D shape. Modified proteins are pinched off from the trans face into
transport vesicles.
What is the structure and function of the ribosomes? - CorreCt Answers -2
subunits, large and small. Made of rRNA . Proteins synthesised here.
What is the structure and function of the mitochondria? - CorreCt Answers
-Double membrane bound. Inner membrane folded into cristae within a
fluid filled matrix. Contain own DNA and 70s ribosomes. Site of aerobic
respiration.
What is the structure and function of the lysosomes? - CorreCt Answers -
Membrane bound sacs containing hydrolytic (digestive) enzymes. break
down old organelles and foreign matter for reuse.
What is the structure and function of the chloroplasts? - CorreCt Answers -
Double membrane bound. Inner membrane forms flat discs filled with
chlorophyll called thylakoids, in stacks called granum. These are
surrounded by a fluid matrix called the stroma. Contain own DNA and 70s
ribosomes. Site of photosynthesis.
What is the structure and function of the plasma membrane? - CorreCt
Answers -Phospholipid bilayer, cholesterol, proteins, glycoproteins,
glycolipids. Separates cell contents from external environment. Controls
what enters and leaves the cell. Identifies cell as self. Acts as a receptor for
various chemicals. site of chemical reactions.
,What is the structure and function of the centrioles? - CorreCt Answers -
Present in animals only. Two bundles of microtubules at right angles. Used
as an anchor point to separate chromosomes during cell division. Form the
basis of cilia.
What is the structure and function of the cell wall? - CorreCt Answers -
Present in plants and fungi only. Bundles of cellulose fibres in plants. Chitin
in fungi. Provides support and strength, maintaining the cell's shape.
prevents the cell from bursting when turgid. Permeable to allow solutions
through.
What is the structure and function of the flagella? - CorreCt Answers -9
pairs of microtubules surround 2 lone microtubules. A membrane covers
the whole thing. Used for moving unicellular organisms around.
What is the structure and function of the cillia? - CorreCt Answers -9 pairs
of microtubules surround 2 lone microtubules. A membrane covers the
whole thing. Present in great numbers. Move together in a wafting pattern
to move single celled organisms. When present on tissues waft to move
fluids such as mucus.
Which structures are involved in the production of proteins? - CorreCt
Answers -Nucleus; RER; transport vesicle; Golgi apparatus
What is the structure and function of the cytoskeleton? - CorreCt Answers -
Microfilaments made of actin - allow cell movement and cytokinesis.
Microtubules made of tubulinsscaffold like structures to give cell shape.
Intermediate fibres give mechanical strength, maintaining integrity.
, What do prokaryotic and eukaryotic cells have in common? - CorreCt
Answers -Plasma membrane; cytoplasm; ribosomes; DNa and RNA
What is different between prokaryotic and eukaryotic cells? - CorreCt
Answers -Prokaryotes have no: Nucleus; centrioles; membrane bound
organelles (mitochondria, chloroplast, RER, SER, Golgi apparatus).
Prokaryotes also have: peptidoglycan cell wall; smaller ribosomes; naked
loop of DNA; plasmids.
How do prokaryotes divide? - CorreCt Answers -Binary fission
State the three main factors that affect the need for an exchange system -
CorreCt Answers -Size, SA:Vol ratio and level of activity
Explain why smaller organisms have a lower demand for oxygen than larger
organisms - CorreCt Answers -Smaller organisms have a larger SA:V ratio
than larger organisms; simple diffusion can be sufficient for unicellular
organisms but due to many-layered multicellular organisms, it would be too
slow. Multicellular organisms therefore need transport systems
Describe and explain three features of a good exchange surface - CorreCt
Answers -Large SA (folded walls; provides more space for relevant
molecules to pass through); thin, permeable barriers (reduces diffusion
distance); good blood supply (keeps high concentration gradients for rapid
diffusion)
Describe how human alveoli are adapted to reduce diffusion distances -
CorreCt Answers -Alveolus wall one cell thick; capillary wall one cell thick;
walls of alveoli/capillaries contain squamous (flattened) cells; caoillaries
