Life processes at the cellular level

Question 1

Cell wall

Answer 1

Present in plants, fungi and bacteria. In plants it’s made of cellulose (a polysaccharide / polymer of glucose molecules). The cellulose molecules form parallel chains linked into microfibril bundles laid down and cemented in place at different angles. The result is a rigid box surrounding the cell wall which provides support and is freely permeable, and allows the cell to develop turgor pressure.

Question 2

Cell membrane

Answer 2

Phospholipids have hydrophilic phosphate group (head) and hydrophobic fatty acid chains (tails). Form two monolayers (a bilayer).
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Surrounds cell and the organelles

Question 3

Cytoplasm

Answer 3

Contents of cell outside nucleus. Consists of a fluid cytosol matrix in which organelles are suspended.

Question 4

Nucleus

Answer 4

Controls cell and contains chromosomes. Only present in eukaryotic cells (except red blood cells). Contains the nucleolus.

Question 5

Nucleolus

Answer 5

Found inside the nucleus in the region where ribosomes are assembled (largest organelle of the nucleus).

Question 6

Chromosome

Answer 6

Found (in euakryotes) in the nucleus and made from DNA and proteins. They become tightly coiled during cell division but are unwound and cannot be seen in undividing cells.

Question 7

Mitochondrion

Answer 7

Site of aerobic respiration. Increased abundance in cells with high energy demands. Bound by a double membrane, outer membrane smooth, inner membrane has cristae to increase surface area. Contain a jelly-like matrix in the centre. Derived from prokaryotic ancestors so have their own DNA.

Question 8

Chloroplast

Answer 8

Site of photosynthesis, green due to chlorophyll pigment. Contain flattened thylakoid disks in stacks called grana which are connected via lamellae and surrounded by the fluid stroma.

Question 9

Centriole

Answer 9

Tiny structures made of microtubules found next to nucleus of animal cells. Involved with chromosome separation in cell division.

Question 10

Microtubule

Answer 10

Hollow tubes made from globular proteins.

Question 11

Cilium

Answer 11

Hair-like structures projecting from cell. Made of microtubules in a 9+2 arrangement. Contract causing the cilium to beat. Found in some unicells for locomotion and in mammalian airways to move mucus.
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Question 12

9 + 2 arrangement

Answer 12

Arrangement of microtubules in cilia. Looks like:

               o    o    o 
          o        oo       o
            o                o
                  o    o

Question 13

Flagellum

Answer 13

Hair-like structures protruding from cell/ Long and fewer in number than cilium. Present in Euglena and sperm for locomotion.

Question 14

Vacuole

Answer 14

Membrane-bound bag, small food vacuoles formed in animals by phagocytosis, contractile vacuoles found in some freshwater unicells to pump out water. Very large in plants, in which a central vacuole stores water compounds to provide support and storage.

Question 15

Ribosome

Answer 15

Made of protein and ribosomal RNA (rRNA), assembled in nucleolus of nucleus. Site of protein synthesis. Free ribosomes make proteins for use inside the cell, those on rough ER make proteins for use outside of cell or in cell membrane. Contain 1 large and 1 small subunit. Eukaryotes have as many as 100 000 ribosomes, while prokaryotes have smaller ribosomes.

Question 16

Rough Endoplasmic Reticulum

Answer 16

Ribosomes attached, part of a network of tubes running through the cytoplasm, more abundant in secretory where the attached ribosomes make proteins for export.

Question 17

Smooth Endoplasmic Reticulum

Answer 17

No ribosomes, part of a network of tubes running through the cytoplasm, involved in steroid production and processing lipids.

Question 18

Steps of protein excretion

Answer 18

Proteins are passed from ribosomes into the ER, from which membrane-bound vesicles bud off and pass the protein to the Golgi body for processing and then on to the cell membrane where they leave the cell.

Question 19

Lysosomes

Answer 19

Small membrane-bound bags of digestive enzymes which can be used to digest food in food vacuoles or to break down worn-out cell components or destroy old cells.

Question 20

Practice test

Answer 20

https://www.nzqa.govt.nz/ncea/assessment/view-detailed.do?standardNumber=91156&_gl=1weijee_gaMTY3NjI0NjU0Ny4xNzI5NjU4MzQy_ga_TFQQ681L2E*MTc0NTU0NDQwMy4yNC4xLjE3NDU1NDQ2OTUuMC4wLjA.
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