Solved Midterm Exam

MIDTERM EXAMINATION IN BIOLOGY FOR 1ST YEAR BIOMEDICAL ENGINEERING STUDENTS November 2007 Time allowed 1 hour .Sec. No

15

.Pn. No

:(‫السم )بالعربى‬

‫ المتحان يقع فى أربع صفحات‬:‫ملحظة مهمة‬ {1} Complete the following with suitable scientific words: (2 marks) 1- The study of food and feeding is called nutrition.

2- The energy coin in the biological system is called ATP. 3- Act as selective transport channels and carriers or Act as enzymes or Act as receptors or Act as markers (cell identification markers) or Cell adhesion is one of the main functions of the protein in the cell membrane. 4- Endocytosis and exocytosis are examples of bulk transport (vesicle-mediated transport). 5- Mitochondrion is the site of chemical reactions and cell respiration. 6- Peroxisomes contain enzymes that degrade fatty acids and amino acids.

{2} The following sentences may be right or may be contain one wrong word. Put (√) in front the right one and a line under the incorrect word then write a correct word above it. (3 marks) : ( ) 1- Sponges and coelenterates such as Hydra reproduce sexually by budding. {asexually}

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2- Plant cells lack chloroplasts, large central vacuole and cell wall. {have} 3- Integral (intrinsic) proteins are loosely attached on surface of the cell membrane. {Peripheral (extrinsic)} 4- Facilitated diffusion can takes place through pores and gated channels. {√} 5- The unbalanced charge across the cell membrane which result from sodium-potassium pump is important for conduction of nerve impulses, muscle contraction … etc. {√} 6- Vesicles of endoplasmic reticulum are divided into macrovesicles, microvesicles and intermediate vesicles. {Golgi apparatus}

{3} Mention one difference between the following scientific terms: (4 marks) (1) Autotrophic nutrition Make their own food by a process called photosynthesis. Or Such as green plants. (2) Asexual reproduction Showing little or no genetic variation from the parent. Or Needs one parents. Or Takes place by different ways. (3) Prokaryotic cell Absence of a distinct membranebound nucleus. Or Absence of membrane-bound organelles. Or They are unicellular organisms. 2

Heterotrophic nutrition Obtain their food from other organisms. Such as animals and humans. Sexual reproduction Showing great genetic variation from the parent. Needs two parents. Takes place by one way. Eukaryotic cell Presence of a distinct membrane-bound nucleus. Presence of membrane-bound organelles. They are unicellular or

multicellular organisms. Or Smaller than eukaryotes. Or Most primitive. Or e.g. Bacteria. 4) Heads of phospholipids Formed from phosphate groups Or Polar Or Hydrophilic (water loving). Or They found on the outer and inner surfaces of the cell membrane. (5) Passive transport It does not require energy. Or It takes place according to the concentration gradient. (6) Rough endoplasmic

Larger than eukaryotes. More complex. e.g. Plant and animal cells. Tails of phospholipids Formed from fatty acids Non-polar Hydrophobic (water fearing) They are directed inwards face to face. Active transport It requires energy. It takes place against the concentration gradient. Smooth endoplasmic

reticulum Covered by ribosomes. Or It is involved in the synthesis of proteins.

reticulum Lacks by ribosomes.

apparatus Immature face. Or Facing the ER and nucleus.

Golgi apparatus Mature face.

It is not involved in the synthesis of proteins or steroid synthesis or regulation of calcium levels in muscle cells or the break down of toxic substances in the cell. (7) Cis face of cisternae of Golgi Trans face of cisternae of

Directed towards the plasma membrane.

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(8)

Exogenic intracellular

Endogenic intracellular

digestion Digestion of the taken substances by endocytosis.

digestion Digestion of some parts of the cytoplasm of the same cell e.g. mitochondria.

Or The process is known as heterophagy.

The process is known as autophagy.

{4} Define the following: 1- Glycocalyx (cell coat):

(1.5 marks)

It comprises both glycoproteins and glycolipids

2- Osmosis: It is the diffusion of water (solvent) through a semi-permeable membrane from an area of high water concentration (less solute) (hypotonic) solution to an area of lower water concentration (more solute) (hypertonic) solution. It does need energy. It takes place according to the concentration gradient.

3- Plasmolysis: When the cell is placed in a hypertonic solution, water diffuses out of the cell till equilibrium is reached. If the cell loses too much water, it will shrink and die.

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{5} Draw a mitochondrion with complete labels.

(1.5 marks)

{6} Explain shortly the mechanism of sodium-potassium pump. (3 marks) 1- Binding of cytoplasmic Na+ to the protein stimulates

phosphorylation. 2- Phosphorylation causes the protein change its conformation. 3- The conformational changes expels Na+ to the outside and extracellular K+ binds. 4- K+ binding triggers release of phosphate group. 5- Loss of phosphate restores orginal conformation. 6- K+ is released and Na+ are receptive again, the cycle repeat.

‫أجمل المنيات بالتوفيق والتفوق‬ ‫شبل شعلن‬

5 ‫أجمل المنيات بالتوفيق والتفوق‬ ‫شبل شعلن‬