Organelles

Question 1

Nuclear envelope and pores.

Answer 1

• double membrane to separate contents of the nucleus from the rest of the cell.
• pores enable larger substances such as mRNA to exit the nucleus.

Question 2

Nucleolus.

Answer 2

• no membrane.
• contains RNA.
• where ribosomes are made.

Question 3

Chromatin (nucleolus and chromatin make up nucleus)

Answer 3

• it is the genetic material made of DNA and proteins.

- controls cells activity.

Question 4

Nucleus.

Answer 4

• controls cells activity.
• stores the organisms genetic material.
• transmits genetic information.
• provides instructions for protein synthesis in the form of mRNA.

Question 5

Rough endoplasmic reticulum.

Answer 5

• Membranes contains fluid filled space which is continuous with nuclear envelope.
• studded with ribosomes.
• synthesises proteins from amino acids at the ribosomes and transports to Golgi.

Question 6

Smooth endoplasmic reticulum.

Answer 6

• membranes with fluid filled space and continuous with the nuclear envelope.
• no ribosomes.
• has enzymes that catalyse reactions: synthesis of lipids, cholesterol and steroid hormones.
• synthesises and transports lipids to Golgi.

Question 7

Golgi apparatus.

Answer 7

• Stacks of membrane-bound flattened sacs with vesicles.
• proteins modified by: adding sugar/lipids to make glycoproteins/lipoproteins and folded into 3D shape.
• proteins packaged into vesicles to be: stored in cell, incorporated to plasma membrane or exported out of cell.
• makes lysosomes

Question 8

Mitochondria.

Answer 8

• double membrane
• inner membrane highly folded into Cristae.
• inner part of mitochondria has fluid filled matrix which has enzymes for respiration.
• site of ATP production.
• abundant in cells which need lots of energy such as in cilia.

Question 9

Chloroplasts.

Answer 9

• double membrane.
• inner membrane continuous with stacks of flattened membrane sacs called thylakoids.
• each thylakoid is called a granum.
• fluid filled matrix is called stroma.
• site of photosynthesis.
• grana is where chlorophyll traps light to make ATP.
• stroma is where carbohydrates are made from water reducing carbon dioxide.
• abundant in palisade mesophyll layer.

Question 10

Definition of ultra structure.

Answer 10

Ultra structure: things inside a cell which can be seen by an electron microscope.

Question 11

Ribosomes

Answer 11

• small, spherical
• made of rRNA
• made in nucleolus
• some free in cytoplasm are site of protein synthesis to be in cell.
• some stud RER to synthesise proteins for out of cell.

Question 12

Lysosomes

Answer 12

• small formed by Golgi
• contain hydrolytic digestive enzymes to separate from rest of cell
• abundant in phagocytic cells (macrophages/wbc that ingest and digest)
• engulf old cell organelles/foreign matter and digest it and return digested components for reuse

Question 13

Centrioles

Answer 13

• consist of 2 bundles of micro tubules
• involved with separation of chromosomes during cell division
• involved in formation of cilia

Question 14

Cell wall

Answer 14

• made of bundles of cellulose fibres
• strong and stops plant cell from bursting when turgid
• provides strength and support
• maintains cells shape
• permeable and allows solutions to go through

Question 15

Flagella

Answer 15

• sticks out from cell surface
• micro tubules contract to make flagellum move
• used like outboard motors to propel cells forward
• e.g. Sperm cell swims

Question 16

Cilia

Answer 16

• on surface of animal cells
• formed by centrioles
• microtubules let cilia to move
• movement used by cell to move substances along cell surface

Question 17

Cytoskeleton importance

Answer 17

• protein micro filaments provide mechanical strength
• keep cells shake stable
• Allow substances and organelles to move in cell by forming a track along motor proteins
• filaments extend between cells for cell signalling

Question 18

Production secretion of proteins

Answer 18

• gene codes for protein transcribed into mRNA
• at ribosomes, instructions translated
• proteins made at RER export out of cell and protein in cytoplasm stay in cell
• proteins folded & processed at RER
• transported to Golgi via vesicles
• Golgi modifies protein by adding sugar molecules, processes and packages into vesicles
• vesicles fuse with plasma membrane to release out of cell

Question 19

Prokaryotic vs eukaryotic cells

Answer 19

Prokaryotic 
-cell small (less than 2um in diameter)
-circular DNA
-no nucleus - DNA floats free in cytoplasm
-cell wall
-few or no membrane bound organelles -no mitochondria
-flagella of protein flagellin
-small ribosomes
Eukaryotic 
-larger cell (10-100um in diameter)
-linear DNA
-DNA in nucleus
-no cell wall
-many membrane bound organelles
-larger ribosomes
-flagella of microtubules